Question |
| Asked by: |
Tom Perkins |
| Subject: |
Torque resistive with no Precession |
| Question: |
Hi there, I hope you can help me. Struggling to get my head around this question.
Think a simple gyro. Now, add a second gyro spinning in the opposite direction. Same weight, speed, axis, identical in every way except each is rotating in opposite directions. Yes? (hypothetical if it helps)
OK, we then apply a torque altering the axis of rotation. I hope that's clear enough to understand the setup.
My thought would be that there is still a force acting to resist the applied torque and that the standard precesion behaviour would cancel eachother out. E.g. if it were vertical it would 'fall over' slowly without spinning as observed with a toy 'top'.
I'd die to hear some thought from someone with so knowhow!
Thanks in advance. |
| Date: |
19 October 2011
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Answers (Ordered by Date)
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| Answer: |
Glenn Hawkins - 19/10/2011 14:57:13
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| | Hi Tom,
Understood up until,
“we then apply a torque altering the axis of rotation.”
Please explain what you mean and how to do that.
“My thought would be that there is still a force . . . resisting precesion. . .”
I don’t clearly understand.
“if it were vertical it would 'fall over' slowly without spinning as observed with a toy 'top'.”
Unclear to me. Try explaining in several different ways, Tom.
I think I can answer most things, once I understand more your questions more clearly.
Glenn H.
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| Answer: |
Tom Perkins - 19/10/2011 15:36:03
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| | Thanks for the prompt response Glen!
I'd like to draw you a diagram but it's a little tough.
I should add to the description this: think a single gyro, axis of rotation vertical acting in the Z axis. Now, imagine that exact same gyro spinning in the opposite direction creating a single system. Two counter rotating gyros, same X, Z and Y axis same speed and mass etc. I don't know if that's clear, best to think of it as a hypothetical thought experiment.
Now the 'system' is subjected to a torque along it's Y axis. My question is, will this system produce a force in opposition to this applied Y axis torque (i.e. would it be 'hard' to rotate?) and would the standard X axis precession effect be 'cancelled out'since the two masses are counter-rotating?
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| Answer: |
Glenn Hawkins - 20/10/2011 01:15:55
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| | Hello Tom,
Yes, precession would be canceled since the two masses are counter-rotating. You will find a detailed answer about seven post below yours, called 'Nested gyros'. The condition is similar to your postulation and the effect and reasoning is the same.
Glenn H.
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| Answer: |
Glenn Hawkins - 21/10/2011 19:05:59
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| | Hi Tom,
I see that I can make this more clear. Your heading is, “Torque resistive with no Precession”
If a gyro on a pedestal or string is stopped by putting something in it's orbital path to keep it from precessing, it will falling in a twisting tumble around itself. There is very little resistance to torque, without precession. Precession (orbital movement) is caused causes by an acting condition called deflections, which works as a countering force to an applied torque.
However, it is necessary for you to explain (in simple terms) how the two gyros are connected and mounted, such as might be on a horizontal shaft and how the force of torque is applied. There are varying outcomes that are possible depending on this and that.
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| Answer: |
Mark Joerger - 23/05/2012 00:13:50
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Two disks spinning in opposite directions at the same angular speed add up
to zero angular momentum -- zero gyroscopic force.
See: http://www.de-monstrare.nl/pdf/Counter-rotating%20disks.pdf
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