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Thread: Knee servos in AX 12 based Biped

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    Knee servos in AX 12 based Biped

    Would there be an advantage to replacing the AX12's in the Knees of my Biped with AX18's ? Less overheating ? More stability ? Eventually I want to replace all my leg servos with AX 18's but for now I can afford Only 2. Am I correct in thinking the Knees are the best place to put them ?

  2. #2

    Re: Knee servos in AX 12 based Biped

    I don't have direct experience, but it looks like the AX18 don't really have much more torque; they just rotate faster. I think that's the wrong trade-off to make for your use case (but I could be wrong.)
    In the same price class as the AX18, you have the RX24, too. I've heard it overheats easily, but it has a lot more torque than the AX18, which is what you want in a knee AFAIK. It doesn't have the same form factor, though.

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    Re: Knee servos in AX 12 based Biped

    The MX-28T looks interesting, "All MX Series servos use 12v nominal voltage, so AX & MX Dynamixels can be mixed without having to worry about separate power supplies." and is also compatible with the CM-510 , Looks like it would just be a matter of swapping out the brackets to mount them. Now that looks like the way to go, a little out of my budget but I can go a few days without eating....

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    Re: Knee servos in AX 12 based Biped

    The MX-28T is very nice, but I'm pretty sure the servo and brackets are sufficiently different from the AX as to cause problems in a Premium Bioloid Humanoid. The main body of the AX-12 and MX-28 are essentially the same size, but the mounting flange around the MX-28 is siginificantly larger and incompatible with AX-series brackets.

    There is a biped in the lab that has AX-18F's in the knees, but I have not used it enough recently to really make a comparison call. It did have a tendency to overheat during motion creation if you left it on one leg too long with the knee bent too much, but from what others have said I doubt even that compares to the speed with which an RX-24F overheats.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh
    more bleh

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    Re: Knee servos in AX 12 based Biped

    Interesting. I see 2 possible solutions to the bracket compatibility issue 1 is a custom made cnc bracket MX-28T on one side and Ax on the other. Or same thing only made on a 3d printer. Put it this way If I had the servo in front of me I could come up with something. The MX-28T looks like a sweet A__ servo.

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    Re: Knee servos in AX 12 based Biped

    Quote Originally Posted by Ron View Post
    The MX-28T looks like a sweet A__ servo.
    ...right up until a drama student breaks it. ಠ_ಠ

    A good sign of their high quality: it takes repeated falls of a DARwIn-OP off of a 4-ft tall table to damage the motor itself (right knee and left elbow) or shear off the horn (right shoulder).
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh
    more bleh

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    Re: Knee servos in AX 12 based Biped

    Quote Originally Posted by tician View Post
    ...right up until a drama student breaks it. ಠ_ಠ

    A good sign of their high quality: it takes repeated falls of a DARwIn-OP off of a 4-ft tall table to damage the motor itself (right knee and left elbow) or shear off the horn (right shoulder).
    Ohh man, those Drama students ! even making robot drama !

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