My father has spent all of his adult life as a chief engineer in the merchant navy and although he’s now retired, I’m sure he still retains lots of useful information which I could tap into. Yesterday he stopped by to drop off a birthday card and I introduced him to the project. I explained some of the difficulties I’d been having trying to find a balance between motor power and battery supply. He suggested using hydraulic motors.

With hydraulics, an electric motor powers a pump, which in turn drives oil at high pressure via flexible hoses to any number of hydraulic motors. The ship’s winches were powered in such a way.

Interestingly, shortly after he’d left I visited the endless-sphere forum where I’d been asking about how power is divided between motors and somebody else had also suggested using hydraulics.

This is a quick representation of what the system might look like:

Hydraulic motor

Before my father mentioned it, I didn’t know there was such a thing as a hydraulic motor so I have lots of research to do. However, it seems a good investment of time because:

• Gear ratio between motor and pump can easily be adjusted to get the right balance of speed torque
• Hydraulic pumps in general have more torque
• The motor can be kept spinning at its optimum range and increase the lifetime of the motor.
• One motor means one battery
• Hydraulic motors are cheaper than electric motors
• Hydraulic motors seem easier to service
• It removes the need for complex sprockets and chains to drive the wheels

First of all then, I need to make sure that such a system would still give the ability to have forwards and reverse on independent sides so that the wheelchair can turn on the spot, and when required that power could be delivered to individual wheels…