pic: Shifting Module for Drivetrain Concept

[lemiant]

Originally Posted by crazyStone

I thought the same thing that they should be the same speed, I was just told by some members of my team that the difference in preformance is great enough between 2 cims that a noticeable amount of preformance is lost when they are linked together. I find that hard to believe, but thats why this has 4 seperate transmissions to appease that belief. The pros of simply using a Supershifter will be raised. Yes the motors are being coded to run at the same speed, it is merely electrical differences within the construction of the motors that will create slight variations. Thats my understanding at least. However I am much more mechanically inclined as opposed to electrical/pneumatics, so I could be totally wrong.

You are right. You're team is wrong. There were issues with motor going different speeds forwards and reverse back in the day, when we were using drill motors - which do have a significant bias. However that shouldn't affect your design for three reasons:

1. CIMs do not have a measurable bias
2. The suggestion that the motors would 'fight' is wrong. They will settle into different points on their performance curve, with one doing more work, but they are still working together
3. Motors in the same gearbox are going the SAME direction.

[Aren Siekmeier]

And besides, even with separate transmissions and all, you still have both wheels on the ground that have the same constraint on them: they must spin at the same speed. The only thing separate transmissions accomplishes is the possibility of independent motion of the wheels, which would only shred your treads unless you had mechanum.

Motors in the same gearbox are USUALLY going the same direction just because of how they are usually geared together, but it is possible to have them switched, by putting them on opposite ends of a shaft or by having an even number of gears between. In fact, one widespread instance of counter-rotating motors this year was minibots. The wheels obviously had to spin at the same speeds, just in different directions (or the motors were often on different sides of the wheels, if the wheels were both on the same side).

[lemiant]

Originally Posted by compwiztobe

Motors in the same gearbox are USUALLY going the same direction just because of how they are usually geared together, but it is possible to have them switched, by putting them on opposite ends of a shaft or by having an even number of gears between. In fact, one widespread instance of counter-rotating motors this year was minibots. The wheels obviously had to spin at the same speeds, just in different directions (or the motors were often on different sides of the wheels, if the wheels were both on the same side).

True, but that definitely doesn't apply to super shifters

[Kyle Love]

AH, got my motor types wrong...whoops.

[Aren Siekmeier]

Originally Posted by lemiant

True, but that definitely doesn't apply to super shifters

I'm confused. What doesn't apply to super shifters?

[Hawiian Cadder]

Unless your wheels are scrubbing, the motors are "fighting" each other just as much. If we assume the wheels, gears, and chain runs are all exactly the same then the motors, even if though they are in different gearboxes will be spinning the same speed, unless your robot is sliding.

[lemiant]

Originally Posted by compwiztobe

I'm confused. What doesn't apply to super shifters?

In that post I am referring to special cases that have the motors in one transmissions spinning opposite directions. They exist, but aren't really relevant because he will be using supershifters. And supershifters do spin the motors the same direction.

[Aren Siekmeier]

Originally Posted by lemiant

In that post I am referring to special cases that have the motors in one transmissions spinning opposite directions. They exist, but aren't really relevant because he will be using supershifters. And supershifters do spin the motors the same direction.

Oh, yeah, duh. Not following my own conversation... Yes that is true that my little "usually" anecdote wasn't exactly relevant. I was mostly showing that it does indeed happen fairly frequently and that it's not really a problem.