Compressed air engine

[Gun Freak]

I've looked at that, this is the part that gets me:

As more air is fed into the chamber, the pressure increases and the piston begins to move down the chamber. When it reaches its maximum length the air pressure is released from the chamber and the spring completes the cycle by closing off the chamber to return to its original position.

I understand that the air is released, I just don't get how. In complex engines they use solenoids right? But in homemade ones, like the one you linked, I don't get how the air is released.

[jrrdw]

Ports, just like in a 2 stroke engine. Most of the video's on Youtube are using ports. JSR's 1st diagram showed them plainly.

[Gun Freak]

Ok thanks. Looks a bit more complex than the coat hanger engine, but I think it is doable.

[warhead052]

If you are really desperate, I can sell you a air powered motor that is used on concrete pumps. The thing is really powerful, and it uses alot of air, but it sounds pretty cool when it runs, and spins kinda fast. It also has a gear on it, and it weighs maybe 5 pounds.

[Gun Freak]

The plan is to just build a model engine. I dont believe in buying stuff you can make, and the whole idea of building it is for the fun. Also I want to show it to my uncle who was an engineer at Pratt and Whitney for a long time, designing jet engines, and he is into this kind of thing.

[jrrdw]

my uncle who was an engineer at Pratt and Whitney

I'd like to talk/listen to him for 10 hours/days straight lol! Pratt and Whitney was a major manufacture for radial engines during WWII.

One version of the 9 cylinder (I think it was the 9) had so much power the force of the twist (crankshaft rotation) would flip the airplanes completely over on their backs if they weren't throttled up slowly. So much for a scrambled type take off. That's power!

[warhead052]

The plan is to just build a model engine. I dont believe in buying stuff you can make, and the whole idea of building it is for the fun. Also I want to show it to my uncle who was an engineer at Pratt and Whitney for a long time, designing jet engines, and he is into this kind of thing.

Ok, well if you ever need it, let me know. I think its 400 dollars, but thats because my grandfather sells around the world pretty much. He sells to everyone from a small buisness to huge companies.

[Gun Freak]

Jrrdw, he sure knows his stuff. He is retired now and he builds motor bikes and scooters 8)

Edit, I thought of a good idea! Like the diagram that JSR originally posted, the piston itself hits a valve at the top of it's stroke and injects the high pressure air into the cylinder. At the end of it's stroke, the piston passes the exhaust ports (4) and can now freely move back and start the cycle over again. My question is, do you guys thing the schrader will have enough flow to push the piston? My concern is that the piston will not push the stem for a long enough period of time and barely any pressure will get in the cylinder. To ammend this, a spring can be added to the pin that pushes the schrader pin, allowing the schrader to be open for a longer time.
Hopefully on the one with the spring, the spring loaded pin will hold the pin long enough for a lot of high pressure air to enter the cylinder and make a more powerful engine.
Edit 2, if I take the spring out of the schrader, it will be easier for the piston to open it. But will the schrader close without it? Taking the spring out will increase the dwell time, which is good, but it needs to close before the piston turns around. I'm fairly certain it would, but I'm asking for assurance on this? Thanks.

[warhead052]

That might work. I am no expert on the workings of air motors, but that looks like it will work. Just figure out how to get it going. Another thing you can do, use a pop off valve, but extend the stem on it that connects to the pull ring on it, and attach a piston to it. That might work, I don't know. If I see a lawn mower engine though I am going to try converting it to air power.

[Gun Freak]

Hey Warhead, that's not a bad idea. But, it requires another bend on the crank shaft, and I'm trying to keep it down to just one. Plus, a pop off valve would be harder to open. But, still its a good idea. See my edits in the above post.

[warhead052]

Depends, a pop off can open as long as you have a constant stream of air. I may try it at some point with a coat hanger set up. Just bend the coat hanger like a crank shaft, and put it through the pop off, apply air pressure and if it rotates then it works.

[saefroch]

The spring inside of schrader valve is rather strong for this, and the flow isn't incredible, but might be passable. I suggest purchasing a check valve from McMaster and using that in lieu of a schrader. They have rather good flow, and a very weak spring holding the valve shut. Should work pretty well.

[Gun Freak]

Yep, but I was trying to keep this one simple. For example...
This...
[youtube][/youtube]
As opposed to this...
[youtube][/youtube]
Not sure if mine works the same as the first one, I don't think it does, but the idea is that it only has one linkage and the second one has two. Mine will only have 1.

[warhead052]

Haha, I like the sound the second one makes. The first one may work the same as yours.

[Gun Freak]

Saefroch, I don't really want to buy a check valve for this. I think with a small enough bore, the schrader valve will have enough flow.

Warhead, the first one is a wobbler type and the valve is on the actual cylinder. When the cylinder is on one side, it fills with air, and when it goes to the other side, the air is exhausted through the other hole. So unlike mine, there are no exhaust ports at the end of the cylinder.