VP Load Rating Chart with 2 Motors

If you’re using two motors, is there any way you should modify the load rating chart?

Yes. The short answer is that you should limit the overall reduction ratio to half of what is normally allowed, because these limits are torque based.

From page 2 of the Load Ratio manual (emphasis mine):

The “Simple Load Ratings” tables use a red/green rating system. If the motor/gear ratio/output shaft combination selected is highlighted green, then it is within the maximum gear ratio recommendations. If the motor/gear ratio/output shaft combination is highlighted red, then the maximum motor torque will be capable of damaging the gearbox (with a significant enough load on the output shaft) and should be used with caution.

If your two motors are 775pros (or Redlines), you can also use the load ratings for a Mini CIM. A 775pro has 0.71 Nm stall torque, and a Mini CIM has 1.41 Nm. That’s almost exactly double, or almost exactly the torque of two 775pros.

That being said, both what I and @GeeTwo said only applies for the 1:1 ratio dual adapters. If you’re using a new VersaDM with a 3.75:1 or 5.33:1 ratio, you need to also divide by that ratio (since the torque from the motors will be multiplied by that before it enters the VP). That does make finding the right ratio in the table a bit harder.

I’m hoping in this offseason Vex will update their ratings guide tables to include all of the options for dual motors. (@Jon_Jack et al) For now, your safest bet is probably to reach out to Vex customer support by phone or email and ask which ratios they do/don’t recommend for the motors and initial ratio you want.