Quote:
Originally posted by Paul Copioli
P.J. is right. The differential idea proposed by Tytus is exactly like the CCT with a 1:1 ratio between the sun and ring gear. Hey, even us unsung FIRST heroes are wrong from time to time.
|
Yes, I was going to mention that, but ran out of time. The bevel/differential gearset can can do the one thing that the planetary gearset can't: achieve a 1:1 gear ratio between the sun and ring gears. In order for this to happen, the sun gear would have to be large enough such that it approaches the size of the ring gear. Of course, this can't happen, but calculus says the limit exists. As the sun gear size increases (and therefore the planet gear size decreases), the gear ratio decreases (assuming that the ring gear is the input and the sun gear is the output and the planet carrier is fixed).
Of course, luckily for us, the stall torques of FIRST motors are never the same. So a more compact dual-motor gearbox can be made by simply using a planetary gearset, taking advantage of the difference in gear ratios.
Quote:
That being said, only one motor contributes to the output torque of the system. The other motor acts like a speed increaser at the same output torque (if balanced correctly). All the equations derived in my whitepaper for the CCT apply to Tytus' design.
-Paul
|
Actually, both motors will contribute to the output torque of the system. However, in order to avoid backdrive, both motors must be configured to have the same stall torque. So basically, you would end up with twice the torque of a single motor. However, the overall top speed will be the average of the two individual motors.
This is complete opposite to the standard spur gear method of combining motors, where the free speed must be configured the same on both motors. The overall torque will be the sum of the two motors, but they will share the load unequally.