Regarding design of rear ejection, there are some tricky components I'm not sure how to design.
1. How do you keep motor mount from sliding up to bulkhead, if not extending the motor mount tube to the bulkhead.
2. How do you attach the kevlar string to the motor mount? Tie it around? Tie it to the rings? Gluing Kevlar ok y/n?
3. Should both the parachute/streamer and BT both be tied to the engine housing? (Induced moment arm across mount?)
For low powered rockets I think rear ejection is probably the best way to go for a couple of main reasons.
A. The hot engine and mount is popped out from the body tube sooner. I suspect having the hot engine remain inside the tube is inherently bad for the rocket tube (and adjacent fin-tube bonds) and leads to material degradation and fatigue.
B. Removing the engine and mount also reduces the weight in the tail of the rocket in recovery, so when it lands it's not as stressful on the fins.
C. Engine housing (mounts) are usually what breaks down in low powered rockets I've noticed. With rear ejection, you can build a couple of engine housings and interchange on the rocket body without gluing...so you can keep firing.
Only drawbacks other than 2-stages becomes trickier for black powder engines?
I've been researching a number of sources and wonder if the Apogee Rockets isn't the leading authority? They have myriad articles and instructional videos..for free.
This is the one on rear ejection:
https://www.youtube.com/watch?v=TuhXsV7OIy0
1. How do you keep motor mount from sliding up to bulkhead, if not extending the motor mount tube to the bulkhead.
2. How do you attach the kevlar string to the motor mount? Tie it around? Tie it to the rings? Gluing Kevlar ok y/n?
3. Should both the parachute/streamer and BT both be tied to the engine housing? (Induced moment arm across mount?)
For low powered rockets I think rear ejection is probably the best way to go for a couple of main reasons.
A. The hot engine and mount is popped out from the body tube sooner. I suspect having the hot engine remain inside the tube is inherently bad for the rocket tube (and adjacent fin-tube bonds) and leads to material degradation and fatigue.
B. Removing the engine and mount also reduces the weight in the tail of the rocket in recovery, so when it lands it's not as stressful on the fins.
C. Engine housing (mounts) are usually what breaks down in low powered rockets I've noticed. With rear ejection, you can build a couple of engine housings and interchange on the rocket body without gluing...so you can keep firing.
Only drawbacks other than 2-stages becomes trickier for black powder engines?
I've been researching a number of sources and wonder if the Apogee Rockets isn't the leading authority? They have myriad articles and instructional videos..for free.
This is the one on rear ejection:
https://www.youtube.com/watch?v=TuhXsV7OIy0
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