Wildman Mach 2 Motor Retention

Hey all, I have a question regarding motor retention for the Mach 2 rocket which is a 54 mm minimum diameter. I have some ideas, regarding disposable vs. reloadable. I would prefer to use disposable motors, but I would appreciate any input regarding motor retention. Thank you.

I’m not sure what you’re specifically looking for. For me however, I found it easiest to friction fit with tape.

Just make sure to practice your ejection testing with the motor fitted in to ensure it won’t get kicked out the back end.

On mine I had it pretty tight. Ended up having to use a spare piece of coupler tubing to help push it back out.

If possible, tie the drogue recovery harness to the top of the motor, and friction fit the case with tape. You only have to tape an inch or two at the rear.

Friction fit with tape. This is a 54 minimum build.
Done correctly as good as anything.
Spiral wraps tape overlapping like a screw so tape edge cannot "roll" when pushing into place.
Wrap of real aluminum duct tape around motor & fincan.
It ain't going anywhere.
Use "bang" stick to push out after flight.
I don't paint bottom inch......tape is so wicked it will pull paint off.

blackjack2564 said:

Friction fit with tape. This is a 54 minimum build.
Done correctly as good as anything.
Spiral wraps tape overlapping like a screw so tape cannot "roll" when pushing into place.
Wrap of real aluminum duct tape around motor & fincan.
It ain't going anywhere.
Use "bang" stick to push out after flight.
I don't paint bottom inch......tape is so wicked it will pull paint off.

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CJ summarizes friction fit perfectly in this post. Should be a sticky.

CJ those are great instructions.

Mach 2 is my first MD project and I wasn't confident enough about friction fit to risk motor cases. I also didn't want to just spend my way out of the problem with an Aeropack MD retainer (which is a very nice solution don't get me wrong about that). I did a hillbilly version of the Aeropack MD retention system. Threaded rod from the forward closure of the motor goes through a bulkhead mounted about 6" from the top of of the airframe, and a nut on the rod from the top side holds the motor in place. I prepped an Aerotech L1000 DMS by bonding threaded rod to the ejection charge well with JB Weld. I haven't flown the L1000 to see how the JB Weld handles the heat, and when I do I'll add a bit of tape per Jim's method as insurance.

Re: nuts - I've got nylon lock nuts for shorter motors where I won't be worried about heat buildup, and I'll use jam nuts for long motors w/ expensive cases. For the jam nuts, I had to fabricate a crows foot wrench out of 1/8" steel flat bar stock to hold the bottom nut in place while tightening the top nut.

It all seems a bit fussy compared to Jim's method, and requires extra tools in the range box, but it will let me run 38mm motors with the Aeropack adaptor and keep things under 5-6K which is a good self-imposed ceiling for a couple of the fields we fly at.