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29mm engine mount
I have two NCR rockets that came with 28mm engine tubes that I am replacing with 29mm engine tubes. But what should I use to keep the engine in? I don't think I can use the Gorilla-Lok™ retainer with the 29mm tubes. I did find a site where someone built an engine retainer out of plumbing parts and I have seen machined metal ones (for $27+). If anyone has a technique that works, I would love to hear it.
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Timothy Gray |
#2
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I've used coat hanger wire made into a hook for years. Just make a loop and screw it into the rear centering ring, the other end hooks over the motor. You can always find coat hanger wire, but the flat windshield wiper material isn't always handy. You can use tape. Believe it or not, it works. I've flown plenty of friction fitted 29mm motors and never had a motor eject. Use good 3M brand masking tape. The cheap stuff (like Manco brand) will melt and it makes it hard to remove the motor. BTW, I've even slipped motors in and just taped the end to the rear of the motor tube, without any friction fitting. It works! You can glue some all-thread against the motor tube also. Just slip in the motor and screw on a nut. You might or might not need a washer according to the O.D. of the nut.
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I love sanding. |
#3
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If you plan to use AeroTech 29/40-120 reloads, they sell motor hooks (similar to the Estes hook, except much bigger). The part number is 19001 and retails for $3.50.
Greg |
#4
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And you are supposed to use two of them. A.S.P also sells them, $2.99 for a pair. MarkII
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Mark S. Kulka NAR #86134 L1,_ASTRE #471_Adirondack Mountains, NY
Opinions Unfettered by Logic • Advice Unsullied by Erudition • Rocketry Without Pity
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#5
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Rather than replacing the tube, I peeled a layer off the inside of mine so the AT motors would fit.
For retention the twist lock thingies will still work on the expendables, but won't fit over the reload aft closure. For those I had to use something called "Kaplow Klips"
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I fought the law, and the law LOST! |
#6
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I have never heard of that before. I suppose you could use two, but you would have to make sure that they were exactly 180 degrees apart to engage the aft closure slots, and you would be adding aft-mass. My AeroTech Initiator only came with only one. Perhaps Bob Sanford or Gary Rosenfield can give us a little history on this. So far I have I have had only one incident where the motor was partially kicked out. I may in the future put a Nylon tie strap around the motor, once it has been installed to add a little insurance that it will stay put with the rest of the rocket. Greg |
#7
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I just use masking tape around the clip and motor to hold it all in one place; has always worked for me and is easy shmeasy! Allen |
#8
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I have only used one of the AeroTech motor hooks in my models, kit or scratch-built. That's all you need. I, also, use a wrap of masking tape around the hook, just for insurance. I've never had a motor (single-use or reload) kick out. I've only flown my NCRBE kits with the long gone & lamented F62 Dark Star motors. I DID replace the motor tube with some 29mm I.D. tube. The red Gorilla-Lok always worked fine for me. |
#9
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I have some 29mm engine tube that I was going to replace the existing engine tube with. I hadn't tried fitting it in there yet. I hope it will fit, the Gorilla-Lok looks easies to implement. Did you have to shave anything off the rings to get it to fit? I see you have the Big Brute and the Eliminator. That's the two NCR rockets I am talking about. I have 2 F and 2 G NCR engines to launch them with. The rockets I with them them (10 years ago) got chewed up by mice in the basement!
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Timothy Gray |
#10
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I did not make any modifications to the NCRBE plastic motor mount rings to use them with 'true' 29mm motor mount tube. I did sand the inside of the rings where the motor mount tube would fit to get better adhesion with the cement/epoxy. Which NCR 'G' motors do you have? The early G50 motors or the G70s? Bob |
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