pic: Team 696 Swerve Drive module



Hi Guys,

I just wanted to show you what I have been working on for the past few weeks between school and robotics. This is a coaxial swerve drive module with 16 pitch 20 tooth miter gears and 35 gear to a 50 gear driving the drive shaft. The wheel is a 3" x 7/8" Colson.

Please make any comment or improvements needed for this module.

The chassis will be posted pretty soon.

Thanks in advance.

I’m sure it’ll be more apparent when the chassis is posted, but how does it attach to the chassis?

Cantilevered upper miter gear shaft might be problematic, even with hardened shaft. Extending shaft support tube down nearer to it might at least help some.

I would attach large gear direct to wheel with stand offs, and moving it as close to wheel as rest of H/W will allow.

Also, bearing of upper horizontal shaft must handle axial thrust of miter gear pair, not sure by PIC if this is adequately handled yet.

-Dick Ledford

A few questions concerning handling of forces:

-Where do top loads go? This is the force applied downward by the robot
-Where to side loads go? These forces are applied by the wheel on the ground, and must be handled without bending things.
-Thrust loads also come from both miter gears. The horizontal one appears to be adequately handled, how about the vertical one?
-While it appears impossible to design a miter gear assembly of this size without one miter gear being in cantilever, shorten the unsupported section of the shaft leading up to that miter gear as much as much as possible.

More questions:
-How is this going to be manufactured? It looks like several pieces of plate magically held together by virtual constraints, with some very tiny bolts holding the top plate to the side plates.

Recommendations:
-Place the upper module support in between the turning gear and the module top, and use a thrust bushing or something equivalent there.
-Make a disc around the bottom of the module to react to several faces on the robot, to react side loads.
-Make the module smaller. There is extra space on both sides of the wheel, that space does not need to exist and any extra shaft length is unsupported under (quite a lot of) load.
-Make the lower shaft dead. Attach the gear directly to the wheel, and attach both to the shaft via bearings. By doing this you can make the axle structural, which should increase the rigidity of the entire assembly.

Why is the miter gear cantilevered so far out? It looks as if you could just move the whole top plate down and it wouldn’t interfere with the gear but it would greatly increase the strength and reduce the loads experienced where the module meets the rest of the robot. I am also curious as to how you are holding the module together?