rocketsam2016
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- Joined
- Aug 31, 2016
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Hi folks, I’ve designed and put together what I guess is called a donut avbay. As the picture shows (only partially assembled), I have a 1/16” fiberglass board in the space between a 54mm tube and the outer 4” airframe. The whole thing is removable and attaches to the motor mount centering rings with all thread. The center 54mm tube will butt against the 54mm motor mount and serves as either/both a conduit for ejection charge gasses and a continuation of the motor mount around the motor depending on the length of the motor used.
I was concerned that the centering rings on the end wouldn’t be a tight enough fit with the outer airframe to keep ejection gasses from penetrating into the bay, so I built a shield (on the left, sitting upside down) that will sit over the electronics and provide a tight seal all the way around by being pressed against the board by the outer airframe (I’m going to line the periphery with high temp silicone sealant so that the seal is good).
So my question is, how many vent holes should I use and where should I place them? They are forced to all be on one side of the rocket by this design. They will obviously also have to be through both the shield and the outer airframe. There is nothing sticking out of the rocket above any of this area so the airflow should be clean. I was thinking that none should be directly over the air pressure sensor and doing either a triangle pattern of 3 or a zig zag pattern of 4:
———
*........
.........
........*
.........
*........
———
or
———
....*....
.........
........*
*........
———
or
———
.*.......
.......*.
.*.......
.......*.
———
or
———
...*....
......*.
.*......
...*....
———
The egg timer quantum has pretty rock solid safety logic as I understand to prevent getting tricked into firing charges before liftoff, but I figure I can never be too safe. Any particular concerns with how I lay these out or do any of the above seem appropriate?
Thanks!
Sam
I was concerned that the centering rings on the end wouldn’t be a tight enough fit with the outer airframe to keep ejection gasses from penetrating into the bay, so I built a shield (on the left, sitting upside down) that will sit over the electronics and provide a tight seal all the way around by being pressed against the board by the outer airframe (I’m going to line the periphery with high temp silicone sealant so that the seal is good).
So my question is, how many vent holes should I use and where should I place them? They are forced to all be on one side of the rocket by this design. They will obviously also have to be through both the shield and the outer airframe. There is nothing sticking out of the rocket above any of this area so the airflow should be clean. I was thinking that none should be directly over the air pressure sensor and doing either a triangle pattern of 3 or a zig zag pattern of 4:
———
*........
.........
........*
.........
*........
———
or
———
....*....
.........
........*
*........
———
or
———
.*.......
.......*.
.*.......
.......*.
———
or
———
...*....
......*.
.*......
...*....
———
The egg timer quantum has pretty rock solid safety logic as I understand to prevent getting tricked into firing charges before liftoff, but I figure I can never be too safe. Any particular concerns with how I lay these out or do any of the above seem appropriate?
Thanks!
Sam
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