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end caps

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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end caps

Unread postAuthor: cfb_rolley » Thu Dec 31, 2009 7:53 am

hi, i'm new at spudding, i built my first simple linear spray and pray a while ago, installed a chamber fan and it worked great, 90mm x 0.5m chamber to 50mm x 1m barrel, i then put a U bend on the back and extended the chamber to be over-under style and the first shot went really well, tons of power but on the second shot the end cap blew off, so i put the spare on and the same thing happened. i've never had this issue before and because i'm in australia, i'm limited to bunnings for my parts and they don't stock end caps that withstand pressure. is there anywhere online where i can buy end caps and other parts that will ship to australia without trouble with customs?
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Unread postAuthor: jrrdw » Thu Dec 31, 2009 7:58 am

This page should help you find what your looking for.
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Unread postAuthor: chinnerz » Thu Dec 31, 2009 9:23 pm

i hear you mate. soo hard to find things in AUS. but what you want is a threaded adaptor and a plug, i know for a fact that bunnings sells these things in the 25mm size.
this is a picture i have of the parts you need:

Image

so essentially you glue the adapter into place, or as mythbusters has demonstrated, simply duck tape it into place.
During use spray your propellant in and then screw the plug into place. Easy as pie:P
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Unread postAuthor: kjjohn » Fri Jan 01, 2010 1:57 am

so essentially you glue the adapter into place, or as mythbusters has demonstrated, simply duck tape it into place.


Actually, I wouldn't use duct tape...
:D
While the Mythbusters demonstrated that a duct tape spray n pray is possible, it's not recommended, and makes your cannon look kind of ghetto.

Try some of Spudfiles' sponsors for the cap.
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Unread postAuthor: cfb_rolley » Fri Jan 01, 2010 2:02 am

i've already got electrical tape holding the battery pack on, but it's black like the cannon and is kept pretty neat, though i'm not sure i'd trust duct tape under pressure anyway since i'm already blowing apart end caps. is it possible i have the spark too close to the end causing it to blow off?
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Unread postAuthor: chinnerz » Fri Jan 01, 2010 2:25 am

nope, it dosnt matter where the spark is, the gasses will expand to the same degree.

i did an experiment this afternoon, my 25mm end caps are quite tight but fly off with 30-40ish psi, which in my books is close to nothing as im planning on shooting at 100 psi.

Try some of Spudfiles' sponsors for the cap.


yeah thats hard to justify in Australia as the part cost like 5 bucks here, but when bought online i can cost as little as 50C but $10 postage

cfb_rolley go and see if your local bunnings has the adapter and plug, cost is under $5
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Unread postAuthor: chinnerz » Fri Jan 01, 2010 3:07 am

just had an idea.
Image
this may or may not work. i have never made a combustion launcher so i dont know if its going to work or not, maybe if we got some help from someone else who can tell us that it will or wont work.

so what i was thinkin was is you cut an "L" shaped slit in the end cap, and screwed a bolt into the chamber so that you can "lock" the ned cap into place. idk was just an idea.
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Unread postAuthor: cfb_rolley » Fri Jan 01, 2010 3:42 am

that would probably work. how srong are those style caps though?
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Unread postAuthor: McCoytheGreater » Fri Jan 01, 2010 6:00 am

^^^Those end caps can blow off relatively easy if they're not secured just right. Even then, you wouldn't want a bolt directly into the pipe of the chamber (props for the suggestion, though). You would definitely want two layers of plastic there. My suggestion to you is to reinforce your screw-in endcap by epoxying a round of thin wood (plywood or something similar) into the hollow part of the end cap.
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Last edited by McCoytheGreater on Fri Jan 01, 2010 6:11 am, edited 1 time in total.
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Unread postAuthor: chinnerz » Fri Jan 01, 2010 6:02 am

i dont know about the caps you can get. but 2 years ago bunnings used to sell good end caps, which were about 1mm thicker than pvc pipe, the ones i use were about the same, so i dont know if it would be strong enough. however there is only one way to find out for sure.
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Unread postAuthor: EvilFish » Fri Jan 01, 2010 6:22 am

Chinnerz, I like your idea for a bolt-operated endcap, but wouldnt it be easier to simply drill hole, instead of the L shaped slit?

And cfb_Rolley, you may want to try large ball-valves. Sure, they're expensive, but they're also easy to use, can hold up to a lot of pressure, and finally,if you place it at the front of your chamber, you can also use it to breach-load your gun.
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Unread postAuthor: chinnerz » Fri Jan 01, 2010 9:00 pm

ahh, some sound ideas there.
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Unread postAuthor: cfb_rolley » Fri Jan 01, 2010 9:15 pm

hmm. took a trip to bunnings again today and picked up an adaptor for 100mm screw on end caps, they seem much thicker so i'll give that a shot when i get a hold of a new fan.
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Unread postAuthor: chinnerz » Fri Jan 01, 2010 9:18 pm

let us know if it works, and take a few picks maybe :P
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Unread postAuthor: cfb_rolley » Sat Jan 02, 2010 1:44 am

this is before the new end cap.
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