SpudFiles

They run on a coke bottle for a fairly decent amount of time, but only about 2/3 of that time is useable power, the rest of the time it has enough pressure to run, but not enough to do much else.

I think that if you built one of these engines with 3 or 4 cylinders instead of one, then you would get more consistent power (not just on the down stroke). It could be run from a regulated dive tank or a paint ball tank and you could use it for applications such as RC cars or boats. It probably would chew through the air quite quickly but it would be quick and clean refilling.

I think it is by far the easiest air motor design to build.

Edit: Have a look here for one of these motors in action

I will be working on an engine design soon that uses air, magnetism, and thermocouples to generate forward motion. Amazingly enough, you should do a search on lego engines. Seems like a lot of lego fanatics have made piston and turbine engines using the air pistons from some of the kits.

http://www.aircaraccess.com/solar.htm

check this out. VERY useful link. If anyone figures out Maxwells demon in practice, call me and I will make you very wealthy.

my air hog engine dosent fit a 2 ltier bottle the threads are 2 small

Ohh, too bad. The engine I had was from their air powered helicopter.

does air hogs sell replacement motors? i should look in to that. it would be awesome to have a canoe or scooter or something running off air, get a few high pressure air or co2 tanks and motors, that would be awesome. anyone ever try building some sort of turbine out of knex?