From: marc@gauss.math.mcgill.ca (Marc Sokolowski)
Newsgroups: rec.bicycles.misc,rec.bicycles.tech,aus.bicycles
Subject: Re: Automatic transmissions for bikes
Date: 29 Dec 92 22:45:06 GMT
Organization: Dept of Mathematics, McGill University

In article <1992Dec28.193402.25148@hpcvusn.cv.hp.com> harry@cv.hp.com (Harry Phinney) writes:
>
>And what makes him believe that 75 rpm is most efficient under all
>circumstances for all riders? 
>
	Of course this does vary according to the rider. As I want to point
out, electronics (i.e. neural net type or analogic) will perform an
immediate adaptation.
>
>The transmission will have to be prescient.  It must know how long a
>hill is, whether it is about to steepen, whether you intend to start
>sprinting, how hard you wish to ride, your current state of fatigue,
>etc.
>
	Not quite true. Future can be sometimes deducted from the past.
Sensors can monitor the load on the pedals and the response of the terrain,
and immediate action taken for optimal transfer.
>
>Perhaps you should try a newer shifting set up such as Shimano's STI
>with Hyperglide.  I think you will be surprised at how simple and quick
>shifting can be.  No form of automatic shifter can lessen the power
>required to climb a steep hill at a given speed.
>
	Well, I am not religiously against manual shifting. But on bikes
(especially the ones not on the high-end expensive side i.e. 98% or so...)
there is nothing more horrible as a bad mechanical derailleur. How many
times did the chain fell off my $ 600 bike (and that's true for many of
my friends "almost high-end" ones)?
	The sure next step will be the introduction of all-electric
shifters. The one portrayed in Pop. Mech. is certainly a very good
candidate, as the computer seems to be highly optional (i.e. you can select
the gears instead of the algorithm). But, as the masses don't like to choose
among 20 speeds or so, there will be a fast transition to a highly automated
device (with perhaps a choice of shifting pattern: Cruise, sport and
slippery/rain).

>opular for commuting bikes, I have yet to hear of any sort which would
>be appropriate for racing.  Note the distinct absence of automatics from
>automobile racing (yes, I do remember Jim Hall's Chaparrals).
>
	Did you even heard of the Tip-tronic? A Porsche 968 equipped with it
completed its circuit lap *Faster* than the equivalent with a stick?
That's because the tiptronic is loaded with sensors,
electronics and accelerometers, figuring out the drivers style and adapting
the shifting pattern to it. In short, light years ahead from conventional
automatics.

>
>So now that we have larger, stronger, higher-torque bike riders the
>automatic transmission becomes more practical, right?
>
	The human legs are actually an engine having way more torque than an
equivalent car engine. This of course with respect to the mass to be
transported (i.e. look at climbers or sprinters: the force generated by the
legs is more than enough to accelerate the athlete at more than 2G's
linearly for a short time, while a Ferrai F40 wouln't be able to do better
than 0.8 G). If the smallest speed available in a bike would be able to
reach down enough, the bike would be able to outrun any of the mystical
supercars existing or to come this century for at least one second.

>
>: BTW: For cars, I *HATE* automatics, because there is still decreased
>: performance (but I'll go for a tiptronic any day!) and increased fuel use,
>
>But you will gladly suffer such a loss of performance and increased 
>energy usage when _you_ are the engine?  I think not.
>
	To maintain the performances of a Taurus SHO automatic (introduced
for the '93 model year) wrt its stick counterpart, Ford increased the torque
of the engine with 3.2 liters intead of 3.0 in displacement (while keeping
the Hp). This example shows that the human engine, having lots of torque but
not much Hp/Unit of mass, would not suffer much from an automatic in a bike.

						Marc
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