SpudFiles

(I'm a long time reader first time poster so bare with me here ) =)

Well, I have been using a basic combustion canon for over a year now, and I think I am ready to take the plunge and make an advanced combustion. I want to give it propane, fan, over-under, the works. Any way, for reasons which are beyond me, there are no stores anywhere close to me that carry any sort of PVC. I have called every Home Depot, Canadian Tire, etc to no avail. However they do have a good stock of ABS. So I used ABS for my first cannon. This worked fine, but is ABS still safe to use with a propane system? And if anybody is in Canada would you mind telling me if/how you get PVC?

Thanks

If your ABS is pressure-rated, you are actually better off using it as opposed to PVC. Even if it's not pressure rated, you SHOUD be fine, as long as you are careful. I don't know where to get PVC in Canada, though... I'm from the U.S.

Solid wall ABS is fine for any propane combustions; it is very resistant to impact, chemicals, UV rays, and temperature changes. I would venture to say that DWV solid wall ABS is more suited to combustion cannons than is pressure rated PVC, and it can certainly withstand more abuse.

Finding pressure rated PVC and fittings over 1" may well be a lost cause in Canada, I have been trying for about 6 months with no success. I'm not a fan of PVC though, so this doesn't really bother me. I have found that, in Canada, solid wall ABS is the way to go for combustions, and for pneumatics and hybrids, a well taken care of steel launcher is almost impossible to break without solid explosives, and lasts forever.

Sounds good guys, looks like my weekends just got fully booked

Just FYI, I have a metered combustion gun with a chamber fan, breech loading, spark strip, etc... (you could call it an "advanced combustion") made of cellular core DWV ABS pipe. It's seen hundreds of shots and shows no signs of failure. If it ever does fail, I expect it to crack open cleanly without throwing off any shrapnel. Just my two cents.

Peace,
Pete Zaria.

BTW Pete, thanks for drawing up those plans, I am going to try to model my gun off of those.

When its pressure rated you can use it, when its not... well be careful since it might break.

Chance of faillure is higher on ABS then on PVC but when PVC fails it shatters and ABS doesnt, it only cracks. (gun will be broken, but leaves YOU intact)

Canadian Spudder wrote:BTW Pete, thanks for drawing up those plans, I am going to try to model my gun off of those.

Let me know before you glue it together, there are a few things about that design I might recommend changing now...

I'll PM/email this to you also.

Peace,
Pete Zaria.

Pete Zaria wrote:

Canadian Spudder wrote:BTW Pete, thanks for drawing up those plans, I am going to try to model my gun off of those.

Let me know before you glue it together, there are a few things about that design I might recommend changing now...

I'll PM/email this to you also.

Peace,
Pete Zaria.

Why not update the plans? I have those plans, too, and was going to construct my next combustion after the plans.

Since I am in Canada, getting my hands on a stungun isn't going to happen anytime soon. Would a bbq sparker work? I don't mind replacing it every few hundred shots, I have lots from raiding trashed bbq's on junk day.

Andrew

yeah, you got any mates in the USofA that could post you the inards of a Stun Gun? and then youd just have to plonk it in a project box.....

Naw I don't , what's the word on Camera Flash vs BBQ Sparker?

A properly built camera flash circuit works very well, the problem with them is that they're generally bulky (including an ignition coil). I've seen some that have been built into a small section of 2" pipe using a motorcycle ignition coil that were pretty clean, though.

I bought a cheap-o ($10) stungun to use for my ignition system for awhile... worked for about 20 launches before it fried. I'm currently using a BBQ sparker, which, surprisingly, jumps all 5 gaps on my spark strip every single time without a problem. I plan on building a nicer ignition circuit soon, though.

Peace,
Pete Zaria.

The chances of DWV ABS failing on a combustion are lower than the chances of DWV PVC failing on a combustion. It isn't really fair to compare DWV pipe to pressure rated pipe. As far as ABS goes, I would recommend that you at least use solid walled ABS, which is, in Canada, far more common than cellular core.. Cellular core anything seems pretty dangerous to me.

I've done tons and tons of digging over the years regarding the pressures built up in combustion guns and after all my digging I've come to one conclusion. Normal combustion guns simply do not build enough pressure under normal firing conditions to blow a chamber. While you are talking about an "advanced" spud gun the difference in pressure between a propane fueled, stun gun fired, fan mixed spud gun firing potatos and a static guard fueled, piezo fired, un-mixed spud gun firing potatos is going to be negligible unless you added a burst disk or something. The potato in either gun is going to come loose at about the same pressure. While I personally don't care for ABS and have only ever used PVC either material is just fine for a combustion gun. You really only need to get concerned with materials when you're dealing with a pressurized gun, either a hybrid or a pneumatic. Check out this link to see what can happen with even well thought out hybrids.

http://www.koolpages.com/potatohell/Hybrids.html

If you REALLY wanted to go with pressure rated PVC all of the LOWES here in AZ carry PVC. That and I have a professional plumbing supply shop that has more PVC than you can dream of not too far from where I work. If you got me a parts list I'll get you a price and shipping cost guess-timate.