27 replies to this topic

[the beast]

I have some questions fore an upcoming homemade air gun im going to be making hopefully.
Firstly i was wondering what a very good type of glue for airtightening something is such as epoxy, hot glue etc?
Also, other than a solenoid valve what would be a good valve for a homemade air gun i have heard a ball valve is good but how bout others?

sorry if i didnt make sense

[The Shadow]

Goop is usually a good one for me, and I've also gotten good results with a ball valve in my time with homemades.

[Thom]

What about epoxy to hold it and goop to make it airtight?

[Carbon]

What kind of parts are you gluing, and how much pressure will it have to hold?

[the beast]

Carbon- i need to airtight a cpvc coupler to a piece of regular cpvc im not exactly sure what type of pressure but hopefully relatively 90psi give or take 15 psi and i could do a double layer as thom suggests

[Carbon]

If you're using PVC parts under pressure, the only glue you should use should be PVC cement (not sure there's a specific CPVC cement, but there probably is). It's the surest and safest way to glue the pieces together, as it chemically fuses the plastic.

After you've used the cement, you can seal up any leaks with Goop or epoxy.

[General Cole]

You could also use modeling glue, it will melt the plastic together.

[Jtcm]

I agree with Carbon and PVC or cpvc under pressure needs pvc cement or in this case cpvc cement (it does exist).

Edited by Jtcm, 31 July 2007 - 06:03 PM.

[the beast]

Thanks guys but how about a good valve for the same gun i know a ballvalve is good but anything else?

[Carbon]

A ball valve is functional and cheap, but has slow air release and a difficult trigger pull. A modified solenoid sprinkler valve has a much faster air release, and can be fired using an air blowgun trigger, but requires that bit of modding for it to work well, and costs more (about $15).

[b00m13]

Have anyone seen that Mythbusters episode where they bust out of Alcatraz?
I remember Jamie making a "Prison-Made" Ping Pong Ball valve that was used to keep the air locked in their "Prison-Made" raincoat raft.
I think he used 2 mini water bottles to make the casing and a ping pong ball to keep the air locked in, and it looked something like this...



Maybe it would be possible to make one similar to this, perhaps with... those mini hotel shampoo bottles, or any small tiny bottles, and to hold the air... a mini ping pong ball? (Maybe from a 99 cent store that just so happens to sell 99 cent mini ping pong ball sets... I bought a mini roulette from one once, so hey, it could happen.

Edited by b00m13, 01 August 2007 - 09:35 PM.

[bjack]

Boom13, correct me if I'm wrong but that would make an effective check valve, a ball valve releases air while a check valve lets air in but not out or vice versa.

[Carbon]

Nerfturtle just made something like that out of tubing, a spring and a marble in his homemade check valve thread.

[b00m13]

Yeah, I read that a while ago.
It's a pretty good device, my Gunblade mod uses the same principle for the "trigger" mechanism.

PS, I got confused, an example of a ball valve is the valve used to open and close your garden hose right?

Edited by b00m13, 01 August 2007 - 09:39 PM.

[monkey with a nf]

I think that's different, as it requires multiple twists to open, whereas a ball valve just takes a quarter turn. The PVC ones are notorious for being very difficult to turn, and while the metal ones are better, they still are pretty slow.


EDIT: Clarification.

Edited by monkey_with_a_nf, 01 August 2007 - 11:08 PM.

[the beast]

Hopefully it will end up looking somewhat like this

Edited by the beast, 02 August 2007 - 02:48 PM.

[SHADOW HUNTER ALPHA]

My suggestion is to move the ball valve closer to the barrel so the air doesn't have to travel as far, and then use the bend where the ball valve is in the diagram as the stock. It will be more effective and durable. Plus, you should add a vertical support connecting the pump behind the foregrip so the frame doesn't get twisted or warped after prolonged use.

Edited by SHADOW HUNTER ALPHA, 02 August 2007 - 03:35 PM.

[monkey with a nf]

You'll want to use a PVC size larger than 1/2" CPVC, as that is pretty small for a tank, and you'll have trouble finding a valve.

[SHADOW HUNTER ALPHA]

More advice:

Get pressure-rated PVC for the tank. Also, you can bolt some wood to one side of the ball valve's handle to make it easier to turn. That, and you'll need a longer barrel.

Edited by SHADOW HUNTER ALPHA, 02 August 2007 - 03:47 PM.

[the beast]

With most of that in mind i changed it to this

The "Outside Tank" could be anything such as a bottle or just something i find at the hardware store.

You'll want to use a PVC size larger than 1/2" CPVC, as that is pretty small for a tank, and you'll have trouble finding a valve.

For that i added the outside tank then i can still use 1/2 inch CPVC hopefully.
And ill remember to look for pressure rated CPVC.
Sorry Shadow hunter i just couldnt get away from the stock.

Edited by the beast, 02 August 2007 - 05:03 PM.

[SHADOW HUNTER ALPHA]

I didn't want you to delete the stock from the equation, but rather use part of the existing tubing in place of an add-on stock (I.e., the bend in the pipe where the ball-valve used to be near would make a good stock).

Also, I would avoid using water bottles as air tanks. Even though they can hold pressure, it is much easier and safer to use a larger pressure-rated PVC tank. CPVC tanks will be too thin to hold enough air for attaining good ranges. However, the rest of the frame could be constructed from CPVC that can withstand the pressure you are using. (By the way, what PSI level are you intent on using for the gun?)

[the beast]

Relatively around 90 PSI hopefully but i could be off by some. And that definetely would be a good idea to make a removeable stock ill definitely try that out. Im hoping to go out and get materials on Sunday.

[frost vectron]

Try these links:

http://nerfhaven.com...zero_ballvalve/

http://nerfhaven.com...?showtopic=3240

[the beast]

Frost Vectron thanks for the links but they didnt help much. Above is a much better picture thanks to 3DBBQ's website at http://61.221.57.37/...pbworkshop.html

Edited by the beast, 02 August 2007 - 10:59 PM.

[SHADOW HUNTER ALPHA]

I would actually recommend the twin-valve design for more flexibility in rate of fire. You can do several quick shots without repumping by opening the rear ball valve and closing it, then loading the gun and opening the first ball valve and closing it. That process can be repeated until the tank is empty. If you want a long-range shot with a slower reload time, keep the rear ball vallve open and just use the gun like your original design with the first valve as the only active one.

P.S.: 3DBBQ has scores of guns on his site if you didn't look through them all, and if you are interested in building several of these types of guns, you should check out some of his other designs.