Author Topic: Fuel injection systems  (Read 46310 times)

Offline Roger B

  • Global Moderator
  • Full Member
  • *****
  • Posts: 3739
  • Switzerland
Re: Fuel injection systems
« Reply #30 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.
Best regards

Roger

Offline Admiral_dk

  • Full Member
  • ****
  • Posts: 1204
  • Søften - Denmark
Re: Fuel injection systems
« Reply #31 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  :)

Offline Roger B

  • Global Moderator
  • Full Member
  • *****
  • Posts: 3739
  • Switzerland
Re: Fuel injection systems
« Reply #32 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.
Best regards

Roger

Offline Roger B

  • Global Moderator
  • Full Member
  • *****
  • Posts: 3739
  • Switzerland
Re: Fuel injection systems
« Reply #33 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.
Best regards

Roger

Offline Roger B

  • Global Moderator
  • Full Member
  • *****
  • Posts: 3739
  • Switzerland
Re: Fuel injection systems
« Reply #34 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.

<a href="http://www.youtube.com/watch?v=2cG9q194h8w" target="_blank">http://www.youtube.com/watch?v=2cG9q194h8w</a>
Best regards

Roger

Offline Graham Meek

  • Full Member
  • ****
  • Posts: 308
Re: Fuel injection systems
« Reply #35 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,

Offline Roger B

  • Global Moderator
  • Full Member
  • *****
  • Posts: 3739
  • Switzerland
Re: Fuel injection systems
« Reply #36 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.
Best regards

Roger

Offline Roger B

  • Global Moderator
  • Full Member
  • *****
  • Posts: 3739
  • Switzerland
Re: Fuel injection systems
« Reply #37 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.
Best regards

Roger

Offline Admiral_dk

  • Full Member
  • ****
  • Posts: 1204
  • Søften - Denmark
Re: Fuel injection systems
« Reply #38 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

Offline Brendon M

  • Full Member
  • ****
  • Posts: 136
  • Melbourne, Australia
Re: Fuel injection systems
« Reply #39 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!
(This signature intentionally left blank)

Offline Roger B

  • Global Moderator
  • Full Member
  • *****
  • Posts: 3739
  • Switzerland
Re: Fuel injection systems
« Reply #40 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.
« Last Edit: September 26, 2015, 07:22:26 PM by Roger B »
Best regards

Roger

Offline Roger B

  • Global Moderator
  • Full Member
  • *****
  • Posts: 3739
  • Switzerland
Re: Fuel injection systems
« Reply #41 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.
Best regards

Roger

Offline Roger B

  • Global Moderator
  • Full Member
  • *****
  • Posts: 3739
  • Switzerland
Re: Fuel injection systems
« Reply #42 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.
Best regards

Roger

Offline cfellows

  • Full Member
  • ****
  • Posts: 1700
Re: Fuel injection systems
« Reply #43 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
So many projects, so little time...

Offline Roger B

  • Global Moderator
  • Full Member
  • *****
  • Posts: 3739
  • Switzerland
Re: Fuel injection systems
« Reply #44 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.
Best regards

Roger