Why the free spinning fin section? Because it's easier to get rock solid roll cancellation of the body tube when not having to fight the velocity variable roll torque from the fins?
The spin can is to reduce what is called control reversal, where the rocket can spin in the opposite of the intended direction. This is a well-known problem. The spin can actually makes roll control more difficult because of the low moment of inertia without the fins.
@@Jiminaus50 Thanks. I don't recall seeing any attempt to perform roll control on sounding rockets. Just the opposite. They intentionally spin some up to be de-spun if necessary prior to payload deployment. So, the only approximation of what you're doing I can think of is in military missiles. Since, as far as I've seen, they don't use rotating fin cans on any of those, how do THEY avoid control reversal?
@@winstonsmith478 Our original purpose for roll control was to avoid accidently exceeding the gyro range. That would be bad. The purpose for making it better is for better video (looking out sideways for example). With better control systems than mine, the relative sizes of the fins can be varied to help avoid control reversal. This, along with CFD design, can avoid the problem.
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Wow that was impressively straight!
Great job Jim!
Thanks. Can't wait for the next flight.
I wonder how feasible it would be to make the roll control gain proportional to the current velocity, which might help for start/end of flight.
It is now possible. I will probably test that on the next flight.
Why the free spinning fin section? Because it's easier to get rock solid roll cancellation of the body tube when not having to fight the velocity variable roll torque from the fins?
The spin can is to reduce what is called control reversal, where the rocket can spin in the opposite of the intended direction. This is a well-known problem. The spin can actually makes roll control more difficult because of the low moment of inertia without the fins.
@@Jiminaus50 Thanks. I don't recall seeing any attempt to perform roll control on sounding rockets. Just the opposite. They intentionally spin some up to be de-spun if necessary prior to payload deployment. So, the only approximation of what you're doing I can think of is in military missiles. Since, as far as I've seen, they don't use rotating fin cans on any of those, how do THEY avoid control reversal?
@@winstonsmith478 Our original purpose for roll control was to avoid accidently exceeding the gyro range. That would be bad. The purpose for making it better is for better video (looking out sideways for example). With better control systems than mine, the relative sizes of the fins can be varied to help avoid control reversal. This, along with CFD design, can avoid the problem.
Nice.