pic: Swerve Module in a Tube

[Chris Hapstack]

loading photo ...

[Chris Hapstack]

CAD can be found here!

This view has the tube transparent.

This shows the pocketing on the bottom of the turning gear which leaves room for the VersaPlanetary's mounting hardware.

[marshall]

What's the gear ratio for the VP?

[Chris Hapstack]

Originally Posted by marshall

What's the gear ratio for the VP?

I figure if we actually build this I'll go with 90:1. The Robostangs' off-season swerve had the same steering setup but they used 50:1 (which I thought was surprisingly low when compared to something like the AndyMark Swerve & Steer module, but they said it worked well for them). I think you'd need something like 120:1 in order to match the steering RPM of the AndyMark module, but I didn't want a 3rd VersaPlanetary stage because I felt that put the BAG motor too close to the ground.

[Chris is me]

Originally Posted by Chris Hapstack

I figure if we actually build this I'll go with 90:1. The Robostangs' off-season swerve had the same steering setup but they used 50:1 (which I thought was surprisingly low when compared to something like the AndyMark Swerve & Steer module, but they said it worked well for them). I think you'd need something like 120:1 in order to match the steering RPM of the AndyMark module, but I didn't want a 3rd VersaPlanetary stage because I felt that put the BAG motor too close to the ground.

Have you considered putting an idler gear on there and doing one reduction in the spur gear stage? Probably a bit more weight and part count but it would give you some flexibility.

[Chris Hapstack]

Originally Posted by Chris is me

Have you considered putting an idler gear on there and doing one reduction in the spur gear stage? Probably a bit more weight and part count but it would give you some flexibility.

I was thinking about that, but wondered if it would compromise the steering encoder setup. Currently the steering encoder is a VP integrated encoder after the last stage, and the external gears are 1:1, which means the encoder is 1:1 with the wheel. Does that mean you can use the VP encoder as an absolute encoder? I should probably make a point of knowing more about the encoders needed here... If you had such an external reduction, would you need to mount a separate absolute encoder somewhere else?

[Chris is me]

Originally Posted by Chris Hapstack

I was thinking about that, but wondered if it would compromise the steering encoder setup. Currently the steering encoder is a VP integrated encoder after the last stage, and the external gears are 1:1, which means the encoder is 1:1 with the wheel. Does that mean you can use the VP encoder as an absolute encoder? I should probably make a point of knowing more about the encoders needed here... If you had such an external reduction, would you need to mount a separate absolute encoder somewhere else?

You don't need a 1:1 reduction for an absolute encoder to work, you just need to be sure you account for reduction in the code (and if your encoder has a deadband or something you need to make sure that isn't a problem). The VP encoder can be used as an absolute encoder. I don't know too much more about the details of electronics, but your mechanical design isn't necessarily constrained by your encoder here.

[Lil' Lavery]

Adding idler gears after your encoder increases the potential for cumulative position error from backlash. Granted, there's already a 1:1 spur gear relationship after the encoder, so that risk exists already. But more gears just compounds that risk further.