Quote:
Originally Posted by 1683cadder
please enlighten me; i honestly have not much of a clue. How do i make two different motors work together?
|
You match the output speeds of the motors.
Here's an example: Let's say that I have a CIM (free speed 5500 RPM) that I want to have work with an RS775-18 (free speed 19500 RPM), in the same gearbox. 19500/5500 is 3.545, so I need an extra gear ratio included somewhere between the RS775-18 and the CIM that is 3.545:1. (There are other considerations--see Tristan's post--but that's a reasonable starting point.)
What Tristan is saying is that if you're doing a quick-and-dirty gearbox design (first iteration), the MiniCIM and CIM can be considered interchangeable. But, your performance may suffer as a result of that consideration, due to the motors being different (say, by 1000 RPM at free speed). So maybe you want to optimize your motors' performance in a later, more refined version. The way you do that is you look at the motor performance curves (like
the one for the CIM, down in the lower middle of the page). As speed goes down, torque goes up; as torque goes up, so do the amps the motor pulls. I don't see the power line, but if you remember that power=torque*RPM you should be able to construct it (it should be a curve).
For example, I seem to remember that a particular team in a particular year designed an arm around operating a particular motor (not in the current KOP) at the top of the power curve. Anybody who has some experience doing the same thing knows what comes next... Unexpected loads caused some loss of power, resulting in the arm failing pretty badly at times. The team has since designed farther to the left on that curve to have extra power in such situations.
Anyways, if two motors are different, matching their speed will work for a quick solution. But to optimize, you probably want to match their available power at a given RPM, which will require slightly different gear ratios than just matching speeds.