help with bumper please

[c11man]

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

[jmeyer1022]

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

[psycix]

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

[c11man]

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

[psycix]

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

[Gippeto]

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.)

[sandman]

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

[c11man]

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?

[c11man]

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!!!

[Gippeto]

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

[jonnyboy]

Half of a nerf football.

[c11man]

thanks for the ideas

[c11man]

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

[SEAKING9006]

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

[c11man]

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