Author Topic: 20 cc Horizontal 2 Stroke Diesel  (Read 48933 times)

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #225 on: December 01, 2018, 02:38:29 PM »
Thank you all  :ThumbsUp:  :ThumbsUp:  Alex, I hope to get this to start without aids as others appears to have done. I had thought about glow plugs (there is a model Lanz Bulldog that uses an automotive one in place of the hot bulb) but I will keep trying without for the moment.

We had some reasonable weather today, up to 9░C, so I gave the engine another try. The first problem was that the injector tappet kept sticking, probably due to some slight damage when it fell apart last time  ::) I smoothed around the fork end with a diamond file and got it working although I need to dismantle it all again to check.
I was getting weak firing without any ether which was improving as I advanced the injection timing a little at a time. Then a problem, the starting dog slipped on the crankshaft gouging both  :(  :(

The dog will need to be redesigned to clamp better, I don't want to key it as something has to give. I can hopefully skim and sleeve the end of the crankshaft and may increase the grubscrew size in the flywheel when everything is dismantled.
Best regards

Roger

Offline Art K

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #226 on: December 01, 2018, 05:28:32 PM »
Roger,
Have you considered a one way bearing as the starter drive. I copied Steve's starter drive to use on VAL. Works great plus it allows the engine to take off when it starts. http://www.modelenginemaker.com/index.php/topic,3653.345.html Here is the link to my VAL build, I had clearance issues and needed to make a spacer to give me the room on the end of the crank. Just a thought.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #227 on: December 03, 2018, 08:27:34 PM »
Thank you Art. I have used such a system on my vertical engine as at 3cc it had problems pushing the dog out. This engine is rather more violent and I need something that will give if something goes wrong. I had hoped that the pin would break but instead the clamp slipped and damaged the crankshaft.
I have modified the design, moving the cut round 90░ and increasing the clamp bolt from M3 to M4. The new dog is made from a piece of fairly high grade steel from the bits box. It gives a nice finish with highish speeds and a carbide tip. When I started to mill a seat for the clamping bolt it migrated in the vise so I added a G clamp to keep it in place. The damage is just cosmetic.
Best regards

Roger

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #228 on: December 03, 2018, 08:31:21 PM »
As I needed to use a slitting saw for the clamp screw slot I used it to cut the other two pieces.
Best regards

Roger

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #229 on: December 03, 2018, 08:34:56 PM »
I could have made a complicated milling set up to cut the dogs but instead spent 15 minutes with a selection of files  :) Next step strip down the engine and hopefully salvage the crankshaft  ::)
Best regards

Roger

Offline Ye-Ole Steam Dude

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #230 on: December 03, 2018, 08:54:38 PM »
Hello Roger,

That is a lot of filing but it looks good.

Have a great day,
Thomas

Offline fumopuc

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #231 on: December 05, 2018, 03:37:37 PM »
Hi Roger,
at my last version of this dog  the soft edges were damaged very quick.
This was much better after a simple heat treatment, for this a CK45 Steel or similar is helpful.

Kind Regards
Achim

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #232 on: December 05, 2018, 07:41:44 PM »
Thank you both  :ThumbsUp: The dog part of the current version survived the horizonal engine and this one, its the connection to the crankshaft that is the problem at the moment  ::)

After it's quarantine period I bought the engine in from the garage to strip it down. Even with the taper bush fully released I had to use a puller to get the flywheel off. The end of the shaft doesn't look very nice  :(  I had to file down a lot of burrs to get the side plate off.  The flywheel has obviously been slipping as well. The piston, bore and big end look fine  :)

I can't increase the flywheel clamping bolts to M4 without a redesigning/remaking the center but I will slightly deepen the clamping holes and use an end mill to give a flat bottom. I hope I can clean up the flywheel portion of the crankshaft but will have to turn down and sleeve the starting dog part.

Next challenge, get the oilway grub screw out of the end so I can get a center in. ( I note that the last picture of the damaged crankshaft is number 666  :mischief: )
Best regards

Roger

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #233 on: December 06, 2018, 07:00:31 PM »
On with the salvage. I worked out the original position for the taper bush and fitted all the screws. I could then carefully run a 12mm reamer through to clean up the worst of the damage.

I was able to release the crankshaft oilway grub screw as I had only used a threadlocker not a retainer grade of Loctite. The damage could be removed by skimming down to 11.45mm, just right for the 11.5 mm reamer I had to buy due to the unique feature on the other end of the crankshaft  ::) The sleeve was made from  a piece of 12mm ground ST50. Due to other experiences supported by Rich's (Firebirds) fun with the bushes on his Conway I needed to bore out the sleeve to ensure it was concentric. Drilling is not good enough.

A bit of Loctite, twist it into place to ensure good distribution and see what it looks like tomorrow.
Best regards

Roger

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #234 on: December 08, 2018, 04:53:55 PM »
I faced off the end of the sleeve and then decided to reduce the OD of the dog to 18mm and radius the fillet to the clamping part. The flywheel was set up on the Proxxon RT and the three plain holes were deepened to 5.5mm with a 3mm end mill to give a flat bottom.
It was easiest to remove the cylinder block to refit the piston as there is a tapered lead. It will go from the cylinder head end but I would need to make some form of ring compressor. The rest was put together with a thin smear of Hymolar in the appropriate places. I then primed the oil system using the electric drill to confirm I was still getting oil to the main bearings and cylinder.
A little bit of work with a diamond file on the fuel pump tappet resolved the sticking problem. I now need to refit the fuel system, time it and bleed it.
« Last Edit: December 15, 2018, 08:03:37 PM by Roger B »
Best regards

Roger

Offline Admiral_dk

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #235 on: December 08, 2018, 06:27:21 PM »
Looks like you are discovering how much heavier load there are on most of the working parts of a diesel compared to a gasoline engine the hard way Roger - but at least you seems to find the solutions too  :ThumbsUp:

 :cheers:      :popcorn:

Offline fumopuc

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #236 on: December 08, 2018, 06:43:23 PM »
Hi Roger, perfect salvage.
Kind Regards
Achim

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #237 on: December 09, 2018, 08:16:29 AM »
Thank you both  :ThumbsUp:  :ThumbsUp:

Per, the parts I have actually designed have been ok, it's the bits that have just 'happened' like borrowing the starter dog from the horizontal engine for the first trials and not updating it that cause problems  ::) Find Hansen bent the connecting rod on his first diesel  :toilet_claw:
I will put the injection system back together today and will then have to wait for better weather to try it again.
Best regards

Roger

Offline Art K

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #238 on: December 09, 2018, 06:28:08 PM »
Roger,
Looks like a good save.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #239 on: December 10, 2018, 07:49:08 PM »
Thank you Art  :ThumbsUp:

I refitted the injection system and then set it up with some cooking alcohol to prime and test it. I could not get any injection so I wondered if the 0.2mm nozzle hole had got blocked  :headscratch: I released the spring and got spurts from the nozzle, as soon as there was any spring pressure nothing  ::) Maybe there was still some air in the system so I span it up with the drill. Fuel sprayed from the back of the injector but none through the jet  :toilet_claw:  I dismantled the injector and checked the needle, still 1.480 +-0.001mm. I tried the other needle still no success  :( The 1.48mm pin gauge felt loose in the nozzle and a 1.5mm drill with a 1.455-1.458 shank would go in  :facepalm2:
I think that the problem was/is the holder for the 0.2mm drill which is made from silver steel rather than brass and has a sharp edge somewhere that cut a/some grooves in the nozzle guide resulting in rapid wear although the fit was originally good. I will lap the outside of the drill holder to remove any possible cutting edges and make a new nozzle (in the fuel injection thread).
Best regards

Roger