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  • need variable cam control design

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

    1. johntargell

      johntargell Member

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      Hi Greg - if you can explain how you loaded your pics I can try doing the same
      Thanks John
       
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    3. GarethW

      GarethW Chief Clicker Staff Member

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      Hi - here are the instructions: viewtopic.php?f=10&t=35
       
    4. musicalavtech

      musicalavtech Member

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      Took a pic with my phone, sent that pic to snapfish, from that site, I clicked on the pic and I copied the image address which I pasted into a post here. Clear as mud eh?

      I'll have a top view drawing posted later.
       
    5. musicalavtech

      musicalavtech Member

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      In this top view, you might see that the upper cam is tilted and has just passed the 11:00 position and the pushrod is about halfway pushed out. When the cam reaches 9:00, that pushrod will be pushed all the way out. The lower cam is well past the lower pushrod (not shown) and has let it come back in fully. Because the cam is touching the edge of the housing, that means that the joystick is maxed out to whatever direction it is pushed. 200 rpm is about what the shaft w/cam is rotating. If the joystick is brought to center, the upper and lower cams will be in the center of the housing...still spinning but not really doing anything to the pushrods. Starting from center, if the joystick is pushed only a partial way towards the 6:00 position, the cam will still be off center but not really coming close to the housing and only moving the pushrod partially in with each rotating cycle.

      If the joy stick is pushed to the 9:00 position, the cam would have an instant effect on the pushrod. If the joystick is shoved all the way towards the 6:00 position, the cam will rotate 3/4 of the way around before it fully pushes the pushrod out. That is where the sync happens between this shaft and another shaft driven from the same source. The pushrods will actuate an advance and retard on yet another shaft. I'm just trying to explain the sync theory. More important is how to "steer" the cam with a joystick, allowing the cam to do it's rotating off center axis without the joystick going any other direction than what is intended. Right now John's ball idea, maybe with some sort of controlled U-joint may help to do the trick. The ball would seem to rotate in the opposite direction, inside of the spinning cone-cam.




      [​IMG]
       
    6. musicalavtech

      musicalavtech Member

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      For a moment that took the wind outta my sails, Then a few minutes later I thought I had that figured out. There would be a cap at the bottom of the inside of the upper cam that would be bolted to a nut in the sphere. The two piece sphere (bottom half bolted to the shaft) would have a large enough hole in the top half to allow for the bolt to tilt with the cam. The 'nut' in the center of the sphere would have a ball behind it to allow tilt with the bolt. The cap would have gripping grooves matching the bottom of the inside of the upper cam. The top & bottom sphere halves would be bolted together through access in the hole. The cam will 'roll' on the inside surface of the funnel housing. The upper and lower halves of the cams would be fastened together around the sphere.

      The housing of all this, would resemble a hourglass funnel(s). A little bit anyway, with no curves. The blue pushrods are large so that as the rolling cam contacts them, it would not have a hard blow. The tips of the pushrods closest to the sphere, are cut so that the sphere prevents the pushrods from coming inwards past the current point, no matter what direction the cams are tilted.
      [​IMG]
       

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