NewEntity1
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- Dec 4, 2003
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Now that I have spare parts, I actually opened my Big Bertha package for the first time. I noticed that the motor mount tube in it is very, very long...215mm long (around 8 1/2"). It also has no thrust ring, rellying on just the motor clip and friction in the mount tube itself to prevent the engine from shooting up through the rocket.
The 24mm mount I'm going to use (from fliskits, with those excellent fiberboard centering rings ), is much shorter. However, since it will be a larger motor, I think there should still be enough ejection gasses to fill the larger open volume left by the shorter mount. However, I am a bit concerned about structural rigidity, and CG.
There are two things I can do:
1) Epoxy the entire length of the BT60 body tube, which would increase the structural strength, and also move the CG forward slightly. The added weight won't be a problem, since this is a rocket already designed to fly on 18mm motors, so the 24mm mount should handle the added weight easily.
2) Hold off on this project (yet again), until I can pick up some BT50 tubing, and find a reliable way to shove the 24mm thrust ring waaay down the tube...well, actually that should be easy enough...I'd just install the motor clip first, then push the thrust ring down until it hits the clip
Which do you think is better?
The 24mm mount I'm going to use (from fliskits, with those excellent fiberboard centering rings ), is much shorter. However, since it will be a larger motor, I think there should still be enough ejection gasses to fill the larger open volume left by the shorter mount. However, I am a bit concerned about structural rigidity, and CG.
There are two things I can do:
1) Epoxy the entire length of the BT60 body tube, which would increase the structural strength, and also move the CG forward slightly. The added weight won't be a problem, since this is a rocket already designed to fly on 18mm motors, so the 24mm mount should handle the added weight easily.
2) Hold off on this project (yet again), until I can pick up some BT50 tubing, and find a reliable way to shove the 24mm thrust ring waaay down the tube...well, actually that should be easy enough...I'd just install the motor clip first, then push the thrust ring down until it hits the clip
Which do you think is better?