Poll: CIM vs. Bike Motor?

[Swan217]

Do you prefer 4 CIMs or two CIMs with the two Bike Motors for your drivetrain?

[Kevin Sevcik]

Where's the option for the less crazy teams that are just using 2 motors for the drivetrain?

[sciencenerd]

We're ordering the two extra CIMs that we're allowed to, because we're probably going to be using one of the bigger ones for our arm, because we need to keep it spinned up and the big one is supposed to be pretty efficient.

[Scythe]

We're using the four cims again.

[Shu Song]

Hmm, I don't know why there isn't much enthusiasm about the bike motors. Our team is really excited about using the bike motors for drive. Is there something that we are not considering?

[Kingofl337]

I would order the 2 extra sims for the drive train. It offers redundancy especially when used in similar designed transmission as the kit bot. Our team built our on own gear box last year and used 2 motors per gearbox. We ended up loosing a pinion on one motor and it saved us.

[nirty]

this year we use the bike motor because he have more power but less speed and the exactly what we need more power less speed

[Kevin Sevcik]

Originally Posted by nirty

this year we use the bike motor because he have more power but less speed and the exactly what we need more power less speed

That's more torque but less speed. They also have a lower peak power rating than the smaller CIMs. But greater efficiency. So as with most engineering decisions, there are tradeoffs to be considered.

[Stu Bloom]

If I'm not mistaken the information we have seen so far shows the new bike motors have less power than the "old reliable" CIMs. Include the significant weight penalty and I can't see a use for the new motors ... I guess if you need more power than the FP and your CIMs are committed elsewhere ...

[JVN]

Originally Posted by Stu Bloom

If I'm not mistaken the information we have seen so far shows the new bike motors have less power than the "old reliable" CIMs. Include the significant weight penalty and I can't see a use for the new motors ... I guess if you need more power than the FP and your CIMs are committed elsewhere ...

Or alternately, if you need 8 powerful motors instead of 6.

FIRST has added 2 new "high-power" motors to the fray, while leaving all the high-power motors from last year. That is how it is.

[EricH]

Originally Posted by Shu Song

Hmm, I don't know why there isn't much enthusiasm about the bike motors. Our team is really excited about using the bike motors for drive. Is there something that we are not considering?

Yes, there is.
1) Are you sure that you want your drivetrain to weigh 10 pounds for just the motors? (It's 5 pounds per motor, almost twice the weight of one small one.)
2) Can you get the belt stuff off? Or are you just going to design around that?

[Henry_Mareck]

The main problem i could see is that just 2 motors isnt enough for the full drivetrain. They wouldnt work too well matched with 2 smaller motors, wierd ratios. Now, if we had 4 bike motors, then it would be a different story. Vroom Vroom.

[artdutra04]

Originally Posted by Henry_Mareck

The main problem i could see is that just 2 motors isnt enough for the full drivetrain. They wouldnt work too well matched with 2 smaller motors, wierd ratios. Now, if we had 4 bike motors, then it would be a different story. Vroom Vroom.

You don't need to have two identical motors with identical amounts of "power" in the same transmission. Think of it this way: you have a train full of 100 cars that you need to move. Locomotive A has thousands of horsepower and can move 80 cars. Locomotive B can only move 30 cars. Neither Locomotive A nor B can get the 100-car train moving by themselves. But if you couple the locomotive together, you get a combined pulling power of 110 cars. You can now move the train, even though Locomotive A and Locomotive B are sharing the load "unequally".

This works the same way for the different CIM motors. The two different CIM motors should work the same way, in that they "combine" together and act as basically one motor.

[Veselin Kolev]

Originally Posted by EricH

Yes, there is.
1) Are you sure that you want your drivetrain to weigh 10 pounds for just the motors? (It's 5 pounds per motor, almost twice the weight of one small one.)
2) Can you get the belt stuff off? Or are you just going to design around that?

Oh the belt pinion comes off rather easily. The interesting part is getting something on that shaft... its an 8mm shaft with a flattened side. Set screws, I would not trust. I would make a broach for it. But thats just me. An interesting problem: how to do it cheap.

Has anyone used flattened shafts like this and know of a way to easily cut that into a gear? Or attach a gear to it some other way...?

[Max Lobovsky]

A set screw is probably the simplest method (use two or three set screws if you want). I don't have numbers on it, but I think you can get sufficient torque transfer with it. But, if you insist, another simple method that many teams have used succesfully in the past is clamping to the shaft. Shaft collars with screws through the side fixing it to the sprocket or other component of your choice. Alternately, some sprockets and gears come with a clamp hub (essentially a hub with an OD only slightly greater than an ID and with slots to cut it into 4 pieces) that you place a collar over to clamp it to the shaft.