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  • need variable cam control design

    Discussion in 'The main mechanical design forum' started by musicalavtech, May 16, 2011.

    1. musicalavtech

      musicalavtech Member

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      Hi all. Maybe the brilliant minds here can help me with, well,,,, design. Picture 2 vertical cones, one upside down, joined at their tips. Actually there is a small sphere between the tips and the tips are cut off. There is a shaft going through top to bottom. The cones always rotate around the shaft. The shaft stays straight vertical always. The swivel point is the center of the sphere. As the top cone tilts, the bottom cone goes opposite acting as a counter-balance so the whole unit does not vibrate. The cones tilt stops when the inside of the cone side wall hits the shaft. Because the cone-cam is tilted and spinning around the shaft, it resembles a doppler effect. It's spinning, circular diameter path is much more than when the cone is not tilted. So far, ez enough.

      The tricky part and challenge is to control the amount of cone-cam tilt with a joystick. At least I haven't figured it out yet. Could be worth mega$ some year. :D
       
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    3. SCIYER

      SCIYER Well-Known Member

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      A picture would immensely help.
       
    4. musicalavtech

      musicalavtech Member

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      Yes it would. Sorry about the crude drawing. So this device would spin with the shaft. The shaft will always be straight. I realize that the shaft would have a means of spinning the mostly hollow "cone-cam" and allowing it to tilt towards the sides while it is spinning. (Not drawn in depth yet) That part is cake. I cannot figure out how a joystick could control how much tilt occurs. Picture the child's toy, a TOP I think, how wobbly it gets just before it falls. That would be the tilt mode. Thanks for any input. Greg


      [​IMG]
       
    5. Dana

      Dana Well-Known Member

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      It will still vibrate.. not in plane but there will be a wobble vibration.

      There are numerous ways it could be controlled... pushrods through a hollow shaft, a yoke on the outside, electronics, etc. What are you trying to achieve with it? The preferred method of controlling it depends on what the rest of the system looks like.
       
    6. SCIYER

      SCIYER Well-Known Member

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      I suggest you read more about Gyroscopes. Gyroscopes have a spin vector and a precession vector. The spinning of top is due to gyroscopic effect.
       
    7. musicalavtech

      musicalavtech Member

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      2nd crappy drawing...single pushrod at top and one on the bottom. BTW thanks for feedback and participation. The cone-cam rotates with the shaft. The pic shows a neutral position. The shaft rotation is in sync with another mechanism not shown. That is why a joystick should control the tilt. When the pushrods are moved, they will interact with gears and belts to introduce variable timing to the other mechanism in relation to the rotation position of the shaft. So if the joystick is moved to a hard left, (9 o'clock) it would force the cam to immediately contact and move the top pushrod with the lower one moving 180 deg later. When the joystick is moved to the 2 o'clock position, the lower rod will soon make contact and the upper one 180 deg later. As the cone-cam spins with the shaft it will contact pushrods each revolution as in a typical car motor. The direction of the joystick has everything to do with the timing of when the cam contacts the pushrods. As in moving the joystick hard right (3 o'clock) makes the top rod contact a half revolution later. I hope i'm not boring you too much. On to the issue...if the joystick is directly linked to the cone (upper) then as the cone spins with the shaft, it will feedback to the stick and move it around as well. Only in the neutral position does the stick not get slammed around. I think there can be a proper way to do this, I'm just not aware of it. I'm sure it's more of a complex design yet with not too many parts involved. Thanks again. Greg
      [​IMG]
       
    8. johntargell

      johntargell Member

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      Hi Greg - if the open top "base " of the top cone could be fitted with a ball in the centre, you could just push, pull or twist the ball with a yoke fixed to your joystick - this is all purely mechanical - I have made a simple sketch in jpg but can't upload it!
      Cheers John
       
    9. pcdcox

      pcdcox Member

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      Hi, The side to side movement should not be a problem.
      You could use 2 stepper motors driving ball screws to give you this movement.
      The joystick would drive each motor in opposite directions.
      This would ensure a smooth movement because the push rods ( ball screw ends) would be in contact with the cam at all times.The speed of movement would be controlled by the speed of the motors and the helix angle of the screws.

      I would be interested to know how you propose to rotate the cone/cam.??
      Regards
      pcdcox
       
    10. musicalavtech

      musicalavtech Member

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      Hi John. I like the ball idea. We would like to see the jpg pic. Lo-tech is fine obviously. The joystick would have 360 deg control over the cam. The cam could/would be "shoved" any direction. The ball would have to stay with the top cone. The joystick, if moving left for instance, would move the cam left...or based on design, the joystick moving left could make the cam go to the right. Or moving the joystick forward would move the cam forward or backwards. Either way, doesn't matter design wise, as long as the joystick can stay where it's moved and the cam can reflect it's movement. The top (upper cone) of the cam would be off center of the axis of the shaft, more so as the joystick is pushed further, in any position except for neutral. I will draw a top view soon.

      The large part that holds the cone-cam, completely encircles it all around.
       
    11. musicalavtech

      musicalavtech Member

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      Ah! side to side is actually 360 deg towards any side. Stepper motors are not as quick as direct mechanical movement. I will soon draw another cruddy top view pic. Thanks. Greg
       

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