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I'm trying to drive a wheel with a radius of 20cm that is 20cm above the motor and horizontally offset by 20cm from the motor, similar to the following:

enter image description here

I wonder what a good linkage might be for a setup like this. I've considered ball joints like below, but I don't think the allowable angle of the shaft is great enough:

enter image description here

I didn't want to go for expensive linkages like those with universal joints. Does anyone know what might be a good linkage for the wheels in this case? The torque required will be around 50Nm.

Any thought appreciated.

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  • $\begingroup$ Could you help me understand what you mean by driving? And how were you planning to use the universal joint to drive? In mind driving in this context would mean to rotate about its axis each disk, however, I think you have something entirely else in mind. $\endgroup$
    – NMech
    Commented Mar 8, 2021 at 6:45
  • $\begingroup$ why drive with linkages? do you not need continuous rotation? $\endgroup$
    – Abel
    Commented Jan 2, 2022 at 21:45
  • $\begingroup$ As drawn the yellow connecting rod will hit the motor shaft after half a revolution. You need a better drawing $\endgroup$ Commented Dec 29, 2022 at 0:30
  • $\begingroup$ why not use a connecting rod like a steam engine with a standoff on the lower wheel so that you can just use a roller bearing? $\endgroup$ Commented Dec 29, 2022 at 0:41

4 Answers 4

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Put teeth on the circumference of the driver and then a gear on the shaft of the driven. Either they can mesh or use a chain or belt drive - depends on the torque/speed/power...

Of course if space is an issue consider a hydraulic link but is the speed ratio to be held constant or is there an acceptable tolerance.

Another option is to put gears on both shafts but below the two existing wheels.

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  • $\begingroup$ Indeed, space is an issue and it'll have to be a linkage of some sort. Speed ratio and tolerance requirements are very low. Can I ask why a hydraulic link and not any link with ball joints? I'd rather not deal with hydraulics if I could. $\endgroup$
    – John M.
    Commented Mar 8, 2021 at 5:55
  • $\begingroup$ @JohnM. Just gave you some ideas to consider, you already had ball joints on your list . I just thought that using a ball joint would need a mount above the surface on one and then due to the sweep nothing else on either surface ... but it’s your project, I just offered things you did not serm to be considering. $\endgroup$
    – Solar Mike
    Commented Mar 8, 2021 at 6:17
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I am still not certain 100% what you are trying to do, but from what I understand the wo solution you might want to consider are

  • chains/pulleys : if the position of the shafts is fixed

  • Schmidt linkage ( Video for operation ): if you want to move parallel one axis of rotation with the others.

enter image description here

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You should connect one of these swivel joint connectors, or similar, on the dependent wheel, and connect to the driving wheel's anchor point by a lever arm. https://www.dsti.com/landing/swivel-joints/

enter image description here

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I suggest that whatever is on the motor shaft at present, take it off. It is easy to extend the shaft, all you need is a shaft of the same diameter and 25cm long and a coupling, such as these at McMaster You then reattach whatever is is that you want to drive your wheel with, as they will then both be at the same level.

You could then use a belt and pulleys for example.

50nm is quite a high torque, at 10cm radius that's like lifting 50Kg! Do you need the wheel to freely revolve, or just change its position? With that kind of torque a chain drive would be more suitable.

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