Author Topic: Two Cylinder Engine  (Read 69466 times)

Offline Roger B

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Re: Two Cylinder Engine
« Reply #330 on: June 03, 2021, 05:29:42 PM »
I am trying a new design of restraint with stop pins above and below the arm. The 10mm square blank was faced off in the ER25 chuck as that was on the lathe at the time.

It seems to work so now I need to tighten everything and fit some locknuts ready for the next trial  :)

<a href="https://www.youtube.com/watch?v=29vGQnIjIII" target="_blank">http://www.youtube.com/watch?v=29vGQnIjIII</a>

Best regards

Roger

Offline 90LX_Notch

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Re: Two Cylinder Engine
« Reply #331 on: June 04, 2021, 01:50:10 AM »
I’m still following along Roger. Great stuff, keep going.

-Bob
Proud Member of MEM

My Engine Videos on YouTube-
http://www.youtube.com/user/Notch90usa/videos

Offline Roger B

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Re: Two Cylinder Engine
« Reply #332 on: June 04, 2021, 06:32:27 PM »
Thank you Bob  :) I often feel like I am the strange kid doing his own thing in the corner, but in a way that is my life  ::)

The delivery valve is leaking under fuel pump pressure which I think may be a problem of the hardened pump element, there seem to be similar problems with the diesel. Maybe I will try an unhardened silver steel version. The earlier mild steel pumps did not have this problem  :thinking:

I gave it a try anyway. It did run but the stroke control system is still not good, more thinking required  :headscratch: In all the excitement I didn't notice that it was running out of (leaking out) fuel when I went to rev it up  :facepalm:

<a href="https://www.youtube.com/watch?v=hqURL3ND1FM" target="_blank">http://www.youtube.com/watch?v=hqURL3ND1FM</a>

<a href="https://www.youtube.com/watch?v=Y9HwO-Sr8q0" target="_blank">http://www.youtube.com/watch?v=Y9HwO-Sr8q0</a>



Best regards

Roger

Offline Admiral_dk

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Re: Two Cylinder Engine
« Reply #333 on: June 04, 2021, 09:51:01 PM »
I'm not completely sure that you are the strange one out in the corner Roger - but I will admit that you have taken on one of the hardest projects in the model world, and as you have mentioned before -these are prototypes to get a working concept -> the appearance do not matter .... and most other people would have given up long time ago  :praise2:

Offline Nobby Sideways

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Re: Two Cylinder Engine
« Reply #334 on: June 07, 2021, 05:40:02 PM »
What an incredible build, it's taken me a while to get up to date!

Offline Don1966

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Re: Two Cylinder Engine
« Reply #335 on: June 08, 2021, 04:56:09 AM »
 :Love:……


 :drinking-41:
Don

Offline Roger B

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Re: Two Cylinder Engine
« Reply #336 on: June 08, 2021, 05:14:43 PM »
Thank you all for your interest and support  :ThumbsUp:  :wine1:

I have been looking at the various problems and have some more things to try:

The leak past the pump element is due to the inlet port in the body being ~1mm too high and too deep so that the cone on the end of the tapping drill has broken through. This makes a fine O ring slicing cutting edge and also exposes the O ring. Solution; make a new body.

The leaking delivery valve can hopefully be fixed by lapping the flat part of the seating.

I think that the inertia of the long brass stroke adjuster rod is part of the problem. I will try a new linkage with a short light arm as on the horizontal engine.

As this is general fuel injection stuff I will post it on the fuel injection thread:

https://www.modelenginemaker.com/index.php/topic,4906.315.html

Best regards

Roger

Offline Roger B

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Re: Two Cylinder Engine
« Reply #337 on: June 29, 2021, 06:59:26 PM »
Some of the injection problems were, hopefully, solved on the fuel injection thread. The new injection pump body was fitted and I started on the new stroke adjuster linkage. The short link was roughed out on my Proxxon  circular saw. Roughed out is not quite appropriate, one end was 4.01mm the other end was 4.06mm. The other pieces were cut with the band saw and filed to size.

There was a fuel leak from the supply pump so I dismantled it to check the membrane. It seemed ok so I tightened the clamp plates a little.

Finally a trial assembly to confirm the sizes for the pins and spacers.
« Last Edit: June 30, 2021, 05:15:33 PM by Roger B »
Best regards

Roger

Offline Roger B

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Re: Two Cylinder Engine
« Reply #338 on: July 02, 2021, 06:53:32 PM »
The forces from the wedge are quite high so I added an additional friction disc to the control arm. As the Hobbymat was in lathe mode I turned the new pivot pin for the wedge on it. Not as easy as on the little Proxxon  :(  I assembled the linkage and had a short trial run. Although I was running out of hands it seems that the stroke wedge has to be almost totally withdrawn to get a sensible mixture  :headscratch: I think I will need to reduce the excentric stroke from 3 to 2 mm and possibly raise the pump a little to get a sensible working range.
Best regards

Roger

Offline Roger B

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Re: Two Cylinder Engine
« Reply #339 on: July 03, 2021, 05:26:26 PM »
A bit more playing/thinking about this one  :thinking:  The 25cc horizontal engine ran with an injection pump stroke around 0.5mm. As this is 6cc per cylinder it will require a stroke of around 0.12mm. This is consistent with the position of the wedge, it also means that a 10° wedge is far to coarse, less than 1mm of movement of the wedge will adjust by more than the total stroke. This results in it being rather touchy to get to run. I now have a new task list:

-Make new shorter stroke excentrics for the feed pump and injection pump.

-Resolve the fuel leak around the pull rod of the feed pump. The bigger version had no problems but I scaled the clamping pieces.

-Make a shallower angle adjusting wedge, maybe 4°

I also noted that the injection pump excentric strap is already ~0.2mm oval  ::)

The first video clip shows what happens if the tripod leg is in contact with the engine bench, quite surreal  :)

<a href="https://www.youtube.com/watch?v=tTEcvJ87pdo" target="_blank">http://www.youtube.com/watch?v=tTEcvJ87pdo</a>

<a href="https://www.youtube.com/watch?v=tJECoGtBc6c" target="_blank">http://www.youtube.com/watch?v=tJECoGtBc6c</a>
Best regards

Roger

Offline Roger B

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Re: Two Cylinder Engine
« Reply #340 on: July 07, 2021, 07:56:40 PM »
The excentrics were offset in the 4 jaw chuck and turned to size. I then moved to milling mode to cut the 4° wedge. The excentrics and the wedge were then drilled, tapped and reamed as appropriate.
Best regards

Roger

Offline Roger B

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Re: Two Cylinder Engine
« Reply #341 on: July 07, 2021, 08:03:01 PM »
Next up was the tappet. This was slotted 2mm in three passes with a 1.2mm slitting saw. The pivot hole was drilled and reamed in the same setup to ensure it was perpendicular to the slot. It was then set to 4° using the wedge as a guide, milled to length, hardened and polished along with the wedge.

Next step was to refit the feed pump, minimising the stroke to minimise the stretch on the diaphragm.
Best regards

Roger

Offline Roger B

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Re: Two Cylinder Engine
« Reply #342 on: July 28, 2021, 06:59:39 PM »
The fuel feed pump still leaked so I made some new 5mm clamping nuts instead of the 4mm hex ones. The inner one was fixed to the rod with Loctite and I drilled a couple of 1mm holes in the outer one so it could be tightened with my circlip pliers. I also decided to make a new diaphragm as the original was showing some signs of distortion and damage.
Best regards

Roger

Offline Roger B

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Re: Two Cylinder Engine
« Reply #343 on: July 28, 2021, 07:06:49 PM »
The pump was reassembled and reinstalled. The next trial was much better, no fuel leaks and fairly consistent running (it would also be easier with three hands  ::):) I need to move the injection pump up a little as the wedge is right at the end of it's travel. More measurements suggest the working stroke is less than 0.2mm which matches the theory. Maybe I need to look at a 1.5mm bore injection pump   :headscratch: Overall Happy with this  :wine1:

<a href="https://www.youtube.com/watch?v=nWIY3J_x7Wk" target="_blank">http://www.youtube.com/watch?v=nWIY3J_x7Wk</a>
Best regards

Roger

Offline propforward

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Re: Two Cylinder Engine
« Reply #344 on: July 28, 2021, 08:35:49 PM »
Looks like a great result to me Roger. Great work all round.

I quite enjoyed the video where the tripod leg was touching the bench. Felt like I was going into a time warp or something.
Stuart

Forging ahead regardless.

 

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