23 May 2012

Two cylinder rotary valve engine done!

I finally finished the latest engine. These things seem to get simpler and easier each time. I tried to make two crankshafts at once, thinking if both of them turned out I could make a second engine. Well trying to finish the second shaft it got mangled. Oh well, I've got a working engine anyway. Cutting the valve rod was tricky, it's running on #2.
I made sure everything was very smooth and in some places just a bit loose. After a good run-in it will run on breath power, which is somewhere near 3-4 PSI max. That amazes me because none of my previous engines were free enough to run on lung power.

I was considering painting some parts of the engine but I couldn't decide which parts or what color and my wife said she likes it raw. Nothing is polished, just sanded to be smooth. I may still go back and paint the steel parts to prevent rust at least.
Overall I don't like this method of valving. it's hard to align the cut so the intake and exhaust open at the right time, and the valve gear makes the shaft unbalanced. At high speed it jumps all over the table. I'm proud that I changed the design for the cylinders from a solid block of bronze to brass tubes. i was worried they wouldn't line up well enough. Also my intake manifold looks better than the plans. I'd like to build some piping to redirect the exhaust too, but it's pretty low priority.

02 May 2012


Finally, I have a crankshaft! The 4th try is the charm, so I made two at the same time. I made two in case one of them got messed up. Well, they have both turned out (almost anyway, not quite done with the second but close).
 First I marked out both parts. This is 1"x3/8" bar. Drill a hole then bandsaw (I love my new bandaw!) the slot. Each end is center drilled in three spots one for each shaft.
 I had to use my cutoff blade to reach into the slot and turn the crank pins. Not as bad since most of the material was cut out with the saw. Continue removing the unneeded material with the bandsaw.
 Finally ready to turn the main shaft. Both crank pins are at correct dimension and the webs are cleaned up on the inside surfaces.
Using bolts and soup can shims to keep the shaft from flexing too much I can turn down the main shaft to 1/4".

I put the one finished shaft into the rest of the engine and it is a perfect fit. Spins smooth and free. I'm still working out a little binding on one of the connecting rods, and the valve gear seems to be a little bit off. Last steps will be to cut the valving and paint.