Sunday, May 30, 2010

Pacing the A2B

Spotted another guy riding an A2B on the bike trail the other day so I thought I'd follow him to see how he used it. He was listening to an MP3 player and didn't have any rear view mirrors.

I clocked him at 20 mph the whole time except when he slowed down in traffic. He used his pedals once, briefly, as he climbed a short, fairly steep hill.

A few days later I spotted him again going in the opposite direction. Now I know where he lives and where he works, brawhahaha!

The A2B is clearly an electric moped, not a hybrid electric bicycle. It accelerates easily to 20 mph without any pedal assist. I had no problem staying up with him but I had to pedal fairly hard to catch up.

From an engineering perspective, safety is all about impact. Impact is a synonym of force. Force is defined as the product of mass and acceleration.

Mass is how much you and your bicycle weigh combined. The weight of a conventional bicycle is not significant. The weight of the rider is a much bigger factor. Getting hit by a 300 pound dude is three times worse than getting smacked by a 100 pound woman.

Acceleration is a function of how fast you are going and how fast you slow down. Hitting a brick wall at 20 mph will create a much bigger deceleration (word often used to mean going from a high speed to a low one) than hitting one at three mph.

Total force imparted to the brick wall or a pedestrian depends on weight and speed. Getting hit by a feather going at 20 mph will not create much force.

Based on its max speed of 20 mph and 75 pound weight, the A2B is no more dangerous than a bicycle or electric bicycle. Any regular bike can exceed 20 mph if the rider is fit and motivated.

The pedals are required to qualify as an electric bicycle, but at some point you have to wonder if having pedals matters. Safety has nothing to do with pedals, although you do need a place to rest your feet.

The definition of a legal electric bicycle varies a great deal from place to place. Following are the most common parameters used:

1) Maximum power drawn by motor
2) Maximum level speed (without pedaling)
3) Maximum weight
4) Maximum of two wheels
5) Pedals connected to drive system

In some parts of Europe the restrictions have reached comical proportions. The maximum power is about the same as a large light bulb and the motor shuts off at 15 mph or anytime you stop pedaling!

IMHO, this is an example of over-regulation and it is not going to do much to reduce carbon emissions via promotion of electrification of personal transport.

Weight can't be regulated. You can't make it illegal for 300 pound people to ride bikes and tandem bikes often weigh more than that with both riders. You can't expect a cop to weigh a bike. Anyone can add a hundred pounds of battery to a bike to increase its range. There is no reason for anyone to build an electric bike the size of a Harley Davidson if it can't exceed 20 mph. The speed limitation will limit weight.

Power drawn by the motor does not matter if the machine will not go faster than 20 mph. You may need a lot more power going up a hill. And, you can't expect cops to measure a bike's power rating.

And what if I choose not to turn the power on? How can you cite a rider of an electric bike if the thing isn't even powered up? The motor, battery, and controller become cargo.

It is easy to count wheels and measure speeds (that's what radar guns are for).

Weight is a factor when you are talking about motorcycles and scooters that also exceed 20 mph. Because of the low cost, lead acid is the preferred battery in China, where electric scooters are typically redefined as electric bicycles if they have pedals on them. You can't just paint a picture of pedals on one, you have to actually connect them to the rear wheel with a chain. However, riders never have to use them. Getting hit with an electric "bicycle" in China is like getting hit with a conventional scooter because they go as fast as they can whenever they can.

Real electric bikes typically weigh in around 75 pounds. This is roughly about 50 pounds more than a cheap bicycle because of the motor, controller, and battery. A large lead battery can make a big difference but here in the states lead batteries are rapidly becoming less common.

I've seen some home-built electric bikes that used huge motors on the front and rear wheels powered by a hundred pounds of lead acid battery. They probably weighed close to 200 pounds without the rider and were capable of doing 40 mph without pedaling. They would have been much better off just buying an electric scooter. If these bikes were limited to 20 mph they would not have wasted their time and money. Getting caught doing 40 mph should get these bikes impounded as illegal, IMHO. They will ruin it for everyone if they become too common.
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1 comment:

  1. Anyway, I recommend them to anyone who comments on my bike as I cycle around San Jose. electric bikes nz