Drivetrain Prototyping Results

Summary of Final Build

Tested with a 12.5lb battery and 5lb weight
Wheels driven via a custom-machined, keyed hub on the outer face + a keyless, 3D printed version on the other face to support the shaft
Motors connected to wheel shaft via a keyed shaft coupler
- 5/6 wheels use two keys in the coupler – one in the motor shaft and one in the wheel shaft
- 1/6 wheels use just one key in the motor shaft. On the wheel shaft, a flat surface was made for the set screw to dig into
1/2" diameter wheel shafts, 3/4" diameter rocker shaft
1/4" thick, MDF belly pan
Used bushings on the rocker and bogie joints, used bearings on the wheel shafts
- Tolerance for the bushings & bearings was+0.003" to its diameter
Powered by a 12V battery. Each wheel driven by a CIM motor to a 50:1 ratio

High-stress locations:
- Connecting plates on the legs. When turning, these pates are getting pushed/pulled as the wheels resist the movement
- Connection point from the legs/suspension to the chassis. Is constantly twisting about that point during turns
Flexing occurs at connection points (i.e. every joint)
The further away the motor's centre of gravity is from the suspension's centre of gravity, the more bending occurs at the local joint
The differential bar must be kept in position (i.e. no vertical twisting) in order for the chassis position to remain stiff
Chassis bounces for on-the-spot turns. Something for EE & Arm team to keep in mind
Totally bidirectional. Rocker arm should be the front for going over large obstacles, whereas use bogie for small & frequent obstructions

Use interference fit on all bushings and bearings (or whatever specified fit is recommended by the bearing manufacturer)
- Maybe even clamp in the bearings to prevent them from coming out?
Use bearings instead of bushings on suspension joints, as bearings are designed to handle loads
Make sure the set screw is digging into a flat surface...
Spec for proper torques

Rover weight, no load: 41.55 kg + 12.5 lb battery + 5 lb counterweight = 49.52 kg
Rover weight, with a 5lb load: 51.79
Current sensors have a tolerance of about +/-0.30 A

Configuration	Type of Obstacle	Most Frequent Current Drawn by One Motor (A)	Max Torque Output Per Wheel (Nm)
Centered mass	Uphill, steep (15 degrees)	5.6	~3.6195 0.07239 Nm @ 6.551A 0.07239 Nm * 50 = 3.6195 Nm
	Uphill, less steep (~5 degrees)	4.5	~2.413 0.04826 Nm @ 5.267 A 0.04826 Nm * 50 = 2.413 Nm
	Uphill, less steep, on an angle	5.2	~2.413
	Downhill	3.5	~1.2065 0.02413 Nm @ 3.984 A 0.02413 Nm * 50 = 1.2065 Nm
Offset mass	Uphill, less steep	4.9	~2.413
	Uphill, less steep, on an angle	5.7	~3.6195
	Sand turns, figure-8	4.5	~2.413
	Sand turns, on-the-spot turns	6.8	~3.6195
	Flat terrain	3.8	~1.2065
	Stairs	> 4.5	~2.413
Offset, 5/6 motors	Uphill, less steep	4.3*	~1.2065