I noticed (10/15/00) Budget Rocketry's 29mm and 24mm Motor Retainer when surfing their website and decided to give them a try. So far, I have only incorporated one 29mm Retainer into my BSD Diablo. They come in 24, 29, and 38mm.

CONSTRUCTION:

Construction is straight-forward, however, Budget Rocketry provides an instruction sheet. Also included in the 29mm kit is a washer, threaded insert and a cap (actual retainer). The threaded insert and cap are made from light weight PVC.

The objective is simple, epoxy the threaded insert onto the end of your 29mm motor tube. The task was a bit more challenging. The 29mm threaded insert did not slide over any of 3 types of my 29mm tubing (from PML, Missile Works or LOC). So I taped the end of my tube, leaving the first 1/8" exposed. Doing this allowed me to get the motor mount to stand straight and snug while the epoxy was drying. I then applied the fillets as indicated in the instructions.

This is not the case for the 24mm. The motor mount tubes I had all allowed the threaded insert to slide completely over them. The 24mm from a Nordic Rocketry fit the best being snug. A 24mm tube from Apogee and Estes were a bit smaller in diameter.

If you plan on using this on a kit then you will need to modify your instructions to add the threaded insert prior to building your motor mount. The addition of the ring will force the motor tube to be 5/8" (29mm) or 1/2" (24mm) from the rear centering ring. In many kits this is fine, however, use caution as doing this on other kits may cause the internal (center or upper) to be out of place which could impact through-the-wall fin installation if the kit has them.

One nice quality of using Budget Rocketry's Retainer is that the threaded insert acts as a protection of the motor mount. It is hard and sturdy giving the motor a solid hole to slide into.

Budget Rocketry says on their website, "Most other forms of motor retention available are either expensive, ugly, or time consuming. Sometimes all three." We would have to agree that this motor retainer looks like part of the rocket.

FLIGHT/RECOVERY:

I have used my 29mm retainer once on a G80 Single-Use motor. Because there is no internal thrust ring in my motor mount, I had to tape the G80. I could only allow about 1/2" of the tape to be on the motor (which is fine) while the remainder had to be off the motor toward the thrust nozzle. This didn't cause a problem for the Motor Retainer as you can see from this picture.

The washer that is supplied with the kit is for 29mm single-use motors only. According to Budget Rocketry, "the washer is just set in the cap and the cap is then screwed on. So it is for ejection only with single-use motors, whereas the lip on a reloadable keeps the motor from going forward or backward. When using single-use motors it is assumed there is a thrust ring. If a thrust ring is not used to allow different length single use motors then friction fitting with tape is the only answer I know of."

My AeroTech 29mm 29/40-120 RMS casing fits perfectly. And again, this type of retainer is attractive and would look good incorporated into many rocket designed.

How did it work? Well, with only one flight it worked fine.

CONCLUSION:

I have bought several of these retainers. Yes, they are more expensive than a screw and some bent spring steel, however, you are paying for looks as well as functionality. I must admit that one flight doesn't fully test the durability, because this system is relying solely on the strength of the epoxy. We simply hope that the epoxy bound is always stronger than the fit of the nose cone so that the ejection pressure follows the path of least resistance. Overall, I would rate these retainers 4 ½ points.