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Thread: Leg suspension

  1. #1
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    Question Leg suspension

    Hello. I am working on a new quad for MW, and have some questions about leg mounting/design.

    I am planning on using a 1/10th scale rc truck chassis as the main frame, and am debating on mounting the legs directly to the hubs where the wheels went. The main reason I see for this being the possibility of the suspension reducing the shock loading on the servos, especially during high speed stepping/ maneuvering. This would also help to stabilize the gun and video feed as the "jitter" when walking would be less pronounced.

    Thoughts?

  2. #2

    Re: Leg suspension

    1/10th chassis sounds heavy.
    Maybe you can buy the shocks and springs separately, and build something slightly smaller/lighter to put them on?

  3. #3
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    Re: Leg suspension

    Stripped chassis with suspension intact weighs under 1 lb. Mostly plastic with a couple aluminum braces

  4. #4
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    Re: Leg suspension

    Click image for larger version. 

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    AX-12A for scale. A little long, but around the same normal length.

    Edit: I already had the chassis, just can't use it for parts for my nitro version. Used everything else though

  5. #5

    Re: Leg suspension

    Well, you're going to need some kind of plate to mount battery, camera, wireless, controller, and all the rest on. Why not try this and see how it goes? :-)

    If the springs are too soft, then they will significantly change how your IK solution works out; you may have to update your coordinate system based on your best estimate of spring deflection based on where you are in the walk cycle. If this is a problem, you can probably get away with a simple linear estimate based on how far "down" the leg end is supposed to be.

  6. #6
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    Re: Leg suspension

    At max extension they are somewhat soft. They were used on a 60+mph brushless monster truck. That setup when going from full speed to max braking would drop the nose around an inch. I will likely have less than 3/8" travel at the hub during normal walking. They are oil filled shocks with progressive rate springs. Can be squeezed easily by hand, but dropping the 7lb truck from 3-4 feet up they didn't bottom out.

    If I have too much compliance, I can double up the springs and add spacers to stiffen the springs, plus heavier weight oil will cause stiffer shocks.

    As far as the plate, I was thinking of mounting that on some extra shocks and springs I have for further damping. The chassis ones are to reduce shock loading on the servos, while the gun mount ones reduce jerking of the aim/camera view etc. Could make for a very smooth piloting experience.

    I just need to get more brackets (waiting on paycheck - yay!) and a way to mount the coxa servos to the hubs. Debating on a bolt through some F3 brackets and the hub, plus some locating pieces, or replacing the hubs with a custom cut piece of aluminum with the bioloid/AX12 hub pattern.
    Last edited by ArduTank; 09-23-2018 at 12:50 AM.

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