A” WEAVER “1CC DIESEL ENGINE

[jimbo7636Participant @jimbo7636]

Keith – thanks for the comments and the idea to check the crankshaft in the crankcase.  This is the front bearing area.  I will check it for temperature and it may very well be the issue.  If it is found to be the issue what would you suggest – take it apart and polish the crankshaft, or just let it continue to break in?  Cheers!

[KEITH BEAUMONTParticipant @keithbeaumont45476]

Hi Jimbo,  It might be a lubrication problem as the crankcase pressure probably finds it difficult to get any oily fuel into the bearing. I see you made the two part crankshaft, On mine I fitted a bronze  sleeve to the case,but I made a conventional shaft ,wIth a collet for the prop driver. I also drilled a central hole 1mm diameter into the crankshaft , linking to a 1mm drilled, shallow groove about half way down the shaft, to allow lube to get into the bearing. If you have not done similar, it might be an idea to do it, but stop short of meeting the front thread!  I will admit that I do lap the shaft and bearing together, by putting a very small amount of 1200 grit carburundum powder in oil and rotating by hand ,until it feels smooth.  If your bearing feels tight ish without the prop fitted,backwards and forwards before compression stops you, it might be a good idea to try lapping it in, rather than hoping it will improve by more running.

Good luck with the engine and keep in touch on progress.

Keith

[jimbo7636Participant @jimbo7636]

Keith, thanks for sharing some of the details on your customization of the design.  I see that small hole now in your photos.  Those are great modifications!  I see a similar lubrication hole in the crankshaft for the Boll Aero 18 engine (and I was wondering why that was there since that engine does not use the hole as part of the carb).  I think I could put the crankshaft into a collet chuck and do the 1mm hole thing (Drill No. 60) and the recess.  Then I could polish a bit with oiled 1200 grit paper.  That should improve things quite a bit!  Ill be back soon with an update.  Cheers!

REF: Boll Aero 18 crankshaft.

[jimbo7636Participant @jimbo7636]

Happy to report the little engine is now running at a consistent RPM until it uses up all the fuel in its tank.  3.5 minutes on 5 ml of fuel!  I have to give credit to Keith who encouraged me to add a “lubrication feature” to the shaft (like what’s on the Boll Aero 18 engine).  For this modification I used Drill No. 60 and cut in a recess to a diameter of 0.2060.  I also lapped the crankshaft to have its bearing surface finish up at 0.2181 (about 0.0005 below the reamed crankcase journal of 7/32 inch).  I believe this is essentially an RC4 close running fit.  Video here: https://www.youtube.com/watch?v=l0dEW3fabr4

[KEITH BEAUMONTParticipant @keithbeaumont45476]

Hi Jimbo,  Glad you have the engine running continuously now. It is always pleasing to do a mod to try to cure a problem and find it works. Did you machine the “belt” into the cylinder,as a matter of interest?

Keith.

[jimbo7636Participant @jimbo7636]

Keith, I ended up making a couple of changes to the cylinder.  One was moving the exhaust ports as you suggested.  The other was to skip the belt and replace the 5 intake ports with 3 milled ports (used a 1/8 dia. ball end mill).  Equivalent areas in both cases.  I did make a cylinder with a belt but I didnt like it.  Check out “Jellyfish” here where he uses a ball end mill: https://www.youtube.com/watch?v=fBQRIjvTfC4&list=PLfmoTh09beM-x2jOvyHXT8hsPYJ91IjLN&index=3

[bernard towersParticipant @bernardtowers37738]

Nice to see another one running and that the problem solving working.

[Clive Brown 1Participant @clivebrown1]

Browsing the design, I notice that the original calls for transfer ports to be drilled no. 52 then opened up to no. 41. I wonder why two stages? I think that I’d be tempted to straight to the larger size and avoid fairly deep drilling with a small drill. The later Ron Chernich CAD drawing leaves them at 52, presumably an oversight.

[jimbo7636Participant @jimbo7636]

I think the issue is that the original design was anticipating the drill to wander.  that just didnt feel consistent enough to me and so since I had the option to mill I went down that road.  I also had the benefit of seeing that “Jellyfish” tried it and it worked.

[KEITH BEAUMONTParticipant @keithbeaumont45476]

Ron Chernich’s drawings have a thin cylinder wall and would not take a much larger drill. Back “in the day” in was all about competing for a good power /weight ratio. hence the saving weight. Jimbo, I assume you made the walls thicker. Certainly “Jellyfish” has ,with his cast iron cylinder.  Interesting that his ended up as a glow plug version.

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