From: Alfio Puglisi (puglisi@arcetri.astro.it)
Date: Mon Nov 18 2002 - 12:25:18 MST
On Mon, 18 Nov 2002 brent.allsop@attbi.com wrote:
>
>spike said:
>
>> Consider a good motorcycle brake: one can lock the front
>> wheel. I good rider can actually lift that back wheel
>> and hold it just above the ground. With its CG position
>> about 45 degrees upward and aft from the front wheel contact
>> patch, one can stop a bike at close to 1 G, at which time
>> the wheel locks and the cotangent model breaks down. Looks
>> to me like you would be lucky to get a third a G on a
>> segway.
>
>But this is a very unstable setup. Not only does the biker have to very
>carefully control the brake, he also has to keep the back wheel from coming
>forward from side to side. Only a very practiced stunt rider could keep such
>an unstable system from going out of control. And even then you would loose it
>on many occasions.
I don't think so. I lift the rear wheel all the time when I brake hard on
my mountain bike (yes, you can pull 1G on bicycles with good front
brakes). Never went out of control, but you must be VERY CAREFUL to have
the rear wheel on the ground when you actually stop. Otherwise, you are in
for a fun descent :-)
>But I bet a segue could have much better stopping ability than a
>motorcycle.
The maximum braking/acceleration that you can have with friction-based
traction is 1G. Or better, it's proportional to your effective weight,
that can be influenced by the air flux around you. For example, racing
cars are designed to have the air push down on them: the nect effect is
that a Formula1 car can do 0-100 km/h (0-60 mph) in just more than 2.5
seconds, and 100-200 km/h (60-120 mph) in less than 2.0 seconds, thanks to
the aerodynamic effect. And when braking from 300 km/h, they can pull 4Gs.
But I have trouble imagining such an aerodynamic Segway :-)
Ciao,
Alfio
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