2 motors with different speeds in one Gearbox

[Joe Johnson]

There is nothing all that magical in this.

For motors with similar power ratings (e.g.250W BB + 340W CIM), the variations between matching stall torques or matching free speeds is not that big of a difference (~5:1 for stall torque, ~4:1 for free speeds). It is not that big of a deal, really.

For my tastes, in high power applications (which is why you want the extra motor isn't it?), I prefer to have the smaller sized (and in the case I discussed power as well) motor do less of the work (so that it will have to dissipate less heat which, because it is smaller is more critical -- heat transfer is a Area X DeltaT thing -- for the same heat to dissipate the less Area the more DeltaT)

In other cases, I only need the more power in one or other of the speed ranges. For drive trains, I think most folks add motors for more torque at low speeds. To that end, I tend to match stall torques. If I give up some speed on the high end, Que Sera, Sera...
Good luck.

Joe J.

[Ether]

circa 2002:

Originally Posted by Joe Johnson

This is a very complex issue.

Originally Posted by Joe Johnson

There is nothing all that magical in this.

The internet never forgets

Sorry Joe, I couldn't resist!

[HammadB]

More specifically speaking, since I am unable to get my hands on more FP 0673's is it viable to put one FP 0673 and one RS550 into the same gearbox at a overall reduction between 5~8

[Aren Siekmeier]

Two different motors do NOT fight. They simply distribute the load and run at a speed according their own characteristics, and you should gear them appropriately to run them at similar speeds, so that one is not doing the brunt of the work (why have two motors?).

[Ether]

Originally Posted by NuclearNK

More specifically speaking, since I am unable to get my hands on more FP 0673's is it viable to put one FP 0673 and one RS550 into the same gearbox at a overall reduction between 5~8

If the 2 motors are geared the same, the 0673 will be working harder (and generating more waste heat) than the 550.

[JamesCH95]

Originally Posted by ToddF

When using mismatched motors, at some point in the speed range, one or the other motor will be backdriven by the other. As a mechanical guy, I have to ask the question to the electrical guys: What is the effect on typical motor drivers (such as the Jags) of having a motor being back driven and acting like a generator when the driver is trying to turn it the other way?

I suspect the short term effect isn't catastrophic, as under-geared robots get pushed backwards quite often. But, I suspect that having this happen continuously, as might happen in a mismatched motor system, might cause something to overheat and fail.

Anyone know?

Not much. Every time a robot is pushed by hand this happens. It has never damaged any Victor or Jag that I've ever seen.