T.5.3 Motor Protection (EV Only)

T.5.3.1 The rotating part of the Motor(s) EV.4.1 must be contained in a structural casing. The motor casing may be the original motor casing, a team built motor casing or the original casing with additional material added to achieve the minimum required thickness.

Minimum thickness for aluminum alloy 6061-T6: 3.0 mm
- If lower grade aluminum alloy is used, then the material must be thicker to provide an equivalent strength.
Minimum thickness for steel: 2.0 mm

This rule references a structural casing for the motor. As shown in the schematic below, our 2023 team was able to use the original motor casing due to the fact that its thickness exceeds 2.0 mm and is constructed from stainless steel.

Schematic - Motenergy ME1616 Motor

It is also noteworthy that the different specifications for aluminum and steel are due to the fact that steel is much stiffer, denser, and heavier than aluminum. Therefore, to maintain the structural integrity of the casing, you have to compensate for the lower material stiffness by adding thickness. The Stress-Strain Curve comparison is shown below.

Stress-Strain Curve - Aluminum Alloy 6061-T6 Compared to A36 Steel

T.5.3.2 A Scatter Shield must be included around the Motor(s) when one or both:

The motor casing rotates around the stator
The motor case is perforated

Photo - ME1616 Motor Casing

This rule references a component called the Scatter Shield, which is a steel or nylon guard placed around the bell or clutch housing to protect driver and spectator from flying parts in the event of part failure at high RPM. Such a shield is often placed around transmissions and differential units. For our cases, we are only operating in one gear. Without a clutch or a flywheel, the driver is solely being protected from a failure of the chain.

In our case, we did need a scatter shield to comply with these rules.

T.5.3.3 The Motor Scatter Shield must be:

Made from aluminum alloy 6061-T6 or steel
Minimum thickness: 1.0 mm

Photo - Scatter Shield from the 2023 Vehicle

Our factor of safety was significant, so this component was well above the one millimeter minimum, which is inclusive of the welded sites. If you were to take a caliper to any section of what was manufactured, it would be in compliance.

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