Motor Retention

My apologies if this should have been threaded elsewhere...

I'm building a LOC ONYX and want to know if, instead of wrapping 1/2" strip of masking tape around the rear of the motor, I could epoxy a motor stop in the top end of the motor tube and employ spacers to keep the motor from disappearing inside?

If yes, for how large a motor can this technique be utilized?

Thanks. -BB

Some people prefer the motor block and spacer method. However, I prefer the masking tape method for single use motors (reloads have a built-in thrust ring). I have used the masking tape route up to J motors and have heard of it on K's.

While masking tape is very reliable to keep the motor from flying thru the rocket during boost, it is unreliable in my experience for keeping the motor from kicking on ejection. Here I generally use a variety of clamps and brackets (aka Kaplow Clips). A simple retrofit that works well, if you have a contiguous piece of body tube exposed below the fins, is a metal wire clip. Make it pass from one side of the rear of the tube, over the motor and by the nozzle, and over to the far end of the tube. On each end, have it bend back slightly making a hook. With it in place over the motor, wind 3-4 wraps of tape around the clip and behind the hooks. I haven't used this until recently but it works great.

This has been discussed serveral times before so you might also try searching the forum. There are other ways to skin this cat.

It's definitely possible. Positive forward thrust plates have been used in rockets with P-power -- so strength there isn't an issue. What becomes an issue is that, by blocking the top of the motor tube, you are limiting your choice of motors to fly. Since composite motors vary in length depending on the amount of propellant inside, if you decide you wish to fly a longer motor (perhaps an Ellis SU or an AT H motor) in the rocket, you're pretty much out of luck. Tape works quite well -- Frank Kosdon has an N motor case that has been flown many times, with wraps of masking tape around the aft end to prevent it from flying through the rocket on ignition.

Seriously!

Hope this helps.

I appreciate your input and will continue to search the forum for pros and cons before settling this issue in my mind. -BB