A look inside the "bleacher reacher" t-shirt launcher

Show us your pneumatic spud gun! Discuss pneumatic (compressed gas) powered potato guns and related accessories. Valve types, actuation, pipe, materials, fittings, compressors, safety, gas choices, and more.
5150cannon
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Thu Apr 08, 2021 1:27 pm

Do you have any pictures of the trigger design?
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jackssmirkingrevenge
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Sun May 02, 2021 8:11 am

I don't have pictures but if I recall well it was a simple poppet, much like a blowgun valve.
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Sat Sep 25, 2021 7:25 pm

i see the diagram and the parts but am lost as to the position of the smaller aluminum piston and it also seems in the pic to have a notch or channel cut out from the tapered end towards the oring any help would be great
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Sat Sep 25, 2021 7:28 pm

nevermind it just clicked in my mind the delrin part does not move and instead acts as the cup seal
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Mon Sep 27, 2021 3:06 am

so from the very helpful posts here and a patent search I came up with this not done yet but its mainly 1/2" & 2" pvc fittings

https://a360.co/3zFl1Vr
mmk8283
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Tue Aug 09, 2022 11:43 am

Does anyone have more information regarding the slot in the piston or its function? I am assuming the piston is not using a standard o-ring, rather a cup seal? I'm trying to draw this assembly in 3D modeling software and i'm confused by that slot
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jackssmirkingrevenge
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Wed Aug 10, 2022 10:15 am

mmk8283 wrote:
Tue Aug 09, 2022 11:43 am
Does anyone have more information regarding the slot in the piston or its function? I am assuming the piston is not using a standard o-ring, rather a cup seal?
Do you mean this one?

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If so, that allows a standard o-ring to serve the same function as a cup seal.

When gas comes from behind the piston, the o-ring deforms into the slot and the gas flows past it to fill the firing chamber.

When the pilot valve is opened however, the o-ring cannot deform in the opposite direction and therefore gas cannot flow from the firing chamber to the pilot chamber.

Essentially the piston becomes a one-way valve, you will see a similar design used in pump piston heads.
hectmarr wrote:You have to make many weapons, because this field is long and short life
mmk8283
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Wed Aug 10, 2022 1:40 pm

Thanks for the clarification, I guess I've never seen an o-ring used in that way. I think I have the concept pretty well figured out here...

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mmk8283
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Wed Aug 10, 2022 2:52 pm

I'm working on a mostly 3D printed version of this that fits inside of a 3"pvc
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jackssmirkingrevenge
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Sun Aug 14, 2022 7:40 am

Looking good! What kind of materials will you be using?

Consider that any surface that interacts with an o-ring will need to be smoothly polished to seal, and that the piston is going to smack into the rear of the pilot chamber pretty hard so an impact resistant material and some kind of elastic shock absorber is recommended.
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Mon Aug 15, 2022 6:50 pm

I'm using PLA for the first time around... I'm really just testing the concept at this point. I'm thinking the piston can be printed as well, less weight will reduce the impact force. I will put adhesive backed silicone rubber on the front of the piston to create the seal. I'm planning now to remove the o-ring on the rear cap, I don't think it's necessary. Also I plan to slightly deform (flatten) an area of the PVC chamber to accept a 1/4npt bulkhead fitting. End goal is for this to be a t-shirt cannon for parade use. Previous testing only required around 30-40psi to toss a shirt safely.
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