[python] Re: Frontal Area & Tire Pressure (was The Python genisis)
- From: George Durbridge <gdurbrid@xxxxxxxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Sat, 13 Oct 2007 00:24:01 +1000
Not a stupid idea, but from the drawings on Henry's site, I doubt this
is the problem. As with a Python, the front wheel drive layout of the
Jetrike requires the rider to sit so close behind the front wheel that a
lot of the weight is carried by the front wheel. For your feet to reach
the bottom bracket ahead of the front wheel means you have to sit close
behind it.
A rough estimate based on the drawings is that the front wheel carries
33% of the weight, perhaps a little more. On a tadpole trike, 33% on
the driven wheel is sufficient to ensure traction on all firm surfaces,
so I don't see why the Jetrike would do any worse (unless possibly
uphill, but that isn't the problem Henry describes).
On Fri, 2007-10-12 at 14:59 +0200, Stefan Bartels wrote:
> Perhaps a stupid idea - but is there just too little weight on the
> driven wheel?
> Then of ocurse the best way to get more adhesion to the road may be
> lower tyre pressure...
> Just a thought.
> Stefan
>
> Henry Thomas schrieb:
>
> > Hi George,
> >
> > With regard to frontal area I was comparing myself to MTB and Road
> > bike riders with those time trial style extensions on the front handle
> > bars that you rest your elbows on. When you look at them, front on,
> > their body is relatively horizontal, so its basically their shoulders
> > and legs. For me its my full torso, on about a 40° recline, plus the
> > rocker arm hardware below me and the rear wheels on either side of me.
> > To my eye, we all look about even. But obviously my trike has an edge ;)
> >
> > On the issue of tire pressure, at 100psi on course bitumen the front
> > wheel does slip under acceleration, probably because as you point out
> > it is bouncing off the road surface. But for some reason tilting on
> > tight turns, harder tires scrub off speed. Its certainly noticeable,
> > but I don't know why for certain. The roads are I ride on are
> > generally very rough -- uneven from heavy vehicle traffic -- so I
> > assume that the hard tires on a lean are some how being repelled by
> > the road surface, or perhaps they are bouncing sideways so I am forced
> > to take a harder angle, thus scrubbing off speed. Either way the
> > softer tires definitely hold the speed better as my tilting trike in
> > corners. It seems about 65psi is a good compromise.
> >
> > -h
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--
George Durbridge
+61 3 9481 3500
+61 409 413 945
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