pic: Shifting Module for Drivetrain Concept
 

Re: pic: Shifting Module for Drivetrain Concept
 

Ok, I'm going to bite. Any reason why you aren't using the gears out of AndyMark's gearboxes and saving all that machining? They have some pretty nice ratios. You can make custom side plates, use the final chain reduction to get any speed you want at the wheels, etc.

Re: pic: Shifting Module for Drivetrain Concept
 

Mainly out of boredom, and in a pursuit to create something that was smaller and cheaper and possibly lighter than a AndyMark Supershifter. SuperShifters will probably be used due to the ease of obtaining them. This is as much design ideas, as practice CADing full assemblies from scratch. Chain drive does give the ability to alter the gear ratio as you pointed out. You also lose some efficency with running 2 CIM's on one shaft because one is always working against the other by a very small amount.

Re: pic: Shifting Module for Drivetrain Concept
 

What do you mean "working against the other" ?

Re: pic: Shifting Module for Drivetrain Concept
 

When you run a two motor set up as mentioned, one motor will be running in reverse of the other, causing an efficiency loss and one motor spinning a bit slower then the other.

Re: pic: Shifting Module for Drivetrain Concept
 

?? If the motors are geared the same and are mechanically connected to the same shaft (as mentioned) they will be spinning at the same speed.

Re: pic: Shifting Module for Drivetrain Concept
 

They will absolutely be running at the same speed (at least I hope so :ahh: ) but they may be at different points on their performance curves, if these curves vary based on direction. This means you aren't necessarily at the peak power of each motor (not necessarily affecting efficiency...). However, the directional bias of a CIM is certainly small enough to disregard (if it exists?).

Re: pic: Shifting Module for Drivetrain Concept
 

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.

Re: pic: Shifting Module for Drivetrain Concept
 

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.

Re: pic: Shifting Module for Drivetrain Concept
 

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).

Re: pic: Shifting Module for Drivetrain Concept
 

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

Re: pic: Shifting Module for Drivetrain Concept
 

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

Re: pic: Shifting Module for Drivetrain Concept
 

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

Re: pic: Shifting Module for Drivetrain Concept
 

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.

Re: pic: Shifting Module for Drivetrain Concept
 

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.