Swerve Modules

Hey all,

Designing mounts for the Revolution Pro V2 Swerve Modules and was wondering if it is a good idea to drive the wheel (forwards and backwards) with a CIM Sport. (http://www.andymark.com/CIM-Sport-p/am-cimsport.htm) Last year using these modules our team needed appx a 4:1 gear ratio and this gearbox has that. We weren’t sure whether or not it would be a good idea to use this planetary gearbox to drive our wheels as opposed to a ratio that could be achieved with gears/sprockets. Have any teams done something like this successfully?

Also: I need to attach an encoder to the CIM motor, are there any good ways to do so?

Images: https://imgur.com/a/0rTyX


I don’t anybody has used the Sport yet, but I don’t see any reason why it wouldn’t work for this. I would, however, caution you against using this in-season if you don’t get it done by January. A gear reduction might be easier and cheaper.
The AMT-102 Munchskull CIMcoder (not the Andymark version) is a good encoder, but you’ll get some backlash due to having it on the CIM instead of closer to the wheel. an SRX Mag Encoder works really well if you have a Talon SRX to read it with.

When I have a gear ratio that close, I try to see if I can manually handle it :

  • Perhaps belts would let you get a smaller driving size on the CIM (Side bonus, this reduces weight!).
  • I know the pivot part is OTS, but can you switch the gears for a slightly larger ratio?

The CIM Sport (and planetary gearboxes in general) looks pretty beefy, I think it should handle it. Disclaimer: I haven’t used it.

If you want an encoder on what you’ve got now, you’ll need to add something on the opposite side of a shaft. See what Vexpro does.
Alternatively, you could use a Vex VersaPlanetary instead of a Sport. Those can have integrated encoders on them.

Last year we used a very similar drive to this one, also based on the Revolution Pro 2.

We used a 14:50 reduction with an idle gear to achieve proper spacing.
As for encoders, I second Anand’s remarks on the SRX Encoder. We used it last year with talon SRXs and had few issues with them.

To mount the encoders, we used these and placed them on plates above the gears.

As to a gearbox, I know teams that have had success with it, but the CIM sports are completely new, so I would be wary using them this year for such an important system as drive is. We used Versaplanetaries for our turning motors, which worked well, but I would suggest just using gears for the drive reduction if you can.

We found that for our versaframe chassis, mounting the motors and module on 2 plates worked well, without the need for brackets.


What he said…

CIMs at 4:1 are rather fast (low torque) for most FRC games. Be sure to consider how fast your robot can accelerate at least as much as how fast it can go once it reaches maximum speed. The only year team 3946 decided to gear our drive CIMs less than 8:1, it was a drastic mistake. That said, I wouldn’t hesitate to use a planetary stage to power a later reductoin!

The Revolution Pro swerve module has its own reduction, IIRC it is 30:48, and it uses the 3.25" versawheel.

with the 14:50 reduction we used last year it was ~13ft/s free, and with a 4:1 as the first stage, it would be ~11.8ft/s free.

So for the SRX mag encoders will I need to bore a .25 inch hole in the cim sport output shaft for the magnet? The current hole size .160 according to the CAD file. I haven’t really used magnetic encoders before.

Here is what I am trying to do:

Yes. The 0.25” hole must be coaxial within a tolerance of 0.01 in. And the end of the magnet must be positioned 0.75 to 1.5 mm from the indentation on the underneath side of the mag encoder housing.

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