- This topic has 19 replies, 7 voices, and was last updated 17 years, 9 months ago by
Conway Stevens.
Conway Stevens.-
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Bruce R. Schaefer
I stopped myself from adding this to an ongoing thread elsewhere, and decided this might be a good topic unto itself. I recently bought a PR G3 kit, and it has all that usually comes with them, all G10. I put my AT 75/6400 motor case inside the 4′ booster tube. Perfect fit. Fin slots are already cut. I have no problem with putting the fins on so they can take the punishment. JW covered how to secure the rail buttons in another thread. Here is a simple question that many of the members in this club know the answer to… how to you keep the motor case IN the booster? The aft closure holds it in nicely from the bottom during thrust, and the harness will be attached to the casing at the forward closure. But how do you keep the motor casing from being blown out the bottom when the ejection charge goes off? I’m thinking nylon screws, duct tape, etc. I know Warren, Conway, and JW have done this successfully, just to name a few. Could you guys enlighten me? This may be a stupid question. But it’s better to ask a stupid question BEFORE you DO something stupid, right? I’ve asked them before, so why stop now? 😉
Bruce R. Schaefer
Got it. Friction fit.
Jeffrey Joe Hinton
Well, friction fit would work but internal clamping or an eyebolt in the forward closure attached to shock cord and/or bulk heads helps keep the worries down.
Bruce R. Schaefer
After I posted the question, I thought worst case, so the casing pops out the back. Everything is still attached, and the main would come out later on. At least, the rocket would be apart and less likely to lawn dart.
Ken Plattner
What about a slimline retainer. Since most likely you would be doing tip-to-tip FG on the fins, you could merge the transition from the retainer to the airframe with FG.
Just a thought…
Bruce R. Schaefer
Ken, that might work. Good suggestion.
Ed Dawson
How much room do you have? How about combining a threaded forward closure, an eyebolt, and a bulk plate epoxied in place at the forward end of the motor casing?
Basically the retention is on the forward end of the motor. The bulk plate keeps the motor from sliding out the back, and the eye bolt is a pretty secure way of tying the case to the rest of the bird.
This would work if you can reach far enough into the 4″ tube to screw the eyebolt into the forward closure of the loaded motor casing.
One drawback is that this would only work for the case it’s designed for.
Bruce R. Schaefer
Ed, that’s a great idea. The rocket would be 3″/76mm, and I will be attaching the harness to the casing at the forward closure. Putting a bulkplate between the eyebolt and the closure would definitely hold that puppy in enough. I plan to use my 75/6400 casing, so I could fit the bulkplate to that length. Fortunately my hands are small enough to probably get in far enough to secure it. Or, I can build a tool to do it. That will work.
Warren B. Musselman
What Ed said…
Warren
Bruce R. Schaefer
You guys have the answers.
Bruce R. Schaefer
Jeffrey Joe Hinton
Ken Plattner
Ed Dawson
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