I just wanted to ask about your experience with the varying motor speeds with the A4WD3. Since only one Sabertooth is delivered with the kit, left and right sides will all receive the same signal (as they are wired to the same output port on the Sabertooth). However, that doesn’t mean that they turn at the same velocity, as I tested it.
I did hook up the encoders too before the final assembly, and measured the motor velocities at different commands. As also described in the specs of the motor, the actual velocities can vary by 10%, although they are fairly consistent on the same motor (it is even noticeable visually, not only by looking at the encoder output). That’s generally not great, I would say, if you attach a track to both motors at varying speeds.
However, with this setup it is not possible to adjust motor speeds of both left motors (or both right motors) independently. For that, we’d need two sabertooths. However, the default is to use one sabertooth, which is how the kit is deliviered, and according to instructions.
Now my question: what is your experience with the different motor speeds? I guess the track holds back the motor that is turning faster, but will that not strain the motor too much? How does this play out in your experience?
By the way, my delivery included the motor with the 1:51 gear ratio, which I only noticed once testing the encoders and checking if the output makes sense. Matches perfectly if I use 1:51 gear ratio.
Most skid steer track system will work perfectly with the two motors getting the same output.
However if you want you can add another Sabertooth and control them with a PID loop using the encoders. We personally think this would be overkill but your choice after all.
The plate inside allows mounting of two Sabertooth mostly for the Mecanum version:
thanks for the quick response. Yes, I saw that the plate is laid out for supporting two sabertooths, which partly is the reason I wanted to ask if in your experience it might work better (be more durable) to use two, and regulate them with PID controllers. I wanted to make sure that the difference in motor velocities is typical, and you have experienced no issues with it. If in your experience that would be overkill, then I can rest assured that it’s fine to continue the assembly. Thank you!
Btw it was the datasheet linked on this page which caused my confusion about the gear ratio. But you are correct that when expanding the “specifications” tab, it does say 1:51.
Thanks for pointing out, in the early development we used that motor and the datasheet should not be there and we will revise the listings.
I would not do anything crazy, just connect as suggested.
There are some mechanical play also between the sprockets and the track but that’s also not of a concern.
