Motor retention help

[Dbarrm]

Ok here is the deal. I have this box of parts I got from someone a while back and finally decided to make something out of it. In the box was a 2 foot 2.6" dia tube with an 8" 29mm motor mount already in it. What Im trying to figure out is how to put in a single use motor and keep it from flying out the end plus poping out the bottom on ejection. If I put a thrust ring at the end of the motor mount the 5 inch single use motors will go to deep and if I put it at that depth then I cant put any longer motors in. I could put in another centering ring with a smaller hole on top of the motor tube to keep anything from flying through the motor tube but then how do I keep the smaller motors from going to deep inside and lighting the rocket on fire.

Dan

 

[WillMarchant]

For single-use motors I'd wrap masking tape around the aft end until that tape reaches the diameter of the motor mount tube. That will solve the forward issue.

For retention you can go to the hobby shop and buy a "threaded insert." You drill an oversized hole in the aft centering ring and the insert screws into that like a wood screw. But the insert has a hollow shart that is threaded for a machine bolt. This lets you use your favorite "Kaplow Klip" arrangement to retain the motor.

 

[heada]

All the reloads I know of have an aft thrust ring. Any of the SU motors can have an aft thrust ring added with either tape (cheapest) tubing or a ring of tubing (copper, steel, aluminum, etc) that has a screw tapped into the side so that you can remove and reuse the ring (very nice)

Once you know that all motors have an aft ring, you can use any number of methods to retain based on that ring (tape it to the MMT, kaplow clips, AeroPac, Slimline, etc)

-Aaron

 

[new2hpr]

Just glue in a thrust ring at the depth of the longest motor.

Then fill excess length with couplers (coarse) and/or centering rings (fine) for adjustment. Won't add much weight, great flexibility, strong, and reliable.

For rear retention, clips, slimlines, screws&washers, etc.

Ken