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Can you get SH80 strength from SH40?

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Can you get SH80 strength from SH40?

Unread postAuthor: BowerR64 » Wed Mar 12, 2014 8:56 pm

A guy i know built his first combustion spud gun but he did it a different way then ive seen.

He used like 5 couplers and cut up 4" in little section and glued all the little section into the couplers creating a chamber that is pretty much twice as thick as a regular SH40.

If this has been discussed before can you post the links so i can read up.
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Re: Can you get SH80 strength from SH40?

Unread postAuthor: mobile chernobyl » Wed Mar 12, 2014 9:27 pm

In short - No.

Just buy Sch80... your life is worth it ;)

BUT.... If you are designing something that you feel PRESSURE RATED sch 40 PVC cannot handle within it's design limits (read: working pressure) then SERIOUSLY consider going to threaded steel fittings. Your good to play with 800+psi at that point rather safely.
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Re: Can you get SH80 strength from SH40?

Unread postAuthor: BowerR64 » Wed Mar 12, 2014 9:39 pm

So then he just wated time cutting all the little sections? Its no stronger?
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Re: Can you get SH80 strength from SH40?

Unread postAuthor: noname » Wed Mar 12, 2014 11:47 pm

It's only as strong as the weakest point, which would probably be one of the many solvent welded joints. Manufacturer errors are hopefully less common than DIY errors.
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Re: Can you get SH80 strength from SH40?

Unread postAuthor: BowerR64 » Thu Mar 13, 2014 1:46 am

That might be better then it shattering and thowing jagged edges.

What about screw on caps? will they blow out before say a Tee or a SCH40 pipe splits?

I think im just getting over paranoid, the more i read on this forum the more paranoid i get with my cannons. Ive yet to see any carbide cannons that have blown, ive seen some using pure oxygen acetylene blow but these are no where near pure. I even read that carbide powder is only 80%

They are big i think thats what makes them so scary loud.
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Re: Can you get SH80 strength from SH40?

Unread postAuthor: BowerR64 » Thu Mar 13, 2014 2:03 am

noname wrote:It's only as strong as the weakest point, which would probably be one of the many solvent welded joints. Manufacturer errors are hopefully less common than DIY errors.


What about reinforcing the solvent welded joints? say with screws or rivets? Say a reducer fitting put 2 screws or rivets at 12:00 and 6:00 then on the short side put rivets at 3:00 and 9:00 to sort of reinforce the solvent joints? Or would drilling holes only weaken the pvc?

What about blow out valves? Say a valve that would blow open when a dangerous pressure level is reached? Before the PVC splits the valve would let go first.
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Re: Can you get SH80 strength from SH40?

Unread postAuthor: mobile chernobyl » Thu Mar 13, 2014 10:14 am

Are you trying to reinforce an existing design, or create something new?

All the suggestions (screws, rivets, yadda yadda) you mention are just going to create points of weakness as noname mentioned - these areas are were it will fail first as they can take the least stress input.

If you are trying to reinforce an existing design with this idea - don't. Just continue using it at a "safe" pressure as-is.

Ultimately just plan on making something beefier for your more powerful/higher pressure experiments. If your trying to approach the working pressure of Sch40 PVC, SERIOUSLY consider going to metal.

But really - let us know what you're trying to do - that will help us help you, rather then tossing ideas and "he did this" "she did that" or using an observative style approach.
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Re: Can you get SH80 strength from SH40?

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Re: Can you get SH80 strength from SH40?

Unread postAuthor: BowerR64 » Thu Mar 13, 2014 1:17 pm

Ive already built 3 cannons but i was just curious about the stuff im using, i dont know the types of pressure im pushing the parts or any way to measure if im getting close to their limit.

Im asking questions so i can better understand its limits, what to look for if things are showing weakness or signs before they let go maybe.

I have some parts left over and wanted to build another with those parts but was wondering about Tees versus just the pipe

Just talking wanting to be apart of the forum

I built one with the trigger in the rear cap, one with the trigger in the Y of a tee and the last one i built i put the trigger at the top of the tee but im wondering if maybe that wasnt good to put a hole at the top of the tee maybe creating a weakness there?

mobile chernobyl wrote:But really - let us know what you're trying to do - that will help us help you, rather then tossing ideas and "he did this" "she did that" or using an observative style approach.


Well i was wondering because i dont know where he got his idea or if he just came up with the plan himself or had seen plans using the many couplers for the breech. His design looks well used so i think its working.
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