Power System

From my initial conceptual sketching I realised that having the motor mounted on or under the deck would be unattractive. I have breifly looked into solutions to these problems.

Out runner brushless motors have permanent magnets attached to a rotating outer case, the internal electro magnets are fixed and do not rotate like they do inside brushed motors, hence they do not need brushes so can achieve up to 90% efficiency. Out runner brushless motors develop a high level of torque for their size because they have a rotating outer case, this makes them suitable for mounting inside the wheel, the outer case can be directly attached to the rim hence they are the solution to the problem of where to mount the motor. There are other advantages which make me inclined to design an out runner in the propulsion system, such as they generate torque from their magnetic field and moving mass rather than their moving mass alone as with combustion engines so they do not necessarily require a gear box to propel effectively, and they can act as their own brake. They also run on DC current which means that batteries can be used as the power source. The downside to brushless motors is that they are expensive and require computerised speed controllers, the batteries required to run them can also be expensive. I am aware that lithium polymer, or lithium ion batteries are light weight and have a supple case, this would make them suitable for embedding inside the deck. A battery and motor combination designed in this way would give the board a more traditional appearance while also making it motorised.

Information and pictures from:

http://electronics.howstuffworks.com/brushless-motor.htm
http://www.hooked-on-rc-airplanes.com/brushless-rc-motors.html
http://www.dynetic.com/pages/brushed.htm
http://www.nitroplanes.com/exi450arfrar.html