2073 Pneumatic Catapult

[seg9585]

Originally Posted by billbo911

Here are some additional details to help explain why it works.

Each cylinder (1 1/16" dia X 10") has a displacement volume of 8.87 in.^3. Each cylinder also has an accumulator tank (2"dia X 6"lng.) in line between it and the valve. The accumulator tanks have a capacity of 18.87 in.^3.

The cylinders are actually only retracted to 2/3 of their total length when the catapult is in the load position. The valve is then opened to allow the accumulators and cylinders to precharge up to 60 psi. The catapult is actually in a below top dead center (TDC) position, thus causing the arms to be forced against the stops and not allowing the arms to move. (There is the secret).
To launch, we just use a small dia. cylinder, or our hands during testing and in the video, to lift the catapult arms into an above TDC position, the rest is history.

So, as you can see, the air through the valves really doesn't move the cylinders during launching, it's the air in the accumulators that does.

BTW, this is not our original idea. We learned it in 2008. We have just modified it to our needs in this game. I wish I knew which team used this back then so we could give credit where it is due.

Fascinating, I never thought of doing it this way. I want to try this now (I'll give you credit, hah).

I assume the tubing diagram would look like this:

Compressor --> Upstream Accumulator (115 psi) --> Regulator --> Valve --> Downstream Accumulator (60 psi) --> Cylinder
T-junction connecting both the downstream accumulator and cylinder to the valve.

Mechanism it's supporting is against a hard stop with a pivot latch, and a second piston on its own valve connected to extend, retract the latch