Author Topic: 20 cc Horizontal 2 Stroke Diesel  (Read 59527 times)

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #345 on: December 30, 2020, 10:04:34 AM »
Thank you Chris  :) Jason B made a similar suggestion. The method you suggest gives a mechanically better job but is wider and will increase the shaft overhang. It's one of the many things to look at if/when I design a mk2 version.

I have  a 4 jaw chuck with a M14x1 thread which fits onto my RT which I used to set out the fixing holes. The holes were then tapped on my tapping fixture. As they were half in cast iron and half in some alloy steel I used a cutting lubricant (using lubricants on cast iron is supposed to cause the end of the world as we know it  :o ) which seemed to work well. I then moved the bush round 60░ for a trial fit. Next step is to slit the bush but I will modify the starter dog first so I can slit both on the same set up.
Best regards

Roger

Offline Laurentic

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #346 on: December 30, 2020, 11:06:00 AM »
Quite right Roger - I did say it was an item to consider for the future!

Out of interest, the drive gear I made is fairly compact - not much longer at about 0.550" (plus cap heads) than it would have been had I used a gear with a boss on the side to hold grub screws (the teeth part of the gear is 0.230").  The bush itself is just 0.250" long and the flange in the gear 0.300", so this style can be made quite compact and certainly no bigger - possibly smaller in fact - than other designs.  Just saying!

I did wonder at your comment about a Mk.2 version, surely you will have had enough of this project by then I thought, then remembering all the experimenting and your perseverance with both this and your fuel injection thread thought, no, that would be quite in character! 

Keep up the good work on both projects - I am following along with considerable interest and admiration.

Chris

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #347 on: December 31, 2020, 07:22:28 AM »
 :ThumbsUp:  :ThumbsUp:

Next I set the starting dog up in the mill to make a clamping screw hole on the opposite side. Then I slit the tapered bush and cut the bottom off the clamping side of the starter dog. The tapered bush could be closed down to a couple of hundredths undersize with just thumb pressure  :) I hope that it grips  ::)

Finally I need to make a new repair sleeve and Loctite it in place.
Best regards

Roger

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #348 on: January 01, 2021, 04:09:26 PM »
On with the rebuild. The sleeve was finished and Loctited in place, the starter dog was clamped on and I went to give it a quick spin with the drill. On close inspection the starter shaft was a little too long and was trying to pull the dog off the crankshaft  ::) A quick spin in the lathe and problem solved. The shaft was made as quick fix to start my original engine and has never been drawn or checked against the later engines. May be this has been part of the starter dog problems  :headscratch:

Finally I checked the injection timing and moved the cam to get what I hope is a sensible adjustment range, 11░ to 28░ BTDC. 20░ BTDC is my best guess.
Best regards

Roger

Offline Admiral_dk

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #349 on: January 01, 2021, 10:29:15 PM »
Nice to see it back together - let's hope the two items in question will last a lot longer this time  :cheers:

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #350 on: January 24, 2021, 05:29:59 PM »
Thank you Per  :ThumbsUp:  :ThumbsUp: The answer is no  :(

I made a few more trials today. I could reproduce the previous results with the 20░ nozzle where I think I have a mixture of real combustion of injected fuel and running on 'atomised' piston blow by. I then tried the original 15░ stainless steel nozzle which I felt was subjectively better. When the engine stopped on that run I fitted the new 15░ nozzle. As I tried to prime it the engine wouldn't go over TDC  :toilet_claw: It was free for all but 20░  ::) I guessed there was another foreign body in the combustion chamber. I tried to see it I could shake it out but no success  :( Pack it up and go home.
When I took the head off there were some small unidentifiable metal pieces and a lot of impact marks. Luckily there doesn't seem to be any damage to the bore but another full strip down is needed  :disappointed:
Best regards

Roger

Offline Admiral_dk

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #351 on: January 24, 2021, 08:06:05 PM »
Strange where does it all come from ..... is there anybody that has access to this engine (other than you) ?

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #352 on: January 25, 2021, 08:33:47 PM »
Per, I generally assume that my incompetence is more likely than some one else's malevolence.

I know that the first piece was one of the grub screws that retained the gudgeon pin (M3 x 3). The bit that was in the combustion chamber did not have the ring around the hexagon socket. I assumed (bad thing to do) that it had been squashed. I think that it may have been in the transfer passage. A part of the piston skirt has been broken away by a ring like item. I can't find any trace of this, just a bit of piston skirt  ::) The crankshaft has a marking where it may have cut something. The transfer passage is now clear (maybe I should have checked it last time  :toilet_claw:)

I need to check the dimensions to see if the top of the piston will still seal the transfer ports, maybe not too much of a problem, or I will have to make a new piston  :(

« Last Edit: January 25, 2021, 08:37:08 PM by Roger B »
Best regards

Roger

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #353 on: January 31, 2021, 07:57:30 AM »
The bite out of the piston skirt is 3-4 mm deep and there is 5 mm between the edge of the skirt and the base of the ports at TDC so I will keep going with this piston for the moment. I took off the cooling hopper to properly check the transfer passage and had a good look around the rest off the engine. There was another piece of piston skirt in the crankcase oil drain so it looks like I got most of it. The oil system was primed as before with the battery drill directly on the shaft of the pump.
I made a new head gasket using the punch template as before and clamped it between two experimental cylinder heads to round it off. Finally a compression test to make sure all was OK. It built up to around 32 bar as before so hopefully no other damage  :)
Best regards

Roger

Offline Brendon M

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #354 on: January 31, 2021, 09:57:06 AM »
Just caught up Roger

Looks like you have been having fun :)
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