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  1. #1
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    Need some help from clever builders...

    I am trying to find an elegant solution to interfacing a rotary pot with a push/pull cable. I am trying to interface a real Cessna Throttle (and Mixture and Prop) cable to a standard 300 degree pot.

    Any great ideas how to do this?

    Difficulty...I don't have access to a cnc, and tools are limited to basic hand tools.

    Rack and pinion seems to be a commont way to translate linear into rotary motion, but how would I do this if it were the rack that had to move?
    http://juneaucessnasim.blogspot.com
    N58243 (virtual)- Low and Slow...

  2. #2
    500+ This must be a daytime job Ronson2k9's Avatar
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    Re: Need some help from clever builders...

    Without going into gearing options you could use a bell crank.



    You could take a look at push/pull throttle group thread. It uses hand made controls but you could adapt the 'back' end to your real controls perhaps.

    http://www.mycockpit.org/forums/show...-pull-controls

    In your case though as you are using 'Rotational' pots not linear you would need a worm gear to convert the linear movement into rotational movement

    Worm Gear


    You could find the parts you need at a hobby shop as they have quite a bit of that for both model railroading and RC cars.
    Up Up and away in my beautiful my beautiful - Amphibian

  3. #3
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    Re: Need some help from clever builders...

    Quote Originally Posted by Ronson2k9 View Post
    Without going into gearing options you could use a bell crank.

    That was my first thought as well. The problem lies in the large angular rotation needed, and the stiffness of the cable. The cable does not want to bend or flex, so I am looking for another way. Thanks for the suggestion though!
    http://juneaucessnasim.blogspot.com
    N58243 (virtual)- Low and Slow...

  4. #4
    500+ This must be a daytime job Ronson2k9's Avatar
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    Re: Need some help from clever builders...

    You could always connect another cable (bicycle cable etc) to that cable to make it a more flexible movement.. In any case I'm thinking your best bet is a worm gear. This will let you rotate to get movement as the controls work in that fashion as well. That's what the button is for on the end of the control. It's to make the control locked in linear movement so that rotational movement will move the control. Pushing the button releases the lock and lets you move the control the linear fashion.

    I calculated it out for you. You will need a 28mm diameter gear to get 360' travel from a linear 90mm movement.

    D = C/pie

    You should be able to find something like that at your local hobby shop (Model Railroading / RC Car) they both employ such gearing in various forms for the models. I tried looking up 28mm gear and got a bunch of photography stuff. 28mm is a popular lens size. Model railroading especially uses worm gears. You should be able to adapt a threaded rod for the shaft of your movement. It will need to be long enough to be held in place.

    NOTE: The Throttle is reversed to the other controls. That is you PUSH to open. So you will want your pot to rotate in the opposite way to the others. You might be able to map that in FSUIPC perhaps I'm not sure though. I'm thinking though that reversing the direction of rotation could be easier.
    Up Up and away in my beautiful my beautiful - Amphibian

  5. #5
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    Re: Need some help from clever builders...

    Hi,
    Why do the hard way?
    Just spend a pound/dollar/yen and buy a sliderpot,
    its very easy to connect.
    If you look at the Simkits website you can see how it is connected.
    I have done it myself, only using household tools.
    greetz

  6. #6
    500+ This must be a daytime job



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    Re: Need some help from clever builders...

    Quote Originally Posted by Ronson2k9 View Post
    Without going into gearing options you could use a bell crank.



    You could take a look at push/pull throttle group thread. It uses hand made controls but you could adapt the 'back' end to your real controls perhaps.

    http://www.mycockpit.org/forums/show...-pull-controls

    In your case though as you are using 'Rotational' pots not linear you would need a worm gear to convert the linear movement into rotational movement

    Worm Gear


    You could find the parts you need at a hobby shop as they have quite a bit of that for both model railroading and RC cars.
    Afraid worm gear would not be the answer, as the cable does not rotate. It goes strictly in and out (left and right in the line drawing). Pretty sure that the answer lies in either a rack and pinion, or in some way to devise a slotted cam that an attaching mechanism could ride in, to spin the pot but allow the cable to have little deflection along any axis.

    Any other ideas based on that?
    http://juneaucessnasim.blogspot.com
    N58243 (virtual)- Low and Slow...

  7. #7
    500+ This must be a daytime job



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    Re: Need some help from clever builders...

    Quote Originally Posted by kermit View Post
    Hi,
    Why do the hard way?
    Just spend a pound/dollar/yen and buy a sliderpot,
    its very easy to connect.
    If you look at the Simkits website you can see how it is connected.
    I have done it myself, only using household tools.
    greetz
    I have been thinking about that, and may go that way if need be. I want to be able to use the full range of motion for the controls, which are more than 60mm. I was also worried about durability on the slide models. Mike Powell's pot tutorial mentions that can be an issue. Have you had problems with yours?
    http://juneaucessnasim.blogspot.com
    N58243 (virtual)- Low and Slow...

  8. #8
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    Re: Need some help from clever builders...

    Hello

    You could take a look at the following threads about String Potmeter
    made easy:

    http://www.mycockpit.org/forums/show...pring+potmeter

    http://www.mycockpit.org/forums/show...pring+potmeter
    Regards,
    Per-Erik
    www.hoddo.net

  9. Thanks AK Mongo thanked for this post
  10. #9
    500+ This must be a daytime job Ronson2k9's Avatar
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    Re: Need some help from clever builders...

    Those seem pretty cool to me too. The friction on the control would need to overcome the springs force though. There is probably a way to reduce the spring force so it still moves the pot but doesn't pull on the control and increase the friction a bit so it stays put but can easily be moved.

    Reduced spring so you don't need so much friction.

    Very interesting stuff though just the same..

    Rack and Pinion was what I was thinking of I just didn't know the name till I looked it up. I was thinking the worm though from a rotational standpoint but your right about the cable from the control. That worm action must happen up front ?
    Up Up and away in my beautiful my beautiful - Amphibian

  11. #10
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    Re: Need some help from clever builders...

    There's a thread somplace, I will go find it in a minute.... where a guy built a throttle control with Legos. I kow it sounds funny, but it's very cool! He translated the linear motion to rotational movement by placing a spur gear on the potshaft and used a rack gear mated to it...

    LINKL

    http://www.simpits.org/articles/lego...20quadrant.htm

  12. Thanks AK Mongo thanked for this post
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