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IHTAHBATMT

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: MountainousDew » Thu Jun 11, 2009 10:12 pm

IHTAHBATMT stands for: I Hope This Acronym Helps Bring Attention To My Topic... I know, its a mouthful! (That's what she said!) Did it work? Were you attracted by the title?

Anyway, I currently going through the stages of designing a new gun to play with, and I could use some help... At the moment, I'm thinking about going for a semi-automatic gumball launcher, kinda like Clide's "GB Semi". My main problem with that design, is that I'm 13 and 11/12ths and I have no access to a lathe or other "machining machines"...

If someone could help me design this gun, I could pay them with imaginary cookies, everyone likes cookies. And if they don't, I kill them with my "bear" hands!

I posted Clide's GB Semi animation below, for reference.
And I found a site, where I can buy 8500 (not typo) 1/2 inch gumballs for ~$64 USD including shipping.
(Another) And I will most likely be using 1/2 inch sch 80 PVC pipe for the barrel, because of the near perfect fit.
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Unread postAuthor: D_Hall » Thu Jun 11, 2009 10:19 pm

Yes, I opened this thread simply to see what the topic was.
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Simulation geek (GGDT / HGDT) and designer of Vera.
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Unread postAuthor: Gaderelguitarist » Thu Jun 11, 2009 10:20 pm

I'm interested in building a large bore semi as well.

I have a small shop with a lathe, drill press, band saw, table saw, bench grinder, scroll saw, and router table. No CNC for me!

Kind of hard to believe that gumballs are very consistent in size.

Back to your needs...

i would just sketch out Clide's animation as a static image and them work out what could go where and how to do it. Calipers will be your best friend i guess.
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Unread postAuthor: mobile chernobyl » Thu Jun 11, 2009 11:16 pm

There is an issue with your dump chamber.

Specifically pointing towards your "Air In" area, and the mechanical sear that will drop to fire it. You have a larger surface area on the chamber side than you do the sear side, so it will not simply slide towards the sear like in the animation. It may slide towards it a little bit, but diameters of sealing spools are not given. This design could easily work and it looks like a hybrid of the "toolies" piston on here and an unbalanced spool valve.

Check out ZDSPB.com for more animations of all paintball semi-automatic operations in use under the "tech" section, and "marker animations".
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Unread postAuthor: dudeman508 » Thu Jun 11, 2009 11:20 pm

mobile chernobyl wrote:There is an issue with your dump chamber.

Specifically pointing towards your "Air In" area, and the mechanical sear that will drop to fire it. You have a larger surface area on the chamber side than you do the sear side, so it will not simply slide towards the sear like in the animation. It may slide towards it a little bit, but diameters of sealing spools are not given. This design could easily work and it looks like a hybrid of the "toolies" piston on here and an unbalanced spool valve.

Check out ZDSPB.com for more animations of all paintball semi-automatic operations in use under the "tech" section, and "marker animations".


That was the diagram from the GB semi, the one clide made. We already know it will work.
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Unread postAuthor: Technician1002 » Thu Jun 11, 2009 11:34 pm

Funny you brought up the topic of gumballs in bulk. I bought a box a few years back too except it was the 1 inch jumbo that is sold for a quarter in th e big machines. The box of large one only had 850 per box. It was my favorite ammo for the Mouse Musket. It wasn't semi auto or anything. I do have plans for a semi or full auto combustion Gum Ball Machine... Gun. Plans are under wraps at the moment on the chance I'll be able to build for the contest.
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Mouse Musket and Plywood with the gumball hole. This is sadly retired.
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Unread postAuthor: THUNDERLORD » Thu Jun 11, 2009 11:45 pm

I was toying with a 1.5" chamber and barreled sprinkler valved gun the other day.

I had lost interest and not finished it, but my parts between two places, I got it finished (felt like spudding).
I had no pump, and no connections for my new fridge compressor.

So I connected a clear hose from a fix-a-flat can with super glue and a small hose clamp to a modified blow nozzle tip. (The cone shaped rubber tipped one, smaller thread section sawn off, rubber tip cut off).

I threaded that into a propane torch base (brass valve part with brass nozzle removed).

I threaded the tire valve part of the hose onto the shrader on my gun chamber and voila, it gave bursts probably rapid enough for semi-auto.
It would be faster if the chamber was one inch or smaller.
It fills faster with the propane inverted because more liquid flows too.
EDIT:It would fill much faster through a hose barb instead of shrader (maybe too fast(?))

The design would be simple to add a blow forward bolt to.
Perhaps the bolt could be constructed from:
two reducer bushings,
a coupling (larger than barrel),
a few large washers (epoxied to bolt),
a spring,
and a "T" for the magazine.

Pretty simple, and no need for much machining.

Oh, a pressure switch (bought or homemade) could be added to the chamber, connected to the solenoid on sprinkler valve for full auto, or an indicator light to show proper pressure between shots.

Good thing when I modded the valve, I left the solenoid intact also.

BTW, noticed it pilots much faster with no hose between the blow-gun.
Guess I'll run a bar from a seperate trigger to the nozzle trigger. :wink: 8)
If you're interested in similar, I can try to check sizes tommorrow on components if I get a chance for you. The candies are 1/2" ??? :)

EDIT: :oops: Duh, "Fit 1/2" shedule 80"
Also that propane (added) smell made me a little sick for a day, mostly when i thought about it. :lol:
Not sure if they have schedule 80 stuff at my local Home depot...Do schedule 40 fittings fit OD on it ???
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Unread postAuthor: psycix » Fri Jun 12, 2009 3:32 am

Your best bet is to use a long threaded rod for the piston, and using huge metal washers with spacers and floating o-rings.

Didnt clide also build it without a lathe?
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Till the day I'm dieing, I'll keep them spuddies flying, 'cause I can!

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Unread postAuthor: mark.f » Fri Jun 12, 2009 6:48 am

No, clide used a lathe, but this can be done without one.

Depending on the size of your chamber and sealing port, you can most probably build without a lathe if you are creative. Post these sizes!
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Unread postAuthor: MountainousDew » Fri Jun 12, 2009 9:38 am

Thanks guys for the input, to answer THUNDERLORD's question, yes 1 inch sch 80 pipe has the same OD as sch 40 pipe.
Does anyone have any ideas on how to consrtruct the blow-forward breech?

P.S. I'm doing this on my new phone, so excuse spelling and grammar, if wrong.
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Unread postAuthor: MountainousDew » Fri Jun 12, 2009 9:39 am

Sorry, double post...
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Last edited by MountainousDew on Fri Jun 12, 2009 10:42 am, edited 1 time in total.
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Unread postAuthor: THUNDERLORD » Fri Jun 12, 2009 9:53 am

MountainousDew wrote:... to answer THUNDERLORD's question, yes 1 inch sch 80 pipe has the same OD as sch 40 pipe.
Does anyone have any ideas on how to consrtruct the blow-forward breech?...


Awesome, I am headed to Home depot nearby to get a free cup o' coffee.
I will check some stuff to get the gears turning and get back later today(?Hopefully)...

For the BFB, I have this idea of cutting slots into the PVC,
then adding a "l" or a "+" with the blocker pin "-" extruding from center. (The rod that the bolt is on to block air). (The preessure will flow around the "+" or "l")
That way, there is less restriction and the valve can open directly into the bolt, (Unlike JSR's first version where the air entered through a small blow nozzle size hole in a larger demonstrational bolt).

I am building a 1/2" OD brass one similar (3/8" bore), and was tempted to test it by threading it onto a 3/4" TORO sprinkler valve, pvc launcher .
EDIT:(My 1/2" version fits in a 3/4" "T" and will be a brass high pressure piston valved gun)...

Dang I'll be giving away contest ideas, but probably won't be ready in time.
Sure would be nice to have a steady schedule and Goals... :( :wink: 8)

EDIT:Now I am thinking the blocker pin design might be less efficient (build-wise) than holes in the bolt similar to Clide's design and several of JSR's.
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Unread postAuthor: Gaderelguitarist » Fri Jun 12, 2009 12:55 pm

Does anyone have any ideas on how to construct the blow-forward breech?


Get three bushings with the same smaller diameter size as your barrel.

Connect two in the back face to face with a piece of barrel material to simulate the back piece of the bolt housing.

For the bolt, since you don't have a lathe, you could do 3/4" PVC with and end cap and a series of couplings to make it the same diameter throughout. This would fit well in a 1 1/4" barrel. I don't know what would work for a golf ball barrel.
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Unread postAuthor: MountainousDew » Fri Jun 12, 2009 2:12 pm

Gaderelguitarist wrote:For the bolt, since you don't have a lathe, you could do 3/4" PVC with and end cap and a series of couplings to make it the same diameter throughout. This would fit well in a 1 1/4" barrel. I don't know what would work for a golf ball barrel.

The thing is, it isn't a golf ball barrel, its going to be 1/2 inch sch 80 PVC...
So that it can shoot gum balls.

Any ideas for this layout?
And maybe can you draw up a diagram to explain the part about the bushings, I don't quite understand...
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Unread postAuthor: MountainousDew » Fri Jun 12, 2009 8:28 pm

Gaderelguitarist wrote:For the bolt, since you don't have a lathe, you could do 3/4" PVC with and end cap and a series of couplings to make it the same diameter throughout. This would fit well in a 1 1/4" barrel. I don't know what would work for a golf ball barrel.

The thing is, it isn't a golf ball barrel, its going to be 1/2 inch sch 80 PVC...
So that it can shoot gum balls.

Any ideas for this layout?
And maybe can you draw up a diagram to explain the part about the bushings, I don't quite understand...

Edit: Chamber Diameter=1 inch...
Barrel Diameter=1/2 inch sch 80...
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