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Thread: Column feedback

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    Question Column feedback

    First layout and thoughts for force feedback on the MD-80 yoke columns.

    The console in which the spring presses will be movable with an actuator, so it can tighten the springs more or less and give more or less force feedback.

    A change in structure is probably on the way because I also have to integrated the autopilot movements to the columns

    Comments are more than welcome.



    Made with google sketchup
    Sincerely,

    Claus


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    Re: Column feedback

    OH! Clever! It's that 90 degree difference between the column and the loading force that makes it work.

    Consider using two springs symmetrically arranged. This will remove the lateral force on the control column torque tube. Also consider using springs in tension. The springs will self-align.

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    300+ Forum Addict nax228's Avatar
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    Re: Column feedback

    I had the same idea, only pulling insted of pushing.
    Bare in mind that you need A LOT of force (Nm) on those springs, but I really like the idea. Make the circular plates as big as you can.

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    Re: Column feedback

    Thanks for the reply.

    Now I think I've solved the problem with autopilot and the force feedback.

    Now the big question is, will this work.

    The actuator for the autopilot will tighten or loosen the lower spring, then the column will move back or forth to align the spring forces.

    The actuator for force feedback will tighten or loosen the spring and the column will feel more or less hard to move.

    Comments are more than welcome

    Sincerely,

    Claus


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    Re: Column feedback

    Claus,

    By using two springs in this arrangement you can indeed inject the auto pilot trim action. Unfortunately, you cannot adjust the degree of control loading.

    The key difference is that in your original concept drawing the spring force felt by the column is dependent upon the sine of the column angle relative to the rest position, and the length of the spring varies as the cosine of that angle.

    In this version these factors are reversed: the spring force on the column varies as the cosine of the column angle while the spring length varies with the sine.

    In the original concept, moving the column changes the spring length relatively little. Therefore the force the spring places on the pivot point varies little. The net torque, basically what is felt by the pilot, depends on how far the column is moved and how hard the sping is pushing (or pulling) and that depends on the position of the other end of the spring. So, move the end of the spring and the column feels heavy or light depending on where you move the end.

    In the new concept, the spring forces cancel out at the rest point. If the column is moved, one spring gets longer and the other gets shorter. The change in lengths mean there is a corresponding change in spring forces. So, yes, the column feels the net force. The problem is that the force depends not only on the column angle, but also on the spring length change and the spring constant.

    The absolute lengths of the springs in the new concept do not affect the force felt at the column. Changing the positions of the ends of the springs will not change the heavy or light feeling of the column. It will depend solely on the spring constants of the two springs (assuming both springs stay in their linear range.)

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    300+ Forum Addict Shawn's Avatar
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    Re: Column feedback

    I feel smarter from just reading that post mike!! Brilliant concept Claus, it's got e thinking about how I can use the idea in my own controls.

    Shawn

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    Re: Column feedback

    Heh... I was going to say that i felt dumber for having read that. lol

    Sines and cosines... wasn't that a song by the Five Man Electrical Band (later covered by Tesla for the young'uns in the crowd)?

    Looks like a neat and fun project. I just wish I was smart enough to smell what Mike was laying down.

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    Re: Column feedback

    Quote Originally Posted by Mike.Powell View Post
    Claus,

    In the new concept, the spring forces cancel out at the rest point. If the column is moved, one spring gets longer and the other gets shorter. The change in lengths mean there is a corresponding change in spring forces. So, yes, the column feels the net force. The problem is that the force depends not only on the column angle, but also on the spring length change and the spring constant.

    The absolute lengths of the springs in the new concept do not affect the force felt at the column. Changing the positions of the ends of the springs will not change the heavy or light feeling of the column. It will depend solely on the spring constants of the two springs (assuming both springs stay in their linear range.)
    You're right, if both springs pressed then the force balance each other out and no force feedback is felt in the column.
    It's hard to see in the drawing but the plan is that the springs just touches in the neutral position, no compression, and only one of them is compressed in one direction and the second spring is only compressed in the other direction. I had not seen that when the elevator trim is activated then it squeeze both springs and they will offset each other and no force feedback.
    The idea was that in one end of the shaft is mounted force feedback and in the other end autopilot, which deliver approximately the same force feedback to the columns
    I work on a modification.
    Sincerely,

    Claus


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    Lightbulb Re: Column feedback

    Here comes third attempt

    In the autopilot side the springs just touches, in the neutral position, no compression, and only one of them is compressed in one direction and the second spring is only compressed in the other direction

    Is there anyone who can see something I have overlooked.



    I can recommend the free program "Google ScetchUp", this is the program in which I have made the CAD drawing. It's super easy to use. http://sketchup.google.com/

    Download my model for your own free Google ScetchUp here http://sketchup.google.com/3dwarehou...67e23b386bc04c
    Sincerely,

    Claus


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    Re: Column feedback

    Some of the first tests



    Comments are more than welcome.
    Sincerely,

    Claus


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