E-bikes -the PAS assistance
Just about all electric bicycles in Australia have had “pedal assistance”. With that control the motor kicks in when you have started pedalling and turns off soon after you stop pedalling.
The simplest control for that is a cadence sensor. This is a small sensor on the bottom bracket. Close to that would be a disc with a ring of magnets on it. As the pedal turns the sensor with detect the magnets moving. Some controllers will measure the rotation speed the pedal and increase or reduce the level of assistance – in steps. Some will just detect the pedal moving or not moving and will give assist or not assist.
Some controls are not very subtle. Sometimes when you just want to give the bike a nudge or to dawdle to manoever the PAS will give you a sudden surge which you were not expecting. The better ones only activate after several turns of the pedal. On the other hand, if you do want a quick take off you need to pedal hard. A throttle was (is) useful for that.
Many e-bikes now come with a handlebar device with which you can select the amount of assistance that the PAS will give you, and you may be able to turn it off. The control may reduce the speed at which the motor cuts out, or reduce the power available.
On the more “top end” e-bikes, particularly european ones, there will be a more sophisticated sensor that measure your actual effort by measuring the strain on the frame or the torque you apply to pedals.
Up till 2013 we had another means of varying the assistance from the motor : a common throttle. That’s not the case anymore… unless the bike has power not over 200 watts.
The europeans, particularly in Holland or Germany, like riding their bikes, so when electric bikes came it was decreed that the motors should only “assist” the rider and not drive the rider. And so it was that all european electric bikes must have assistance only when they are being pedaled. In 2013 those who make the rules decreed that electric bike riders in Australia should be like the europeans. And so allowable power is increased to a big 250 watts and throttles are not allowed…unless the bike complies with the old 200 watt rule.
That is unfortunate. I’ve found that all the customers would prefer to have a throttle.
So, if we are limited to 250 watts, how much is that? If you get on one of those machines at a gym that tell you how hard you are working out you would find 250 watts is a good workout – for most people. It is about what a fit person can sustain. Tour de France guys can do twice that, but that is not you or I. On a flat road 250 watts will take you to about 25 kmh with minimal effort on your part. And at 25 kmh the motor is supposed to cut out. (Speed uphill is another topic).