pic: Coaxial Swerve Drive Module with 2-speed Ball Drive and Nitrile Tread

[Kevin Ainsworth]

Originally Posted by fb39ca4

Fancy. How much does each module weigh?

This module is approximately 7lbs.
A little under in Solidworks, a little over with fasteners in the real world.

Originally Posted by Oblarg

Great-looking design. With just 1 CIM per wheel, though, isn't that top speed a bit high, unless you're planning to use autoshift code?

My apologies, I stated the wrong speeds. The speeds listed on the description are for a 3.25" wheel, with a 3" wheel the speeds would be around 4.55/5.55 fps in low and 14.47/17.65 fps in high (actual speed/theoretical).
It was easier to chance the wheel diameter than the gearing.

Originally Posted by Tyler2517

What is the benefits in running this one over the last design? 2 speed shifting is nice but you have decreed mechanical efficacy and a higher center of gravity.

I posted what we feel the benefits are on my other reply with the CAD link.
We will loose around 4% efficiency due to the 3rd gear stage but should gain efficiency by using roller bearings over the delrin rollers on the cim end caps like the "In Wheel" module. Should be close to the same efficiency.
We were just talking about the higher center of gravity last night during our Mechanical Team meeting and this is a trade off. We have another version of this unit where the CIM comes out to the side but for that version there are two more stages of gearing and the extra weight and loss of efficiency didn't seem like a fair trade off. Ground clearance is an issue if the CIM is tucked under the robot. But if being low to the ground or having a low center of gravity is valuable than we can modify the design. The "In Wheel" modules center of gravity is 3.25" off the floor and the coaxial unit is 5.75" off the floor. This version puts 20% of the robots total weight 2.5" higher, not really enough for concern with the center of mass.

Originally Posted by nathannfm

Are you planning on building a drive with these before the season?
I really like the bevel gear embedded in the drive wheel eliminating an extra stage.
What kind of module rotation speeds are you looking at (rps)?
Did you design your own ball shifter? From the cutaway it looks different then the VexPro one.

I think we would all appreciate you posting the CAD or a few more views, you can hardly see the rotation motor.
Very nice work!

We are starting machining of the prototypes at our next off-season team meeting. All purchased components are on order.
The rotational speed is 48 RPM at peak steering motor power, "In Wheel" module was 40 RPM. They can spin faster during driving with no pushing.
The ball drive is the 217-2792 unit from VexPro with a modified output shaft.
CAD link is posted in my other reply.