BPS Space and moveable fins for roll control

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Michael L

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The first flight didn't go perfectly but he did recover it. The "large sugar motor test" that someone else did was spectacular even if it was off camera.

 

cerving

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Looks like it was fine as long as there was thrust... went unstable at burnout. That's the problem with hobby rocketry TVC... the motors generally don't burn long enough for stability through the entire ascent. Maybe some small fins would help.
 

Charles_McG

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Looks like it was fine as long as there was thrust... went unstable at burnout. That's the problem with hobby rocketry TVC... the motors generally don't burn long enough for stability through the entire ascent. Maybe some small fins would help.
But this wasn’t TVC - the fins were servo driven. Aft fins, rather than canards. It looked like the gain was too high to me. And I didnt listen all the way through (the pie finished warming up) - but did he loose one of the servos in flight?
 

Bowman

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But this wasn’t TVC - the fins were servo driven. Aft fins, rather than canards. It looked like the gain was too high to me. And I didnt listen all the way through (the pie finished warming up) - but did he loose one of the servos in flight?
He lost linkage between the fins.
You can see them shortly after launch going opposite directions.
 

Michael L

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the motors generally don't burn long enough for stability through the entire ascent. Maybe some small fins would help.
I recently misread the specs on a 29mm motor. I thought it said 17s burn time not 1.7s. For just a few seconds I was dreaming of a 17s burn motor. :D :saintnick: and then... reality struck...

I watched it to the end, he said that he used epoxy to connect the linkage (no comment) and that as the rocket sat on the launch pad for an hour it heated up and softened the epoxy. I know it (30m Bob Smith specifically) will do that because I recently heated an epoxied in fin to move it just a tad and that worked. He said that when the rocket was indoors and cooled down the epoxy hardened and the fin rigidity returned but if heating softens epoxy what does that say about a rocket built with epoxy? Idk... I think that, even though I've seen that heating it will allow movement, unless he's launching in hell it's not all that likely for epoxy to soften that much. His servos, gears, and 3D printed parts were all plastic. I guess he'll lets us know when he finds out.
 
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