pic: 2 speed ball shifting swerve module



I’ve wanted to design a shifting swerve module for a while now, but I finally decided to give it a try because there was another shifting swerve module posted here recently. It’s certainly not a finished model, and any constructive criticism is welcome. (I’ve only spent a few hours on it)

It is based on this design that I posted here previously:
http://www.chiefdelphi.com/media/photos/40805

Hard to tell from this angle, but do you have enough space between the CIM and the ground to properly route the CIM’s wires?

How far off the ground is the bottom of the CIM? Any concern for wires dragging or catching on field debris? What is the spread on the gearbox?

What was the weight estimated at? I knew you were shooting for a low number, how’d you end up?

Do you have a weight / weight difference from the single speed?

(What is this, the week of swerves? 2015 should be fun :smiley: )

I’m not sure what the minimum bend radius is. I left 0.3in of ground clearance, but that can easily be changed.

.3 not including wires? Thats not gonna work, even on a “flat” field there are usually 1/4" bumps.

If I am understanding it correctly, the minimum bend radius of AWG 14 wire is 0.3846".

Sources: Hereand here

Sorry, I forgot to post the specs.
6.7lbs including most of the hardware, but not all.
Final ratios ar 3.66 and 5.866 to 1. With 2.7" wheel.
Smallish spread for auto shifting code.
Dimensions 3" wide, 10" tall and 9" long.

The single speed version is about an inch shorter, and should weigh 5.9lbs.

Looks good. Where are the encoders going to be?
I would have gone with a little less lightening on the frame, but JMO. Are you sure you can’t get a little more spread out of there? I know Vex offers a 34t and a 44t ball shifter gear.
Also, you might consider making the bevel gear shaft in the part of the module with the wheel be 3/8" hex on one side, and 8mm keyed on the other. That way you can accomodate 11t or 12t gears. Or you can use 14t gears there.

Thanks. The encoders are included in the CAD model already, but they are hard to see from this angle. I’ll post another view so that it is more obvious.

If my team used this design, the frame of the module would be well supported. Because the module’s frame is only 3" wide at it’s widest, its job is much easier than for most swerve module designs.

I probably could get more spread out of the shifting shaft, but a four CIM swerve drive is never meant to be a pushing machine. In this case the low gear would be for acceleration, precise movement, rolling off of defenders, and playing effective defense.

I would really like to avoid using key ways as much as possible. I will look into using different gears in the lower caster though.

One of our swerve revs had a similar ground clearance (for 2011).

The wires survived… but had visible wear and slight damage.

I wouldn’t recommend such minimal clearance (especially with the CIM so far from the wheel).

Yeah, you’re probably right. As I said it’s pretty easy to adjust, so I’ll jack it up a little. probably closer to 5/8".

I’ve found a few options for gear ratio.

Quoting free speed and inches per CIM rev:

Current configuration
11.5fps (1.48ipr) in low, 18.3fps (2.36ipr) in high

or
9.15fps (1.18ipr) in low, 14.5fps (1.88ipr) in high

or
10.9fps (1.41ipr) in low, 30.5fps (3.93ipr) in high

Any of these could be adjusted further with the belt on top. Although, I’d like to avoid that if I can, because it would mean that two types of pulley stock would be required. Let me know which one seems more appealing and why.

I would go 18.3fps personally, but more spread would be necessary to make it traction limited. 14.5fps is too low for my tastes.

I tend to agree; especially sense those are at free speed and being traction limited is not a major goal of this drive.

Those are free speed? Then you might even be able to gear higher…