Remember those Razor Scooters that were all the rage a few years back? Well, these days they’re fodder for garage sales. So, with fall coming, you might still have a chance to pick one up.

Now, with your victim vehicle in hand, let’s look at one of the most important questions to consider when you’re converting a two-wheeled vehicle to electric power. How are you going to transfer power from the electric motor to the wheels? Unless you are using a giant motor, it’s likely that your motor will be turning much faster than the wheel, so you also need to figure out how to gear the motor down.

The two most frequently used methods of power transfer are a roller wheel or gearing the motor.

We looked at roller wheels in an earlier article about electric bicycles, but in that article we focused only on the single potential design. A roller wheel is used to press directly onto the wheel you wish to turn with your electric motor. Based on the size difference (as the roller wheel is much smaller), the difference in rotational rates is eliminated as an issue. The roller can be used to transfer energy from the motor to the wheel for propulsion and from the wheel to the motor for recharging purposes, and can be moved out of contact from the wheel as necessary. While this is the simplest way to transfer energy, it is also the least efficient, as the introduction of water, dust, dirt, or other small particles can cause slippage in the connection between roller and wheel.

The other primary method of transferring power in a two-wheeled vehicle is be geared in power. This is where you integrate the motor into the mechanics of the bike or scooter, so it can directly turn the wheel. While this is by far the most efficient of these two options, it has downsides as well. With the electric motor geared permanently into your system, you can downgrade the ability of your system to be powered by its human component (you). Bikes will be harder to pedal and scooters will be harder to scoot. While it is possible to disengage the motor from the mechanics of the bike, it is certainly not as easy as with a roller system. Also, as a more complicated system, it requires greater knowledge to convert and maintain.

Essentially, as with most hybrid vehicles, the choice comes down to what fits your needs, as each method has benefits. So weight the advantages and disadvantages, and look for the one that suits you best.