new piston gun now with damage pics

[keep_it_real]

You glue a presta valve inside the tubing. A presta valve is a check valve so you don't even have to worry about the equalization hole being too big because there's a check valve inside. Haven't you heard of using check valves to equalize the pilot area on the chamber? I also think this is a good idea because I doubt duct tape that makes a seal is going to move very easily. Without a check valve, the chamber could loose quite a bit of air through the equalization hole.

[subterranean]

kinda off topic,but earlier on in the thread someone said that abs will hold higher pressures than a coke bottle, because of the thickness of the pipe. well i don't think thats true, the reason the coke bottle can hold those pressures is because the plastic expands. abs will just fail insted of expanding. soo, no abs will not hold higher pressures than a coke bottle.

[Bubba05]

subterranean said!
kinda off topic,but earlier on in the thread someone said that abs will hold higher pressures than a coke bottle, because of the thickness of the pipe. well i don't think thats true, the reason the coke bottle can hold those pressures is because the plastic expands. abs will just fail insted of expanding. soo, no abs will not hold higher pressures than a coke bottle.

Dude I didnt even click to that? WoW thats true. Hey off topic but have you guys ever made a dry ice bomb with a coke bottel. I've seen em go off and you can like see the borrle expand 4 times its original size!!

Sorry flash backs.

Bubba

[super spuder]

ok all you people that said that my gun will not work, i just went out and tried it, i am not going to tell you the result right now, i am going to give all of you people a chance to change your mind and say that it will work, this is your last opportunity, video will be posted at 4:00.

[joannaardway]

When people said it wouldn't work, you had only given them half the evidence.

With the two fill valves, it could possibly work, but I doubt that it would go very well at all.
And I still think the blowgun is the wrong way round. If any of that deathtrap holds pressure for long at all, I will be very stunned.
It will probably leak like a drunk on a street corner in the early hours of the morning.

And I'm not going to change my opinion until after evidence of success.

[super spuder]

crap, the batteries in the camera are dead, and the second fill valve leaks, that is because i did not put that sealing tape on it, it is easy to fix thou.
Edit: no video today but i just went out and shot a big marble through 1/2 inch press board

[rad14701]

@keep_it_real (revisiting the presta valve idea)

Although I am familiar with using check valves for equalization, I have never considered using a schrader valve (not sure we have presta valves in the US) for this purpose... Whether using a presta valve or a standard inline check valve it should be noted that it has to be installed in the correct direction... A simple bleeder hole, due to its simplicity doesn't have such a requirement...


@super spuder

Along with the video can you also include some details on overall performance, such as success to mis-fire ratio...??? I think the crux of our help has been along the lines of ease of use, safety, and consistency rather than simply whether your design would or would not work...

[super spuder]

well, i have fired it about 15 times today and it has not misfired once, the only thing that i don't like is that the accuracy gets really bad after about 80m, the golf balls seem to curve to one side or the other, i could probly fix that by rifling the barrel. i really wish i had a chrony, but i don't, so i have no idea how fast it goes. if someone wants to use GDT to find out i will tell you all the dimensions tomoro, i would have to say about 700FPS but that is just a blind guess. if there is anything else you want to know tell me

[keep_it_real]

rad14701: of course there are presta valves in the US. Every single bike store has a presta valve. I just go ask them for flat tires and viola! 5 free presta valves. Also schrader valves don't work the same (I'm almost 99 % positive). If you pump into a schrader valve without the depressor pin it won't fill. You need a pin to open a schrader.

Gluing a presta valve in some tubing sure can be a chore...

[super spuder]

well no video once again,i do have some damage shots thou, I don't know if that will make you believe me, but i have nothing else that would do this kind of damage so here they are, they are taken at about 3 meters at about 70 psi.

[Bubba05]

Thats pritty kewl dude! keep up the good work.

Bubba

[iPaintball]

-Off topic- Super spuder, Adam Savage said the "I reject you're reality..." thing, not both of them...

[subterranean]

the damage shots don't look likethey came from a golfball at 700fps. give me the dimensions and ill ggdt it, but im not sure what type of valve stlye i should input. chamber sealer?

[super spuder]

umm, you are right, it was not a golf ball, it was one of those big marbles i probly should have said what did it, but oh well, i am telling you now, edit: chamber length=25 inches chamber diameter=3 inches Chamber volume= 707 cubic inches dead space= 28 cubic inches Barrel length=80inches barrel diameter= 1.5 inches Barrel volume=565 cubic inches

[frankrede]

@frankrede dude I come over to back you up on some things mate but iamb not gunna let you diss this bloke mate.
He's only 15 and as he said parts is not the most available to him. I think for his age and circumstances it's a damn good spud gun.
I know that he put alota effort into it.
I think he should get a Mcgiver award boys coz this gun was built almost from scratch with limited componets.

Tell me mate that when you was 15 you was a master engineer pumping out semi-automatic spud guns with a spring fed magazine. Give him a go!
I'm 24 and I bet I couldn't make one of those things as good as he's done.


Bubba

Its funny, when I was 15, I wasn't a master engineer,but I did make a semi-auto spring fed magazine spud gun.


Topic kicked for the sheer fact to show what you shouldn't do with ABS.
Its a strange world, and the fact that this cannon could fire still bewilders me to this day.