To follow on to my above post, below is a photo of the retainer method I got from Adrian Adamson. It takes two of the pressure test fittings to get the right parts, but it's very easy to use and can obviously be moved from rocket to rocket since it stays with the motor. The motor shown is the Aerotech with the 5/16th bolt size. I wouldn't use it with a cardboard tube rocket unless fiberglassed. (EDIT) So far, I've only used it with 38mm MD rockets and I don't know if parts are available for larger diameters.
To use, you tighten the bolt and compress the large rubber washer until it just barely fits into the motor tube. Slide the motor into the rocket and then turn to compress the washer against the sides of the motor tube. Once tight, it is basically impossible to move the motor. I've thought about also attaching the recovery harness to the bolt as well, but haven't yet. But I will try it on my next 38mm MD build.
Tony
design credit to Adrian Adamson of Featherweight –
@Adrian A
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