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Camlock Coupling Pressure

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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Unread postAuthor: Moonbogg » Tue Dec 22, 2009 4:58 am

I use an aluminum 2" camlock for a hybrid, but I use it at 2-3x and wouldn't feel safe at 5x or more. Its true the Striker is not welded, but keep in mind that the threaded parts are not regular bolts. They are B7 grade studs and grade 8 nuts, which are like twice as strong as regular bolts and way the hell stronger than most stainless steels. 1100psi in a hand held cannon demands one hell of a solid design and construction, preferably as simple as possible. I would forget the camlocks totally for this. Generally speaking, many things are designed with a safety factor of about 4. So if the camlocks are rated for 250 and you are using them at 1100, then you are already pushing their structural integrity on the first shot, according to their pressure rating. You can assume they are being overly conservative, but thats a scary assumption while holding it in your hands.
For your breech load, you may consider a sleeve with o-ring seals.
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Unread postAuthor: kjjohn » Tue Dec 22, 2009 8:27 am

Would regular threaded galv fittings be strong enough for a 5x mix?
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Unread postAuthor: kjjohn » Tue Dec 22, 2009 5:41 pm

Could sch 40 galvanized pipe and fittings bought at my hardware store (using a sleeve or union for the breech) withstand 600-700psi safely? Would the threads be able to handle it?
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Unread postAuthor: SpudBlaster15 » Tue Dec 22, 2009 6:04 pm

Yes. I have used regular SCH40 galvanized fittings at up to 10x hybrid mixes with no issues. The calculated burst pressure of those fittings is much higher than what you plan to use.
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Unread postAuthor: kjjohn » Tue Dec 22, 2009 6:08 pm

Well, I guess that solves a lot of my problems. I am thinking of constructing the breech load sleeve from just a stainless tube bought from OnlineMetals. Would it be safe to even go up to 800 or 900psi with these fittings (safe enough for me to hold it in my hand)? Also, how would one go about making a sleeved breech in a metal barrel? How would you cut halfway through the pipe? I have an angle grinder, but I don't think it would be precise enough.
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Unread postAuthor: SpudBlaster15 » Tue Dec 22, 2009 6:43 pm

A stainless steel tube with decent wall thickness will easily handle 800-900PSI.

As for cutting the slot in the barrel, I used a rotary tool with a heavy duty cutoff wheel to cut the slot for this breech loader, and it turned out well.
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Unread postAuthor: ramses » Tue Dec 22, 2009 8:48 pm

yes, galvanized is considered safe to 11x.

as to the chamber dimensions 2"x24" might possibly be somewhat nearing - dare I say it?- DDT

Seriously, though, that is 12 diameters running a pure oxygen mixture, with MAPP.

For the breech, I would suggest some kind of bolt action system, maybe like the one on the Decimator.
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Unread postAuthor: kjjohn » Tue Dec 22, 2009 9:06 pm

More spark points prevent DDT, am I right? I am planning on having 10-20 spark gaps, and testing at low mixes first.
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Unread postAuthor: inonickname » Tue Dec 22, 2009 11:36 pm

More spark gaps will generally prevent DDT because each individual flame front will have less distance to travel, and therefore less distance to accelerate to a supersonic velocity.

However, the general consensus is that with standard propellants and air as an oxidizer you won't run into DDT.
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Unread postAuthor: starman » Wed Dec 23, 2009 1:14 am

kjjohn wrote:More spark points prevent DDT, am I right? I am planning on having 10-20 spark gaps, and testing at low mixes first.


You should forget attempting a 10 plus gap ignition, especially in a hybrid. It just isn't necessary and will become increasingly very difficult to jump all the gaps in a high x environment.

You'll be lucky to get 2 gaps to fire much less 10. I would design for 2 very narrow gaps say 1 mm or less each, one at the 1/4 point in the chamber and the other at the 3/4 point in the center of the chamber.

If you use air as your first "x", in other words, keep some "inert" nitrogen in your chamber during combustion to act as a buffer gas, you won't have to worry about DDT.
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Unread postAuthor: ananddurga593 » Wed Jul 24, 2013 4:11 am

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Unread postAuthor: jrrdw » Wed Jul 24, 2013 5:46 am

ananddurga593 wrote:http://www.flexotechhoses.com/camlock-coupling.php

Link added to "Useful Links & Information" page.

http://www.spudfiles.com/forums/viewtopic,p,155830.html#155830

Edited by jrrdw.


Fixed your post. :D
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