Does Your Team Use 4 CIMs on Your Drive?

[davidthefat]

I am taking a survey to explain to my mentor that it would be a disadvantage to use only 2 CIMs on the drive, especially if playing as a feeder. His argument is that we used 2 CIMs for the past 3 years, but my argument is that we do not have enough power to overcome opponents, let alone push them around. Last year, we DQed in the semi finals because we were pushed into the scoring zone due to the fact that we only used 2 CIMs. Also, using 4 will draw less current per motor and will not trip the amp breaker. Our robot tripped the amp breaker too much that it was almost undrivable. I want to prevent that this year, but he does not think it is necessary.

[MikeBrock]

I think you are actually correct.

[EricH]

While you were using 2 CIMs since the year when the number of CIMs to the floor didn't matter, everyone else went back to 4 on the floor. (Or at least some reasonable substitution for the extra CIMs.)

That means that everybody else has 2x the power available in the drivetrain. You can do the math for available acceleration, pushing power, and all that other stuff, but the simple way to look at it is you've got a 1/2 power robot in terms of drive.

[Mk.32]

We are definitely planning on using 4 CIMs in drive this year.
FP/Banebots/etc for shooters and the rest.

While we're not willing to sacrifice our first 4 CIMs from the drivetrain, we are willing to use our pseudo-CIMs for shooters, etc.

Essentially, an RS-775 or FP motor through a Cim-Sim gearbox will be almost exactly like a CIM motor.

[Djur]

2 CIMs are lighter than 4 (and their gearboxes), but they offer so much less power that many robots with 4 CIMs can bully 2-CIM robots very easily. While having 4 CIMs isn't strictly necessary -- you can easily drive a tank style bot with only two -- it removes the power inequality with only 2 CIMs and makes a more responsive/maneuverable/powerful robot.

[davidthefat]

Originally Posted by Djur

2 CIMs are lighter than 4 (and their gearboxes), but they offer so much less power that many robots with 4 CIMs can bully 2-CIM robots very easily. While having 4 CIMs isn't strictly necessary -- you can easily drive a tank style bot with only two -- it removes the power inequality with only 2 CIMs and makes a more responsive/maneuverable/powerful robot.

That is my argument FOR 4 CIMs. Because we will be a feeder, we would be spending our whole time on the opponent's side, we need to resist being pushed.

[rich2202]

Originally Posted by davidthefat

That is my argument FOR 4 CIMs. Because we will be a feeder, we would be spending our whole time on the opponent's side, we need to resist being pushed.

Not only resist, but as a feeder, you are a defender, and have to be able to push them around.

[waialua359]

Of all the years in FIRST, we got the largest selection and amount of motors with lots of COTS options for CIM-ulating.
Its a no-brainer. Use all 4 CIMS in your drive.

[Hawiian Cadder]

Almost all of the Andy-mark Gearboxes are set up to support 2 motors, every gearbox on our robot will have 2 motors in it. 4 cims in the drive-train, and then pairs of 500 series motors elsewhere. Even if you want to avoid the 775 problems, the 500 series motors will more than handle what you need. We are planning on 4 total in our conveyance system.

[Marc S.]

Definitely go with 4 cims. There are plenty of other motors for everything else(especially this year). If your looking into pushing other robots check different tread types. McMaster-Carr sells the same material as the andymark tread in different abrasive qualities.
Also check out this match(and cad below) when 973 pushed 469 with 4 cims in drive.

[Dad1279]

4 CIMs + at least 2 more......

You could demonstrate your idea by using the JVN motor spreadsheet, entering the data for your gearing, it calculates current draw and pushing force.

[JamesCH95]

Originally Posted by Dad1279

4 CIMs + at least 2 more......

You could demonstrate your idea by using the JVN motor spreadsheet, entering the data for your gearing, it calculates current draw and pushing force.

I read a team's post about trying a 6-motor drive train and they found that pushing performance was hurt (vs 4-motor) because the extra two motors dragged down system voltage so much. YMMV though.

We've used 4 CIMs for the past several years. When coupled with an OTS 2-spd transmission from AndyMark and high traction wheels they're very hard to beat.

[Dad1279]

Originally Posted by JamesCH95

I read a team's post about trying a 6-motor drive train and they found that pushing performance was hurt (vs 4-motor) because the extra two motors dragged down system voltage so much. YMMV though.

We've used 4 CIMs for the past several years. When coupled with an OTS 2-spd transmission from AndyMark and high traction wheels they're very hard to beat.

I'm sure that depends on the application, wheels, gearing, etc......JVN spreadsheet is your friend..... we will confirm with testing.

Back to OP, check the following chart (thanks to team 358): http://team358.org/files/mechanical/...nRefTables.jpg It clearly shows the advantage to 4 CIMs in a conventional traction drivetrain.

[Taylor Hawkins]

We always use 4 sims in out drive train because we found that with 2 you needed to use more power to get the same result. We also found out last night that with 4 cim's you have so much torque the robot was able to push a mentor across the floor. (with Ease!!)

Definitely suggest using 4 cims