1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

B Control moment gyroscope design - question

  1. Aug 9, 2015 #1
    Hi all,

    Like a lot of folk on here I am interested in the idea of a CMG used to stabalise a single track vehicle.

    << Link to CMG info added by Mentor >>

    I have designed this;

    2015-08-09 18_59_41-SolidWorks Premium 2013 x64 Edition - [gyro stabaliser].png

    the pink discs spin in opposite directions and the pendulum rotates them.

    My question is could this replace a complex control system? or am i making it to simple?

    (i tried to simulate it in SW but have not got the premium license)

    keen to hear your thoughts

    Last edited by a moderator: Aug 13, 2015
  2. jcsd
  3. Aug 13, 2015 #2
    I don't understand. The pendulums swing in opposite directions. Is this intentional?
  4. Aug 14, 2015 #3
    it is just one pendulum joined with a pin. (i could have made that clearer)
  5. Aug 14, 2015 #4
    Though your intent is not clear, I don't think it's going to operate as you wish. If the assembly tilts 5 degrees what happens? In which direction do things move?
  6. Aug 14, 2015 #5
    2015-08-14 22_21_53-SolidWorks Premium 2013 x64 Edition - [gyro stabaliser _].png 2015-08-14 22_22_32-SolidWorks Premium 2013 x64 Edition - [gyro stabaliser _].png

    my intention is that the frame should be rigidly bolted into a motorcycle frame.

    when the motorcycle stops the pendulum provides a negative feedback system tilting the counter rotating gyroscopes so that the rider never has to put his feet down.
  7. Aug 14, 2015 #6
    OK, so the axis at the bottom of the box is inline with the long axis of the motorcycle, right?

    Then, with the way the gyros are gimbaled, you're counting on the procession of the of the gyros to move the pendulums. I'm not sure how the angular velocity could effect pendulum displacement.
  8. Aug 14, 2015 #7
    I think you see what I am trying to do.

    the pendulum is acted on by gravity and g force and it dictates the gyros position.

    "I'm not sure how the angular velocity could effect pendulum displacement." - if by this your saying the gyros may try to move the pendulum (equal and opposite) then I am not sure either.

    on this Wikipedia page a similar system is discussed under principles of operation;


    what i am trying to find out is can a simple mechanical linkage/mechanism replace what lit motors are doing with software/complexity.

    The above links and below seemed to without software.
  9. Aug 15, 2015 #8
    It's interesting what you are trying to do. The modern approach is to use some electronics feedback to obtain stability.

    Consider the limits. When the gyros are spinning at zero angular velocity, the pendulums don't move at all. In some classical limit of high angular velocity of the gyros, the pendulums will move to their limits.

    Somewhere in between, a full dress Harley might slowly tip over waiting for the light to turn green.
    Then you've got to correct for the lean coming out of the red light. It won't do If you have to
    change lanes to do it. I think you just have to try it to see how how it handles. It might suck in the turns. So go for it, and see how it handles. It could be really stiff; impossible to turn. Put a prototype on a bicycle so your friends can laugh at you.
    Last edited: Aug 15, 2015
  10. Aug 17, 2015 #9
    i think i understand what your saying; - your concerned the gyros wont always return to center.

    on the wikipedia page i referenced there is the figure of 5% of total vehicle mass required for gyros. we had the same idea, first i will check it on SW at work then if it seems workable i will make up a little prototype, say a pair of 200mm diameter 10mm thick steel discs (2.5kg each) at say 5000 or 9000rpm. (depends on which motors i buy) and bolt it to the back of my bicycle (in a sturdy box!)

    would you say its better to mount them lower or higher?
  11. Aug 17, 2015 #10


    User Avatar
    Science Advisor

    A differently loaded vehicle will need different gyro action for the same lean angle. How would pendulums, affected only by the lean angle, account for this? And since the gyros have to be powered anyway, what is the point in removing the powered control system?
  12. Aug 17, 2015 #11
    I think the pendulum will provide a negative system
  13. Aug 19, 2015 #12
    A japanese gentleman makes these for a hobby;

    notice how they seem to lean like a bike into the corners.
  14. Aug 19, 2015 #13


    User Avatar
    Science Advisor

  15. Aug 20, 2015 #14
  16. Jan 5, 2017 #15
    what is mobility of this mechanism?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted