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Sch 80

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Sch 80

Unread postAuthor: Spyider » Wed May 02, 2007 11:08 pm

is sch 80 the best choice to use for my hybrid chamber? besides a metal of corse, id love one them but i don't got a welder, so w/e

anyways if anyone could tell me the best chamber size (4"?) and whats a good minamal psi ratting 300+?
thanks,
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Unread postAuthor: hi » Wed May 02, 2007 11:35 pm

I would personally use a 2'' or 3'' sch 80 chamber. 4'' it way to big ( for me anyway) it would only handle a 3x mix before bad things happen.

If i were you i would use a 2'', trust me when i say that is plenty of power. I used threaded sch40 metal pipe for mine, but sch80 really is a better choice.
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"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
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Unread postAuthor: CS » Wed May 02, 2007 11:43 pm

You can use just threaded metal components, no need to weld. Chamber size depends on your intentions, if you want to slap a ten foot GB barrel on the launcher, a 4" chamber may be the way to go. Personally I would prefer a smaller, more manageable launcher, so "hi's" two-three inch suggestion may apply.

Just for your understanding the safety rating does not holds on physical properties. The safety rating is a low-balled figure, although following this value will no doubt reduce failure.
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Unread postAuthor: Spyider » Wed May 02, 2007 11:45 pm

can u use all threded metal pipes?, would that be good or would i still have to weld it ? because i could prob just bring the pipes to school and weld them up their i guess..

i was thinking 3" the smallest
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Unread postAuthor: Spyider » Wed May 02, 2007 11:53 pm

if i did make a metal one, how would i put in my direct propaine injection? would i drill/ tap the hole for the selected elbo then put plumbers tape on so it wont leaak? same with the hole for the air compressor to connect to? and the stungun ignition would have to not tough the pipe or it could get short circuted right?
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Unread postAuthor: hi » Wed May 02, 2007 11:55 pm

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"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
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Unread postAuthor: CS » Thu May 03, 2007 12:06 am

Provided you use teflon tape, and tighten them hard enough it will work. All this leaking you hear of in threaded joints is just because of improper procedure. How many industries have you seen use threaded metal pipe, and never weld them?

Sounds like you have a welding class, so if you wanted you could weld them. Although I don't necessarily see the need. Not to mention your teacher may not let you weld it, I know my welding teacher won't let us.

In our welding class recently we welded up a 6"x6"x6" box with single sided 1/4" diamond plate. The corners were fillet welded, using a MIG with straight CO2 shielding gas. (generally this is the case, although some schools play with Argon mixes) A 1/4" hole prior to the box being welded is pierced. With this the objective is for your box to hold 120PSI air pressure. This is done by pushing a rubber tipped blowgun in the pierced hole, and spraying the weld beads with a soap-water mixture. (surprisingly the blowgun-hole connection does not visibly leak) Why am I telling you this? Well I out of the 90 students doing this, I was among two people to actually achieve this on the first try. Basically that means without having to grind out any part of the weld bead or the corners to be re-welded.

So I may suggest to weld the fittings would be to your dis-advantage as it is hard to get a welded joint of such specifications. Especially having to weld on a round surface would present a challenge in itself. So again I would suggest even if your teacher will allow you to weld, to be extremely similar with your equipment, and of fairly good welding skills to do this. Not to mention there is nothing wrong with the teflon method...

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Please don't double post.

Yeah you can either tap the thread into the wall of the pipe, or us a series of fittings off the chamber to reduce down to the proper size. I might say tapping into metal is fairly hard, so you may want to practice on a scrap piece or something. For the ignition you can use a spark plug, although if I recall correctly the proper taps are hard to come by. (I could be terribly wrong on this point) So you may have to look into alternative means of ignition.
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Unread postAuthor: Spyider » Thu May 03, 2007 12:23 am

well the drill/tap would be easy because if i bring in just the unassembled chamber (pipe only) im sure i can drill and tap the holes to the exact size without them getting suspitious. as for the spark plug, i can connect a BBQ or stun gun to that and it'll still work ? right.

any other tips on metal hybrids would be appreciated.

thanks,
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Unread postAuthor: CS » Thu May 03, 2007 1:20 am

Yeah a one lead of the the BBQ/ stungun will be wired to the chamber, while the other one will run to the top of the spark plug. Just thinking since you are considering drilling, and tapping this at school, possibly you could just weld the spark plug in real fast? Well hope this works out.
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Unread postAuthor: mark.f » Thu May 03, 2007 6:22 am

pimpmann22 wrote:Chamber size depends on your intentions, if you want to slap a ten foot GB barrel on the launcher, a 4" chamber may be the way to go.


I disagree. I remember a hybrid a while ago by some guy named iusemyopensights that used a 2" chamber only around ten inches long for a 5' long GB barrel. You could probably use a 3" chamber for a ten foot or longer golfball barrel. I'd avoid using a longer 2" chamber, though, as the geometry isn't too conductive to a "safe" burn. :wink:

Spyider, as my Fine Arts Survey teacher would say, "It would be my humble, but accurate, opinion" that you use simple threaded connections. Cheap and simple, (unless you get 3" fittings and pipe, then you'd have to go buy a huge-ass pipe wrench, tons of teflon tape, etc.)
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