Barrel sealing Marble Sawed-Off to Sniper

chaos · Thu Mar 29, 2007 7:28 am

i dont know how you get that speed from a marble i use 260psi and i get roughly 600fps unless i stuffed up the ggdt calculations.

oh and very nice gun man cant wait for that 160psi part

Mitchza89 · Thu Mar 29, 2007 7:37 am

Haha thanks alot for that. Wow...260psi?? thats a hell of alot of pressure. I just GGDT'ed my gun with 260psi and I got 938fps. Thats really weird... I could get 600fps with my previous cannon. Just a simple Modded Sprinker Valve gun that was set to 110psi.

With that program, the simplest error makes a hell of alot of difference with the speed. But eh....I think I might have my calculations wrong. I know I have everything right except the marble weight.

Regards,

Mitch.

(P.S.....Does anyone know the weight of a marble?? 16mm in diameter? Cheers.)

chaos · Thu Mar 29, 2007 7:58 am

yer well i started a post on those marbles. from the answers i got they range from 4.6g - 5.2g wow all that diff. lol yer ill run mine through ggdt again see what i get

Mitchza89 · Thu Mar 29, 2007 8:06 am

Ah cool! I was right then. I am getting around 700fps!....Hey if you keep getting the same fps....Give us your messurements and I'll see what answer I get on mine.

chaos · Thu Mar 29, 2007 8:20 am

ok man i pm'd them to ya thanks for that.

idea: keep that sprinkler valve on when you go for the new chamber. it will help the performance a lot

Mitchza89 · Thu Mar 29, 2007 8:28 am

I just send the info to ya just then chaos. I hope it gets through. Yeah I don't know if the sprinkler valve can take it though....I wanna crank it up to 160psi and the valve is only rated to 150....so I'll just take it to 150 then

chaos · Thu Mar 29, 2007 8:33 am

man it would take it rated to 150 and it probably fails at 450. has there been a test on this?

i got the info mate cheers.

Mitchza89 · Thu Mar 29, 2007 8:36 am

I wouldnt have a clue aye. I know the burst pressure of PVC is WAAAY higher then the rated amount....so I might crank it to 160 and see what happens. All that can happen is the rubber diaphram breaks and the gun goes off haha no biggy.

chaos · Thu Mar 29, 2007 8:47 am

yer lol whats the worst that could happen....hmm let me go back to that thursday night...
tinkering away in the shed (as ya do), i load it, then charge it....then go get a beer out of the fridge

now im back in the shed a little sidetracked, so then i start lifting it out of the vice...i say to myself "hey... is it leaking?" as i wave my hand near the muzzle, then i turn away from the vice and farking BANG!... i diddnt know what happened then i see the top of a nice shiny little sphere embedded in mi hand, i go "hey wtf??"

the marble was in bedded in my hand and against the bone, accomplished at 50psi somehow. as i turned from the vice the trigger hit the bench.

i ended up with a fractured right index finger and 7 stitches.

dang i dont want to to that again.

peace man

Mitchza89 · Thu Mar 29, 2007 8:55 am

Holy fark dude. Thats gotta hurt. Your cannon must have some serious power. Gee thats funny, the 1st pneumatic I made was with my best mate after a sixer of beer in the shed on a thursday night hahahahaha. I'm surprised we ever hit anything, we managed to hit a foam box at 20m with 50psi. Good times and damn good times to come

Anyways mate I'm gonna hit the sack. Hey if you have msn, give us your email address

.

All the best,

Mitch.

mobile chernobyl · Thu Mar 29, 2007 9:59 am

That FPS sounds a little high, not doubting you, but are those actual Chrony readings, or GGDT outputs? if thats actual Chrony readings im impressed! I made a design somewhat similar to yours thats putting marbles through steel 55 gallon drums with accuracy (shot a marble through an existing marbles hole lol) now that I have access to any machine i need in college, ill be putting some test designs to work hopefully getting a 300psi marble gun in the works, there quite fun and accurate haha.

On another note, has anyone experimented with UHMW polyethelene material for pistons? It machines like butta and I have access to alot of it, and i'm going to try some designs out piston and bbmg alike.

keep_it_real · Thu Mar 29, 2007 11:52 am

I think you should leave the sprinkler valve on and just use it at 150 psi. It's probably more powerful than a blow gun for a pilot valve at 160 psi. Does GGDT include the pilot valve in the calculations?

Sweet gun though. I liiike it...

rna_duelers · Thu Mar 29, 2007 5:11 pm

Well in Metric systems all pressure rated plumbing parts are rated to 3x there running pressure before it bursts,so 450psi before that valve goes pop.But keep it down to the rated pressure for saftey

.Cant wait for the polly chamber because that shit it tough!500psi running pressure so the weakest point would be the sprinkler valve.

How about you take it to 25 Bar and use a ball valve as the exhaust valve then yor in buisness.

Chaos-Ouch!That has got to hurt alot broken fingers/nuckles are the worst.I mean u cant even have a wann...I mean Write anything

.Ohh what kind of beer as I love the Golden Elixir Of Life (beer).

Mitchza89 · Thu Mar 29, 2007 5:20 pm

mobile chernobyl, this was only a GGDT calculation. Not a chrony and yeah....I think its abit too quick myself but I'm only going by what it tells me.

Id like to keep the modded sprinker valve so I can hold it and shoot it abit more like a gun so Id have some better accuraccy. Ive tried it with the ball valve and its just hopeless to try and hit anything hahaha. Id go to 25 bar but I've only got a bike pump that I can use. I've seen one that goes up to 260psi.....that would be an absolute killer to have

Thanks alot for comments,

Mitch.

(P.S.....BEER RULES!)

Mitchza89 · Thu Mar 29, 2007 7:48 pm

OH YEAH! I just picked up a near new 2.3kg empty fire extinguisher for 3 bucks! Damn thats gonna looks unreal instead of the Poly chamber. As soon as I get it painted and attached, I'll take some pics straight away!