Pneumatic Ram Question

[MrForbes]

Last part first, no, they are two separate parts of the robot, the smaller second cylinder is mounted to an arm at the top of the robot that lets the ball fly up when it is activated. The big cylinders at the bottom are what propel the ball up.

On the cylinders that propel the ball, they will have up to 60 psi in the 3" long portion between the piston and one end of the cylinders, and atmospheric pressure in the 7" portion between the piston and the other end. When the ball is released, the piston moves with the force of that 60 psi pushing on the piston, but as the piston nears the end of it's travel, the pressure on the other side will build up and slow down the action. Air does not need to enter or leave the cylinders to launch the ball.

This is hard to explain.....

[TubaMorg]

Aha! Now I think I've got it, sort of. There are still some details that aren't clear. If no air leaves or enters the big cylinders, then it is a closed system. How do you know what pressure exists on each side of the cylinder? Also if the bottom is at 60 psi and the top is at atmospheric, then you must have a latching mechanism that keeps it from flinging the ball until released. You must then also have a mechanism that "recocks" the cylinders. I believe the GDC has ruled on this and said it is a no-no. If you had pressure gages installed to the top and bottom and could show that 60 psi would not be exceeded, maybe it would be ok. I admire the creativity you guys have though! Have you considered using gas springs instead? They are way FIRST legal and have lots of sproing.

[AdamHeard]

Originally Posted by squirrel

Last part first, no, they are two separate parts of the robot, the smaller second cylinder is mounted to an arm at the top of the robot that lets the ball fly up when it is activated. The big cylinders at the bottom are what propel the ball up.

On the cylinders that propel the ball, they will have up to 60 psi in the 3" long portion between the piston and one end of the cylinders, and atmospheric pressure in the 7" portion between the piston and the other end. When the ball is released, the piston moves with the force of that 60 psi pushing on the piston, but as the piston nears the end of it's travel, the pressure on the other side will build up and slow down the action. Air does not need to enter or leave the cylinders to launch the ball.

This is hard to explain.....

It sounds like a better solution would be to use COTS gas springs that are exempt from the pneumatics rules.

[s_forbes]

Gas springs were considered, but they have they have the problem of being terribly dangerous. If you have a gas spring catapult latched, then it is very hazardous when it is fired without a ball sitting on top of it (think getting hit by a baseball bat).

The system squirrel described is very safe. The system doesn't have pressure built up unless there is a ball sitting on top of the catapult; the ball acts like a latch of sorts. if you fire without a ball, the catapult just slowly raises due to flow control valves.