Another rotary valve engine

[PaulR]

My next project will be a two cylinder single-acting engine with the cylinders set opposite each other in 'boxer' style. I just need a bit of help with the valve.

I'm planning on an air inlet on each side of the valve/shaft with a second parallel tube on each side leading to the cylinders, as per this image which shows a cross section of the shaft below each position. I drew this up without any initial regard for the depth of the flats and as a consequence, find that when the shaft is rotated 45 degrees the situation at (a) pertains ie the in and out ports would still be fully open - would it be better for the flats the be shallower so the passages are almost closed by this point as at (b)?

[Jasonb]

I am almost inclined to say that the flats want to be deeper so that you have less dead time when both are closed.

If you think of a typical wobbler the ports are only both closed for a very short time when the cylinder is vertical. It only needs move a few degrees before they open and does almost a full 180 deg before they close again and then connect to the opposite exhaust or inlet.

As an example if the valve shaft were 6mm and your side holes 2mm I would say the web in the middle could be as little as 2.2mm so 1.9mm deep notches.

[PaulR]

I am almost inclined to say that the flats want to be deeper so that you have less dead time when both are closed.

If you think of a typical wobbler the ports are only both closed for a very short time when the cylinder is vertical. It only needs move a few degrees before they open and does almost a full 180 deg before they close again and then connect to the opposite exhaust or inlet.

As an example if the valve shaft were 6mm and your side holes 2mm I would say the web in the middle could be as little as 2.2mm so 1.9mm deep notches.

Thanks Jason. Based on the deeper flats in (a), cutoff to inlet and exhaust happens at about 165 degrees so there's about 15 degrees of 'dead zone'. I suppose it would be best to try it like that then make the flats deeper if it runs poorly?

[Jasonb]

Sounds like a cunning plan

[PaulR]

Sounds like a cunning plan

I was thinking of a name for this new creation and you have just provided it 

[Jasonb]

Baldrick it is then