Rotary valve in-line twin (take two)

[dgjessing]

After a couple of attempts I was unable to make a workable built-up crankshaft for "take one": http://www.homemodelenginemachinist.com/index.php?topic=17090.0

I might try it again now that I've straightened up my mini-mill per these excellent instructions: http://www.homemodelenginemachinist.com/index.php?topic=6007.0

But at any rate, I've started on a completely new version. This time, I did the crank first, and am building around it. The crank is carved out of one piece of 3/8" CRS plate:

... after some time on the lathe:

Much better than the built-up attempts!

Also, since I know how to make gears now, the new version is going to have the valve shaft up in the head, gear driven:

It's going to have a 5/8" bore, 3/4" stroke. The crank will run in ball bearings, but they haven't arrived yet. (I'll be boring out the end plates for them once they get here...)

 

[dgjessing]

Cylinder head, valve shaft:

Everything spins freely and the valve shaft is a nice tight fit in the head. Now it's on to drilling all the air ports in the head and milling flats in the shaft. Then pistons and rods, a flywheel, and it oughta run ;D

 

[warranator]

Looks very nice. I made one last year, not sure if you seen the post here.

http://www.homemodelenginemachinist.com/index.php?topic=14879.0

As stated in the post I had trouble with the ports bleeding into each other but sorted it out with o-rings. I still get people asking me about this motor as it looks great on the mantle piece.

 

[dgjessing]

Looks very nice. I made one last year, not sure if you seen the post here.

Neat - that is pretty much the same thing, no?

 

[warranator]

Yeah I would say the same. Interested to see how yours runs when finished. Something I also found was it needed a fairly heavy fly wheel for it to run continuously. I didn't put bearings in the head for the cam shaft but I did put bearings in for the crank shaft. Did you fit bearings for the crank shaft? What material is your cam shaft?

 

[dgjessing]

The valve shaft is brass - I would have preferred stainless steel but the hobby shop was out of 1/4" SS rod... That pointy screw goes into the head on the left side and holds the shaft in place by protruding into that recess near the left end.

The slot in the end of the shaft will help with getting the timing adjusted:

Ball bearings for the crank are supposed to be here tomorrow

 

[warranator]

My cam shaft has a head at one end to stop it coming out. I scribed a line at the end of the cam shaft to help with the timing. My cam shaft is also brass, make sure you lube it up very well before running, mine almost seized after running the motor the first time properly. Are those flats on your cam shaft the open and close positions? If so they don't look right, one set should be 90 deg opposed to the other. What does the under side of the head look like?

 

[Billzilla]

Do you have any photos of the combustion chamber? I've always been interested in rotary valve heads.

 

[warranator]

Mine doesn't have combustion chambers as such, just holes that match up to the intake and separate holes that match up to the exhaust.

 

[Billzilla]

Ah okay.
I'm mostly familiar with the Bishop Rotary Valve setup and it too only has a tiny chamber.

 

[dgjessing]

"Running in" the new pistons, cylinders, and rods on the lathe:

Still need to make a flywheel and air manifold.

The "combustion chambers" are nothing to look at - just a hole into the cylinder from the flat underside of the head.

 

[dgjessing]

Hey it runs nicely on one cylinder (either one). I'll try to make the manifold tomorrow (so it can run on both simultaneously) ;D

 

[dgjessing]

It lives!

http://www.youtube.com/watch?v=OHkrNX0t4OE&feature=youtu.be

I'm going to take it apart and smooth & polish things, make a wood base for it, etc., etc. ;D