Model Engine Maker

Supporting => Engine Ancillaries => Topic started by: Roger B on May 01, 2015, 06:56:18 PM

Title: Fuel injection systems
Post by: Roger B on May 01, 2015, 06:56:18 PM
Most of my future projects require fuel injection systems, both paraffin (kerosene) and diesel. These will be around 20 - 25 cc per cylinder and as the smallest commercial engines with mechanical injection are around 200 cc per cylinder I decided that I need to start experimenting and developing some manufacturing techniques.
The first step will be a fuel pump and injector hopefully suitable for a 25 cc engine. The fuel pump will have a plunger diameter of 2mm and a target stroke of 2mm. The injector will have 1.5mm diameter needle with a 0.35mm diameter nozzle.
I hope to trial this on my current horizontal engine injecting petrol into the inlet with a later step of injecting paraffin into a vaporiser.
This will require lower pressures than for direct injection in a diesel engine, but petrol is of low viscosity and has no lubricating properties.
I have made a start on the injector with a body from 10mm square black bar. To make the nozzle concentric I need to drill the hole from the needle side so I had a go at drilling a deep (12mm) hole in the end of some brass bar turned down to 1.5 mm diameter. This seemed to work (the centre drill has a 0.5mm diameter tip.
Next I need to look at making a needle and seat cutting tool from hardened silver steel (drill rod).
Title: Re: Fuel injection systems
Post by: Roger B on May 02, 2015, 06:12:15 PM
I had decided to try and grind the D bit and the needle as with these small sizes even at full speed (2000rpm) the cutting speed is minimal. For a previous project I had made a tool post support for my Proxxon hand tool, this is not so rigid but was sufficient for some trials.

The lathe bed was protected with a sheet of plastic covered with a damp paper towel. I arranged the setup so that the sparks would be downwards. This required running the lathe in reverse.

I was able to grind 30° and 45° points as well as parallel without the Proxxon colliding with anything.

The D bit was hand filled to half thickness and then hardened by heating to dull orange and quenching in water.

I am happy with the basic techniques but they will need some refinement.
Title: Re: Fuel injection systems
Post by: Roger B on May 02, 2015, 06:19:52 PM
Next I tried some of the steps for making a nozzle to see if I could drill the 0.35mm hole from inside.

Starting with some 6mm round brass I drilled a 1. mm hole 20mm deep and then reamed it out to 1.5mm. Using my D bit I then went down to 24mm which would leave around 1mm for the nozzle hole.

Finally I put my nozzle drill in, marked the expected starting depth with a marker pen, put a drop of oil on the brass shaft, started the lathe at 2000rpm and carefully pecked until the resistance went away.

The drill came out complete and removing the bar showed the hole had gone through  :whoohoo: 
Title: Re: Fuel injection systems
Post by: Admiral_dk on May 02, 2015, 07:31:49 PM
Hi Roger

Very interesting project - many has tried and few has succeeded in making a working injection system in miniature size.

I for one hope that you will be among them   :ThumbsUp:

That way the rest of us can learn  ;)   .....  :popcorn:
Title: Re: Fuel injection systems
Post by: Roger B on May 03, 2015, 08:04:50 PM
Thank you  :)

I am well aware of the level of the challenge I have set myself  ::) From these first trials I need to improve the finish and fit by an order of magnitude to have any chance of success  :headscratch:

Maybe my machines and I can reach this, but anyway it will be good experience. The 1.5mm silver steel I am using is actually 1.49 mm. This is within specification,  but if my 1.5mm reamer cuts on size the clearance is already too much before I start lapping/polishing.

I have source of reamers in 0.01mm steps, but they are not cheap  :( Acrolaps also supply needle laps in this size range so I have some ideas for the next steps.

Valves for the injection pump are another challenge. The current Bosch type jerk pump with the spiral spill edge is out of the question in this size. I need to look to earlier designs with inlet and exhaust valves with variable stroke or fixed stroke with a separate spill valve. The earliest Benz design I have a drawing of used cone valves and the Lanz Bulldog used cone valves backed up with ball valves. Good cone valves 3 or 4 mm in diameter will be interesting to make :thinking: .

I am always happy for people to learn from me, even if it is how not to do things  ;)

Suggestions of how to do things better are also welcome  :)
Title: Re: Fuel injection systems
Post by: jerry kieffer on May 03, 2015, 10:58:20 PM
Thank you  :)

I am well aware of the level of the challenge I have set myself  ::) From these first trials I need to improve the finish and fit by an order of magnitude to have any chance of success  :headscratch:

Maybe my machines and I can reach this, but anyway it will be good experience. The 1.5mm silver steel I am using is actually 1.49 mm. This is within specification,  but if my 1.5mm reamer cuts on size the clearance is already too much before I start lapping/polishing.

I have source of reamers in 0.01mm steps, but they are not cheap  :( Acrolaps also supply needle laps in this size range so I have some ideas for the next steps.

Valves for the injection pump are another challenge. The current Bosch type jerk pump with the spiral spill edge is out of the question in this size. I need to look to earlier designs with inlet and exhaust valves with variable stroke or fixed stroke with a separate spill valve. The earliest Benz design I have a drawing of used cone valves and the Lanz Bulldog used cone valves backed up with ball valves. Good cone valves 3 or 4 mm in diameter will be interesting to make :thinking: .

I am always happy for people to learn from me, even if it is how not to do things  ;)

Suggestions of how to do things better are also welcome  :)

Roger
  I suspect that your .35mm injector hole is far to large to get the spray needed for air saturation if that is the final hole size.

For example.
                   My 1/8th scale grease fittings have a .25mm passage with ball and spring and the 1/8th scale grease gun easily pumps regular grease through them.       I suspect with Diesel fuel you will need to be less than .1 mm but a good starting point for experimentation.         

Jerry Kieffer
Title: Re: Fuel injection systems
Post by: Roger B on May 04, 2015, 09:01:55 AM
Thank you for the interest Jerry.  My intention (hope) is that this will operate more like a pintle injector with the actual orifice being the annulus between the nozzle hole and the point of the needle (hence the 30° needle and the 45° needle seat). The 0.35 mm hole is much to big to act as a conventional jet. Full size engines tend to be around 0.2mm so in this size I think it would have to be less than 0.1mm (outside my current abilities  :(  ).
Title: Re: Fuel injection systems
Post by: Graham Meek on May 04, 2015, 09:58:10 AM
Hi Roger,

A tip given to me by a Designer at Woodward's Diesel engines was to have a Pintle nozzle for a small engine. That way the orifice can be more easily controlled as the pintle diameter can be made just a shade smaller than the hole. Some of the full size Pintles were tapered, such that as the pintle lifted off the seat the taper closed the orifice slightly thereby giving a finer spray. The biggest problem I have had is seeing the pintle to grind the shape and to get a very fine finish. My latest attempts have been with Diamond charged rotary lap after rough grinding which has given a big improvement, but it is still early days, I hope this helps.

My best regards
Gray,
Title: Re: Fuel injection systems
Post by: Roger B on May 04, 2015, 11:04:19 AM
Thank you Gray, If I remember correctly you are also working on a diesel engine (along with everything else  :) )
Title: Re: Fuel injection systems
Post by: lohring on May 04, 2015, 02:20:33 PM
I've been thinking about variable stroke pumps for flash steam engine control.  There is a lot of information if you search on variable stroke or variable valve mechanisms.  The Pattakon site (http://www.pattakon.com/) has a lot of ideas for variable valve lift.  My favorite variable stroke pump designs are pictured below.  The first two pictures are the same mechanism.  The last picture is the valve timing method used on large marine diesels.

Lohring Miller
Title: Re: Fuel injection systems
Post by: Roger B on May 04, 2015, 06:19:21 PM
Thank you Lohring, those are some interesting variable stroke linkages to think about  :headscratch:  I guess that flash steam uses a significant quantity of water. I am looking a maximum of 2 - 3 mm3 per stroke.

These are the pump mechanisms I have been looking at. The Lanz pump uses a wedge between the eccentric and the plunger to vary the working stroke. The Benz pump uses a linkage to vary the stroke and the timing. The Compur pump has a separate spill valve and also allows the timing to be varied.

The Lanz picture is taken from 'Lanz von 1859 bis 1929' by Kurt Häfner  (Franckh-Kosmos)

The Benz picture is taken from 'Schlepper' by Armin Bauer (Bechtermünz Verlag)

The Compur  pump is taken from 'The Modern Diesel' Fifth Edition (Iliffe & sons Ltd)
Title: Re: Fuel injection systems
Post by: Graham Meek on May 04, 2015, 08:23:51 PM
Hi Roger,

Yes my Diesel is coming along, but my progress is very slow, the injector pump has been a bit of a stumbling block up until recently. I had been going down the variable stroke route and tried all sorts of different designs. Then talking to Jim at Woodward's he suggested restricting the in-flow. Apparently this was how they used to vary the fuel supply in the very beginning. He said the type of engine that I am building is not going to have such a demanding injection regime as one fitted to a vehicle.

I have therefore been experimenting with some differential screw thread combinations to give me a range of fuel supply that I think the engine will need.

The real problem now is getting this design to fit my engine, I do not want end up with an injection pump as big as the 10 cc engine.

My best regards
Gray,
Title: Re: Fuel injection systems
Post by: Roger B on May 04, 2015, 08:43:44 PM
Hi Gray,

I choose to start at around 25 cc as the biggest I could comfortably make with my machines to give me more chance of getting the bits to fit.

I have looked at a couple of simple variable stroke mechanisms, but the problem is keeping the angle of injection commencement the same (or similar. I don't know how important this really is  :headscratch: ). I am probably going to try a cam like the one on the Benz pump where the working angle is quite small to start with. This should also give a quick pump stroke (less time to leak  ::)  )
Title: Re: Fuel injection systems
Post by: Graham Meek on May 06, 2015, 10:16:43 AM
Hi Roger,

Several years ago when I started out on my Diesel engine design I came across the engine below. The photograph was all the information I could find, not helped with my limited knowledge of German. I was wondering if you, or anyone else on the Forum has come across this engine before and knows more about the design?

My best regards
Gray,
Title: Re: Fuel injection systems
Post by: Roger B on May 06, 2015, 12:21:10 PM
Hi Gray,

A limited search suggests that the drawing you have is an Eisfeld. I have a short German description that I will translate later, but it suggests that it was 15cc, ran, but was too heavy to fly.

http://www.kleinstmotoren.eu/histori15.html

I have attached a picture of a petrol Eisfeld engine, there are similarities.
Title: Re: Fuel injection systems
Post by: Roger B on May 06, 2015, 12:48:10 PM
And a little bit more. I found the article your drawing came from along with a translation on the RC groups forum:

http://www.rcgroups.com/forums/showthread.php?t=1054975&page=148

Thank you to JMP_blackfoot  :ThumbsUp:  :ThumbsUp:
Title: Re: Fuel injection systems
Post by: Ian S C on May 06, 2015, 01:48:42 PM
Twenty or so years ago i made a new injector piston for a Lanz Bulldog, can't remember the actual size, but near an inch diameter, the stroke is only a few thou. Other than the Lanz, the only fuel injection system I'v had anything to do with is that used by Continental on their aircraft engines,ie., the IO 470 etc. this system is a constant flow directed directly behind the intake valve, probably not the most economical method, but it's simple, and it works, and at a low pressure.
Oops, forgot there is also the Ruston Hornsby HR 6 at the museum.
Ian S C
Title: Re: Fuel injection systems
Post by: Graham Meek on May 06, 2015, 04:16:18 PM
Hi Roger,

Thank you for finding out so much information on this engine, as well as the translation. I honestly did not expect to find any more information, given the date I am surprised the information has survived at all, especially as this developement was going on before and during WWII.

My best regards
Gray,
Title: Re: Fuel injection systems
Post by: Roger B on May 08, 2015, 02:24:36 PM
Hi Gray,

The search required some lateral thinking as well as using German  ::)

The stated injection pressure seems very high, especially as the article suggests that an open nozzle was used. The fuel metering looks to be using the inlet valve as a spill valve (like in Lohring's picture) but part of the mechanism is not illustrated. It's always encouraging to know that someone has made it work before.

I also have a copy of Maschinen in Modelbau in the attic in England that has some details of a 7cc true diesel based on a Deutz horizontal prototype. I must dig that out next time I go back.
Title: Re: Fuel injection systems
Post by: Roger B on May 09, 2015, 10:25:59 AM
A few more tries at making bits. I made a new bracket for the grinder. Its only two bits from the offcuts drawer with a few holes but I managed to get both wrong the first time  :facepalm:

I then tried to improve the finish from the grinding operation with the following variables: Lathe at 2000rpm or 250rpm, grinder at 5000rpm or 25000rpm, aluminium oxide or silicon carbide grinding wheel, grinding with or against the workpiece direction.

None of the results were very good, but the best so far was both at low speed, aluminium oxide wheel and grinding with the workpiece. I need to get some sort of microscope to really see what is going on  ::)

Next I wanted to make some filing/polishing guides for the D bit. They were to be 8mm silver steel with a 1.5mm hole down the middle, a flat milled on the end to just over half diameter and hardened. On the first attempts the drill wandered way off the centre line  :headscratch: I then tried a brand new, hopefully good quality, drill which seemed to improve things. Yet more to learn  :headscratch:
Title: Re: Fuel injection systems
Post by: cfellows on May 09, 2015, 04:13:37 PM
Don't know if you are familiar with Find Hansen's engines, but he has had a fair degree of success with model injected engines.  Here is a link to his youtube channel...

https://www.youtube.com/channel/UCxv370lnEXq7MLmLuXMqklA (https://www.youtube.com/channel/UCxv370lnEXq7MLmLuXMqklA)

and a link to his website...

http://www.findsminimodelhotbulbengines.dk/ (http://www.findsminimodelhotbulbengines.dk/)

Here's some further links to his website that show pictures of his injectors and injector pumps...

http://www.findsminimodelhotbulbengines.dk/Side9.html (http://www.findsminimodelhotbulbengines.dk/Side9.html)

http://www.findsminimodelhotbulbengines.dk/Side1.html

He doesn't offer any drawings or plans for his work but he did tell me that a possible method for making the injector pump was to fill the pump cylinder with melted solder then insert the plunger, coated with oil.  You can see pictures of his pumps on his website.  His website makes tantalizing reading and is worth exploring thoroughly.

Chuck
Title: Re: Fuel injection systems
Post by: Roger B on May 09, 2015, 05:07:17 PM
Thank you Chuck  :ThumbsUp: Yes I do know his website, and he doesn't give many details. That's a rather interesting way of making a very close fitting cylinder  ::)  :headscratch: it deserves some thought  :wine1:
Title: Re: Fuel injection systems
Post by: Roger B on May 11, 2015, 08:13:22 PM
Next steps on the D bit guides.
I mounted both in the milling vice and milled flats down to almost half thickness. The silver steel was 7.98mm diameter so the one for filling was taken down to 4.10mm and the one for polishing to 4.03 so that the flat on the D bit will not quite reach the centre.
Whilst still in the vice both were drilled and tapped for an M2 grubscrew. I don't like doing hot work at the end of a session so I will harden them tomorrow.

I don't know if I am taking this too far  ::) , but it seems to me that the quality of the finish from the D bit, especially on the cone, will depend on the finish of the cutting edges. The literature generally says 'file to exactly half diameter' but again it seems to me better to be slightly above half than below  :headscratch:
Title: Re: Fuel injection systems
Post by: Roger B on May 12, 2015, 07:15:35 PM
I hardened and tried my D bit guides. The results look much better than my free hand efforts, but I need to do some more work on grinding the tips   ::)

I also received some 0.01 mm step reamers and pin gauges ready for my experiments on making precision bores. I am also going to order the appropriate needle laps from Acrolaps.

Looking at the pin gauges and their cost (~12 CHF/EUR/USD or £7) they are much better finished than anything I could achieve with my current machines and may be a useful/sensible source of precision pump plungers  :headscratch:
Title: Re: Fuel injection systems
Post by: Frank Boyle on June 05, 2015, 10:00:28 PM
Hi.   Rodger
I am trying to make an injector in 3" scale ,if succesful will continue with the hot bulb hornsby engine.I have the full plans for the injector and the fuel pump and have scaled these down to construct the injector .I would be willing to send a copy of these to you they may help.
Regards Frank
Title: Re: Fuel injection systems
Post by: Roger B on June 06, 2015, 07:40:39 AM
Hello Frank,

That would be very kind of you  :) All information is helpful  :ThumbsUp:  :ThumbsUp:
Title: Re: Fuel injection systems
Post by: Ian S C on June 06, 2015, 02:46:51 PM
I can hardly imagine making a working nozzle, I'v got 4 nozzles from a Continental IO-470 engine (some where), these ones are not direct injection, but inject petrol into the intake manifold, just behind the inlet valve, so they work at low pressure.  They are about 1.5" long.  The only other one I'v had anything to do with would not be too hard to scale, it's on a Ruston Hornsby 6 HR, and is about 6" long, my nephew, a diesel mechanic, over hauled it for me, he'd never seen anything like.
Ian S C
Title: Re: Fuel injection systems
Post by: petertha on June 23, 2015, 04:31:57 AM
I'm fascinated by your micro-drilling Roger. Very interesting tooling arrangements.

Would these 35K dental type drills provide appropriate rpm for those teeny drills & reamers? The electrics like pic tend to go for $100-150-ish with dedicated speed control boxes (ebay). I'm told by my dentist friend the pro versions have pretty high quality ceramic bearings & low run-out, but he might be referring to pneumatic drive which I thought he said was higher rpm yet. No idea if that's what is contained in these units.
Title: Re: Fuel injection systems
Post by: Roger B on June 24, 2015, 08:34:44 PM
Peter (I guess),

I do have a Proxxon hand drill which will reach 25,000 rpm and a Proxxon bench drill that will do 8,000 rpm. The problem is drilling in the lathe which has a top speed of 2,000 rpm.

I decided to make some experiments on an injection pump. The first version will have an inlet port in the barrel like a full sized one. If this is not successful I will make one with an inlet valve. The piston will be 2mm Silver Steel (drill rod) hardened and polished/lapped. The body is from 10mm square hot rolled mild steel. The bore was drilled 1.8mm and reamed 1.95mm. My 1.98mm pin gauge would not enter so there is hope. The delivery valve will screw into the recess at the square end. the other end is turned down to 6mm for a return spring.
Title: Re: Fuel injection systems
Post by: fumopuc on June 25, 2015, 04:10:45 AM
Hi Roger, I am following along.
Title: Re: Fuel injection systems
Post by: Roger B on June 25, 2015, 05:57:03 PM
Thanks Achim.

Finishing the inlet port (except for the thread, I'm waiting for an M5x0.5 tap) and starting the plunger.
Title: Re: Fuel injection systems
Post by: Admiral_dk on June 25, 2015, 09:06:36 PM
Still on the "straight and narrow" are we ?  ;)

I think there are more than a few following this thread quietly  :)
Title: Re: Fuel injection systems
Post by: Roger B on June 29, 2015, 07:55:37 PM
Hopefully straight and definitely narrow  :)

I hardened the non threaded end of the plunger by heating to dull read and dropping it into water. It grew from 1.99mm to 1.995mm. I polished back to 1.98mm using fine abrasive cloth (I may need to make a proper lap, time will tell   :headscratch:  ).

I then tried out my needle eye lap. With some diamond paste and oil I slowly opened up the bore until my 1.98mm pin gauge just fitted. (I know it's bad practice to mix measuring instruments and abrasives  ::) ) The plunger was then a tight but smooth fit  :whoohoo: .

Next I need to wait for the M5 fine tap, thread the inlet and exhaust ports and then put it all in the ultrasonic bath.
Title: Re: Fuel injection systems
Post by: Roger B on July 01, 2015, 07:19:15 PM
I received my M5 x 0.5 tap and set about tapping the holes. Unfortunately I was a little clumsy and stripped the thread on the inlet port  :facepalm: I decided to silver solder a 6mm plug in the hole and re-tap although the heat for silver soldering will probably damage the bore.

After soldering and tapping the plunger no longer fitted so I lapped the bore a little more until it fitted again. I will keep going with this body for the moment, but I expect I will have to make a new one  ::) .

Finally I cleaned the body, plunger and pin gauge in the ultrasonic bath to remove any traces of diamond paste.

The next step is to machine the ends of the two unions so they seal on the end faces not on the hexagon.
Title: Re: Fuel injection systems
Post by: Roger B on July 02, 2015, 06:04:42 PM
I turned the ends of the unions to size and then soldered a temporary plug into the end of the delivery union. With a bit of fiddling I filled it with oil so that the plunger felt solid as soon as the inlet port was covered.

As a first test I rested 1kg piece of steel on the plunger and it moved down over a few seconds. This is a pressure of 30 bar (450psi) on a 2mm plunger so not too bad but I will need to remake the body and probably the plunger. Diesel is somewhat less viscous than the oil I used.

http://www.youtube.com/watch?v=2cG9q194h8w
Title: Re: Fuel injection systems
Post by: Graham Meek on July 04, 2015, 11:57:42 AM
Hello Roger,

I have been following your progress from the wings. I am progressing steadily with my design but keep getting bogged down with other things. As regards your leakage test, I intend to use penetrating oil to test my pump fits. If the pump will stand up to this then I am certain it will work with diesel. There has to be some clearance no matter how small to allow the two parts to slide. Labyrinth seals down the pump stem are a good idea as they also trap fuel to act as a lubricant.

When I worked for Dowty Fuel Systems, (aircraft fuel systems) the fits of the various spool valves were permitted a certain amount of leakage per unit time. These systems were never ever static as the effects of acceleration, rpm and altitude were all accommodated mechanically.

My best regards
Gray,
Title: Re: Fuel injection systems
Post by: Roger B on July 05, 2015, 09:18:29 AM
Hello Gray,

Thank you for the thoughts. As I am moving into a new area of precision for me I want to make a few experiments to see what is possible and what is not. I want to make a running trial with petrol injection on my horizontal engine I was going to use alcohol as a test fluid (it doesn't smell as bad as petrol or diesel for use in the cellar). I suspect that quite a lot of leakage is acceptable as the injection time is quite short.
Title: Re: Fuel injection systems
Post by: Roger B on August 15, 2015, 07:40:03 PM
Back on this one. First I would like to thank Frank Boyle for copying and sending me the information he has collected on hot bulb injection systems  :ThumbsUp:  :ThumbsUp:

I also located the details of the German model diesel. This is in Maschinen in Modellbau 3/06. Erich Beyer wanted to make a 6.5 cc model of a Güldner hopper cooled horizontal diesel (as fitted to the family tractor). He started when at technical college, but without success and then over many years made various trials including converting a moped engine to diesel operation. Finally, after 38 years, he produced a working model with the following details:

Bore 20 mm
Stroke 22mm
Capacity 7 cc
Compression ratio 21:1
Injection pressure 100 Bar
Injection volume 1 mm3 at full load
Pump plunger diameter 2 mm
Pump stroke 0.3 mm
Running speed 2,000-3,000 rpm
Two 90 mm diameter flywheels
This engine has a Lanova style combustion chamber and operates on pump diesel. He claims that it will cold start without any aids.

I have started making a new injection pump. To try and keep things concentric I set the body up 1mm eccentric in both planes and turned the boss for the return spring. I then centred and drilled 1.5 mm halfway through. The boss was then held in a 5mm collet and I drilled 1.5 mm from the other end. This was followed with a 1.8mm drill and a 1.95mm reamer. Finally I drilled 4.5mm 4mm deep for the M5 x 0.5 thread and flattened the bottom with a 4mm end mill. This should form the seat for the delivery valve.
Title: Re: Fuel injection systems
Post by: Admiral_dk on August 15, 2015, 08:11:00 PM
Hi Roger

Hot Bulb and "normal" Diesel injection are two very different things (as I'm sure you're aware off) .....

I'm guessing that you are pursuing the Diesel injector pump - though I'm sure many off us here would like the Hot Bulb info too - or rather, we would like to be able to do both  ;D

Still following and hoping that you succeed  :ThumbsUp:

Per
Title: Re: Fuel injection systems
Post by: Brendon M on August 23, 2015, 02:52:37 PM
Hello Roger, I am following along with great interest in how this turns out :)

For fuel metering, one design to consider could be based off the "Sleeve Metering" system:

http://constructionmanuals.tpub.com/14264/css/14264_173.htm

It does require drilling some very small holes since it's a 2mm plunger!
Title: Re: Fuel injection systems
Post by: Roger B on September 26, 2015, 06:46:25 PM
Thank you both for your interest. This is intended to be a normal diesel injection system (although its first trial will be as petrol injection). I have looked at various metering systems and will initially stick to variable stroke. I also looked a another sleeve metering system (the EH pump) but these seem to require the pump to be immersed in diesel oil with attendant sealing problems.

I've made a little more progress with the new pump body.
Title: Re: Fuel injection systems
Post by: Roger B on October 07, 2015, 07:50:13 PM
A couple more little bits. First the end piece and return spring for the plunger. Nothing special there just a DIY store spring cut to length.

I then decided to make a lap for the plunger rather than using fine abrasive cloth as I did on the first one. Its a piece of 16mm dia. brass 10mm long, the central hole was reamed 2mm. I added the possibility for a grub screw to open it up/limit the closure. I don't know if I will need it. When it came to slitting it the easiest solution was to clamp it in the lathe tool post.

Next step make and harden a new plunger from 2mm silver steel then some more lapping.
Title: Re: Fuel injection systems
Post by: Roger B on November 04, 2015, 08:06:46 PM
On with the lapping. My external lap seems to work quite well and the plunger is 1.98mm diameter and parallel  :) . I purchased an additional 1.97mm pin gauge for checking the bore so I can go first to 1.97 and then to 1.98 to try and keep things straight.
Title: Re: Fuel injection systems
Post by: cfellows on November 04, 2015, 08:37:39 PM
Interesting territory you're exploring here, Roger.  I applaud your efforts and hope against hope you come up with something that really works.  I think many of us would like to explore fuel injection considering the vagaries and uncertainties of carburetion in model engines.

Chuck
Title: Re: Fuel injection systems
Post by: Roger B on November 08, 2015, 08:01:58 PM
Thank you Chuck, I think this is going to be long slow process as I gradually learn new skills.

This pump body was not successful  :( I lapped it with 5 micron diamond paste until the 1.97 mm pin gauge would just pass and the 1.98 mm wouldn't. Unfortunately it appears that the original hole was slightly bent and the gauges go much deeper from the wrong (delivery valve end) than they do from the correct end.

On the first body I drilled all the way from the valve end but the other end was noticeably off centre. This time I drilled from both ends but seem to have got a bent hole  ::)

I think that next time I will open up the first part of the plunger end to 2.00mm to reduce the length I have to keep straight.
Title: Re: Fuel injection systems
Post by: Roger B on November 11, 2015, 07:36:25 PM
Next attempt. I still have enough raw material for around 30 pump bodies so maybe one day I will get it right  :headscratch:

This time I finished the delivery valve pocket before drilling through with a new good quality 1.8mm drill. The hole depth is just over 20mm so not too far away from the 5d rule of thumb. It looks fairly central at the other end so I have some hope. I have started lapping and this time the 1.97 pin gauge passes through quite easily and the 1.98 still doesn't enter.
Title: Re: Fuel injection systems
Post by: Roger B on November 15, 2015, 05:30:13 PM
I finished lapping this body and gave it a try. It was difficult to get the air out of the pump until I found that the back fixing screw hole had just broken through into the pump bore  :facepalm:  :facepalm:  :facepalm: Time to start body number 4  :(

I have a set of diamond lapping paste syringes from RDG. I used the coarsest (40) for lapping the cylinders on my engines and the first pump body. I then realised that this may be too coarse and used 5 until I got to 1.97mm and then 1 to reach 1.98.

Once I got the pump cavity full with the same grade oil as I used in the last test the plunger was essentially solid. With the same weight on top it just sat there, probably taking around 10 mins to fall, so no video.

I then cleaned the oil out with some cooking alcohol (as used in spirit lamps) and tried with this alcohol as a fluid in this case the plunger sank in 3-4 seconds so it should work well enough with petrol as the require injection pressure is much lower.

I think that this body, in spite of my mistake, will be good enough to test an injector. So an injector here we come  :)
Title: Re: Fuel injection systems
Post by: cfellows on November 15, 2015, 05:38:41 PM
Hate having to redo things because of mistakes.  However, it happens to me much too often.

What did you use as a lapping tool?

Chuck
Title: Re: Fuel injection systems
Post by: Roger B on November 15, 2015, 06:15:08 PM
I have plenty of 'trial' pieces   ::)  like many others on here I suspect   ;)

I'm using Acro needle eye laps for the fuel pump and injector. I also have some of their larger barrel laps that I have used for my cylinders.

http://acrolaps.com/index.htm



Title: Re: Fuel injection systems
Post by: Roger B on November 22, 2015, 08:20:56 PM
The next stage was to make a new D bit to cut the seat for the injector needle. This was a piece of 1.5mm silver steel (actually 1.49mm) lapped down to 1.45 mm. The 60° point was ground and polished with the Proxxon grinder held on the tool post. The flat was then filed and polished with the fixture I made and the end was hardened.

The needle was hardened before grinding, the point is 50° and the reduced section is 1 mm.
Title: Re: Fuel injection systems
Post by: Roger B on November 22, 2015, 08:32:42 PM
The shank of the needle was lapped to 1.48mm and it was cut to length.

The spring adjusting screw and nozzle were made from a piece of 8mm brass rod threaded M8x1 for 20mm.  If (when  ::) )I make another nozzle I will cut the thread at the end. The spring adjuster was no problem, but the 0.35mm drill pulled out of it's holder (I'd tried soft soldering it in place). Luckily by tapping the end of the nozzle with a small hammer I was able to get the drill out  :)

This time I used Loctite to hold the drill in place and was able to drill the jet hole.

When I tried to put the parts together I found another problem  :( The D bit had opened the bore out to 1.48+ mm and the needle was already a running fit  :facepalm:

New D bit and nozzle time  ::)
Title: Re: Fuel injection systems
Post by: Roger B on November 24, 2015, 07:33:44 PM
Found the problem  :) There was a little burr on the edge of the D bit (probably from the filing  :facepalm: ) that was enough to open out the hole the extra couple of hundredths. I carefully stoned the edges and made a quick trial hole. The 1.47 pin gauge wouldn't go in so just another nozzle to make  ::)
Title: Re: Fuel injection systems
Post by: Don1966 on November 25, 2015, 01:17:30 AM
Cool Roger, I am still following you. I am really interested in how this turns out. It would be interesting to make an electrically solenoid version. I have even considered looking into making and electronic governor for these engines. I am still making steam engines but will be venturing into IC's later.

Don
Title: Re: Fuel injection systems
Post by: Roger B on November 25, 2015, 06:12:21 PM
Thank you Don  :ThumbsUp: There are a few people following this little exercise, I hope I manage to make something that works but anyway I am learning a lot  :)

If you are looking at solenoid injectors this is some pretty amazing stuff:

http://www.f1-2000.co.uk/index.php?f=fuel_injectors

Title: Re: Fuel injection systems
Post by: Roger B on November 28, 2015, 05:54:43 PM
The new nozzle was machined more conventionally, cutting the thread (turning the lathe by hand) at the end. This time it all went smoothly including the 0.35mm hole and there is some material to lap out for the needle  :)
Title: Re: Fuel injection systems
Post by: Don1966 on November 28, 2015, 10:37:17 PM
Hi Roger, have you ever thought of using a clock bushing for the nozzle orfice? They do make them in multi sizes. I use one on my mini propane burner. Time savers has them http://timesavers.com/search.html?q=Bushings&go=Search.


Don
Title: Re: Fuel injection systems
Post by: Roger B on November 29, 2015, 08:25:14 AM
Thank you Don, I didn't know that such things existed   ::) I will have a look for European suppliers (I was surprised that the US ones were metric  :headscratch: are clocks generally metric?)
Title: Re: Fuel injection systems
Post by: 10KPete on November 29, 2015, 09:56:24 AM
Yep, generally metric.

Pete
Title: Re: Fuel injection systems
Post by: Roger B on November 30, 2015, 08:19:37 PM
Before I can lap the nozzle for the needle I need to drill the feed hole. I have been through many iterations of this design. The whole high pressure side of the system needs to the minimum number of sealing faces and the minimum number of places where air can be trapped. Rubber O rings are out as they will give too much under the pressure pulses.

In the end I went back to an earlier idea with a 60° cone directly in the side of the nozzle. As this is the same as a centre drill the cone and connecting hole could be drilled as one using the union nut as a guide. The union nut is turned from 8mm hex steel with an M5 x 0.5 thread and a 3.15 mm bore to suit the centre drill. The centre drill has a 0.8mm dia. tip.

I now need to make the brass nipple. I have some 1mm bore 2mm od copper tube for the connecting pipe.
Title: Re: Fuel injection systems
Post by: Myrickman on November 30, 2015, 10:28:13 PM
Roger, been quietly following along with great interest. Your perserverance in this challenge is admirable. All those teeny tiny bits and requiring such a high degree of precision....it will be so neat when you get it sorted out. I'm fascinated with your work. Paul
Title: Re: Fuel injection systems
Post by: Admiral_dk on December 01, 2015, 08:23:35 PM
Quote
Roger, been quietly following along with great interest.

Me too - the very few who has solved this puzzle before are not sharing their knowledge (not that I blame them), but you are doing it in public and if (I should say when, shouldn't I ;) ) you solve it = we all win  :whoohoo:
Title: Re: Fuel injection systems
Post by: Roger B on December 02, 2015, 07:53:24 PM
Thank you both for your interest and support as I slowly plod away at this  :ThumbsUp:   :wine1:

I turned the nipple with a 59° cone to try and ensure that it sealed at the end. A quick check with marking blue suggests that it's a reasonable fit. Unfortunately I did it up a bit too tight for the trial and crushed the end so the pipe no longer fits  :(  I will make a new one with a slightly shorter land to get an extra thread engaged.

When I make the next one (for the actual diesel I will need to silver solder a clamping flange on) I will offset the bore to get yet another thread and also probably use M6x0.5 instead of M5x0.5
Title: Re: Fuel injection systems
Post by: Roger B on December 06, 2015, 06:41:08 PM
A little bit more: This time I soldered the pipe into the nipple before screwing it up tight. The 1mm drill is in the end of the pipe to stop any solder getting in. The bore for the needle was lapped in the same way as the pump bore and the pieces were all cleaned in the ultrasonic bath.

Next I need to sort out the delivery valve for the pump as well as an operating mechanism.
Title: Re: Fuel injection systems
Post by: Admiral_dk on December 06, 2015, 11:26:11 PM
Great progress  :ThumbsUp:
Title: Re: Fuel injection systems
Post by: Don1966 on December 07, 2015, 12:56:24 AM
So does this mean we have a working injector? Looks great and you have my attention.

Don
Title: Re: Fuel injection systems
Post by: Roger B on December 08, 2015, 11:21:29 AM
Thank you both  :ThumbsUp: I don't know yet if it will work, but I have managed to make all the parts according to my plans  :) I need to order a selection of springs to allow me to set the injection pressures. The first planned trial with petrol injection into the intake will require a much lower pressure (10 Bar ??) than for the true diesel operation (50 Bar+). I did think about winding my own, but to get consistency I would rather pay a little and have correctly post heat treated ones.
Title: Re: Fuel injection systems
Post by: Stuart on December 08, 2015, 05:35:33 PM
Roger

When you come to silver solder very small stuff I use silver solder paste no extra flux required

I have used it for doing nipples on 1/16 odd copper pipe and never had a bung up you need just a smear

Cup alloys have it

http://www.cupalloys.co.uk/home/

Lee springs are good and provide the data that you will need


Stuart
Title: Re: Fuel injection systems
Post by: Roger B on December 09, 2015, 08:59:08 PM
Thank you Stuart  :ThumbsUp: This time I have soft soldered the nipple to the pipe so I can remove it later if needed but that paste looks interesting for the future. I have ordered the springs from HPC as they also had 2mm key steel which I have been looking for as well as no minimum order quantity  :)
Title: Re: Fuel injection systems
Post by: Roger B on January 04, 2016, 07:08:07 PM
Finally back on this. I have started making a simple stroke adjuster that will use a tapered wedge based on the system used on the Lanz Bulldog. I have also received my selection of springs so I can continue with the pump delivery valve and injector.

As I don't have a 2mm slitting saw I cut down the middle of the plunger with a 1mm saw and then made two additional cuts to bring it to 2mm. I was concerned about the saw deflecting but this did not seem to be a problem.

Unfortunately I broke the tip of a centre drill in the stroke adjuster body  :( This time I followed a suggestion from one of the posters on here and ground the middle of the broken drill away and used it to trepan around the broken tip so I could remove it  :)
Title: Re: Fuel injection systems
Post by: fumopuc on January 04, 2016, 09:12:45 PM
Hi Roger, I am quietly following along.
Title: Re: Fuel injection systems
Post by: Don1966 on January 04, 2016, 10:52:22 PM
Still with you Roger.............. :cheers:

Don
Title: Re: Fuel injection systems
Post by: Roger B on January 05, 2016, 07:04:51 PM
Thank you both  :wine1:

I milled out the slot for the control wedge and then milled the wedge (4mm key steel) to 10° and used this to set the plunger to mill a matching 10° on the end.
Title: Re: Fuel injection systems
Post by: Roger B on January 31, 2016, 03:32:08 PM
As I had received the required springs I decided to try the pumping system. The delivery valve holder was drilled 3.1 for a 3mm ball. The annulus left is of similar area to the 1mm bore connecting pipe.

Unfortunately, but not unexpectedly, the thread on the injector union failed so I opened out to M6 x 0.5. I was able to centre the nozzle using the original 0.8mm centre drill then cut the old thfread out with a 5 mm end mill, open out to 5.5 mm and retap. I also made a new nut with a small recess to allow an extra thread or so to engage.
Title: Re: Fuel injection systems
Post by: Roger B on January 31, 2016, 03:39:18 PM
Having fixed the damaged thread I could put the system together with a temporary tank (part of a float chamber for my first engine) and try it with some cooking alcohol. It took a lot of effort to get the air out of the system but was finally rewarded with some dribbles and drips along with one or two good sprays  :whoohoo:

There was quite a lot of leakage from the back of the injector. I'm not sure if it was past the needle or from the union.

I've tried to capture some of the spraying on video, but it's not very good  :(

http://www.youtube.com/watch?v=Au2usbHQmKg
Title: Re: Fuel injection systems
Post by: Don1966 on January 31, 2016, 04:00:40 PM
Cool Roger, it's a start anyway. It does look like some progress to me. Keep it coming......... :ThumbsUp:

Don
Title: Re: Fuel injection systems
Post by: Kim on January 31, 2016, 04:13:33 PM
That's great Roger!  You're getting there!  :ThumbsUp:
Quite the fiddly little gizmo isn't it?
Kim
Title: Re: Fuel injection systems
Post by: Roger B on May 20, 2016, 06:54:22 PM
The next step is to make an excentric so I can drive the pump. The excentric rod is a piece of 2mm brass. I could have had lots of fun with the RT but decided in this case a hacksaw and file would be quicker.
Title: Re: Fuel injection systems
Post by: Roger B on May 26, 2016, 07:10:30 PM
The excentric was turned from free cutting mild steel to 16mm and then offset 1.5mm in the four jaw chuck and turned down to 12mm.

I then needed to put a slot in the end of the stroke adjusting wedge. This is made from 4mm square key steel and the deflection was too much using a 2mm end mill. I couldn't hold it sensibly to use a slitting saw or slot cutter so finally hacksawed and filed the slot. Next time I will cut the slot before cutting the wedge face.
Title: Re: Fuel injection systems
Post by: Jo on May 26, 2016, 07:38:59 PM
Next time I will cut the slot before cutting the wedge face.

 ;)

Jo
Title: Re: Fuel injection systems
Post by: fumopuc on May 26, 2016, 07:45:05 PM
The next step is to make an excentric so I can drive the pump. The excentric rod is a piece of 2mm brass. I could have had lots of fun with the RT but decided in this case a hacksaw and file would be quicker.
Hi Roger, sometimes this old fashioned way is the best and easiest way to go.
Title: Re: Fuel injection systems
Post by: Roger B on May 28, 2016, 06:36:00 PM
Thank you for your interest and support  :ThumbsUp:  :ThumbsUp:

I finished off the excentric and then made a mounting plate to fit the pump and stroke adjuster onto the side of my horizontal engine. For the trial video I removed the spark plug and motored the generator with a 6V battery.

http://www.youtube.com/watch?v=Gh_DrUwlSgI
Title: Re: Fuel injection systems
Post by: Roger B on May 29, 2016, 06:10:35 PM
I then set the pump in place, using a 1mm drill in the inlet port to ensure it was fully open. The next pieces were a link to connect the wedge to the adjustment block and the adjustment block. As the adjustment block was brass rather than key steel I could cut the 2mm slot without problems using a 2mm end mill.
Title: Re: Fuel injection systems
Post by: Roger B on May 29, 2016, 06:16:15 PM
I had a commercial (RC Machines?)M2 bolt that was suitable for the top pivot pin of the link. I still need to make a couple of proper 2mm pivot pins as well as the adjusting screw and top bearing but enough bits moved to make another video clip (apologies for the quality, poor light and hand held).

http://www.youtube.com/watch?v=W5TFGkM3ujo
Title: Re: Fuel injection systems
Post by: fumopuc on May 30, 2016, 02:20:09 PM
Hi Roger, interesting mock up. Waiting for the next experiments.
Title: Re: Fuel injection systems
Post by: Roger B on May 31, 2016, 06:03:19 PM
Thanks Achim  :ThumbsUp: With luck I will be trying petrol injection in a couple of weeks  ::)

Before I went back to lathe mode for the pivot pins and adjusting screw I decided to make the inlet manifold/adaptor for the injector. I milled an 8mm diameter recess at 30° in some 6mm dia. brass tube and silver soldered it onto the side of some 8mm dia. brass tube. The passage was then opened out with a centre drill followed by a 5mm drill. I will reuse the flanges from an existing carb adaptor so I can use a carb simply as a throttle.
Title: Re: Fuel injection systems
Post by: Roger B on June 04, 2016, 07:58:52 PM
I fitted the flanges to the manifold. Unfortunately the engine end flange cracked when I removed it from the original pipe but I was able to soft solder it back together.
I finished off the pivot pins and adjusting screw and put it all together. As expected the pump had problems reaching a suitable pressure with cooking alcohol so I will need to make a new pump body and possibly a new plunger.
Title: Re: Fuel injection systems
Post by: Roger B on June 18, 2016, 06:36:29 PM
I took a video clip of the adjuster in operation but the aspect ratio seems to be confused  :headscratch: The engine was being driven with a 6V battery via the generator. I have started on a new pump body and plunger, I'm following the same way as before but hopefully without mistakes  ::)

http://www.youtube.com/watch?v=4kLwTbrFDtA
Title: Re: Fuel injection systems
Post by: Roger B on October 02, 2016, 04:24:27 PM
I started making a new body but was still puzzled as to why I got the pump to work by hand for the first test. Careful measurement showed that the last 2mm of the plunger tapered by around 5 microns, this being the section used when being driven by the engine. When I did the hand trials I was using more of the plunger length.

I decided to try and cut the tapered 2 mm off the plunger using a cutting disc in the Proxxon as the plunger was otherwise a 'trial piece'. The mounting screw holes were then slotted to compensate.

This actually produced a sort of spray that could be adjusted and seemed to have a range of 100-150mm  :)  :)  :)

http://www.youtube.com/watch?v=1LbJLUJa0-k
Title: Re: Fuel injection systems
Post by: Brendon M on October 09, 2016, 02:30:22 AM
5 microns is not much! If I understood your posts correctly, this was enough to prevent sufficient pumping?
Title: Re: Fuel injection systems
Post by: Roger B on October 09, 2016, 07:18:51 AM
5 microns clearance is definitely too much. With careful lapping I am trying to get to 1 micron or less clearance.
Title: Re: Fuel injection systems
Post by: fumopuc on October 09, 2016, 12:33:35 PM
5 microns clearance is definitely too much. With careful lapping I am trying to get to 1 micron or less clearance.


Hi Roger, very optimistic challenge, I wish you good luck.
Title: Re: Fuel injection systems
Post by: Brendon M on October 09, 2016, 03:16:49 PM
5 microns clearance is definitely too much. With careful lapping I am trying to get to 1 micron or less clearance.

Oh, my apologies, I have conveyed the wrong meaning.

I was expressing my surprise at how 5 microns (roughly 0.2 thou) was able to stop the pump from functioning properly.

Given the tolerences involved, I wonder how much life you will get out of a pump before wear on the punger causes a malfunction? Or do you not anticipate this to be a problem?

Title: Re: Fuel injection systems
Post by: Roger B on October 10, 2016, 05:58:32 PM
Thank you Achim  :wine1:

brendonm, no problem  :) When I started thinking about this project I thought that a piece of ground silver steel (drill rod) in a reamed hole would be sufficient. As I move on it became clear that this was nowhere near good enough so I am no trying to reduce the clearances as much as I can with the equipment that I have.

The plunger is hardened and the pump body is mild steel. I have no idea how long they will last, but if I can get it to run even for a few minutes I will be happy  ::)
Title: Re: Fuel injection systems
Post by: Laurentic on October 13, 2016, 05:10:48 PM
Roger, Have only just become aware of both this thread and your other one on making a horizontal 2 stroke diesel engine.  I have now read threads both from start to finish and am full of admiration for what you are doing and the skill you are doing it with.  I will be following both with upmost interest and wish you well - I sincerely hope you are successful in your quest and am sure you will be, seeing what has gone before.

Whenever I have wondered in idle moments about the making of a model diesel the big block has always been "but to be a diesel it needs a HP fuel pump and injector, not things that the vast majority of home workshops can produce".  Having worked with diesels of all sizes extensively in an earlier life I am only too well aware to which the very fine tolerances diesel pumps and injectors are made, which is why I thought it beyond the scope of most workshops.  You seem to be showing a way of achieving that standard of engineering required.

Also of interest is the use of the injectors for low pressure use in petrol or glow plug engines, in particular in 2 stroke engines where instead of the fuel/oil/air mixture being pumped into the cylinder via the crankcase and the action of the piston, the air, devoid of fuel or fuel/oil glow plug mixture, is pumped into the cylinder via a blower and the fuel injected after the exhaust port has closed.  This would have the benefit of ensuring complete scavenging without blowing excess unburnt fuel into the exhaust.  Whether the oil in the fuel/oil mix would cause a problem in blocking the injector nozzle holes I don't know; in theory not, as it readily vaporises going through a carby, but the injector nozzle holes present a much finer hole.  Just a thought.

Keep up the good work,

Regards, Chris
Title: Re: Fuel injection systems
Post by: Roger B on October 20, 2016, 06:33:44 PM
Thank you for your interest Chris  :) I know others have made small, true, diesels successfully and I hope that I can follow in their footsteps  ::) I think that I am moving in the right direction, but lapping to these tolerances is definitely something to practice  :headscratch:
Title: Re: Fuel injection systems
Post by: Roger B on October 20, 2016, 06:49:14 PM
A sort of success  :)  :wine1: It was a sunny evening here so I thought I would try the petrol (gasoline) injection on my horizontal engine.

I warmed it up with the carburettor and then fitted the injection manifold with a carb as a throttle. The tank was filled with petrol, there may have still been some alcohol in the pipes from the last trial. Then came the fun, I had a throttle lever, a stroke adjustment handwheel for the pump and a starter button to press (and a drip oiler for the cylinder to remember) all with two hands. After various adjustments it started  :whoohoo:  Control was somewhat difficult as due to the leakage from the system the fuel quantity increased significantly with speed so as I opened the throttle I had to reduce the pump stroke. If the revs dropped for any reason it would just stop and I had to increase the stroke to maximum again to get it to start. There was a significant quantity of fuel dripping out of the injector pressure adjustment screw.

So it worked, my calculations regarding the size of pump required were not too far out, I just have to tighten up the tolerances even more  ::) (actually it might be better with diesel as it is more viscous and may leak less).

Apologies for the video quality, it was starting to get dark and I was quite excited  :cartwheel:

http://www.youtube.com/watch?v=dKPaKwHfrPs

dKPaKwHfrPs
Title: Re: Fuel injection systems
Post by: Jo on October 20, 2016, 06:58:26 PM
 8) Nice one

Jo
Title: Re: Fuel injection systems
Post by: Admiral_dk on October 20, 2016, 10:22:22 PM
Congratulations on reaching this point  :praise2: and look forward to see improvements  :)
Title: Re: Fuel injection systems
Post by: Brendon M on October 21, 2016, 08:53:34 AM
Yes indeed, congratulations. :)

I wonder if you can do away with the throttle altogether and control engine speed through the amount of fuel injected alone?

*edit: apparently not (http://www.eng-tips.com/viewthread.cfm?qid=75499). The reason why it works for Diesel is that it works with a wide range of air/fuel mixture ratios.

Essentially the throttle is there to help control the air/fuel ratio in injected engines.
Title: Re: Fuel injection systems
Post by: steamer on October 21, 2016, 11:31:12 AM
That's Awesome!!!!


Dave
Title: Re: Fuel injection systems
Post by: Roger B on October 25, 2016, 07:27:51 PM
Thank you all for your kind comments and support  :ThumbsUp:  :wine1:

This project is really on the limit of my abilities and equipment, but maybe I will get there  :headscratch:
Title: Re: Fuel injection systems
Post by: Roger B on December 10, 2016, 10:26:27 AM
I dismantled the injector to see what I could do to tighten up the tolerances and found that I had left the strong spring in  :facepalm: This gives a needle loading of around 10N which is a calculated opening pressure of 50bar, rather more than is needed for manifold injection. If we get some good weather I will try again with the correct spring.

I have also been looking at the pump again. I originally thought that using a metering helix like the full size pumps would be too difficult, but I came across a design that just used a simple helical groove. A quick sketch suggests that a groove around 0.6mm wide and a pitch of 4mm could work. My lathe only goes to a 3mm pitch but by playing with the gears I can reach 4mm, which should be ok as it will only be hand turned. If I can mount the Proxxon tool with a cutting disc at the required angle and on centre I will have a go at cutting a helix on a scrap plunger.
Title: Re: Fuel injection systems
Post by: BillTodd on December 10, 2016, 05:33:47 PM
Excellent :)  and really impressive !

Bill
Title: Re: Fuel injection systems
Post by: Roger B on December 10, 2016, 07:49:16 PM
Thank you Bill :ThumbsUp:

I put the correct spring in the injector and had another more successful trial  :cartwheel: There was more throttle response than I expected and it generally ran quite steadily. One puzzling point was the appearance of bubbles in the fuel pipe to the injection pump  ::) As far as I can see the only possible air leak could be down the plunger and if air leaked in there should have been a significant fuel leak out  :headscratch:

http://www.youtube.com/watch?v=7eHHEhll59U

7eHHEhll59U
Title: Re: Fuel injection systems
Post by: Brendon M on December 11, 2016, 03:02:34 AM
Wow, that's working really well! Fantastic. :)

By the way, I had a look at your helix plunger diagram, and I look forward to seeing it be made. Mind you, I will have to wait until you build it to understand what I was looking at (d'oh)

Keep up the good work. I've been trying to build a simple part that requires a smidgen of accuracy (I'm on my fourth attempt :facepalm:), and I now have an appreciation for how much precision is required in a fuel injection pump!
Title: Re: Fuel injection systems
Post by: fumopuc on December 11, 2016, 07:29:21 AM
I am following with interest.
Title: Re: Fuel injection systems
Post by: BillTodd on December 11, 2016, 02:43:13 PM
Quote
bubbles in the fuel pipe to the injection pump  ::) As far as I can see the only possible air leak
May not be air , could be fuel vapour if the pressure is low.

Bill
Title: Re: Fuel injection systems
Post by: Roger B on December 11, 2016, 02:52:59 PM
Thank you  :ThumbsUp:

Brendom, the diagram was the helix unrolled and scaled up 10 times. It was unrolled along the long edge and as it was 2mm diameter it is 2 x pi x 10 = 62.83. The other direction was the pitch, 4mm so times 10  = 40 mm. This diagram then gave me the helix angle, 32° and allowed me to see how it would work with the 1mm port in the pump. The pump stroke will be 3mm so the first mm closes the port and the next two mm will do the pumping. As soon as the port reaches the helix the pressure will drop and the pumping will stop.

The next thing was to try and grind a trial helix  ::) I added a few holes to the Hobbymat milling support angle plate so I could mount the compound slide along the axis of the lathe and at the helix angle. The 4mm pitch required the change gears to step up 1-4. I found a suitable set up with the available gears, 70-35 and 60-30, but the arm hit the spindle before I could get a good mesh. As the foul point was just rough cast a quick bit of filing made enough clearance.
The actual feeding will be done with the leadscrew handle so I left the drive belt off and the lathe unplugged. I also made a quick 'sanity check' that four turns of the leadscrew handle gave one turn of the chuck.
Title: Re: Fuel injection systems
Post by: Roger B on December 11, 2016, 02:59:44 PM
I made an initial attempt on a piece of unhardened 2mm silver steel. I let the wheel cut in both directions but that may have been a mistake due to the general play and lack of rigidity of my set up. The second attempt on a hardened scrap plunger was made with a different grinding wheel held in a collet rather than the drill chuck. This time I only cut on the in stroke. The cut was taken to 0.5mm deep in 0.05mm steps. I think that it was harder to get a good picture of the helix than it was to make it  :headscratch:
Title: Re: Fuel injection systems
Post by: Roger B on December 11, 2016, 03:02:43 PM
Thank you Bill, I was coming to that conclusion as well. The only mechanical petrol injection systems I know of (Lucas and SPICA) fed the petrol into the metering pump under pressure rather than a very small head. At least vaporisation shouldn't be a problem with diesel fuel  ::)
Title: Re: Fuel injection systems
Post by: Graham Meek on December 11, 2016, 06:21:39 PM
Hi Roger,

You are to be congratulated on your progress.

I have been looking in from time to time but totally missed the engine running. You have been busy, and I like your helical groove. You are doing some real methodical trail blazing as regards the small "True Diesel" engine. I do hope that one day you will publish your design.

My best regards
Gray,
Title: Re: Fuel injection systems
Post by: Don1966 on December 11, 2016, 06:46:00 PM
That's awesome Roger and congrats I do hope you perfect it. Great following your progress...... :praise2:

Don
Title: Re: Fuel injection systems
Post by: philjoe5 on December 11, 2016, 10:40:27 PM
Fantastic Roger.  A real leading edge effort at fueling these small engines :ThumbsUp:

Cheers,
Phil
Title: Re: Fuel injection systems
Post by: BillTodd on December 12, 2016, 12:01:28 AM
Just came across this :

https://oldmachinepress.com/2013/01/02/inside-the-cylinder-of-a-diesel-engine-by-harry-ricardo/

worth a read :-)

Bill
Title: Re: Fuel injection systems
Post by: Roger B on December 12, 2016, 01:50:21 PM
Thank you all  :ThumbsUp:

I looked up the vapour pressure of petrol and it is around 0.5 Bar at normal temperatures. When the plunger on the 'jerk' type pump returns it will create a vacuum which will certainly vapourise the fuel. If the feed pressure is not higher than the vapour pressure the vapour will remain and this is probably what I have been seeing in the feed pipe. Petrol vapour is around three times the density of air. The initial air bubbles I get when I prime the system tend to flow back up into the tank. The bubbles when running tend to float just above the intake pipe.
The SPICA (Alfa Romeo) and Bosch (Mercedes Benz) mechanical petrol injection systems both fed the metering pump at around 1 Bar which should be enough to overcome the vapour pressure.

Based on this I think that my current metering is probably fairly random and I will need a pressure fed system to get consistent results. The vapour pressure of diesel fuel is much lower so vaporisation won't be a problem but I don't think that I am ready for that step yet.

Next challenge: Design and build a ~1 Bar constant pressure petrol feed pump that can be fitted on my horizontal engine (which already has two unplanned pumps  ::) ). Another option may be a separate electric feed pump, but the more pressurised petrol I have around the more nervous I become  :zap:
Title: Re: Fuel injection systems
Post by: Admiral_dk on December 12, 2016, 02:20:15 PM
Congratulations Roger - nice step forward  :praise2:

All diesel engines I know of has a feed pump before the metering pump - often together with the filtering system .....

Best wishes

Per
Title: Re: Fuel injection systems
Post by: Graham Meek on December 13, 2016, 11:00:44 AM
Hi Roger,

You could pressurise the delivery by raising the height of the fuel tank above the pump. You might find in doing this that by increasing the tank volume you can also influence the amount of pressure. I am not saying this will give you what you need, but you can do this with relatively little work and it might prove your theory.

My best regards
Gray,
Title: Re: Fuel injection systems
Post by: Roger B on December 13, 2016, 07:29:14 PM
Hi Gray,

I think I will need a few meters of head to overcome the vapour pressure. I am looking at a couple of electric pump options, one from Conrad:

http://www.conrad.ch/ce/de/product/224413/Kavan-Kraftstoff-Zahnradpumpe-Foerdermenge-18-lmin?ref=list

This is capable of 3.8 Bar however it is not continuously rated at full output. It may be ok on reduced voltage but would need a pressure regulating/release valve. It is suitable for petrol and diesel fuel.

The other slightly larger option is an automotive pump:

http://www.fuelpumpsonline.co.uk/facet-solid-state-fuel-pump-40107-70-10psi-9-p.asp

I used to use Facet (or Bendix as I think they were then) fuel pumps on my competition cars and they are certainly robust and reliable. There are other versions available up to 15psi/1 Bar.

I am tempted by the Facet pump as I am certain it will do what I want. I will just have to make some NPT adaptors.

Title: Re: Fuel injection systems
Post by: Roger B on January 20, 2017, 08:48:43 PM
I have purchased a Facet pump with a 10psi rating along with a couple of 1/8" NPT fittings that I will be able to adapt. As the R&D Dept is closed again due to snow the next tests may be a month or two away.
Title: Re: Fuel injection systems
Post by: Roger B on January 25, 2017, 07:48:30 PM
The 1/4 NPT fittings that came with the fuel pump had 5.5mm bores and the connections I wanted to use had M5 or M5 x 0.5 threads so I had to make a couple of adaptors from some 8mm brass hex. The fittings were tapped M6 x 0.5 to allow for future developments.
I have fitted the pump to the engine base and connected it up. The copper pipe was bent using my old Girling former (Autojumble? Don't remember  ::) ) and I had purchased some small bore automotive fuel hose that is supposed to be OK with Petrol, Diesel and Alcohol to connect to the tank. The pump will be switched together with the coil.
Title: Re: Fuel injection systems
Post by: fumopuc on January 26, 2017, 06:57:41 PM
Waiting for the next pops.
Title: Re: Fuel injection systems
Post by: Roger B on January 28, 2017, 06:33:48 PM
The weather was kind today so I was able to try the new fuel pump. It was quite difficult to get all the air out as it is designed to feed into an open float chamber rather than a closed system. In the end I used a temporary pipe to circulate the fuel back to the tank for a couple of minutes.
The response was quite different, I was able to reduced the pump working stroke from maximum (around 1.5mm) to ~0.5mm. It would also run quite steadily without needing frequent adjustments or restarts.
The throttle response is also quite interesting, off load it will run over quite a wide speed range without needing to adjust the pump stroke. I haven't tried this system under load and may wait until I have the helix spill system working as it will be quicker to adjust/respond.

http://www.youtube.com/watch?v=uXUiAfTQvHQ

uXUiAfTQvHQ
http://www.youtube.com/watch?v=bI5pCyaTkbY

bI5pCyaTkbY
Title: Re: Fuel injection systems
Post by: Admiral_dk on January 28, 2017, 07:47:11 PM
Wonderful Roger - it sounds very good with a very even running / firing  :ThumbsUp:
Title: Re: Fuel injection systems
Post by: Roger B on February 07, 2017, 09:07:13 PM
The next step was to work out a control rack system for the metering helix. I had some 0.5 Mod 20 tooth pinions for the diesel engine lubrication pump with a 5mm bore. The projection on the fuel pump body is also 5mm but unfortunately the one I have already was only rough turned to support a spring not finish turned as a bearing surface. It will work for the first trials.

I could purchase some 0.5 Mod rack, 4mm x 4mm from Conrad. I cut off 30mm and milled it down to 3mm thick. The boss of the pinion was turned down to 7mm for a return spring. I decided to leave the existing system intact and start again on a new 5mm thick aluminium back plate. This now has fixing holes to attach to my horizontal engine, fixings for the pump body and a couple of slots for the rack. This all fits together and has 13mm rack travel which is around 150° rotation.

I need to devise a coupling between the pinion and the pump plunger and make a fixed guide rod for the excentric in place of the existing variable stroke one.
Title: Re: Fuel injection systems
Post by: Roger B on February 16, 2017, 06:54:27 PM
Having recently purchased a 4 jaw self centring chuck I thought I would see how it helped with the new excentric guide, new injection pump body and new injector body.

The excentric guide and injection pump both have the bore offset 1mm in both directions. This was easily resolved with two 2mm thick aluminium shims. Set up time effectively zero. The stub on the injection pump was finish turned to a good running fit for the rack pinion. I also turned a 0.8 mm deep 7mm dia. recess on the end of the body to locate the return spring. The 5mm dia. stub will then be held in a collet to machine the bore and the delivery valve recess and seat.

The injector body was even easier as it is concentric. The bore for the nozzle was drilled 5.9mm and then reamed 6mm. The end was flattened to the correct depth with a 6mm end mill. The top of the body was then opened out to 7mm and tapped M8 x 1
Title: Re: Fuel injection systems
Post by: Roger B on March 26, 2017, 07:36:05 PM
I'm still struggling with this one. I tried reaming out the next pump body with the tailstock clamped as tight as possible this resulted in the bore being even more oversize. The 1.97 plug gauge would pass through a nominal 1.95 reamed hole. I think that I will have to get a floating reamer holder  ::) £ £ £
I decided to continue with the body anyway. I turned a bronze bush to fit the tappet guide and then set the tappet guide and the pump body in the Proxxon to drill and tap the fixing holes. The centre drill tip broke off in the pump body  :facepalm:  I couldn't get the broken bit out, so another trial piece  :( At least it's only 25mm of 10x10mm black bar.
I then turned up the start of another injector nozzle and spring plug. I will wait for the floating reamer holder before I finish the injector (and the pump)
Title: Re: Fuel injection systems
Post by: Tennessee Whiskey on March 26, 2017, 07:38:31 PM
Roger, make sure you aren't bottoming out the reamer, this will cause an oversized hole.

Eric
Title: Re: Fuel injection systems
Post by: Roger B on March 26, 2017, 07:52:37 PM
Thank you Eric  :ThumbsUp: It's a through hole, but I am trying to work to micron tolerances and it appears that the reamer has to be aligned to better than the desired tolerance to get the best results  ::) I'm still in the learning phase on this, but think I am going to have to spend some money  :headscratch:
Title: Re: Fuel injection systems
Post by: freefuel on May 06, 2017, 11:56:29 PM
Hi Roger,

for small holes have you taken a look at EDM wire cutters? the process might prove you with the ability to cut holes smaller then your tools permit.

https://en.wikipedia.org/wiki/Electrical_discharge_machining
Title: Re: Fuel injection systems
Post by: Roger B on May 15, 2017, 09:17:27 AM
Thank you for that. The link suggests that EDM drilling will work down to around 0.3mm which I can currently drill. I am not sure if there is a need to go any smaller. Full size nozzles tend to be around 0.2 mm but I think that attempting to scale them down would just result in frequent blockages.
I chose to use an open needle valve (Pintle type) as the annulus gives quite a fine opening. Graham Meek is also working in the same direction.
I am not completely sure of the Physics/Fluid Dynamic but for a small engine the fuel pressure and penetration must be less than for a full size one otherwise the fuel will just be sprayed onto the combustion chamber walls or the piston.
Title: Re: Fuel injection systems
Post by: freefuel on May 15, 2017, 03:05:45 PM
the trend in modern diesel fuel injector design is for even finer fuel droplet size to maximize combustion efficiency, this is a problem compounded by our desire to use much smaller displacements and thus combustion chambers. it's a physics problem we are working against, in that we are not scaling the molecules of fuel and air we are working with down with our machines.

from what I can recall about full size diesel engines is that the injection pressures have increased as the nozzle orifice sizes have decreased to produce smaller fuel droplets. another major innovation has been the introduction of the multi event injection procedure, where a series of small injections precede the main delivery of fuel. doing do permits better control of the combustion chamber temps and noise reduction.

some more fun reading material, http://www.mmsonline.com/articles/non-traditional-methods-for-making-small-holes and https://en.wikipedia.org/wiki/Electron_beam_machining
Title: Re: Fuel injection systems
Post by: Roger B on July 04, 2017, 06:48:43 PM
Having learnt how to ream holes accurately (see the floating reamer holders thread) and had the engine running as a petrol engine it was time to move back to the injection system.

I started yet another pump body, this time with the correct size drilled hole and controlling the reamer at the correct feed rate with a floating holder I got a good bore without bellmouthing.

I then used the same experiences on the injector nozzle. Drilling 1.4mm was too much, the 1.45mm reamer passed straight through. Using a 1.3mm drill produced an acceptable result. I don't have a 1.46mm pin gauge, but the 1.47 didn't enter.

I then cut the seating with my previously made D bit, taking more care over the hole depths than on the last attempt.
Title: Re: Fuel injection systems
Post by: Roger B on July 04, 2017, 06:53:28 PM
The nozzle was then drilled 0.35mm with the same drill as before. I then moved onto the flange for the injector body as this one will have to be clamped to the cylinder head rather than just resting in the inlet manifold. This was done the traditional way with hacksaw, files and filing buttons rather than setting up the mill.
Title: Re: Fuel injection systems
Post by: Brendon M on July 19, 2017, 11:42:41 AM
I am amazed that a 0.35mm drill bit actually drills and not simply disintegrate. How do you do it?
Title: Re: Fuel injection systems
Post by: Roger B on July 20, 2017, 05:45:15 PM
No real problems. I am drilling less than a millimetre through brass. These are some good quality drills, some of the cheaper ones I looked at did not have real points and would not cut. I would have liked to have used a higher speed but my lathe will only reach 2000rpm.
Title: Re: Fuel injection systems
Post by: Roger B on July 23, 2017, 11:20:32 AM
The next step was to make the pump plunger and injector needle from 2mm and 1.5mm silver steel respectively. They were cut to length end the end of the pump plunger was threaded M2 before hardening. The pump plunger was lapped to 1.98mm diameter and the bearing surface of the needle was lapped to 1.48mm. The 50° point was ground on the end of the needle as before.
When I tried to grind the shank of the needle down to 1mm diameter the finish was bad and the end snapped off  :( I tried again with the same result  :headscratch:
I looked back to see how I successfully made the first one and what was different.
The solution was as follows:
Harden ~20mm of the 1.5mm silver steel, don't cut to length yet.
Grind and polish the point.
Grind the shank to 1mm diameter with the lathe at 250rpm in reverse and the grinding wheel at ~5000rpm.
Reduce the depth of cut from 0.05mm to 0.025mm.
Feed in at the chuck end and cut towards the point.
Polish the shank.
Lap the bearing surface to 1.48mm and cut to length.
Title: Re: Fuel injection systems
Post by: Roger B on July 23, 2017, 12:33:00 PM
Next I needed to change to milling mode to cut a screwdriver slot in the end of the nozzle so I could insert and remove it.
Whilst in this setup I cut a slot in the end of the operating plunger for a small ball race to run on the cam and cut the slot in the control gear for the piece that will turn the plunger and set the helix position.
I then went back to lathe mode and lapped the bores of the nozzle and pump body.
Next step put it all in the ultrasonic bath to remove the diamond paste residue.
Title: Re: Fuel injection systems
Post by: Roger B on August 06, 2017, 04:37:59 PM
Having removed the contact breaker from the diesel engine I wanted to try the roller follower for the injection pump. The follower housing was held onto the crankcase with a small milling clamp and a steel ruler was used as a return spring. Unfortunately, but not unexpectedly (which is why I did the trial) it tended to run at an angle  ::)

I could either slot the plunger and add some sort of guide pin or key or change the design to a swinging link type follower  :headscratch:

http://www.youtube.com/watch?v=vjbnAhMha0Q

vjbnAhMha0Q
Title: Re: Fuel injection systems
Post by: Brendon M on August 17, 2017, 09:00:57 AM
I am up to date again Roger, keep at it :)

I found the procedure for forming the injector needle quite interesting.
Title: Re: Fuel injection systems
Post by: Roger B on September 03, 2017, 04:46:02 PM
Thank you Brendon  :)

I made the union and nipple for the injector in the same way as before. This time I drilled the cone in the nozzle a little deeper and filed a flat on the nozzle to allow a couple more threads to engage.

I then ground the helix in the plunger and trimmed it to length, again as previously. The next bit was the tappet to go on the end of the plunger and transmit the rotation from the rack gear. This was sawn and filled from a piece of 4mm square silver steel so I can harden it. Having just purchased a set of edge finders I tried one out to centre the hole in the tappet.
Title: Re: Fuel injection systems
Post by: Roger B on September 03, 2017, 05:52:57 PM
Problem  :( When I assembled the system it would not turn freely and jammed completely in a couple of places  :headscratch: After a series of checks I found that the bore was not concentric with the running surface for the rack gear by ~0.2mm. This was a result of drilling from the other end to give the delivery valve seat a better chance  ::)

OK, start yet another injector pump body with a different machining sequence. This time I turned the spigot for the rack gear and then drilled and reamed the bore. As a further, hopeful, refinement I started with the drill as far into the chuck as it would go and then moved it out in stages as the hole got deeper. The process was the optimum one from my experiment with the floating reamer holder.
Run at 2000rpm
Center drill deep enough to leave a countersink.
Drill 1.85mm
Ream 1.95mm with a controlled feed of 0.08mm per rev.
This seemed to work, the 1.96mm pin gauge passed straight through, the 1.97 mm barely entered. It was also concentric to better than 0.02mm and when reversed and mounted in a collet the run out of the bore was not detectable   :)
Title: Re: Fuel injection systems
Post by: Admiral_dk on September 03, 2017, 09:13:20 PM
Quite an improvement in precision  :ThumbsUp:

Hope that you will have much more "luck" with the next test  :)
Title: Re: Fuel injection systems
Post by: Roger B on September 30, 2017, 05:23:28 PM
Thank you Per  :ThumbsUp:
I lapped the bore as previously and this time it all fitted together and turned without jamming  :) All the bits that had been in contact with diamond lapping paste went in the ultrasonic bath for cleaning and I machined the unions and delivery valve.
I tried to repeat the oil pressure tests that I had done with the previous pump. The much shorter leakage paths were obvious and as it leaked it reached the spill point and collapsed. Maybe it will work, maybe it's a step too far  :headscratch:
I had to slot some of the holes in the mounting plate to get the correct positions of the pump plunger but otherwise it all seemed to fit together  :)
Title: Re: Fuel injection systems
Post by: Roger B on September 30, 2017, 05:32:55 PM
I tried the horizontal engine with the original fuel pump and injector as a check before I experimented with the new system. It didn't run as well as before  :(  :headscratch: but I was able to test the new injector which worked much  the same as the original.
When I went to install the new pump I noticed that the soldered joint holding the fuel inlet nipple had cracked  ::) The solder hadn't penetrated at all  :( I cleaned the parts and resoldered them, maybe this caused small air leak that upset the first trial. I then installed the helix pump and tried to get it to run, without success  :(
Many problems: The delivery valve leaked so the fuel feed pump would blow past it. A quick clean solved that, but I was not getting any pressure feed from the pump at all. If I took the spring out of the injector it would dribble but no jet/cloud  ::)
I need to recheck that I have phased the rack to the plunger correctly but otherwise back to the drawing board  :headscratch:
Title: Re: Fuel injection systems
Post by: Roger B on October 11, 2017, 05:33:00 PM
A bit of a post mortem on the problems  ::)

I had drilled the delivery valve too deep so that there was not enough pressure on the ball  :facepalm: The bore was also too big due to a drawing error. It should have been 3.1mm for a 3 mm ball. I had put 3.2mm on the drawing and the drill I used resulted in a 3.3mm hole. Solution: make a new valve body  :ThumbsUp:

The tip of the plunger was again too small yet it was a tight fit  :headscratch: Problem: the length of Silver Steel I was using was not straight and round. Solution: Try using the pin gauge.

I annealed the end of the gauge, holding it in an old pair of pliers to act as a heat sink, and was then able to thread it. I tried it in the existing pump body using a light machine oil and with a 4.5kg weight it sunk in around 10 seconds. This is a pressure of around 140 Bar / 2000psi. As the gauges cost CHF 10 and will make two plungers I will continue down this route.
Title: Re: Fuel injection systems
Post by: Roger B on November 19, 2017, 09:25:23 AM
The original gear train used to cut the helix didn't quite mesh properly so I tried a different set up this time. This was tight against the drive motor but was free from backlash.

I then needed to reduce the length of the pump to make it an easier fit on the diesel engine. I was able to shorten the tappet guide by 2mm and annealed the gear connector block for the pump plunger and milled 1mm off.

Title: Re: Fuel injection systems
Post by: Roger B on November 19, 2017, 02:20:22 PM
I had looked at the possibilities of using a swinging link rather than a tappet when the pump was installed on the diesel engine but decided that a slot and guide pin would be better/easier. I annealed the tappet an then using a rather dodgy set up I cut a groove with a 1.2mm slitting saw. Due to the various runnouts (the arbour was barely in the ER collet) the final groove ended up at 1.4mm.  I drilled and tapped an M2 hole in the guide, taking the centre from a length of 5mm SS. The end of an M2 x 5 grubscrew was turned down to fit the groove and Loctited into place. Finally I trimmed 2mm from the tapped and then re-hardened it and the gear connector.
As my horizontal engine had not run so well during the last trial I removed the piston and conrod to check the rings (I had had previous trouble with them sticking in the grooves). The piston is fairly rough due to previous seizures, but both rings were free although they did not look fully bedded in. I think it just needs some more running time.
Title: Re: Fuel injection systems
Post by: Roger B on November 26, 2017, 01:27:24 PM
I had enough of a break in the weather to try the new helix system. It was 3 or 4°C out there which may not have helped the running. The trials were more successful than last time (even though the plug cap popped off  :facepalm: ). It would run fairly consistently for a time but would occasionally suddenly stop. The response to the rack position seemed variable, sometimes there was an obvious richening/leaning and at other times the position made very little difference  :headscratch:

I experimented with the pressure on the needle valve. Running seemed to improve as I increased the pressure (until I reached the point where the needle was jammed shut). Looking at the spring details and the compressed length I was getting a maximum opening pressure of around 14 Bar.

When I was doing some bench trials with the pump reaching the spill point on the helix resulted in a shot of oil being fired out of the inlet port. May be this is causing a disturbance in the inlet tract? There is a small space under the union which may also cause some of the priming problems. I don't think I can easily reduce it to zero volume so making it bigger may help ::) At least there is very little time in making a new union if it doesn't work.

Apologies for the dark and grainy videos. I have tried both embedding and just putting the URLs as the embedded version is not always visible.

http://www.youtube.com/watch?v=hnD6E87YyTw

hnD6E87YyTw
http://www.youtube.com/watch?v=YtH6HoTQbeQ

YtH6HoTQbeQ
Title: Re: Fuel injection systems
Post by: Roger B on December 10, 2017, 05:40:39 PM
Well I have found some of the reasons for the running problems  ::) The exhaust valve was leaking and the water pump shaft that is used to drive the injection pump has some wear. The details are here:

http://www.modelenginemaker.com/index.php?topic=7701.new#new
Title: Re: Fuel injection systems
Post by: Roger B on January 07, 2018, 08:10:35 AM
There was a short break in the weather so I tried the helix pump on the diesel engine with diesel fuel. No success  :( The delivery valve would not seat properly and the system would not prime. My fingers were rapidly too cold to fiddle with these small pieces so clean it all off and back to the workshop.

I set it up on the bench with the fuel tank fixed to the front of the mill. After experiments with cleaning alcohol I found that the problem with the delivery valve seemed to be that the body was not quite concentric with the seating. I opened the hole out to 3.2mm and it sealed. This is probably due to modifying a commercial union rather than turning it all from brass hexagon in one operation.

I also wonder if the helix pump might be a step too far and am looking at fitting the earlier (and successful) variable stroke pump. For this I needed to modify the first plunger to take the small ball race cam follower and fit a guide pin to stop it twisting. I annealed the plunger, opened the fork out to 2.5mm and milled a 1mm deep 1.4mm wide slot for the guide pin.
Title: Re: Fuel injection systems
Post by: Roger B on January 07, 2018, 11:04:56 AM
I put the system back together and got it primed. The atomisation looks reasonable, but operation was not consistent. I think that there is still a problem with turbulence in the inlet port when the spill helix opens. I removed the fuel inlet flexible pipe and small droplets were shooting out. I'm not sure if they are visible in the video  ::)
According to the calculated injector spring load, 14N, the injector needle was opening at around 60 Bar.

OTfKmEFqr94
A5-OEu7dfp0
Title: Re: Fuel injection systems
Post by: Admiral_dk on January 07, 2018, 09:27:56 PM
The spray Looks fine - so far so good  :ThumbsUp:

Best wishes with the rest  :)

Per
Title: Re: Fuel injection systems
Post by: fumopuc on January 08, 2018, 07:06:55 PM
"Spannend"
Great project with a lot of interesting challenges.
Title: Re: Fuel injection systems
Post by: Laurentic on January 25, 2018, 11:00:21 PM
Can't believe you are still trucking on Roger, gees but you have some stamina and application.  More than 1 1/2 years on and you are still at it like a dog with a bone, well done that man, you have my admiration and respect, many a lessor man would have given up, but I am so pleased you are staying the course as you seem, little by little, to be winning.  Like how many body's have you made, I've lost count.  Really willing you on here, wanting and hoping you will finally succeed.  Where do you buy all your small - tiny even - drills, reamers and laps from?  Haven't been able to source them in the UK myself so far.

Cheers, Chris
Title: Re: Fuel injection systems
Post by: Roger B on January 26, 2018, 08:43:08 AM
Thank you all for your continuing interest in this somewhat long term project. I knew at the start it wasn't going to be easy  ::)

Chris, there have only been 5 or 6 pump bodies so far, but I made around 10 simpler versions when I was learning how to ream.

The 0.35mm drills came from a workshop clear out at work but are also available from Brütsch-Rüegger where I get the other drills:

https://www.brw.ch/3/BRW-ToolShop/1/Category/417/Product/Details/P_20532/Twist-drill-TITEX?pSearchId=18968cfa-1ccc-42c5-8874-feaaffc72f38&pOnlyPromotion=False

The 0.01 step reamers are from the same source:

https://www.brw.ch/3/BRW-ToolShop/1/Category/523/Product/Details/P_189574/Machine-reamer-MAGAFOR?pSearchId=375fe529-1341-4eb3-a3b8-cdaec2ffe2f5&pOnlyPromotion=False

As are the pin gauges:

https://www.brw.ch/3/BRW-ToolShop/1/Category/194/Product/Details/P_18228/Pin-gauges-MT?pSearchId=a6f6ce3f-a392-4ebb-86b7-5dd855770f9b&pOnlyPromotion=False

The needle eye laps are from Acro in the USA (I also use their barrel laps for engine cylinders):

http://acrolaps.com/index_007.htm

Title: Re: Fuel injection systems
Post by: Laurentic on February 02, 2018, 02:33:02 PM
 Many thanks for the info Roger, been away for a few days and only just catching up - will take a look at the links you gave right away.

Cheers, Chris
Title: Re: Fuel injection systems
Post by: Roger B on February 28, 2018, 08:09:24 PM
Not much is happening on here at the moment as I need to do some more trials with the horizontal engine but with -10°C and snow they are going to have to wait. I am continuing to modify the variable stroke pump to fit on the diesel. The problem with this is that the start of injection varies with the stroke. Maybe ok maybe not  :headscratch: I have made a new plunger from the other half of the pin gauge with a larger flange to suit the same spring type as the helix pump.
While doing this I did find that the inlet union to the pump was a failed delivery valve body and had been drilled out to ~3.3mm giving a reservoir above the pump inlet. I will modify the helix pump to match.
Title: Re: Fuel injection systems
Post by: Roger B on April 14, 2018, 07:44:30 AM
I modified the backplate of the variable stroke pump so I could access the unions if it is fitted to the diesel. Hopefully the helix pump will work though ::)
The inlet union of the helix pump was opened out to 3.2mm to hopefully give a space for surge/turbulence during spill. I then refitted the injection system to my horizontal engine. Previously the injector was vaguely held in place by the fuel pipe so I decided to make a proper clamp to keep the O ring compressed and remove the variable air leak. Ready for another trial  :)
Title: Re: Fuel injection systems
Post by: Vixen on April 14, 2018, 10:08:49 AM
Hi Roger,

Top marks for your persistence. A direct fuel injected model engine will be a remarkable achievement.

When you have a spare moment, could you please post the latest schematic of your injection system.

I for one, and I am sure there are others, have lost track of where all these individual piece parts and modified parts fit into the system.

Mike.  :ThumbsUp: :ThumbsUp: :ThumbsUp:
Title: Re: Fuel injection systems
Post by: Roger B on April 14, 2018, 04:31:21 PM
Thank you Mike  :ThumbsUp:  :ThumbsUp: Here is a summary of where I am today:

First system:

2mm bore variable stroke pump with 1mm diameter inlet port and ball delivery valve. Stroke adjustment 0-3 mm. The bore is drilled reamed and lapped. The plunger is made from a commercial pin gauge. I started out using hardened and lapped silver steel but had problems with a non-circular piece and at 11 chf each which will give 2 plungers they seem the best option.

The pump is driven by an eccentric to give a long injection period while the inlet valve is open.

Plain bodied injector with 1.5mm diameter needle ground down to 1mm. 0.35mm diameter nozzle. The nozzle seating is 60° and the needle 50° to give a line seal at the entrance to the nozzle bore. Adjustable spring tension, opening pressure around 15 bar. The needle is made from hardened and lapped silver steel.

This operated successfully as manifold petrol injection but required a feed pump to avoid vaporisation of the petrol.

Second system:

This pump has a helix ground in the plunger following full size practice. The plunger is rotated by a rack and gear. The gear is wide enough to allow for the 3mm stroke of the pump.

This pump can be driven by the eccentric for manifold injection or by a fast-acting cam for diesel injection.

The injector is the same as above except for a mounting flange to fit to the diesel cylinder head. A stronger spring can be fitted to give a higher release pressure (estimate 60 bar)

This has also run successfully as manifold petrol injection.

Reaming:

Reaming the bores has required significant development of my technique to avoid bell mouthing. I am following the manufacturers recommended speed and feeds for the reamers which are higher and lower respectively than I had been using. The drill size is important as is a slight lead on the hole. I found that a floating reamer holder gave less bell mouthing but was expensive.
Title: Re: Fuel injection systems
Post by: Roger B on April 14, 2018, 04:41:24 PM
I made some trials with the helix pump today. As ever priming is a problem and I have a small leak from the inlet union to the fuel pump due to partially stripped threads  ::) I may need to make a new pump body  :(

It ran well and would run between 1500 and 6000rpm at the same setting of the pump  :)

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I then connected the load bank and was getting nearly 8A into 1ohm so around 64W. Previously I achieved a maximum of 80W using the same carb as I am using for a throttle. This was at the same setting of the pump as before.

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Finally it settled down to a 1500rpm idle still at the same setting.

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There were some problems with the feed pump. It seemed to keep pumping/clicking even into a closed pipe which resulted in the fuel overheating and vaporising  ::)

Generally a good day  :wine1:
Title: Re: Fuel injection systems
Post by: Vixen on April 14, 2018, 07:12:10 PM
Roger

Thanks for the update on your design and experiments

MIke
Title: Re: Fuel injection systems
Post by: Roger B on April 15, 2018, 01:55:05 PM
I tried to determine the working stroke of the injection pump. During the trials moving the rack up and down by one tooth each way produced too rich and too lean. Looking down the inlet port the start of injection was fairly easy to see but when the helix was exposed was more of a problem. I took the following measurements which I expect are too large due to chamfers on the edges:
Best running 1.2mm
1 tooth rich 1.5mm
1 tooth lean 0.8mm
With the variable stroke pump I estimated 0.5mm

I then decided to see if I could rescue the damaged thread. I set the body up on the mill and removed the damaged thread with a 5mm end mill. The hole was then tapped M6x0.5 and I made a bush to take it back to M5x0.5. This has been Loctited in and is curing.
Title: Re: Fuel injection systems
Post by: Admiral_dk on April 15, 2018, 05:26:46 PM
Still following along and glad to see some progress for you  :ThumbsUp:

The measurement will be extremely difficult if you insist on doing it geometrically - as you say yourself - how about camfers etc. ....

In my book you will have to ensure a reasonable constant rpm over a certain amount of time and measure the amount of fuel drawn from the tank / how long it will run on a known amount of fuel at a constant rpm.
I would use a calibrated syringe or laboratory "beaker" with a fine graded scale as the fuel tank.

Best wishes

Per
Title: Re: Fuel injection systems
Post by: Roger B on April 16, 2018, 08:42:57 AM
Thank you Per  :ThumbsUp:

The stroke measurements were more to confirm the mechanical design was ok and I was not reaching a limit. Making a proper test rig so I could also see how much the output varied with speed due to leakage would be interesting but is almost a project in itself  ::)

I was surprised how flexible the engine was with a fixed stroke set on the pump. It was better than with the carb (although the carb is not properly calibrated to the engine). I suppose that a metering pump takes speed out of the fuel map equation, the same amount of fuel will be injected per stroke however fast the engine is running. Throttle position and load may then by partially compensated for by the speed related leakage  :headscratch:  :headscratch:
Title: Re: Fuel injection systems
Post by: Roger B on April 21, 2018, 04:03:09 PM
As spring has finally sprung here I thought I would give the diesel a try  ::)

I primed and tested the injection system in the workshop with alcohol and then took it outside and filled the tank with diesel. As I first trial I held  lighter in front of the injector and got some puffs of yellow flame whilst turning the engine by hand.

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I then fitted the injector and gave it a try. There were a few puffs of blue smoke and then nothing. I removed the spring adjusting screw from the injector so I could remove and check the needle. Unfortunately I didn't realise how quickly it would fly out under compression pressure. Result one lost needle  :( I  hunted around with a magnet without success so I tried again with the needle from the other injector.

This time I got fairly consistent blue smoke that was controllable with the rack but no real firing  :headscratch:

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Obviously the needle was not the best so I need to make a new one. I think that the compression is sufficient but I could make a compression tester although the non return valve would have to be right where the tip of the injector is to get good results. The atomisation also seems ok, but the penetration may be too much and most of the fuel is just hitting the piston crown. Lots to think about but overall not to bad. Blue smoke was more than I was expecting  :wine1:
Title: Re: Fuel injection systems
Post by: Admiral_dk on April 21, 2018, 07:54:37 PM
I really hope that this indicates that you are close to a runner on diesel  :cheers:
Title: Re: Fuel injection systems
Post by: Roger B on April 27, 2018, 11:09:31 AM
I hope so too  :ThumbsUp: I have a few more things to try with this injector like a weaker spring and altering the timing. As the blast of fuel from the injector tended to blow out my lighter I think that it may be too strong.
I will make a compression tester to fit in place of the injector. It's always best to have real numbers to work with.
Title: Re: Fuel injection systems
Post by: Roger B on May 03, 2018, 05:38:55 PM
I decided to try and make a 'mushroom' valve injector. This is easier for petrol injection as it doesn't require a leak off and has also been used successfully in small diesels by Find Hansen.

The valve is turned from 3mm silver steel. I did wonder about upsetting the end of some 2mm silver steel but decided the heat treatment stuff was too much bother. The shaft was turned down to 2mm and the section before the valve was reduced to 1.6mm. The valve cone was turned to 15° inclusive. The top of the shaft was threaded M2 and the valve end was hardened. This was then finish ground and polished.
Title: Re: Fuel injection systems
Post by: Roger B on May 03, 2018, 05:42:44 PM
The nozzle is turned from a piece of brass bar. This follows the dimensions of my existing injectors but could be made smaller. I have some 3mm AF nuts for the valve that will fit inside the 4.5mm clearance for an M5x0.5 thread.
Title: Re: Fuel injection systems
Post by: MJM460 on May 03, 2018, 11:46:11 PM
Incredible work Roger.  Your whole thread has been a masterclass in tiny precision work, along with great instruction on the ins and outs of injectors.  I never miss following along

MJM460
Title: Re: Fuel injection systems
Post by: Roger B on May 06, 2018, 04:55:15 PM
Thank you for your support  :ThumbsUp:  :ThumbsUp: I know that progress is usually slow due to work, life, etc. but I think I have made some progress. I am fairly happy with both the injection pumps and operation as manifold injection for petrol engines. Diesel injection still holds some challenges (discussed in the diesel thread).

The injector body was turned from a piece of 7mm hex brass and tapped M5 x 0.5 at both ends. the first tests were not a success  :( I did not leave enough grinding allowance on the needle so the final diameter was too small. When I tried it in spite of this there was a fuel leak between the body and the nozzle. When I tightened it some more I stripped the threads  :facepalm:

The cause of the leak was running the die right up to the end when cutting the thread in the nozzle which resulted in some score marks in the sealing face. Luckily I could salvage both parts by reducing the lengths a little and re-cutting the threads. I then made a new needle, leaving the cone larger, then grinding it down to length at the end.

When the diesel has had a couple of days quarantine in the garage (after the last trials) I can bring it back into the cellar for some more trials with alcohol.
Title: Re: Fuel injection systems
Post by: Roger B on May 11, 2018, 07:30:45 PM
The trials with the 15° mushroom injector were not satisfactory so I decided to make a 30° mushroom. This was much the same as before except that the clearance when grinding the tip was somewhat reduced.
I also decided to open out the normal nozzle to 0.5mm and had to make an extension holder for a 0.5mm drill. This was ok, I had a 0.5mm centre drill to start off with and running the lathe at the maximum 2000rpm all went ok.
Title: Re: Fuel injection systems
Post by: Roger B on May 11, 2018, 07:38:21 PM
The drill was Loctited into the extension and the nozzle was open out to 0.5mm without problems  :) I then used the Proxxon micro mill to put a couple of spanner flats on the mushroom nozzle and set it up for a try.
Turning the engine over with the drill, as in a starting trial gave quite a close spray pattern at 30 cm, maybe still to much penetration  :headscratch:  ::)  :help:

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I will try the conventional injector with a 0.5mm nozzle later.
Title: Re: Fuel injection systems
Post by: Admiral_dk on May 11, 2018, 08:32:40 PM
Looking good Roger  :ThumbsUp:

Regarding the "perfect" spray pattern -- I do believe that it depends on the size and shape off the tube you spray into and the angle of doing so. It's "fairly easy" to get it to run, at lot more work to make it run good and a hell lot of work to get it perfect.
So there are a great amount of solutions for the easy, still quite a good number that will run good, but probably not that many that will run perfect.

The simplest I remember is the "carburettor" on the Velo Solex moped. There is a membrane pump on the side of the crankcase driven by the pumping pressure in the crankcase. It lifts the gasoline from the tank to the "carb" where there is a very fine nozzle that sprays the gasoline into the venture, a spring operated valve that allows the surplus to return to the tank and a throttle ... and that is it (if memory serves some 43 years after I opened one). This system isn't a bad as it sounds even though the throttle isn't very good as you get between 60 to 90 Km. on a litre gasoline.
Title: Re: Fuel injection systems
Post by: Roger B on May 13, 2018, 04:05:41 PM
Thank you Per  :ThumbsUp: I have plenty of variables to play with on this before I start thinking about turbulence in the combustion chamber  :headscratch:  :headscratch:

I tried the normal injector with the nozzle increased to 0.5 mm (double the area of the original 0.35mm) I think that the penetration is reduced, but the real test will be on the engine. Until I get actual firing it's hard to know in which direction to go. I will also try the mushroom injector on the petrol engine.

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Title: Re: Fuel injection systems
Post by: Admiral_dk on May 13, 2018, 09:10:30 PM
I forgot - the finer the mist, the better the mixture => less fuel needed for the same rpm.
Title: Re: Fuel injection systems
Post by: Roger B on May 19, 2018, 04:27:44 PM
I fitted the mushroom injector and variable stroke pump to the horizontal engine for a petrol trial. It ran well, still showing a surprising throttle response for a fixed stroke setting on the pump. The fuel feed pump is not happy pumping into a closed system and tends to heat up and vaporise after a while. I need to add some sort of bypass or try a different style of pump.

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Title: Re: Fuel injection systems
Post by: Vixen on May 19, 2018, 04:35:16 PM
Good progress Roger. The engine sounds like it is running nicely

Mike
Title: Re: Fuel injection systems
Post by: Art K on May 19, 2018, 10:59:27 PM
Roger,
I have to admit not having followed this thread much, due to how far along it is. Curiosity got to me and I finally tuned in. Very interesting lots of very fine work. At some time in the near future I'll have to start from the beginning. Won't belong and you'll have that diesel running.
Art
Title: Re: Fuel injection systems
Post by: Roger B on May 20, 2018, 06:42:38 PM
Thank you both  :ThumbsUp:  :ThumbsUp:
I am still surprised how well the petrol injection system works, I think the horizontal engine runs better than with the carbs.  :headscratch: I am tempted to make a 360° crankshaft and camshaft for my twin cylinder engine so I can try it with fuel injection using a single pump driven from the crankshaft. This would also work for Dave (Steamer's) Wallaby. 
If anyone else wants to try and build a system I am more than happy to support/help them  :)
Title: Re: Fuel injection systems
Post by: Roger B on July 11, 2018, 07:56:27 PM
As I said previously the Facet fuel pump I am using is not happy pumping into a closed system as it is really designed to work with a float chamber. All the mechanical petrol injection systems I am aware of circulate the fuel via a pressure relief valve. I bought a smaller gear type fuel pump designed for transferring fuel into the tanks of models. It is not continuously rated at full output but I am expecting I can significantly reduce the supply voltage so overheating shouldn't be a problem.
I then needed to make a pressure relief valve to operate somewhere between 0.7 and 1 bar. After playing with a few designs I decided to base it on the delivery valve of the fuel injection pump using a weaker spring. This puts the tank return at the top which will also help with bleeding the air out of the system. The body if 8mm square brass tapped M5x0.5 on the side and at the top to take the fuel inlet union and the valve cage/return union. The connection to the injection pump is via a long nipple soldered into the body.
Title: Re: Fuel injection systems
Post by: Admiral_dk on July 11, 2018, 09:33:13 PM
Still hoping that you solve all the problems with this project, but it is a bumpy road you travel here  :cheers:
Title: Re: Fuel injection systems
Post by: Roger B on July 30, 2018, 07:10:07 PM
I shortened a 'trial' delivery valve to use as the inlet connector and then having received some 0.2mm wire springs I put it all together for a trial. Using the Facet pump it would hold 0.6 Bar but if I unscrewed the valve body 1 turn (0.5mm) it would let by so the spring looks about right. Now I need to mount the gear pump and try again.
Title: Re: Fuel injection systems
Post by: Roger B on August 08, 2018, 05:54:47 PM
I mounted the pump with a couple of angle brackets and used some of the existing pipework along with a couple of flexibles. I intended to use a bench power supply for the trials but the ones I had had a maximum output of 1A which was insufficient at the start (after some running time the current did drop). The back up plan was my sealed accumulators with the load bank to give some variation. I started with the 12V battery but as things eased off was able to use the 6V one.

5V 0.9A gave the expected 0.8 bar with some warming of the motor. Adding another 1mm washer under the relief valve gave 4.5V 0.75A and 0.5 Bar. The return flow was quite sufficient at these values. More voltage resulted in splashing out of the cap.
Title: Re: Fuel injection systems
Post by: AlexS on August 23, 2018, 09:51:44 PM
Hey Roger, I admire your ingenuity and tooling skills!

Reading this topic I might have an idea for fuel pump. Just an idea.
Applying a stage plunger pump. If I am right, this is 'approximately' applied to the VAG diesel systems in the future. You could possibly pump this pump to the motor mechanically. Or by means of a strong electric motor.

The idea is that the supplied diesel is sucked in by the first plunger. Where then compressed to medium pressure, where the second plunger can actually generate a higher pressure. Above the plunger, the supply and discharge can be equipped with, for example, a membrane. A spring or the like can be mounted against the diaphragms. An amount of pressure can be generated on the basis of the bias, spring constant and surface of the opening of membranes. This could easily be changed.
An electric pump can supply the diesel under-pressure to the first plunger. The nice thing is that the amount of diesel can be dependent on engine speed. Optionally, the output membrane of the second stage would be opened externally during partial load or heating of the engine. However, the pump did labor on the diesel, which resolved in warming diesel.
Title: Re: Fuel injection systems
Post by: Roger B on August 26, 2018, 08:16:02 AM
Thank you Alex  :) An interesting concept for a pump  :ThumbsUp:

After some running time the electric pump would operate on 5V drawing less than 1A so I made up a board with a 7805 regulator and appropriate decoupling capacitors (based on previous experience). As I have now fitted a 12V coil to the horizontal engine the regulator could go where the 6V regulator for the previous coil was installed. This all seems to work although I have not had the opportunity for long runs.

I had previously ordered some Titex 0.2 mm drills for the next injector trials and wanted to see if I could actually drill some holes. This was going to be difficult as if I wanted to carry on as before I would have to drill a 5 or 6 mm deep hole in the brass drill extension. This is 25-30d which is hard enough with 'normal' size drills. I did manage to make a few holes with several broken drills but this was fairly obviously not going to work with the equipment I have.
The next trial was to drill 0.35 mm hole as before and try Loctiting a 0.2mm drill in, hoping that the surface tension would keep it central. This appeared to work, in the last picture it is turning at 2000rpm with no obvious runout.
Title: Re: Fuel injection systems
Post by: Vixen on August 26, 2018, 10:50:36 AM
Hello Roger,

Drilling 0,2mm holes 5 to 6 mm deep, in brass, is always going to be a big "ask".

I cannot tell you how to do it successfully, but here are some pointers.

Chose the hardest possible brass ie. one that produces fine chips NOT long spirals.

To achieve the recommended surface cutting speed for brass, you need a spindle speed in the order of 20k to 25K RPM. Wow thats fast!!!!

Peck drill at a few thou (50 microns) per step. This will break the chips which helps prevents clogging the drill flutes

Withdraw the drill completely every 0.5mm to clear the chips and re-apply lubricant (WD40 or kerosene)

Provide a very, very precise centre mark. A slightly larger drill may help start the hole.

Consider drilling part way with a slightly larger drill and breaking through with the 0.2mm drill.

Consider EDM with a fine wire

Consider using a watchmakers pivot jewel as the nozzle. You are in the right country for watchmakers.

Not sure if any of that will actually help. Let us know how you get on

Goodluck

Mike




Title: Re: Fuel injection systems
Post by: Admiral_dk on August 26, 2018, 12:01:53 PM
Best of luck with the drilling Roger.

I'm with Mike on the minimum rpm on the drill bits !!!!

I can't think of a single kind of injector system where the depth of the hole is more 5-10 times the diameter of the hole - the rest of the depth is done in a bigger diameter ..... are you sure that the only way your system is going to work are done with a single diameter the whole way ?
Title: Re: Fuel injection systems
Post by: 90LX_Notch on August 26, 2018, 03:59:21 PM
I haven't dropped in on this thread in a while Roger; awesome stuff going on here.  I need to get caught up.

-Bob
Title: Re: Fuel injection systems
Post by: Roger B on August 26, 2018, 04:06:29 PM
Thank you for the suggestions  :ThumbsUp:  :ThumbsUp:

This is not for the nozzle itself but for the tool to drill the nozzle. To keep the nozzle concentric with the seating I need to drill from inside. I successfully made extended drill holders for 0.5mm and 0.35mm. I was aware that moving down to 0.2mm would be a challenge. The most successful attempts were made starting with a spot from a 0.5mm centre drill, pecking at the hole and wiping the swarf off with my fingers every few pecks. My WD40 equivalent made things worse by causing the chips to stick together  ::)

I do have a back up plan as 0.2mm drills are available with a 1mm shank so drilling the brass extender 1mm is no problem. The actual nozzle hole is only planned to be 0.5mm - 1mm long.
Title: Re: Fuel injection systems
Post by: zeeprogrammer on August 26, 2018, 04:21:41 PM
Very interesting!  :popcorn:

I'm still confused about the use of WD40, kerosene, or equivalent when drilling/cutting brass.
I thought lubricant was not needed. I may also be confused with 'not recommended'.

For brass..

When is lubricant not needed?
When is lubricant recommended (or needed)?
Is there a case where lubricant is not recommended?
Is it a matter of the type of brass?
Title: Re: Fuel injection systems
Post by: Vixen on August 26, 2018, 07:13:47 PM
Hi Zee

Under normal circumstances (read normal size drills) lubricant is not needed for brass.

However, with a small diameter 0.2mm drill  (that's less than 8 thou, or 8 mils, as you guys say) rotating at something like 25, 000 RPM, it sometimes helps to use a light lubricant to cool the drill and flush the chips. But as Roger points out, even that does not always work as intended.

Mike
Title: Re: Fuel injection systems
Post by: zeeprogrammer on August 26, 2018, 07:24:48 PM
Thanks Mike.

Apologies Roger. I should have asked in my thread.
Title: Re: Fuel injection systems
Post by: Roger B on August 27, 2018, 05:37:00 PM
Absolutely no problem Carl  :) Everything I post on here is about learning and understanding (generally on my behalf  ::) )

I also have the same question about lubricants and cast iron. If you read some UK books it appears that using lubricants when machining cast iron will result in destruction of the world as we know it but my German books suggest using kerosene (which I guess is the most widely used description of Paraffin, Petroleum, etc maybe it should just be called Jet A1?).
I guess in the end it is what works  for what you are doing. My lathe will reach 2000 rpm therefore holes have to be drilled at 2000rpm. My Proxxon drill will do 8000 rpm and the Proxxon mini mill will reach 20 000rpm but they won't drill concentric holes in a round item.
On with plan B  :wine1:
Title: Re: Fuel injection systems
Post by: Roger B on August 31, 2018, 07:58:45 PM
I received some (expensive) reinforced shank 0.2 mm drills. The first attempt at a holder was made in brass as before, but it broke at the end of the 1mm hole. The 0.2mm wall thickness was not enough  :(  I then tried again with silver steel. I wasn't sure about drilling a 1mm hole 15mm deep but it was ok. I had made a trial nozzle to check the diameter and for polishing I supported the bore with a reversed 1mm drill in the tailstock drill chuck. OK so far  :)
Title: Re: Fuel injection systems
Post by: Roger B on September 01, 2018, 06:49:32 PM
Having made the drill I then tried to make the nozzle. The blank was 27.3mm long so it was drilled 1.3mm dia 26mm deep, reamed 1.45mm 25 mm deep and then finished with the D bit to 26.8mm. I then pecked with the 0.2mm drill until the resistance went and luckily the point was still there  :)

I had bought some stronger springs for the injector but they had a smaller bore so I had to turn down the adjuster and the needle cap. I normally use ER collets but the thin needle cap was a good use for the Hobbymat spring collets.
Title: Re: Fuel injection systems
Post by: Admiral_dk on September 01, 2018, 09:19:20 PM
Looks very good Roger  :ThumbsUp:

I really hope this one works to your satisfaction  :cheers:
Title: Re: Fuel injection systems
Post by: Roger B on September 04, 2018, 10:31:13 AM
Thank you Per  :ThumbsUp: The stronger spring certainly made a difference (video is in the diesel thread) but I need to lap the bore on the 0.2mm nozzle before I can try it.
Title: Re: Fuel injection systems
Post by: Roger B on October 07, 2018, 08:10:07 AM
When I tried the 0.2mm nozzle in the engine I had problems with fuel leaking from the injector union which I couldn't solve at the time. This are was not really designed, just made up as I went along so I decided to revisit it.

The original injection piping was 1mm bore 2mm od copper pipe sleeved into a commercial 3mm union at the delivery valve end with a home made nipple and nut at the injector end. The connection into the injector nozzle was via a cone made with a 0.8mm tip 3.15mm od centre drill.

Since this time I found some 2mm unions from Regner with the same M5 x 0.5 threads. They appear compatible with the original ones from Holzapfel Dampfmaschinen but I need to check the cone angles.

Looking at the original pipework the nipple at the delivery valve end seems quite distorted and the nipple at the injector end has a noticeable ring. I think that the Regner type nipple will be better at the delivery valve end. The problem at the nozzle end is that the nipple is 4mm diameter and the centre drill used was 3.15mm diameter so if the cone is drilled too deep it won't seal. I check the dimensions around that part of the nozzle and I can use a 4mm diameter 1.6mm tip centre drill which should resolve the problem. I will need to make a 4mm bore guide nut for the drilling operation. Previously I used the actual union nut. Some means of depth control will also be required.
Title: Re: Fuel injection systems
Post by: Vixen on October 07, 2018, 12:03:26 PM
Hello Roger,

Is there anything to be gained by hard soldering (use silver solder) a short length of pipe to the injector body and having a standard (bought in) union joint a little way away from the injector. That way you may be able to divorce the injector design from the union problems.

Just a thought

Mike
Title: Re: Fuel injection systems
Post by: Roger B on October 07, 2018, 02:42:20 PM
Hi Mike, the problem joint is between the injector body and the nozzle. This is why I have tried to make a cone fitting at that point. If I move the fuel connection to the body I would probably have to lap the nozzle into the body to gain an adequate seal. O rings are too elastic for the high pressures and small volumes. A variation on your thought is to combine the nozzle and the lower half of the body and then screw the spring assembly on top. This would allow me to silver solder the fuel connection to the nozzle and move the union away. I may move to this when I have the design more fixed but currently a new nozzle is a short length of 8mm brass rod and an evenings work.

I have attached a PDF of the current state of the injector design.
Title: Re: Fuel injection systems
Post by: Roger B on October 20, 2018, 07:58:53 PM
I moved on with this making a new union nut and a guide bush for the larger centre drill. The Proxxon drill makes it quite easy to set the depth using a drill of the appropriate diameter. I also used a drill shank to check the depth of the union nut.
Title: Re: Fuel injection systems
Post by: Roger B on October 20, 2018, 08:03:38 PM
I shortened a Regner nut to match the delivery valve and then silver soldered both ends on the pipe using my small Portosol torch rather than the big blowlamp.
Title: Re: Fuel injection systems
Post by: Admiral_dk on October 21, 2018, 08:41:43 PM
Looks nice - have you pressure tested them after soldering ?
Title: Re: Fuel injection systems
Post by: Roger B on November 05, 2018, 08:29:11 PM
Thank you Per  :ThumbsUp:  I can only test them by assembling the system, maybe I need to build a test fixture using something other than diesel oil.
Title: Re: Fuel injection systems
Post by: Vixen on November 05, 2018, 08:52:22 PM
Keep a close eye on the pipework, every injection pulse creates a shockwave which can fatigue the pipe joints.

I even had it happen with one of our companies cars. I was miles from home when one of the injection pipes fractured and the engine went on to three cylinders. I did not wish to be stranded, so limped slowly back to base. The engine sounded really rough and stank of the diesel oil which was being squirted all over the engine. Arrived back at base leaving an oil slick under the car.

Mike