This positive motor retainer system is not only effective, it also looks pretty cool on just about any model rocket. At around $14, these are more expensive than some other options. The price is easily made up for by the ease of installation and use. Once installed, simply twist off the retainer cap, insert the rocket engine and screw the cap back on. As it is made from aluminum, it is lightweight, the Hesperis 24mm PMR motor retainer is lightweight. It only adds 4.7 gram (0.165 oz) to a model rocket, not counting the adhesive used.

The image above shows the retainer body (top left), cap (top right). An assembled unit is shown at the bottom.

Parts List

The motor retainer is sold as a whole unit. From what I saw, you can not purchase body rings or caps seperately.

- aluminum retainer body
- aluminum retainer cap

To attach the motor retainer to your model rocket securely, you'll need a strong bonding agent, such as epoxy. Personally, I use JB Weld as it can withstand the heat of the motor, making it one of the best solutions.

Installation

The HTL 24mm motor retainer can be installed on a model rocket during construction or on existing rockets. All you need is 6 to 8 mm of motor mount tube sticking out of the aft centering ring.

Simply put epoxy (JB Weld) on the motor mount tube and slide on the retainer body. Let it cure fully and you're done. In cases where the fit it too lose, I'd suggest gluing a strip of paper around the motor mount until you get a better fit. Let the glue dry fully and apply the epoxy.

For rockets where the airframe diameter is not much larger than the motor mount tube, this system is best of all. It doesn't need much free space to be installed.

Field Testing

This 24mm positive motor retention system has been tests on the Estes Big Daddy and TLP Falcon.

The Big Daddy has been flown on both black powder (Estes E9) and composite (E18 & F24) model rocket engines without a problem.

Both rockets will be flown more over time and if anything happens with regards to the HTL motor retainer, this web page will be updated.