Cardiff - Dozens of illegal e-bikes seized in Crackdown

[Tony1951]

Just watched a Police Officer showing a BBC Wales Reporter one of the illegal Ebikes that could do 80 mph . The rear motor was the size of a dinner plate and he lifted the rear wheel up and used the throttle to show the speed on the bike speedo . I wonder what speed that would equate to when under load ?

I have a couple of low powered motorbikes, a 125cc Cg125 and a Honda CB250 twin. They have 11hp and 20 hp respectively, which runs in watts to and 8.08kw and 14.7kw.

The 8.08Kw bike can just about do 62 miles an hour and the 14.7kw one gets to about 71 if you can wait long enough.

It is quite interesting that once you get over about 50 miles an hour in the real world (as opposed to the silly police check world) any increase in speed, needs shed loads more power. There is an exponential element involved in pushing through the atmosphere at increasing speed. These people announcing that a dodgy e-bike can do 70 miles a hour with about 1kw of power are into Star Treck physics. If they had any understanding at all of what they are talking about they'd be embarrassed.

You can see the same effect, on steroids in the history of powered flight at speed - the breaking of the sound barrier for example. They were doubling power output to achieve small margins of extra speed.

 

[saneagle]

Just watched a Police Officer showing a BBC Wales Reporter one of the illegal Ebikes that could do 80 mph . The rear motor was the size of a dinner plate and he lifted the rear wheel up and used the throttle to show the speed on the bike speedo . I wonder what speed that would equate to when under load ?

The wheel was not spinning at 80 mph. The LCD wasn't setup to show the correct speed. If the wheel speed really was that fast, the motor would run so inefficiently that something would catch fire. The bike's actual top speed on the road would be around 30 mph, and no-load around 40 mph.