SpudFiles

i am almost done building a 4inch piston with 3inch porting valve. the piston is a 3inch coulpler modded to fit very nicely inside of a 4inch pipe. i am still waiting to get my vent valve so i have not tested the valve yet. the vent valve will be HUGE compared to the standard for piston cannon providing aproxametly 4times the flow of a 3/4 inch sprinkler valve so i am expecting the piston to be MOVING! I was just wondering if my bumper is enough. it is a 3/4inch thick of this blue foam stuff that i think is used for around a houses foundation. here is a pic of the cannon

http://s696.photobucket.com/albums/vv32 ... 0_8210.jpg

If its what I'm thinking it is, it should be fine. Best of luck can't wait till you test it.

If it is squishy, but not too soft to be pressed completely flat with a low force, then it will be okay.

one more question

if i attach the bumper to the rear of the piston it would work right?

if i couldnt then i would have to cut a hole out of the center of it and i already think that it might be too soft

-Yes.
-You would indeed have to make way for the pilot opening.

Is this what you're thinking of using?

http://www.ujr.ca/EN/dow_sm.htm

Might work for the short term, but I think you'll have to keep changing it as it gets beat up.

For bumper material selection, I use a simple, "low tech" testing method.

I hit it with a hammer.

If the material survives, and returns to its original shape, I'll consider it useable.

Check your local dollar store for "viable" materials. (silicone bake ware, mouse pad, etc.)

well, if its the foam i think it is, its Styrofoan, which is not squishy, as if to say it will compress but not spring back up

this is NOT sryrofoam and it IS squishy. i will go do a hammer test soon. if it fails what do you guys suggest as a bumper?

FAIL!!!

well that was not good
did good for like first 2 hits then it started tearing and just went down hill

now i REALY need ideas for a bumper! PLEASE HELP ME!!!

Half of a nerf football.

thanks for the ideas

i found a good material for a bumper and it is this 3/4in thick wrist support that you are supposed to put infront of your keyboard. did the hammer test and it held up great. so once i get my new sealing face i will glue it onto the back of the piston

Same stuff as mousepads. You owe gippeto some thank-yous.

thanks gippeto 8)
it is like mouse pads except it is like 4~5 times thicker and a little stiffer and heavier. only thing is that it is not quite 4inches wide its more like 3 so i just glued a little strip on the sid so it is a full circle