Today I was able to get this engine to run smoothly at 48 RPM.
[ame]http://www.youtube.com/watch?v=9AWVbPX2B2A[/ame]
I did a number of things to achieve this low speed.
I was looking for some material to make a counterweight for the valve beam and a counterweight for the power piston beam. It turned out that the material was right in front of me all the time. The weights were hiding in a piece of 3/8" x 1" brass bar stock. I cut off three pieces, silver brazed them together and milled off the excess.
The valve beam weight is moved to achieve the minimum force required so the beam stays in contact with the eccentric.
I also used some powdered graphite on the area of the valve beam that contacts the eccentric.
I also added a weight to the power piston beam. This weight seems to help the engine get past the point where the crank shaft wants to stick at TDC.
What really freed it up though was when I loosened up the head bolts on the power piston. I discovered this by accident when I was checking to see if they were tightened evenly. I left them finger tight.
This was an interesting project and as I watch it run I see pieces that I know I can make better or little tweaks that may help it to run better. I may try to add some weight to the flywheel. Perhaps that will smooth out the rotation so it doesn't try to stop when the crank is TDC.
Thanks for stopping buy to visit.
SAM