Advice regarding a 29mm Motor Mount.

Bryshereyy

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I was going to build a rocket capable of handling F & G motors. However, the site that I normally use does not have seem to have the parts I would need. They do have an engine hook (I prefer this retention system for smaller rockets), they do sell the engines as well, I found a motor tube on another site, but I am not sure where I could get some centering rings from. The rocket would have a tube size of BT-60 or BT-80. Any ideas? Or does the hobbling motor mount for D+E motors hold Fs?
 

heada

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LOC has most sizes of plywood centering rings. There are others out there so pick the vendor you like best.

BT-60 = 1.64" or 41.6mm

BT-80 = 2.56" or 66mm

I for nearly all 29mm motor mounts, I would recommend the Estes retainers. They come in 2 packs and are dirt cheap for what they do. They're loose on some MMTs so you may have to use extra glue(epoxy) for those but for the cost, can't really be beat.

I would also get a set of 24mm to 29mm adapters so you can use 24mm motors in the same MMT. Being able to use D and E in the same MMT as your F and G is really nice on windy days.
 

Rocketjunkie

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29 mm motors vary widely in length and all except Estes have an enlarged rear closure or thrust ring at the nozzle end. Your retainer needs to keep the motor in during ejection. If you want to use Estes style, cut off the forward end so it doesn't block the front of the tube limiting you to 4.5" motors. Then glue and tape it to the motor mount leaving enough unglued to get it out of the way to insert the motor.
 

Jmhepworth

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I’m rather partial to screw-type retainers for 29mm and up. The Estes one works fine. I’ve seen dozens of college students with 3D printed retainers. And I like the Aeropack retainers, despite the significant price compared to Estes or 3D printed retainers. If you use a hook with APCP motors, even at 24mm, a wrap of masking tape around the hook is good insurance. It just doesn’t seem as secure to me as it is with a black powder motor.
 
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neil_w

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I use hooks with all my 24mm rockets and don’t tape the motor. I have never ejected a motor.

But again, a hook really isn’t a realistic option for 29mm and up.
 

Dane Ronnow

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I second that. I just bought parts for a 3"x 55" 29mm scratch build, everything from body and motor tubes, to centering rings, bulkheads and couplers. Parts fit great, good quality. And, to address the OP's concern about CR's and such, Bills stuff is a tight, but not too tight fit between CR's and MT's. Perfect for my style of building. No slop in any of the parts I bought.

All my rockets are 29mm, so there's no reason for me to use an engine hook. I can't speak to the quality and durability of the Estes retainer. I know it's like 1/3 the price of an Aero Pack or AeroTech. But I launch from a dry lakebed. Very unforgiving on retainers that impact before the fins on landing. So I spend the extra on aluminum.
 

prfesser

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Buy some 1/8" wood at the local store and cut out your own centering rings.
I do it often using a hole saw.
Menards and other big-box stores often have small cuts of 1/4" 5-ply plywood (possibly 1/8", I haven't looked) that are perfect for centering rings and for some fins. I had half a sheet of 1/4" 5-ply underlayment (actually just over 0.21" thick) left over from the kitchen. It's a bit heavy but it made fins and centering rings for a dozen rockets. Check for curvature of the sheet before you buy.

Caution advised on 1/8" "Lauan" plywood, it's usually 3-ply and not very strong.
 

techrat

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Buy the plastic 29mm estes retainers. They are a good bargain and will do the job for 90% of all 29mm motors. All of the single-use composite F motors come with a ring that will butt up against the retainer and hold the motor in place for both the thrust duration and ejection charge. Just make sure you are using epoxy to glue the retainer to the 29mm motor mount tube as that is going to have to deal with a lot of stress.
 

techrat

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As for centering rings, if you've got some wood-working skills and tools, you can build your own, OR you can find an online vendor who will sell you a BT-80 to 29mm set of rings that are laser cut. FYI: I've heard that some public libraries have 3D printers and Laser cutters. Also see if you have a local "Makerspace" in your area. You may be able to rent time on their equipment which would be a real time-saver if you're handy with a computer. Then you can laser cut your own rings and make what you want, not just what you can get.
 
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