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SDR-21 for a noob

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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Unread postAuthor: ALIHISGREAT » Sun Sep 07, 2008 3:39 pm

yeah, i can't imagine cheap golfballs being too consistent size wise, maybe more expensive ones will be though?
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Unread postAuthor: LongT » Sun Sep 07, 2008 10:10 pm

psycix wrote:Thats tight, but I guess that the insane force worked out by the pressure is not much compared to the friction it has.
Also note that the difference in balls can be larger then the difference in pipes.
How many different balls have you tried?


A couple of dozen (I work at a golf course part time).. I'm gonna keep sanding.. Small price to pay for avoiding potentially lethal equipment failure.. I have this thing about shapnel wounds.. They're bad and should be avoided.
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Unread postAuthor: man_o_brass » Mon Sep 08, 2008 11:09 am

Well, different companies use different extruders to make their pipe, so you could easily have a slightly small bore. The average ID for SDR-21 1-1/2" is 1.7 inches with a maximum of 1.72. By golf rules, balls must be at least 1.68 inches in diameter, but can be slightly bigger. The tolerances don't leave a whole lot of wiggle room. Pipe I've bought in the past (couldn't tell you the brand) worked wonderfully; balls will roll through the pipe if it is held at an incline of more than a few degrees. If your sanding efforts are not to your liking, take a golf ball with you the next time you go pipe shopping and see what you can find. If you're still concerned about safety, sleeve the 1-1/2" inside some SCHD 80 2". It should slide in with a little lubrication, and some 5 minute epoxy worked in around an end will hold it well if you clean off the residual lube.
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