[Duncan]

Hi Guys,
I need to pick some brains, some of you have managed to destroy motors by over-speeding them.
How much escapes?
My car has the motor (an 11 inch Hitachi forklift motor) in a tunnel between the drivers and passengers knees and ankles

I can't find anything definite on the maximum speed for this motor but I intend running direct drive - I think I may be running it at up to 5000 rpm (80mph)

What do I need between my legs and the motor?

The only holes are the brush cooling gaps - if It gives way do bits of the commutator fly out of these holes?

What thickness steel should I use for protection 1mm?, 3mm? more?

Any thoughts?

 

[major]

The only holes are the brush cooling gaps - if It gives way do bits of the commutator fly out of these holes?

Hi Dunc,

Yep. If the commutator comes apart due to overspeed, those segments (sometimes called bars) can become detached and exit the motor at pretty high speed. Most times the bars mushroom out and it comes to a grinding halt. But they can and do fly out of there, like copper bullets. I think that automotive body panels and floor pans made of steel would be sufficient protection. But when series motors were used in racing applications, tech required scatter shields. Some guys used flak jackets.

major

 

[EVfun]

My car has the motor (an 11 inch Hitachi forklift motor) in a tunnel between the drivers and passengers knees and ankles

What thickness steel should I use for protection 1mm?, 3mm? more?

Here is what the NHRA and NEDRA (National Electric Drag Racing Association) has to say about it.

“Exposed-motor electric-powered vehicles with open frame, vented, or brush replacement window motors must install a motor shield, minimum 0.024-inch steel or 0.032-inch aluminum, or 0.120-inch Lexan.”

I would recommend more than the minimum if you are putting the commutator between your legs! The cover should not be fitted tight against the motor, you need air flow for cooling.

 

[Duncan]

Hi Guys

0.024 inch is only 0.6mm -
Thats great I am using 1mm steel for my panels so that should be OK

Thanks for the input

The motor is where the gearbox would be in an IC Locost or lotus 7
Its between our legs not between my legs!!!