Model Engine Maker
Engines => Your Own Design => Topic started by: Roger B on December 16, 2018, 09:31:44 AM
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A Junkers pattern opposed piston 2 stoke diesel has been on my build list for some time. I now think that I am close enough to getting my horizontal diesel to run to start on the design for this.
The prototype is the smallest of these engines with 65mm bore and 90 + 120mm stroke which was used in tractors and boats and was manufactured under licence by CLM in France.
There are a number of interesting design features:
The unequal strokes are supposed to allow better port timing. This will require some simulations to reach a suitable design.
The scavenge pump is mounted on top of the top piston and is square. I think this will have to be redesigned round even if this reduces the capacity.
The top of the liner is unsupported and the ports open directly into the crankcase.
The top bearings on the pullrods are ball races, I assume due to borderline lubrication
I am basing my design on a 25mm bore which gives strokes of 35 + 46mm. This will give a liner around 135mm long which I think I can bore using an idea from Jason B of an asymmetric boring bar mounted between centers and the liner clamped to the saddle. The crankshaft also appears possible. Checking on the lathe the clearance over the cross slide is 33.5mm rather than the 31mm in the manual. That extra 2.5mm will allow me to use a chucking piece supported by the tailstock.
I do also have the option of reducing the bore to 20mm but from the diesel point of view the larger the capacity the better.
I am planning to fabricate the cylinder block and crankcase from steel rather than carve it from aluminium so I need a bit of welding practice first.
The outline design is attached in .dwg and .pdf
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Hi Roger,
looking good, I am ready to watch every posting.
What a challenge.
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Good luck Roger :)
Jo
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Hello Roger,
Very ambitious project, I to will be following along.
Have a great day,
Thomas
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Same here Roger. should be a great project!!
Bill
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A modern version was built by Eco Motors. As far as I know, they're not in business anymore. They had a large version with an electrically boosted turbocharger and a small version with piston pumps. See the attached files for the small version..
Lohring Miller
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Very interesting project Roger! :popcorn:
I'm looking forward to follow along on your progress. :ThumbsUp:
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Thank you all :ThumbsUp: :ThumbsUp: I like a challenge :wine1:
Lohring, I shall have a good look at those papers thank you :)
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Nice sweet running engine
I have owned one left over WW2 that worked 20 years in abrick factory.
They were made 1,2 and 3 cylindered and used as generators on some danish ligthships.
https://www.youtube.com/watch?v=jUQ_OFa-WKw
from ca 39:00.
The upper crosshead/scavenge air piston cannot be cirkular without making the two paralel side conrods figth instead of sharing work
Last minute of video is interesting
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Thank you for the video Niels - I wasn't aware of an engine museum in Rødvig, but after my dad moved to Nødebo. I sometimes take the ferry from Rødvig to visit him, so I will definitely visit it in the future.
I do not see any transfer port in the previous drawings - is that through the upper scavenge piston down towards the upper piston and out the sides of it into some short transfers ?
As I said elsewhere, you're in for a challenge here Roger - one I very much would like to follow and hopefully see run in the end.
:cheers: :popcorn:
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Thank you for the video Niels - I wasn't aware of an engine museum in Rødvig, but after my dad moved to Nødebo. I sometimes take the ferry from Rødvig to visit him, so I will definitely visit it in the future.
Museum is in Rødvig ,not Rørvig.
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Thank you for the warning.
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Thank you for the video Niels :ThumbsUp: I have a short clip from somewhere else of the coin balancing on the same engine. The top piston and pull rods must be heavier than the bottom piston but the stroke is less :headscratch: Has someone done something clever :headscratch: ::) :headscratch:
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Per, as far as I can see there are no transfer ports as such. The scavenge pump fills the complete crankcase and the short inlet ports at the top of the liner are the effective transfer ports :headscratch:
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There is a longer paper on Eco Motors big engine. The most interesting feature to me was the electrically boosted turbo. It's too large to post here, however.
Lohring Miller
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I have given this a bit more thought. The basic dimensions will be taken fron my horizontal diesel, the short connecting rod will be identical but the long pull rods are in tension so all the firing load is on the big end bolts. I did some stress calculations for the horizontal engine which gave a good safety margin with M3 bolts but I think these will have to be increased to M4. As the stroke is shorter the additional width of the bearing won't require a bigger crankcase. As the rods are in tension buckling won't be a problem so I think they can be reduced to 8mm diameter. The big ends will be reduced to 10mm wide to keep the crankshaft as short as possible.
I had a dig through my material stocks and have a cylinder block, cylinder liner, crankshaft and pistons.
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Roger,
Here is another OP diesel engine design from Achates Power currently in a joint research project with Cummins Engine Co. for development of combat vehicle engines for the US Army. It is a compact engine following more contemporary engine package design features. It does use a blower for scavenging which might complicate a smaller model engine design. Watch their video.
Jeff
http://achatespower.com/our-formula/opposed-piston/
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Thank you Jeff :ThumbsUp: There seem to have been many attempts at opposed piston engines but they have only been successful in larger sizes :(
I am slowly working through the design. I now understand the square scavenge piston :) It is so the ends of the pull rods for the top piston can go into the scavenge cylinder and reduce the height of the engine (and the piston).
The next step is to work out a governor design. It is mounted on a vertical shaft in the front part of the crankcase driven by a pair of helical gears. The principle is similar to the one I was experimenting with for the horizontal diesel:
http://www.modelenginemaker.com/index.php/topic,5545.195.html
In this case the bottom plate is mounted on a bearing and the balls are driven by a spider keyed to the shaft. A PDF of the principle is attached. I think I will have to make a trial version. The shaft is 6mm diameter and the overall diameter is 32mm with 6 6mm diameter balls.
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As I continue with the drawings the governor is a key part of the front of the crankcase so time for experiments :)
I decided to make the drive spider from Delrin and the thrust plate and cone will be steel (case hardened if it works ::) ) The basic form was turned and the keyway cut. As it was Delrin it just needed finger pressure on the broach :) The blank was mounted on a short length of 6mm rod with a key slot and put in my Proxxon RT. I cut the slots with a 6mm 3 flute end mill in two steps.
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A quick check with some 6mm ball bearings and onto the cone. This and the thrust plate were turned from a length of 35mm free cutting steel. The thrust plate was polished before parting off. Next the cone was reversed in the 3 jaw chuck using a couple of parallels (6mm HSS tool blanks) to keep it in line with the face of the chuck.
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The cone was then drilled 9.8mm and reamed 10mm. The cone itself was turned using my little top slide. I used the body of a square to align the thrust plate at the front of the chuck so it could be faced and then moved it back for drilling and boring.
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And due to the 8 picture limit
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That’s an ingenious, compact design, Roger. It will be interesting to see how it performs, and how much force it can produce on the levers. I assume the top cone also spins so the balls only move in and out?
Still following and enjoying.
MJM460
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In this version the top cone is fixed so it is it's own thrust bearing. The thrust plate will rotate at twice the shaft speed. I tried a couple of other variants in my diesel thread. This design is the same as was used on the full size version of the engine.
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The bronze bush was turned, pressed in place and reamed again. The sleeve was made from 8mm silver steel, hardened and polished. I made a trial shaft from 6mm silver steel and cut a 2mm keyway to drive the spider.
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I drilled and tapped an M3 hole in the side of the cone to be able to apply a load and assembled the system for a trial in the bench drill (it has a speed indicator). With the two springs I was using it would lift between 2000 and 2500 rpm depending on the preload (set by winding the table up and down).
https://www.youtube.com/watch?v=kuLW0hDWwog
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That works pretty well! :ThumbsUp:
Kim
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As my diesel trials were not as successful as I hoped I moved away from this project. Now I have running diesel I have restarted. Along the way I have picked up various pieces of information and pictures of the engine components. There are a number of different variants with different configurations. Some appear to have round scavenge pistons, some have the inlet ports at the bottom and the exhaust at the top. Some have a closed transfer port system, others fill the complete crankcase.
I have decided to keep to my original prototype of the sectioned engine with the open inlet ports but with the bore reduced to 20mm to make machining easier with my lathe. Studying the other information I have collected and thinking about the design has shown me a number of things:
1) The scavenge piston is coupled to the shorter crank throw. This means that the area of the scavenge piston must be at least 2.5 times the area of a working piston. This fits fairly well with the scavenge cylinder fitting around the pull rods for the top piston.
2) The slots for the top piston yoke are carried on below the inlet ports. This allows the length of the piston and the total height of the engine to be reduced. This is visible in the cutaway picture.
3) The forces are not insignificant. The 40 bar compression pressure of my horizontal diesel gives a load per piston of 125kg. If the combustion pressure is 80 bar that is 250kg per piston. The bottom connecting rod is based on the horizontal engine so that will be ok but the design of the pull rods will need some calculation. The rods themselves are in tension so will be free from buckling problems but the loads on the top bearings and the big end bolts may be a problem.
4) Some versions have a float chamber feeding the injection pump but I don’t understand what this is for.
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:ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
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I
still have just found some tech info on this engine type :
https://www.thesahb.com/technical-talk-3-1929-junkers-diesel-engine-for-cars/ (https://www.thesahb.com/technical-talk-3-1929-junkers-diesel-engine-for-cars/)
So I'm finally wise to how the Intake / Transfer took place - see middle of page + text.
I find your example of the Injection pump peculiar Roger .... It appears to have both an adjustment for the stoke, by moving the roller hinge sideways + the modern turning the piston to change the inlet port height too :headscratch:
Oh and no - I can't explain the float very well either Roger - but I'm glad to see you back on this one again :cheers:
Per
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:popcorn: :popcorn: :cheers:
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That's cool!!! I'll be watching Roger! that's a neat engine!
Dave
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Hello Roger, I have now discovered your construction report for the Junkers engine. An interesting project.
In my stable there is a 1 HK 65 with a 7.5 Kw generator. And I've been waiting for a power outage for a long time 😁.
It could be that I still have a spare parts list for the operating instructions.
If it helps you.
Greetings Michael
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Thank you all :ThumbsUp:
Michael :) I have a rather poor PDF of the spare parts list for a 1 HK 65 (NDZ 9/12) and some French operating instructions for what CLM called a CR1. More information is always welcome :cheers:
Per, the French information I have suggests that the helix part was used by the governor in the conventional way to control the speed and the other rocker roller on the cam was used for stopping.
I have attached the current state of the design, some way to go ::)
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Finally cutting some metal. The crankshaft is made from 60 x 15mm key steel which I have used before but the design of this shaft is on the limit for my Hobbymat (I can cheat if I have to, but model engines should be made on my machines). Marking out is also stretching my equipment but so far all is ok.
Hacksawing the waste away is somewhat of a change from fuel injection systems :)
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:ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
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Hello Roger,
I watch with interest.
Especially if someone is still sawing by hand.
Greetings Michael :cheers:
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Off to a good start. Hope you're enjoying the part size "paradigm shift"! I'll be following along for sure. :popcorn:
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It's fun to mix it up a little bit, isn't it! :D :popcorn:
Kim
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Thank you all :) It is fun to play with some (relatively) big stuff for a while :ThumbsUp:
A bit of 'dodgy set ups are us' machining of the exhaust crankpin. OK at 500 rpm for the webs and 250 rpm for the crankpin.
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On with hacking out the crankshaft. For the outer two crankpins I need to support the centre webs. This is done with a bolted on bridge piece as before. Some more was hacksawed away and the first outer crankpin was rough machined using a variety of tools to deal with the narrow (10mm) gap.
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:ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
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Great start. Sometimes designs or hobby work need some time to "cook" before to get started. Now you have more knowledge about making model diesel engines! Some crazy opposite engine is something on the list to design.
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On with the crankshaft, it looks to be possible with my lathe.
There are a few more challenges to come ::)
The cylinder liner will be 105mm long, bored 20mm. I may need to look at making a between centres boring bar. The maximum diameter will probably be 15mm so making a fine adjuster for the cutter will be difficult.
The scavenge pump is mounted on top of the upper piston. The original piston and cylinder were rectangular. I could possibly fabricate the cylinder from 4 pieces of flat steel silver soldered together :headscratch: The piston will need to be aluminium on weight grounds. Leakage will not be too much of a problem on the compression stroke as it will be leaking into the crankcase that it is filling.
The valves for the scavenge pump are also difficult to fit into the space. I am looking at fitting reed valves to the underside of the piston as delivery valves, the suction valves can then be mounted on top of the cylinder. The original appears to use disc valves. I have some carbon fibre reeds that I bought when working on the two stroke diesel that I may be able to adapt.
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I may need to look at making a between centres boring bar. The maximum diameter will probably be 15mm so making a fine adjuster for the cutter will be difficult.
A fine adjuster would be nice but not really necessary, since the piston can be sized to fit? I've had success in the past with such a boring bar. Takes a bit of patience, but we all know you have that covered! Looking forward to learning from your solutions to the various challenges to come. :cheers:
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Hello Roger,
I checked the parts list. It is also just a paper copy. But maybe this will be of use to you.
If you need specific parts to view let me know.
Greetings Michael
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Thank you Michael :ThumbsUp: That looks similar to the copy I have. I will let you know if I need any details. I will have to change a few elements of the design to allow for the small scale and for fabrication rather than castings.
On with the crankshaft. I have had to use a variety of tools for turning the crankshaft due to the small size of my lathe and the deep slots between the webs. The full stroke of the crankshaft is 65mm, the same as the centre height of the lathe ::)
https://www.youtube.com/watch?v=nBqRCy_7ZXE
The first section of shaft I turned ended up with a rather poor finish although the earlier cuts looked ok :( This is not a critical problem as I still have 1 mm left for the finishing cuts. The set up will also be more rigid as the opposite shaft will be held in a collet chuck rather than between centres.
I received a parcel with a huge warning label stating 'Fragile' and 'Open immediately and check for damage'. The contents: 25mm and 35mm cast iron for the cylinder and pistons and aluminium plates for the crankcase ::)
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Hello Roger,
the crankshaft looks very good. 👍 For me, this is an exciting work process on this type of crankshaft.
And was something broken in the package?
Greetings Michael
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Crankshaft is coming along well. It's always fun to get small machines to a good job of big jobs! Just take care with that fragile cast iron. :Lol: :ThumbsUp: :ThumbsUp:
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Nice work on that one piece crankshaft! That's a lot of material to remove on that spindly part! Nicely done :ThumbsUp:
Nice to see that your fragile package arrived with all the CI in tact!
Kim
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Thank you all :) Nothing in the package was damaged, it did not pass through the British Postal system or airport baggage handling ::)
I changed to a DCMT tip and got a much better finish on the shafts, I think the original tip may have been worn or chipped but not visibly. Next I moved over to the Keats angle plate to finish the crankpins. The inlet (shorter stroke) ones were ok with a reasonable finish. Next the exhaust (longer stroke one).
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Great to see that you have made progress, while I was on extended Weekend :ThumbsUp:
A very interesting project :Love:
Per :cheers:
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:ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
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you've embarked on a great and very original project, and the crankshaft is already a feat!
I've found quite a bit of documentation in French on this engine, which seems to have been very popular here in agriculture and industrial locomotives...
https://wikimaginot.eu/V70_glossaire_detail.php?id=1000986
http://vieux.tracteurs.free.fr/pdf/moteur_CLM_type_LC_et_CR.pdf
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Thank you very much for the Service Manual Zephyrin :LittleAngel: :ThumbsUp:
That explains a lot more than what I've seen so far + much more if I understood French better :embarassed:
Per :cheers:
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:ThumbsUp: :ThumbsUp: :ThumbsUp: Thank you for those links Zephyrin :) :) CLM and Peugeot seemed to produce a lot of these engines in smaller sizes, Junkers developed them as the Jumo aircraft engines and Napier then produced the 18 cylinder Deltic.
There are some interesting features of the design. The two different length strokes seem to give a balance to the engine that I have not really analysed:
https://www.youtube.com/watch?v=yi2XD8PY5dk
The exhaust crankpin was clocked true and finished to 12mm and then on to the oilways. The 2.5mm dia. 57mm long holes through the shaft were my biggest worry but they were ok. As the stroke on my tailstock is only 40mm there was a lot of sliding in and out to clear the swarf. The only big problem was drilling one of the inlet crankpins, the drill dug in when breaking through but luckily just bent.
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Reaching some of the holes required a variety of tools and threading for M3 grub screws will also be fun ::) I think I will have to make a special tap holder for the inlet crankpins :thinking:
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Ouch on the bent drill bit, Roger! Glad it didn't ruin anything!
Were you able to straighten it and use it more? Or did you have multiples of that drill in stock?
Kim
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Close call on the Drill Bit :hellno: - glad it didn't ruin anything :cheers:
The Crank looks to be very nicely staight and smooth :ThumbsUp:
Per
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Thank you both :)
I broke and then binned the bent drill, too much risk otherwise ::) I bought 4 originally as I felt they would be 'disposable'. The next step was to tap the ends of all the oilways M3 for sealing grubscrews. As expected I had to make a special tap wrench for a couple of the holes. Finally I drilled the oil holes to the journals. This now defines the orientation and rotation direction for the crankshaft.
I have been thinking further about boring the liner. By the time there is a revolving tailstock centre and some means of driving the boring bar there is barely enough space. As it is not actually a single cylinder but two separate cylinders with a space between them I could bore from both ends in the usual way. With careful clocking of the outside of the liner any final errors would be removed by lapping.
The connecting rods have required some thought. Assuming a peak pressure of 80 bar the load per piston is 2500N. The exhaust piston (single) connecting rod is copied from my other diesel and should be ok. For the inlet piston (twin rods) this is 1250N per rod if all is balanced. For the bearings at the top of the rods I am looking at some model RC car units with a dynamic load of 1321N and a static load of 530N, a bit close but we will see what happens. The big end bolts will be M4 in a 6mm wide rod. The proof load is 5100N (8.8) which with 2 bolts per rod is fine. I could reduce to M3 with a proof load of 2920N (8.8) which still has a good factor of safety.
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Hey don't be glossing over that faceplate fixture! Looking for details here!
8)
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Roger, I like your special tap wrench! Very nice ;D
I'll be interested in how you do this on your lathe. I can see that it is a little challenged in the bed length department... I'm sure you'll figure out a way! :ThumbsUp: :popcorn:
Kim
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Thank you Kim :)
Dave, I guess you mean the Hemingway Keats Angle plate:
https://www.modelenginemaker.com/index.php/topic,4275.0.html
An excellent tool/accessory for a small lathe :ThumbsUp:
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Great progres again :ThumbsUp:
I have two comments :
1) The ballance of the different strokes probably matches the fact that the Inlet-Double Piston is a lot heavier than the longer stroke Exhaust Piston ....
2) I'm not comfy with the close match off Max Load allowed on the Top Bearings, and the Calculated Load ....
Any Pre-Ignition or too much Fuel - and you will have a Catastrofic Failure :zap: :cussing: :'(
Just my two Cents (for what ever they are worth) ....
Per :cheers:
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Impressive work on the crankshaft Roger!
I have one similar to that in my future, taking notes here.
Dave
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Thank you :ThumbsUp:
I'm not too worried about the load rating of the bearings as that will be for a defined life span rather that than being the ultimate load. Here the the potential side connecting rod and bearing, plenty more machining to do ::)
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A start on the cylinder liner. This is a piece of cast iron rod. I marked one centre with it resting on V block, marked it and cut it to length with the bandsaw. The other end was then centred and both ends were drilled.
I didn't have a big enough driving dog so I improvised with a 38mm exhaust pipe clamp ;)
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A little bit more on this. The outside was roughed out from one end and then the blank was turned around. Unfortunately the tool dug in (hard spot?) and cut a groove. This doesn't look good but will be turned off at a later stage. It was then finished to size using an aluminium insert.
The blank was then set up in the four jaw chuck, drilled 5mm from both ends with a standard drill and then finished through with long series drill. The hole was then opened out to 15.5mm using the bench drill.
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The cylinder was then set up in the four jaw chuck with the fixed steady and was faced to length. It was bored to 19.5mm from each end and than finished to 20mm. The lap just enters and the 20.1mm plug gauge wont go in.
As with the outside there is a visible difference in the cutting from both ends but no discernible step.
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That is a rather thick walled Liner - will you be removing more material on the outside, before it is finished ?
Still following this interesting build :popcorn: :cheers:
Per
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Hello Per,
There are inlet and exhaust ports as well as water spaces to be machined from the liner. It's easier to turn from the outside of the liner than to bore in the cylinder block.
Next up is to rough out the sections of the cylinder block. There is a long section that surrounds the liner, a short piece around the inlet ports, a cast iron section for the scavenge pump cylinder and finally another aluminium section for the scavenge pump inlet valves.
I was quite pleased with the similarity of the sectors sawn from the round scavenge cylinder blank. I am sure they must have some use :thinking:
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Slow progress carving out the various parts of the cylinder block. After some experimentation I ended up with a 16mm roughing end milling cutter and 1mm depth of cut. There was not sufficient travel to use a flycutter.
https://www.youtube.com/watch?v=EsDqwiQb_8E
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:ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
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Nice to see some progress, Roger! :ThumbsUp: :popcorn:
That's a pretty beefy chunk of metal for your cylinder block! :Lol:
Kim
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Thank you both :) The block will get smaller over time.
The next step was to set the block in the four jaw chuck to core drill out the bulk of the material. My hole saws will reach a depth of 40 mm so the 79 mm high block was on the limit cutting from both ends (but planned so). It is easier than drilling out when the tailstock travel is only 40 mm. There is also very limited clearance between the chuck jaws and the bed, but again I knew I can hold 60 mm in the full jaws. As Chris Rueby often demonstrates with small machines careful planning is required.
The centring was checked again, not easy on a square workpiece, but seemed top be within 0.1 mm so OK and the block was bored out to 34 mm to be a running fit on the cylinder liner. All the sealing between the liner and the block will be with O rings.
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More of your always nice work, Roger. I like the use of a hole saw to rough out the bore. The picture of the chuck jaw just clearing the bed looked very familiar; been there done that! :ThumbsUp: :ThumbsUp: :cheers:
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Nice work, Roger! :ThumbsUp: :popcorn:
That's a LOT of work on a little machine like that. You're certainly stretching it to its limit!
Kim
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impressive work with the cylinder block Roger, whew!
this little hobbymat is a rather man machine !
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Thank you all :ThumbsUp: :ThumbsUp:
The next step was to turn the various grooves for the port belts, water passages and O rings. First I turned a centring plug so I could support the liner with the tailstock. The water passages and exhaust port belt were cut with a 2.2mm parting/grooving tool. There were some chatter marks but they are not a problem.
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The O ring grooves were cut with a 1.5mm Aplitec tool. There was again a little bit of chatter which cleaned up easily with a square Swiss file. The liner was then turned round to machine the inlet port belt. Still a lot of bits to go ::)
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The liner is looking good, Roger! Nice photos showing the sequence of your work. :ThumbsUp: :popcorn:
Kim
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That was rather more involved than most cylinder liners. Nicely done! :ThumbsUp: :ThumbsUp:
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Plenty of oppertunety for things to go wrong here - so I'm sure you are happy that there were no mishaps so far :ThumbsUp: :ThumbsUp:
Do you put five O-Rings on the liner, or ...?
Per :cheers:
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Thank you all :) Per, there are five O rings as the top of the inlet section is open to the scavenge pump.
The next step was to fix the liner to the cylinder block. Due to the design of the engine there is very little load on the liner so I decided to hold it in place with a tapered dog point grubscrew. The tip is tapered from 3.8 to 4.2mm and the hole in the liner is reamed 4mm. The injector is mounted opposite so I drilled 5mm for the nozzle, cut an 8mm recess for the O ring and then opened out to 10mm to clear the nozzle clamping nut. There is some more work to be done for the injector fixings but that will come later.
The next step is to mill the angled inlet and exhaust ports. Luckily using a Proxxon V block I need a simple 12mm spacer under the small Proxxon RT.
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The liner was set up in the Proxxon mill and offset from the centre line to create the angled ports. These were cut with a 3mm carbide end mill at 6000 rpm in 0.5mm steps. The inlets and exhausts were machined at the same settings, the exhaust ports are 1mm longer. The liner was then further offset to cut a chamfer on the inlet ports.
This could have been done on the Hobbymat mill but it's much easier to see what is going on with the little one.
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Next I moved to the Hobbymat mill to cut the slots for the top piston yoke. This was cut in 0.5 mm steps.
Now there is some deburring and smoothing work before lapping the bore.
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A little bit more progress. I had to remove the milling head to repair the controls for the lathe and assumed that removing and replacing the round column from its socket would not upset things too much.
Unfortunately it was way off true :( I did a quick check with an angle plate an DTI and it appeared that the head had tilted so I did a quick basic realignment with a ground rod and the angle plate.
The cast iron block for the scavenge pump was squared up next. This will be my next challenge as it requires a precise rectangular cut out for the scavenge piston ::)
The clearance slots were for the pull rods were cut in the inlet block and it was set up for boring.
https://www.youtube.com/watch?v=0tDWx67H7qU
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Great to see another instalment of this special saga - you do pick the less traveled roads Roger :ThumbsUp:
Funny to think that this kind of engine was very common back in the day - yet most people (including myself) had never heard of the type, as a small workhorse ....
Per :cheers:
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Sorry for your setback there Roger, and having to re-tram the mill head. But it's good to know it's square now!
Enjoying watching your progress. :ThumbsUp: :popcorn: :popcorn:
Kim
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Thank you both :ThumbsUp:
I am slowly working my way through the cylinder assembly. The inlet block was bored out to 34mm and the fixing holes were drilled 4.2mm so they could be spotted through to the cylinder block. I then opened the holes out to 5mm and spotted them through to the scavenge pump section.
The next step was to bolt the inlet block to the cylinder block so I could mill the slots for the top piston yoke. It would have been easier to make them in one but it would have bee too long to bore on the Hobbymat. The 8mm slots were milled in one setup with a long series 8mm end mill.
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Next the water cooling ports were drilled to link the two cooling jackets. The top and bottom will be joined by a vertical hole and the open ends will be plugged. The exhaust port was drilled 8mm and then the port band was then opened out using a 20 x 8 mm T slot cutter. This was a bit on the limit for my machines but seemed to work ::) Now the exhaust needs to be opened out to 10mm and there is some work with riffler files to smooth and blend all the edges.
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Hello Roger,
nice progress.
It's always surprising what can be done with small machine tools.
Greetings Michael
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That is a very wide Port - I'm guessing that you don't plan to use Piston Rings .... or will it get a sleeve inside ?
Good to see that the project is going forward :ThumbsUp:
Per :cheers: :popcorn:
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Thank you both :ThumbsUp: Per, yes there is a cylinder liner, That is just the collector from the actual ports.
Next up was milling a recess for the injector in the cylinder block and drilling and tapping various fixing holes.
Having been thinking for some time how to hold the top of the crankcase for milling to size I realised I could drill two fixing holes where the slots for the pull rods for the top piston would be. This allowed me to machine one side and one end at the same setting which would ensure they are at right angles to each other (I know that in theory the cross slide on a lathe is not quite true to ensure that surfaces are turned slightly concave but I don't think this will matter). I was able to use the power feed on the lathe when cutting the long edge :) I know I should really have taken the chuck off but there was enough clearance ::)
https://www.youtube.com/watch?v=ND03Spe3BV8
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Roger, it always impresses me; the incredible work you do on that little machine! :popcorn:
Kim
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Thank you Kim, I think Chris Rubey must be the master of small machines though :ThumbsUp: :wine1:
I finished milling the crankcase top and then out of interest checked it for accuracy. It is square to the limits of my equipment, a couple of hundredths of a mm under size on the width and flat/parallel to a couple of hundredths as well :) I'm happy with that.
https://www.youtube.com/watch?v=PyFGa-grlbs
Next I centred the bore for the cylinder liner and cut the bulk away with a 29mm hole saw. I am tempted to cut a bit more off the length of the boring bar but the chatter does not seem to be too bad.
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And it all seems to fit together :)
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Nice work Roger, it's coming very well. I find that shapely cylinder liner interesting to just look at! :wine1: :cheers:
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Thank you Ron, All those who think two stokes are simpler to make than four strokes should look at that liner ::) Everything is in that. If the timing is wrong I can't just modify a camshaft it's a complete new liner :(
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Hello Roger,
I also have a centrifugal pump on the Junkers engine.
It is mounted on the frame.
This is an engine with generator and cooler and everything is attached to the frame.
Michael
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Thank you for the pictures Michael :ThumbsUp: Is that an electric control of the governor in the second picture or just start/stop?
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Hello Roger,
yes, that is a magnetic switch. He switches the engine off again.
The engine with generator was in a signal box for switches and signals on the railway. It served as a backup in the event of a power failure and switches on and off automatically. But for me the only option is to start by hand.
Greetings Michael
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I have a Kohler direct lighting set that is currently in a museum in Southern England. It is designed to start when a load of 40W is applied and shut down when the load is reduced below this. As it delivers 110V DC it is not that much use in Europe.
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On with cutting the plates that will make up the crankcase. Due to my small milling table and limited Y travel the set ups took a bit of thought but I was able to mill two sides in each set up and all ended up square and on size. Next I cut the slots for the pull rods for the top piston. These were roughed out with a 10mm slotdrill and finished with a 6 mm endmill.
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Ready to start drilling and tapping for the fixing screws.
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Good to see that you are making progress and really good to confirm it all ligns up as it should :ThumbsUp:
I also see where you got some of the inspiration from - though having it home to look and measure from might be a bit more conviniant than it being in a British Museum ;)
Per :cheers:
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It often seems that the number of steps (and time) required is inversely proportional to the size of the machines. I always enjoy the examples you offer of how to get the most from what you've got. Nicely done!:ThumbsUp: :ThumbsUp:
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Yes, what Ron said! You get a lot done with your small machines! Very impressive. :ThumbsUp: :popcorn: :popcorn:
Kim
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Thank you all for the support :ThumbsUp:
First a mistake :( I picked up the centre plate rather than the endplate and drilled a set of holes in the wrong place :facepalm2: Not a disaster as they are not in an important place and can be plugged.
Lots of aligning pieces then drilling and taping, this time marking the pieces for identification and orientation. When the three plates for the crankcase were screwed together it would stand on the surface plate without rocking :)
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The next step was to bore out for the crankshaft. The centre plate just has a 16mm hole that the bearing will be pressed into, the endplate is bored out to 55mm for a bearing housing to allow the crankshaft to be fitted and removed. The plates were clamped together and drilled and reamed to 16mm. the centre plate was then removed and the end plate was re-centred using the reamer. I used my largest hole saw to remove as much as possible and then bored out to 55mm.
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Hello Roger,
It's all starting to come together and we can see an engine emerging. Quite a robust structure, must be testing your small mill/lathe,
Mike
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Thank you Mike,
Yes, each design stage is a challenge both for how the engine will work and how I can make it. I started out thinking about a 25mm bore version but too many parts were just too big. The 20mm bore version is ok so far but I have had to make the cylinder block in two pieces due to my limited boring capabilities. The next big challenge is the rectangular scavenge piston and cylinder. I have a few ideas of how I could make the cylinder but I am tempted to take the easy way out and have it made at work (EDM?) to reduce the level of uncertainty when I finally try to start the engine.
I am currently sorting out the lubrication system which has an interesting 3 gear oil pump so it can scavenge oil from the main crankcase and the governor/fuel pump section. Not quite as complicated as your MB system but something to think about :thinking:
Next up is the main bearing housing. This starts as a dog end of 70mm aluminium which was turned to fit the endplate. It was then drilled 13.5mm bored out to around 15.7 mm and them reamed 16 mm. There was a bit of chatter but it is only the housing for the main bearing. After some fairly heroic parting it was ready to finish the other side.
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Hi Roger,
chips again.
I enjoy the progress.
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Interesting solution to your 'Getting the Crank Into the Engine' and closing the hole again :ThumbsUp:
I have never seen an Oilpump with three Gears before - but as the sketch shows - you do end up with a two scavenge and (kind of two into) one pressure Out :thinking:
I can't blame you if you decide to use the Company Tools (EDM) - as it will not be an easy task to make @ Home ....
Per :cheers:
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The three gear pump is interesting, saves 1 gear at the expense of a less intuitive oil routing and possibly tighter tolerances (or tolerance stack up)?
Also interesting is to think about failure modes. If no oil is supplied to one pump intake, it can be viewed that both pump halves will have 1/2 as much oil but still have oil all the same. How the pump performs in this case I don't know, maybe its intentional (i.e. some is considered better than none)?
Mike
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Thank you Mike,
I am currently sorting out the lubrication system which has an interesting 3 gear oil pump so it can scavenge oil from the main crankcase and the governor/fuel pump section. Not quite as complicated as your MB system but something to think about :thinking:
Roger, as you say, an interesting and innovative 3 gear scavenge pump arrangement. I guess the sump will be providing mostly liquid oil, whereas the flow from the governor/fuel pump section will likely be an oil/air froth. Gear pumps are usually quite happy on a diet of air and oil, so I would not expect any scavenging issues.
Mike
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Thank you for all the interest :) :wine1: The oil system on this is quite interesting, it appears that the top piston and scavenge pump are lubricated by oil mist. I don't see where the oil for the governor fuel pump section comes from other than the centre main bearing :thinking:
A quick family picture with the governor I started some years ago.
Next step some main bearings.
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:ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
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Thank you Jeff.
The bearing housing was then centred in the Proxxon drill using a stub of 16mm silver steel and offset the required 31mm. The holes were drilled through with a 3mm spotting drill. These were then spotted through to the endplate and tapped M3. A length of 16mm bar fitted smoothly through the bearing bores :)
The main bearings are turned from RG7 bronze. They were drilled 6mm, then 11mm, bored to 11.5 mm to ensure the concentricity and then reamed 12mm.
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The two main bearings were completed and then pressed into their housings. Due too the interference fit they needed to be reamed again. Luckily my planning was correct and the centre plate could be held in the 3 jaw chuck. I assembled the crankcase and the crank turned fairly smoothly :)
https://www.youtube.com/watch?v=wh_XvW12ZZY
Next the oil grooves were cut with a 3mm radius tool to a depth of 1 mm. Access was a bit awkward but the small compound slide just fitted. Finally I drilled the oilway for the centre main bearing. The end bearing housing needs a slightly more complex setup.
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Making nice progress, Roger! :ThumbsUp: :popcorn: :popcorn: :popcorn:
Hope that's not blood up there in post #118 (third picture down, just below the ball-peen hammer?)
Kim
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Thank you Kim :) That's just red marked pen to keep the orientation until I make some permanent marks.
Due to my small machines I could not make a long enough crankshaft so now I need to add an extension to drive the water pump etc. As the crankshaft was in the lathe I turned a small radius on the webs to make it easier to fit into the crankcase. The extension will be in two parts, a sleeve and a sacrificial extension shaft. I chewed up the end of the crankshaft on my diesel trying to start it and expect similar problems with this engine so I shall make it replaceable. The starting dog is not keyed to the shaft, just clamped, to act as a mechanical fuse.
The end of the crankshaft was turned down to 8mm and a 12mm sleeve was drilled and reamed to fit. The sleeve was then broached for a 2mm key. It will be Loctited to the end of the crankshaft and the extension will use the same key but be held in place with a couple of grubscrews.
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Hello Roger,
An ingenuous way to extend the shaft to compensate for the small size of your lathe. Excellent !! :ThumbsUp: :ThumbsUp:
Will there be an outboard bearing to support that long shaft?
Mike
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Thank you Mike :) Yes there will be a ball race fitted in the end plate to support the shaft.
The keyways in the crankshaft and extension were cut using the small Proxxon mill. This was also used the mill a flat for the grubscrews. Two M2 holes were drilled and taped in the sleeve using the Proxxon drill. After a trial dry assembly the sleeve and key were fixed to the crankshaft with Loctite 648. This will be allowed to dry completely before I try the extension piece as I don't want it getting stuck in.
A quick check showed the run out on the shaft and sleeve to be the same, around 0.1mm, probably due to a bit of stress relief in the C45k that the crankshaft is made from.
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great thread on the built of this engine Roger, as always...
I wonder how you succeed to mill steel shaft with such a flimsy cross table, hats off to you !
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:ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
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Thank you both :)
Zephyrin, it actually works well, it is just in a completely different range to 'normal' milling. This was done with a Proxxon 2mm carbide end mill running at around 8000 rpm. Depth of cut was 0.2mm and the feed was as fast as I could turn the handle. It would have taken more depth of cut but I wasn't in a hurry.
I fitted the extension into the crankshaft nose and tightened the two M2 grubscrews with a key about the size of a paperclip. I seems to run true :)
https://www.youtube.com/watch?v=oxWnaVTn-gE
Next up is the side connecting (pull) rods, another part on the list of things that are too big for my machines. These will be made in two pieces, the big end with be fixed to the rod with an M6 x 0.5 thread and Loctite. I am modifying the original with a three piece big end so I can fit shims to adjust the top piston position. The prototype only has shims on the lower connecting rod.
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:ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
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Before I made a start on the connecting rods I made the oil connection for the main bearing. This was set at the correct orientation and angle using the angle vice my father made as an apprentice :) I started with a 6mm centre cutting end mill followed by a 2.5 mm drill through into the bearing. Not quite into the middle of the oil groove but fixable with a rifler file. The hole was then opened out to 4.5mm and taped M5 x 0.5. Finally I milled a flat for the sealing washer.
On with the conrods.
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Nice work Roger. :ThumbsUp: :ThumbsUp:
I see you have wisely put some tissue into the headstock taper, but do you ever get swarf ingested into the fan of that motor alongside it?
Cheers
Mike
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Lots of excellent progress, Roger. Nice to see the picture of the full size example, especially the piston/rod assemblies laid out. :ThumbsUp: :ThumbsUp: :wine1:
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Thank you both :ThumbsUp: Mike, the long swarf tends to go the other way so no problem. I believe the lathe originally had a filter on the end of the motor but this stopped the chuck jaws being fully opened.
On with the con rods. The little ends were marked and then drilled and reamed 6mm to act as a reference. Next the ends were marked and centre drilled so the rod could be turned down to 8mm. Finally the end was turned down to 6mm for the M6 x 0.5 thread to fix the big end assembly in place.
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Now a not unexpected problem :( When I designed the sealing O rings between the cylinder liner and the cylinder block I went for 1.5 x 31mm rings. I knew from the O rings I used in sealing the helix fuel injection pump that there was a risk of the O ring being damaged by the various openings in the cylinder block.
The various ports were carefully radiused and smoothed. The first trial O ring passed through undamaged but the subsequent attempts were broken, sometimes in more than one place. One piece had gone down one of the water passages.
There are several possible solutions:
- Glue the O rings into the grooves so they can't drop into the openings.
- Open out the grooves and use a 2mm section O ring.
- Seal the liner with an appropriate Loctite type liquid.
Still thinking about this one :thinking:
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Hi Roger
The most obvious culprit is the Exhaust Port in my book. It is big enough to let the O-Ring 'fald out' of it's groove => resulting in a Cut much closer to 90 degrees, than one should think possible :censored:
I have sometimes successfully used Grease to 'lock/park' the O-Ring during assembly ....
Call off Nature ....
Sitting on the Throne (some do their best thinking there) ...:
... No the Grease won't work here .... Need to plug the big Ports and other places the O'Ring can 'drop into' (the small ones can usually be ignored) .... 3D Print stoppers ...?... they need to be water solvable ..!!.. (being in the bathroom) how about Soap …?
String some hand soap and apply a drop or two of water to the mix. Apply to all desired places. Press the Liner through (without the O-Rings) to ‘clean’ the bore. Install the O-Rings and mount the Liner into the Cylindercase.
When all is well – soak in hot water for some time, followed by circulating tap-water under normal preasure through every single Port and hole, to get rid of the rest ….
Hopefully a fully functional Cylinder assembly that is sealed and flowing in all the right places 😊
Per :cheers:
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That's an interesting idea :) :) I think that it would work to assemble the cylinder once :ThumbsUp: As this is very much an experimental engine I am assuming that I will need to remove the liner at some point for modifications.
Maybe I can develop it to use a low melting point metal/alloy. I have some what I think is tin based from New Years Eve Blei Giesen which hopefully will melt out without damaging the O rings.
Interestingly the damage seemed to due to the two slightly offset water cooling ports at the top of the cylinder. The exhaust port is big enough to see what the O ring is doing.
Development is fun ::)
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On with the pull rods. The second one was turned to 8mm for most of the length and then reduced to 6mm at the end. I then modified a grooving tool I had previously made to give an (approximate) 0.5mm radius. This was then used to cut a stress relief groove for the end of the thread and to radius the transition between the 6 mm and 8mm sections. The end was then threaded M6 x 0.5mm.
Next I need to machine the little ends to fit a 15mm diameter ball race. I have a 15mm plug gauge so I will try to get the fit correct. There is always Loctite as a back up ::)
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To mark out for radiusing the little end I needed a centring plug. This was quickly made on the Proxxon lathe from an offcut of 6mm silver steel (drill rod).
Finally I needed to look at how to cut the three slices for the big ends. They could be sawn on the band saw and then milled true but it looks like I can just about use a slitting saw in the lathe which will be easier in the long run.
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I get why you need to make the Long-Rods in two pieces - but how do you ensure thay are the same lenght afterwards :thinking:
Having threads in the pieces themselves introduce another problem in my mind (I really hope I'm wrong here) - where you now have both length and angles interlocked (360 more potential problems) ....
Best wishes
Per :cheers:
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Hello Per, I have a solution planned. The thread is 0.5mm pitch so half a turn is 0.25mm. I will able to skim this much off the pad on the end of whichever rod is longer. I could also just shim it as the big ends are designed in three pieces so I can adjust the compression ratio. The little end and the pad we be aligned parallel on the surface plate and then be left there for the Loctite to cure. (The drawing is in picture 296)
The next step was to centre the rotary table and set up to radius the little ends. I knew that the clearances would be tight. The pair came out quite nicely :) I will leave the 'ears' on for the moment to help with clamping to bore for the little end ball races.
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The rods are coming along nicely, Roger! :ThumbsUp: :popcorn: :popcorn:
Kim