Potty three cylinder radial

[Gordon]

I have been building the Potty three cylinder which has free plans on this site. This was built as a team build a couple of years ago.

I have a question on the return crank (Item 19) on the pin which actually drives the orbital valve. In the photos on the team build it shows the pin in the brass prototype in a position looking at the pin end as being left an below center and the final pieces being right and below center. I have made it right and below but it does not work as I think it should. The flywheel would have to run CCW in order to work and that loosens up the nut holding on the flywheel. It would seem like it should be 180° off from that. Am I missing something or did I do something wrong?

I certainly have something wrong because I cannot even get it to try to run in either direction. I even tried cutting another slot in the face which makes it like I think that it should be but still it does not run.

 

[SBWHART]

Hi Gordon

Pleased to her that you've built the engine.

To answer the ? regarding the drive pin, looking at the pin from the top it should be on the right as shown in the drawing and 100 deg from the drive slot, getting these features along with the two flats on the crank and the corect orientation of the ports, contols the valve events of the engines:- sending the air to the correct piston when its at the top of its stroke.

Make sure that you've assembled the little drive pins square into item 19, you can check this by seeing how it drives the orbital valve with the steam chest removes, the valve shoild be flat on the valve port face, also check that you've got the correct width of the valve chest, too wide and and the orbital velve will lift off the port face and leak air, to narrow and it won't allow the valve to rotate.

If you've made it more or less to drawing it should work with just a little fettling.

Hope this helps

Stew (Potty)

 

[Gordon]

If that is the case then the engine runs CCW viewed from the flywheel end.Is that the case or am I doing something wrong? I obviously have done some wrong because the engine does not even try to rotate. I am sure that it is like so many of my projects seem to go, I have missed something rather minor and suddenly things come together and I hit myself beside my head and wonder how I could have been so dumb.

 

[SBWHART]

It runs CCW if you feed the air in the other way through the centre it will run in reverse, I know some guys who have built this type of engine with a two way valve so they can reverse it.

I had to check the vid of my engine running as i couldn't remember which way it ran [ame]http://youtu.be/lNPtbzcx89w[/ame]


This is the build log for my engine if you read it through it may help solve you're problem.

http://madmodder.net/index.php/topic,2317.msg24744.html#msg24744

Hope this helps

Stew

 

[Gordon]

Like I said, I just do some little dumb thing. It ended up that I had not cut down the hub on the rotary valve so there was no place for the exhaust to get back out of the cylinder. Turns out that just putting air in the cylinders is not enough. It also needs someplace to get back out. Sometimes the laws of physics are just so unforgiving.

 

[SBWHART]

Hi Gordon

Pleased you got it sorted

Stew