What I want in an anti-tank cannon.

[TheTramp]

If you're using a quick change all you'll need is a small dump chamber between the changer and the valve.

To determine the sizes of everything you need the barrel volume, dump chamber volume, dump chamber pressure, and velocity you are trying to get.

For example mine has these stats:

Barrel: 15"x2"
chamber: 7"x3"
chamber pressure: ~75psi (one 12gr)
Vel.: ~250fps

One 12 gram CO2 cartrage fires a nerf rocket at around 250fps. If fired at an angle it will sail at least 75 yards.

[rkjunior303]

ok so a 2'' barrel will fit those nerf rockets cool. >That's probably exactly what I need then since That is what I was looking to use... now, what do I make the dump chamber out of? (sorry for so many questions!)

Also, on any threads, will Loctine 545 (pneumatic thread locker) be sufficent? I use it on all of my fittings.

[rkjunior303]

Oh, using that setup how long is your completed LAW? Would that be moutable onto a wood stock for a grenade launcher type look?

[doc_Zox]

this one is a good guide:

http://spudtech.com/content.asp?id=22

[Rhinopkc]

A 42 cubic inch chamber will give you 100 psi from a 12 gram. Zox, did you buy one of those from Joel?

[Rhinopkc]

Also, I have had better results with 2" sch 80 for the barrel, the nerf rockets fit tighter. The rockets fit too loose in sch 40 and fall out sometimes.

[rkjunior303]

rock on.. thanks guys! i'll make sure I post pics when I finsh. now the dump chamber before the sprinkler valve can be made of PVC as well, correct?

[doc_Zox]

Joel's launcher is a great value

and has all the right parts

like the guage and the 125 psi safety valve

you need that on any PVC chamber

i have not bought one from Spud Tech yet...

Right now i'm working on a low tech, low cost Piston valve design

[TheTramp]

I bought Joel's 100psi gauges for my launchers. The nice thing is that you only have to drill the hole. THe threads of the gauge will tap for themselves.

I am suprized to hear that there are problems with the Sc.40 pipe letting rockets fall out. I've never had that problem.

[Rhinopkc]

They get real loose with temperature changes, sometimes they fit real good, sometimes they don't. With the sch 80, I get a nice, tight fit, with better accuracy. I spent a lot of time and money experimenting with different designs, my final design is breech loading, with constant air. If you build one, you MUST INSTALL A POP-OFF VALVE! If you don't, 1 malfunction can kill you!

[TheTramp]

Originally posted by Rhinopkc
If you build one, you MUST INSTALL A POP-OFF VALVE! If you don't, 1 malfunction can kill you!

Even when only using 12 grams?

One 12 gram only gives me ~75psi and I only charge it when I'm ready to shoot so it's not going to heat up. I can see if I was using reg'ed constant air but....

[doc_Zox]

wanna see my new ghetto charger concept?

http://www.performancebike.com/shop/Profile.cfm?SKU=16499

a pop off will prolly be required by a thorough judge on a plastic chamber

its a $9.99 investment in anti-Darwin logic

http://www.spudtech.com/detail.asp?id=17

[rkjunior303]

that's pretty cool. just have a fill nipple on the charge chamber and fill it with a 12g connected to that?

[TheTramp]

I use one of those! Well, not that exact one but still.

I just got a 12gr quick changer that I'm going to start using.

I guess it won't kill me to order a pop-off from Joel and put it on.

I'll put up a picture on mine tonight.

[doc_Zox]

yep! a schrader tire valve and i'm GTG

with a quick change one co2 shot is all you can load, you could double fill with the schader valve

some folkes claim if you use a rubber tire stem for the fill port, it can act as a pop off too...

my other LAWS have crossman quick fill CO2 but the bike dealie is on sale this week for 13 bucks...

heres some other good hardware:

http://www.cooper-t.com/expansionchambers.html

http://www.cooper-t.com/miscellaneous.html