Motorized Bicycle - Power Sources

Power Sources

Historically, internal combustion engine (ICE) designs dominated the motorized bicycle market, and still do today. Most still use small two stroke or four stroke IC engines.

Power can be applied to the drive wheel in a number of ways:

• the front or rear wheel may be powered directly by a motor built into the hub (e.g. Singer Motor Wheel, Copenhagen Wheel). This avoids the need to transfer power to wheel by some other means. The downside of this system is that often, the original wheel must be replaced for the wheel with the hub motor.

• an engine or motor mounted in the frame (called a frame mount), under the frame, or behind the rider (called a rack mount) may drive the rear wheel via a sprocket with a chain or a rubber belt. This is called "chain drive" and "belt drive" respectively. Besides connecting the engine to a sprocket, the engine can also be connected directly to the crank. This is called "crank drive" or "mid-drive" and also allows incorporating the gears of the bicycle in the motorized system. Most of these bikes and kits are under 50 cc's and do not have to be registered in most states (the exception being the Whizzer NE5).
• power may be transferred to a wheel from a motor mounted directly above, by bringing a powered roller or rubber belt into contact with the tire. These are called "friction drives".