Bumper Piloting Issues

[clemsonguy1125]

On my rocket launcher launcher the piston works fine if the bumpers attached to the piston but when I add the second part of the bumper to the back of the adapter, the piston wont move. The bumpers part of a pool noodle.

[Gun Freak]

Try using some softer foam for the back bumper (th one not on the piston). The noodle may be too hard for the piston to push against.

[clemsonguy1125]

But ai just slowly comes out the pilot valve , not only when the bumpers are touching.

[Gun Freak]

did you put some lube in?

[clemsonguy1125]

yeah piston seals and pilots fine without bumper part 2, it has to be there since without it bumper part 1 slide into the adapter and the piston slams into the adapter

[Gun Freak]

ok then take the bumper off the piston and just use one on the back or just cut the bumpers down a bit

[mark.f]

Are pool noodles closed or open cell foam?

I think you need to use a different approach for constructing a bumper. They're designed to absorb the impact of the piston, not push on it the entire time it's traveling backwards.

For 2" piston valves, a good bumper can be made from a section of a tennis ball. Cut the ball roughly in half, cut a 1/4"-1/2" hole in the center of the cone, then cut a slit from the edge of the cone through the hole in the center. This can then be "rolled" to fit in the piston track.

[clemsonguy1125]

Thanks, I think the problem was the bumper was getting sucked into the pilot and clogging it up

[cannon monkey]

im going to try the tennis ball bumper idea im working right now on a bumper so far i put a 1-1/4 inch slip to 1/2 inch thread bushing inisde my 2 inch slip to 1 inch thread bushing and stuffing rubber in the space between the two bushing walls

[Technician1002]

The bumper should not "Fill" the entire pilot area. If it does, then the bumper can provide enough pressure by itself to hold the piston closed. Be sure there is some freedom for the piston to move before it hits the bumper. In my cannons, both QDV and conventional, I try to allow about 1/2 the piston travel to be free before reaching the bumper and then the 2nd half is the deceleration zone. This permits the piston to open with air pressure and open 1/2 way at least before it starts to slow down due to hitting the bumper.

Does your pilot have any pilot space? If not, then all you have is the bumper to vent out the trigger valve.

I make all my bumpers with a hole through the center, both for QDV with a rod and conventional without a rod. This permits rapid venting of the pilot area from the back of the piston out the pilot vent without blowing the bumper out the hole.

[clemsonguy1125]

Yes it did, Ive confirmed that the issue was the pool noodle getting sucked into the valve, I tried the tennis ball bumper and it worked ok but I need to order the threaded bushing to get it to work up to its potential.

[mark.f]

Glad it worked out for you. Make sure to check the shape of the bumper after a few firings and periodically to ensure it retains it's shape.

[clemsonguy1125]

Ok, I took your suggestion and shortened the piston length, I will post updated pictures as soon as I find a shorter bolt

[mark.f]

My suggestion was to shorten the overall valve length by replacing the male adapter and bushing combination at the rear with a 2" threaded plug, which might require a shorter piston if it is sliding into the male adapter...

Just shortening the piston will create more pilot volume (although greater opening distance).

Ideally, your piston should be just long enough to leave your opening space (~ 1/2 the port diameter if you've got space to spare) plus room for a bumper behind it when contacting the barrel port.

What length is your new piston and what is the distance between the barrel port and the front of the bumper (when compressed)?

[Gun Freak]

I took apart my valve to paint my gun today, my raquet ball bumper was destroyed. I'll have to try the tennis ball.