Just joined + My propane WIP

[chenslee]

I knew that there were people like me building these things out there. A few pics of what I refer to as the "cocker".



2.5" bore air cylinder bodies, bolt feed, and pin valves to meter the propane when cycled.

Still in design phase, but I have over $190 in parts so far including: barrel, the combustion chamber, the ignition system, 90% of the fittings, the bolt material, the magazine springs, the grip, the carburetor nozzle, the o-rings, the pin valves, the air lines, the purge cylinder (of needed), the propane tank adapter, propane tank, the 5/16x24 tap, the 8mm stainless magazine guide rails, the 8mm die for threading the guide rails, a bag of tennis balls, the adjustable regulator and a smattering of the 8020 plates, fasteners and brackets I need.

hopefully I'll be putting the bolt on the lathe today and cutting the o-ring grooves!

I've been blogging it for funzies at http://propanetennisballcannon.blogspot.com/, but now that I've found this place, I'm going to start posting here too.

[starman]

Welcome to Spudfiles! Nice concept drawing you have there. I'm interested in the term "carburetor" you use. What are your ideas around that? What are your plans for ignition?

You mention lots of parts there that are really meaningless to us unless you show them in context. This looks like a highly involved project. Can you provide us a few more details on its workings.

[ALIHISGREAT]

The design looks pretty......but how am i supposed to know how it works as starmam said; a few details on the workings would be Appreciated

Welcome to spudfiles.

[chenslee]

Sorry for the vagueness, I'm just getting started over on spudfiles.

I guess it's time to start chunking up pics. Standby.

Carburetor: nothing fancy, just a 1/8NPT nipple, a 1/8NPT to 1/4NPT bushing and a 1/4NPT cap with a small hole drilled in it. I'm hoping to get enough velocity through the orifice to mix the propane and air.

Ignition: BBQ grill starter. http://www.walmart.com/catalog/product. ... id=8587363

I'm not looking to make planet shattering velocities. I want something that is easy to load, operate and maintain.

[chenslee]

It started with this.



[youtube][/youtube]

...And has progressed into a 3d model and a pile of parts.

The concept is pump action, spring fed over-barrel magazine. 5 shots.

This picture shows the metering "box" which is a hollow piece of structural aluminum extrusion on the lower right.




The regulator is a "Bayou Classic" 0-20 psi grill reg.



Instead of using ball valves, I'm using 2 Clippard mjv-2 pin valves to fill, then dump the metering box during cocking.

Everything is held together with 1x1 aluminum extrusions and water jet cut 1/8" 6061-t6 aluminum plate.

It's a work in progress, so a lot of details are missing like the ignitor and tank straps.

The balls are fed with a UHMW plate pulled by constant force springs:



The regulator is a "Bayou Classic" 0-20 psi grill reg.

[starman]

Much better, thanks for your effort to get those up. Actually looks like it will be a fairly compact unit for its complexity.

Tennis balls aren't known for their performance. You might get 100 - 150 yards with this, but if you can get the 5 loader function working right, you can keep the kids and the dogs ran ragged.....

Keep us posted on your progress.

[Radiation]

interesting video, you seem to slam that ball in place pretty quick, what's the reason for that? Does it mix the fuel? I don't understand, are you metering your fuel?

[chenslee]

I got about 50 yards out of the blowtorch strapped to the barrel and jamming the ball in about 2", so 100-150 I would think is about right once there is actually a barrel on it.

I want it to be non-lethal. It hurts less when my friends inevitably "accidentally" shoot me with it.

I just saw the "spark strip" in the wiki. Probably going to use that even though the ignitor came with probes.

[chenslee]

interesting video, you seem to slam that ball in place pretty quick, what's the reason for that? Does it mix the fuel? I don't understand, are you metering your fuel?

I cludged that whole thing together in about 10 minutes.

1st, it's just a Berzomatic propane torch with some air fittings, and it mixes fuel and air through ports at the base of the neck. If there is a big fuzzy ball in the barrel the propane just comes out the air ports so I have to jam it in after fueling.

2nd, the piezo is in the blowtorch, several inches from the combustion chamber. if I wait too long before sparking, the A/F is too lean in the blowtorch and I end up having to fish a tennis ball out the end of the barrel.

If I get it just right, the propane in the tube lights and sets off the propane behind the ball.

[Radiation]

Ahh I see, you are relying on the air fitting to approximate the fuel air mixture necessary to ignite.

[chenslee]

Ahh I see, you are relying on the air fitting to approximate the fuel air mixture necessary to ignite.

Actually, the blowtorch head mixes fuel/air. I could partially hold the trigger on the torch for 10 minutes and mixed fuel would just keep pouring out. It also mixed a bit with the air in the chamber. What was good about this was I could shoot back to back without blowing out the chamber; the requited air came in with the fuel.

[psycix]

Welcome to spudfiles!
Great job on the blowtorch mixed fuel thing. You get a perfect 4,2% mix out of that thing or what?

[chenslee]

Welcome to spudfiles!
Great job on the blowtorch mixed fuel thing. You get a perfect 4,2% mix out of that thing or what?

Not sure, but the blowtorch mix sure made a pretty blue flame. It really was just an oversized pop-gun.

[Lentamentalisk]

you don't get exactly 4.2% of course, because the blowtorch is designed to have a fairly long flame, but when the rich mix enters the chamber, which already has some air it it, it gets to well within the combustibility limits.
On a similarly basic concept to your first thrown together launcher, if you stick a plastic bottle over the head of a blowtorch, and hold the trigger down for a few seconds, and then, (while wearing sufficient protective gear of course) press the trigger down all the way, it ignites, and sends the bottle flying.

That really looks great.

One question: Where did you get those sweet air cylinder bodies?

[chenslee]

http://shop.ebay.com/items/_W0QQ_dmptZP ... &_osacat=0