Re: Emergency braking and bird anatomy [was: Re: DVD copying and CSS]

[Richard Lyons <richard@the-place.net>]

On Thursday 26 February 2004 00:41, Pigeon wrote:
> On Wed, Feb 25, 2004 at 05:04:26PM -0500, Bijan Soleymani wrote:
> > On Wed, Feb 25, 2004 at 10:46:08PM +0100, Richard Lyons wrote:
> > > It's not too difficult to work out the maximum breaking force that can
> > > be applied before you get thrown onto the road.
> >
> > I believe it is 0.67g. Of course you can't achieve this with the rear
> > wheel alone so by not using the front wheel you're sure not to flip
> > over, but you're also getting much less deceleration.
>
> It's g tan theta, where theta is the angle between the vertical and a
> line drawn from the point where the wheel touches the road and the C
> of G of the (bike + rider).

Thanks Pigeon -- I was too lazy to sketch the diagram.  

> However, the available friction force
> between the tyre and the road places an upper limit on this, which
> will probably be something between 1 and 1.5 g depending on how sticky
> your tyres are.

Which means that, for given conditions, there is a position which you have to 
move your butt behind to ensure you don't flip.  Unfortunately, in dry 
conditions at least, on most push-bikes this position is way behind the 
saddle (and probably out of reach of the pedals, handlebar -- and thus out of 
reach of the brakes too!).

-- 
richard