SpudFiles

So theoretically speaking run a 3in steel/malleable iron, chamber, to a 2.5" camlock, to a 2.5" barrel?

Just so you'd know...
Above 2" diameter, pipe prices start getting ridiculous. You can get 2" fittings fairly cheap in usa, but go for "3 and you'll probably be looking at $20 or more for, say, an elbow. I think it's possible to build a 1.5" piston for under $100, but I'd start with a burst disk design then upgrade later.

Even with a 1.5 or 2" valve, you have no idea how much recoil you'll get from cola cans at 10x (hint: you'll need a padded stock and someone to catch you). Going from a simple combustion to a large 10x hybrid will be like suddenly acquiring superpowers anyway, so I think you can get away with a smaller chamber/valve for starters. Look up HGDT on the spudwiki and play with the program a bit. It'll give you ballpark figures as to the power you can get.

Should I try to stick with a .6 to .8 to 1 c:b ratio?

That'll give you a good balance between power/efficiency, but you could probably go much lower if you need to.

Oh, I guess HGDT doesn't have a wiki page for some reason... here:
http://www.thehalls-in-bfe.com/HGDT/

Could I run a over under design? Or is that a waste of power? Or unsafe?

It'd be fine, if you go with a piston valve you pretty much are forced to go over-under if you want inter-changeable barrels.

As Fnord suggested, it's probably best to go with 2" fittings so you can stick to your budget. The recoil will be immense at 10x mixes. You wont be firing it from the hip or shoulder, that's for sure.

Have you decided whether to go with a 2" burst disk valve or a 1.5" porting (housed in a 2" tee fitting) piston valve?

03cumminsguy wrote:Could I run a over under design? Or is that a waste of power? Or unsafe?

Just remember that this gun will have significant recoil. For an over under design that can put one heck of a lot of stress on parts that are already being pressurized up over 1000 psi (1000 psi would be what about a 7X gun?). Mostly because the barrel is what recoils the most, the chamber wants to stay where it was. So make sure the barrel and chamber are well braced to each other.

And you might consider not going for 10X on your first try. I'm to lazy to do the calc but a water filled soda can fired from a suitably sized barrel of a 10X gun is going to have a heck of a lot more kinetic energy than say an M-16. That soda can will do things like pass clean through a house (at least it will if it can hold itself together).

I would like to run a piston setup. But don't fully understand the concept of constructing one. Or the porting. So if there is a piston 101. I'd be willing to take some notes and give it a go.

As far as the mix goes. 10x was a figure stating I don't need to be able to tell my friends I constructed a cannon capable of a 40x oxy-propane mix. I just want a reliable, yet powerful cannon.

Lowering the mix will open up some options and will let you choose a burst disc material that is easier to work with, unlike aluminum cans or tons of layers of foil. Cam locks are rated to 250psi, which is perfectly safe for a 2x hybrid. If your chamber is of a decent size, the large volume at 2x will be very very powerful.
You said your budget was $100 or something like that? You'll need to make this thing really simple and I honestly think any piston design will cost more than you think at first. I'm talking about replacement parts for making a new pistons after you realize your first one sucked and didn't work, as well as the endless fiddling and nickel and diming that will likely take place trying to get it to work. Once you invest in it, you are committed and you won't want to stop until it works and that could get expensive. It might end up being a really big, heavy door stop and never work due to the frustration in trying to get the thing functioning.
First hybrid, I say go burst disc. At least you know it will work. Just my opinion and thats what I did and I have had about 2 years of fun, reliable use from my hybrid. Guess how many parts i've had to replace? NONE! ZERO! Only the batteries for the stun gun. It works every friggin time.

I will probably go with a burst disk at first. As far as camlocks or screw unions go. Are there any particular stores that carry these? Ace hardware, Home Depot, Lowes? or a plumbing retailer? Or mostly just internet? I am in North Florida if anyone is near here and has somewhere they know of.

Internet is the easiest. McMastercarr has them. You can find them elsewhere online as well for less money maybe.

http://www.mcmaster.com/#cam-lock-fittings/=ehbj5k

MrCrowley wrote:It'd be fine, if you go with a piston valve you pretty much are forced to go over-under if you want inter-changeable barrels

FWIW... I'm finally committing to paper(*) my next design. It'll be a 2" valved hybrid with a 6" diameter valve housing... Which means that the valve housing can be short enough that it's a coaxial design with interchangable barrels. There'll be more dead space after the valve than I prefer, but I don't think it'll be too bad.

I mention it only to present options.



(*) When I commit to paper, steel usually isn't too far behind.

D_Hall wrote:FWIW... I'm finally committing to paper(*) my next design. It'll be a 2" valved hybrid with a 6" diameter valve housing... Which means that the valve housing can be short enough that it's a coaxial design with interchangable barrels. There'll be more dead space after the valve than I prefer, but I don't think it'll be too bad.

I'm liking what I hear (read). More piston valved hybrids the better IMO

Any ideas about what mixes it will run at or the primary ammo (I assume cannons like these are primarily built for one or two different types of projectiles as that's what the pre-build performance calculations are based on)?

I would like to run a piston setup. But don't fully understand the concept of constructing one. Or the porting. So if there is a piston 101. I'd be willing to take some notes and give it a go

Unless you can get someone to machine one for you, I'd recommend going burst disk. Piston valves can be a pain in the ass to troubleshoot and the best way to learn how to build them and troubleshoot them is through experience; trial and error.

MrCrowley wrote:Any ideas about what mixes it will run at or the primary ammo (I assume cannons like these are primarily built for one or two different types of projectiles as that's what the pre-build performance calculations are based on)?

Roughtly 4-6X. Primary ammo will be golf balls. It'll be a breech loader like the last one I built (identical barrel/action). It'll also have a removable rear plate that will allow the gun to be converted to simple pneumatic operation in about 5 minutes.

And yes, it'll be very heavy. Thus, I'm building a mount that will drop into the trailer hitch receiver on my truck... I'll be able to drop the tailgate and use that as a chair while I aim/shoot.

D_Hall wrote:

MrCrowley wrote:It'd be fine, if you go with a piston valve you pretty much are forced to go over-under if you want inter-changeable barrels

FWIW... I'm finally committing to paper(*) my next design. It'll be a 2" valved hybrid with a 6" diameter valve housing... Which means that the valve housing can be short enough that it's a coaxial design with interchangable barrels. There'll be more dead space after the valve than I prefer, but I don't think it'll be too bad.

I mention it only to present options.



(*) When I commit to paper, steel usually isn't too far behind.

Will this be a piston design?