SHOWALL HIGH VOLTAGE ROBOTICS
Figure 2 - A large motor pair salvaged from an old shopping scooter
Figure 2 - A large motor pair salvaged from an old shopping scooter

There are many varieties of power chairs and shopping scooters, and often they can be purchased on a budget because of some part that is no longer manufactured or compliant with the extremely stringent safety regulations. For more compact robot projects, the shopping scooter style power chair will offer the best drive train, often having the wheels directly attached to the motor output shaft rather than using a belt drive. These types of power chairs usually have 6 inch to 8 inch wheels and are designed with all weather urban terrain in mind, so they fit the bill perfectly.

The motor pair I found were from a very old four wheel power chair that is no longer manufactured, and besides having dead batteries, all of the other components including the motors were in perfect running order. These motors are huge, and the torque is unreal at about 250 RPM. I have no doubt that if I connected only a single motor to the drive shaft on a full sized pickup truck that it would easily accelerate the truck up to a few miles per hour. The base motor is 2.5 horsepower, and after the gear reduction, this is multiplied many times. They are slow (250 RPM), but are also power brutes!



Figure 3 - The motors are cleaned up and the magnetic brakes are removed
Figure 3 - The motors are cleaned up and the magnetic brakes are removed

Every power chair motor pair I have (about 10 sets) have included an electromagnetic braking system on the rear output shaft, forcing the motor to freeze if power is lost. This is a great function to have in a power chair for safety reasons, but it's a power waster in a robot project, so the braking mechanisms are both removed. To remove the brake from a power chair motor, just take off the end cap and then remove the clutch solenoid that is bolted to the end of the casing. The motors will now turn at all times, and won't require extra current to hold the brakes open during use.

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