Compressed Air Engine

[cfellows]

Just wondered if anyone knows how this valve mechanism works? The Inlet valve is supposedly a self actuating piston valve. I'm wondering if the compression stroke pushes the inlet valve open? There is also an exhaust port which looks like it is at the bottom of the stroke. Maybe the inlet valve is also spring loaded and the drop in air pressure in the cylinder, when the piston uncovers the exhaust port, allows the spring to close the inlet valve?

[ame=http://www.youtube.com/watch?v=hdWIMNBXmco&feature=PlayList&p=692F73423D14F11F&index=60]http://www.youtube.com/watch?v=hdWIMNBXmco&feature=PlayList&p=692F73423D14F11F&index=60[/ame]

Chuck

 

[bigal2749]

Have no idea but would love to find out

 

[GailInNM]

Chuck,
It looks like it is what was commonly called a bash valve engine like what was used on the model airplane CO2 engines that were popular in the 1940's and 50's. They are still being made today.

A small post on the piston would push a ball off of a seat when the piston was at the top of the stroke and admit the air/CO2 until the piston passed top dead center far enough to allow the valve to close. Exhaust was like a uniflow engine with just an exhaust port that the piston uncovered near the bottom of the piston stroke.

The one in the video appears to have a guided valve rather than the more typical simple ball valve. They were also used so make it easier to put a small spring in to help close the inlet valve.

Gail in NM,USA

EDIT: This is the same type of engine that is on the Air Hogs compressed air toy airplane being sold today.

 

[Powder keg]

Birk (oldmeckthings) built 2 or 3 of those in different configurations. You might ask him;o)

Wes

 

[GailInNM]

Here is an animation of how I think it works.
http://www.keveney.com/co2.html

 

[cfellows]

Gail, I think you're right, that the piston is mechanically opening the valve with a pin or something. However, it doesn't appear that the valve closes until near the bottom of the stroke. So something else seems to be keep the valve open even after the piston has travelled back down the cylinder.

By the way, where is Birk? Haven't seen any of his postings for a while...

Chuck

 

[Powder keg]

He's still around. He's been Emailing me a couple times a week with pictures of a 1/2 scale rifle he's building. Neat stuff!!!

Wes

 

[Oldmechthings]

Wes is right, I'm still around, but being slothful and lazy have not posted anything for a while.

And yes I did build a couple of those little engines, however fortunately I did not get any plans with the castings, so I had to design my own valves, which is what I like to do anyway.

The near engine uses a cam operated spool valve, and the far engine has roller cams operating poppet valves.
Both engines run fine, but I realize that did not answer your question, so you will have to figure it out yourself.

I do not know what this picture is doing here, but I think there is some heavy discussion going on between Oldmechthings left, Powerkeg center, and Lee right.

And yes again, I do have a half size 44-40 Winchester model 1892 under construction. That is the one John Wayne used in his movies. After building several engines in a row, a little change was in order, however there is not much difference in machining parts for a miniature rifle or an engine, it is all chip making. I plan to have it functional, but do not know where to find bullets unless I make them too.
Birk