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Resleeved DD1... And Fluting question...

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Resleeved DD1... And Fluting question...

Unread postAuthor: jeepkahn » Tue Jun 02, 2009 12:27 pm

I never realized until the other day that I originally sleeved DD1 with sdr26 into sch80, and because of this the sdr had started cracking due to the pressures I'm running... Sooo... I went and got some sdr21, and set out removing the cracked sdr26.... You think it's a pain sleeving, try unsleeving(without damaging the sch80...)...

Well anyway, I got it unsleeved/resleeved and have noticed that with the better fit of the barel and GBs, the accuracy is way better, (3ft grouping at 100yds, and can consistently hit 2litre soda bottles at 50yds)...

Now, with the size and configuration of DD1, I do get a little barrel flex(with 70" of unsupported sch80/sdr21, what do you expect, right), Would fluting the sch80 help make it a little more flex resistant, ( I was thinking 6 flutes , using a .5" half round router bit, set to about .125" depth{leaving .093" thickness at the deepest part of the flute}).... At the very least it would look cool...

Or do I just need to run some tension cables to maintain barrel straightness????
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Unread postAuthor: jmeyer1022 » Tue Jun 02, 2009 12:37 pm

How heavy is that barrel?! Can I ask how big your chamber is that your using 70" barrel? Is it over under style? More info would be helpful, if it's not over under I'd suggest getting a stand as crazy as it sounds.
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Unread postAuthor: jeepkahn » Tue Jun 02, 2009 1:09 pm

It's a coax over 11ft total length, the barrel is exactly 10'1" long, the chamber is 56".... It has a tripod, but it's the barrel I'm trying to make more rigid...

Search DD1 in Pneumatic showcase... or is it DD-1... one of te 2 should pull up the thread..
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Unread postAuthor: jeepkahn » Wed Jun 03, 2009 12:00 pm

Double posting to add diagram of support wire concept...
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Unread postAuthor: thedeathofall » Wed Jun 03, 2009 12:28 pm

I think your best bet would be the wire. I hate support wires because they are really ugly and can get in the way, but you probably need it.

The other option would be to run a rod parallel to the barrel, but that would be more expensive and probably not work as well.
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Unread postAuthor: jeepkahn » Wed Jun 03, 2009 12:51 pm

I just got finished doing some research on fluting and I think it'sdefinitely NOT worth the trouble...


What's you guys' thoughts on shortening the length of the sch80 to about 30" and the having the last 40" just sdr21??? would definitely cut the weight of the barrel down and I think the 30" of Sch80 would support the main weight of the barrel, and the lighter sdr21 would be stiff enough to not flex the last 40"... or am I just better off supporting the barrel somehow???
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Unread postAuthor: thedeathofall » Thu Jun 04, 2009 11:14 am

Actually, that might work you just have to try it.
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Unread postAuthor: Technician1002 » Thu Jun 04, 2009 11:49 am

thedeathofall wrote:Actually, that might work you just have to try it.


The use of spreaders expands the triangle volumes and increases rigidity by reducing the amount of wobble that a given stretch and compression of materials will provide. Many Pumpkin Chuckers use it as well as sailboats.
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