05-11-2014 14:28

Bryce2471

Re: pic: 2 speed ball shifting swerve module

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

05-11-2014 15:13

Lil' Lavery

Re: pic: 2 speed ball shifting swerve module

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?

05-11-2014 15:15

MrBasse

Re: pic: 2 speed ball shifting swerve module

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?

05-11-2014 15:16

nathannfm

Re: pic: 2 speed ball shifting swerve module

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

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

05-11-2014 15:18

Bryce2471

Re: pic: 2 speed ball shifting swerve module

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

05-11-2014 15:24

nathannfm

Re: pic: 2 speed ball shifting swerve module

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

05-11-2014 15:33

Mike Marandola

Re: pic: 2 speed ball shifting swerve module

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

Sources: Here and here

05-11-2014 15:47

Bryce2471

Re: pic: 2 speed ball shifting swerve module

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.

05-11-2014 20:30

asid61

Re: pic: 2 speed ball shifting swerve module

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.

05-11-2014 21:34

Bryce2471

Re: pic: 2 speed ball shifting swerve module

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.

05-11-2014 21:54

AdamHeard

Re: pic: 2 speed ball shifting swerve module

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).

05-11-2014 22:44

Bryce2471

Re: pic: 2 speed ball shifting swerve module

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".

06-11-2014 14:14

Bryce2471

Re: pic: 2 speed ball shifting swerve module

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.

06-11-2014 20:29

asid61

Re: pic: 2 speed ball shifting swerve module

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.

07-11-2014 01:40

Bryce2471

Re: pic: 2 speed ball shifting swerve module

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

07-11-2014 03:16

asid61

Re: pic: 2 speed ball shifting swerve module

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