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Thread: High Torque Application - Thinking of using cam - need some advice

  1. #1
    Associate Engineer
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    Feb 2013
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    High Torque Application - Thinking of using cam - need some advice

    I am currently undertaking a project to upgrade a fork lift. The requested task is to change the hydraulic tilt mechanism used to tilt the fork lift to an electrically powered system that enables precise position control.

    So far I have narrowed a solution down to using some form of electric motor (to be defined) with a CAM shaft. The required movement is to tilt the fork carriage from -2degrees to +2degrees and output position.

    The system is configured with the carriage hung from a pivot, the current hydraulic system pushes the carriage at a vertical position 270mm below this pivot and the worst case scenario for loading is a load of 2666 Kg loaded on the forks at a horizontal position of 1270mm from the pivot.

    I have calculated that the moment about the pivot due to the load applied to be 33140 Nm and therefore the force pushing horizontally from the current hydraulic system, and therefore required by the new electrical system, to be 132031.9 N

    Could anyone suggest how to go about sizing a suitable motor and gearing system for this application and if it is feasible to use a cam to move the carriage?

    The alternative to a cam is to use a dog bone rod to connect the carriage to the shaft and have the shaft only rotate by 90degrees in order to achieve the motion.

    Thanks

  2. #2
    Technical Fellow
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    Welcome to the forum, but wouldn't the force be very dependent on the max-load plus a bit so it isn't working right at the limit?

    Also, unless I missing something from the very sketchy description, this sounds pretty much like a simple Trigonometry exercise.

    As to a cam, again unless I am missing something, would that not only work in one direction? How do you bring it back?

    Do some research on electrical linear actuators. Might have just what you need, for a price.

  3. #3
    Technical Fellow jboggs's Avatar
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    I'm with Dave. A simple direct replacement of the hydraulic cylinder with an electric linear actuator seems like the way to go to me.
    Lots of companies make them. The most heavy duty brand I have personally used is RACO (http://www.racointernational.com/) and it worked well.

    Then your decision will be acme screw (which is intrinsically self-locking) or ball screw (which is more efficient and longer life but requires a brake).

  4. #4
    Technical Fellow jboggs's Avatar
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    You might also check this white paper:
    http://www.linak-us.com/techline/?id2=3514

  5. #5
    Principle Engineer
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    Mar 2011
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    The cam isn't a bad idea but you would need braking to hold a position and would be less precise than the linear solution proposed by the others.

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