From: marc@gauss.math.mcgill.ca (Marc Sokolowski)
Newsgroups: rec.bicycles.misc,rec.bicycles.tech,aus.bicycles
Subject: Re: Automatic transmissions for bikes
Date: 31 Dec 92 08:50:53 GMT
Organization: Dept of Mathematics, McGill University

In article <1992Dec30.002047.5034@hpcvusn.cv.hp.com> harry@cv.hp.com (Harry Phinney) writes:
>marc@gauss.math.mcgill.ca (Marc Sokolowski) writes:
>: In article <1992Dec28.193402.25148@hpcvusn.cv.hp.com> harry@cv.hp.com (Harry Phinney) writes:
>
>With what sort of sensors?  Perhaps a catheter sticking in a vein to
>measure blood lactate levels, or sensors over the rider's nose and mouth
>to measure respiratory ratios?  In any case, any system that expects to
>find one perfect cadence for a rider is entirely misconceived.  If you
>can make it controllable via brain waves, I'll be interested.
>
	This is way too much. After all our muscles are only the equivalent
of the engine's car. Your legs provide power, that's all. If you want to go
faster, you simply press more on the pedals. That's it. What the
transmission will do is to make sure the acceleration to the fastest
possible speed proceeds in the most smooth way. Say you pedal at 60 rpm and
that the speed that your bike reach is 30 kph on the 7th speed. If you're
exhausted, you simply decrease the pressure on the pedal, reducing the rpm's
to 50 or so. The auto transmission will try to maintain you at a speed as
fast as possible while not making you decrease your rpm's (which means "I'm
exhausted! The gear is too high!!"). It doesn't take Firefox like
brain-waves decoders to do that. A tach for the wheels vs tach for the
pedals vs variation in rpm on the pedals is all it takes.

>I don't care what your sensors can tell about the terrain, I don't
>believe you can currently design, or imagine a design for, any sensors
>which will know what I want to do.  Your "transmission" will have to
>predict whether I'm about to jump, whether I want to stand on this hill
>rather than sit, etc.  Nor will your sensors detect when I am becoming
>dehydrated, or low on carbohydrates, or my legs are starting to cramp.
>
	Simple: you put more torque on the pedals to accelerate. An
automatic transmission will keep you accelerating at a pace proportional to
this torque NO MATTER what your speed is (well... rapidly there's the effect
of wind, etc... but the ideal interpretation is "acceleration proportional
to the torque on the pedals -> Increased torque -> increased acceleration).
Who would be against that? When you shift manually, you simply try to
reproduce this effect more or less ideally.
   The point for a car transmission is to keep the engine at
the same torque from 0 to 10000 rpm's (0.7 factor of demultiplication for
the 4th speed, with an engine which redline is 6000 or so). The point for a
bike trans. is to maintain constant acceleration no matter what the speed is
up to the limit possible with air resistance etc... i.e. reach this limit as
fast as possible given the torque you apply on the pedals.
	Again, I don't see the need for god as your shifting master on a
bike.
>
>Riders sponsored by Mavic have already used electronic derailleurs in
>professional races.  These are manually controlled - the rider pushes a
>button to effect a shift.
>
	Btw, the transmission presented in Popular Mechanics can easily be
converted to an all-electric manual: Just replace the computer by a set of
switches. Don't forget that mechanical devices loaded with electronics can
easily have better performance and cost less than high-quality all
mechanical elements (i.e. fuel injection vs carburetors in car engines).

>
>Yes, I've heard of Porsche's Tiptronic.  I also know that the
>virtually-unlimited-budget F1 folks still use (electronic, "clutchless")
>manual transmissions.  What a bunch of heathen fools, huh?  I also
>contend that it's easier to load up an engine with sensors than it is to
>load up a human with equivalent sensors.  What's the equivalent of
>....
>Also, an engine does not fatigue the way we organisms do.  How do you
>measure fatigue?  How do you measure pain?  Engines don't generally have
>good days and bad days.
>
	As an analogy, just picture switching to lower gear in a car with a
stick as INCREASING your torque on the wheels, thus INCREASING your
acceleration. Same in a bike where you suddenly put more weight on the
pedals, which in term translates to more torque on the wheels of the bike
for faster acceleration. The transmission is in charge of making sure you
get the acceleration you deserve for your energetical investment up to the
target speed you want. And I think electronics can figure that out way more
effectively than me, suffering from the sprint I try to make to outrun my
opponents near the finish line of the 7th etape of Tour de France, just as
ABS can pump the breaks more effectively than me manually when I try not to
crash on to a concretewall at 300 kph in Indianapolis. Just a few sensors on
the wheels and pedal...

>: 	The human legs are actually an engine having way more torque than an
>: equivalent car engine.
>
>What exactly is "an equivalent car engine"?
>
	
>Burrell, Lewis, and Johnson combined couldn't match the 4G acceleration
>of a (single speed) top fuel dragster off the line.
>
	And a dragster cannot match the final phase of the Saturn V first
stage acceleration at 9 G. I was talking about practical things here (for as
much as a Lambo Diablo or F40 is practicall as a mean of everyday
transportation).

>In any case, torque is not an interesting number 99+% of the time when
>one is riding a bicycle.  The limiting factor is the sustainable power
>output of the rider at their chosen level of (dis)comfort.
>
	Totally false, this in accordance to basic laws of physics. Bikes
are known to reach speeds in exess of 200 kph whith appropriate drag
reducing mechanisms (check the solar energy cars and other hybrids). This is
certainly not an indication of low energy output wrt the mass involved (less
than 100 Kg).

>
>Fine.  When you find a way for me to purchase some addition
>"displacement" for my legs, let me know.  Until that time, I will prefer
>the highest possible mechanical efficiency in the drive train.
>
	Torque is the human muscle best asset. We are not renown for running
fast, but we can lift weights over 400 kg (thanks to steroid ladden
athletes). Of course, Gorillas are a little better, but I have yet to see an
elephant transport 25 tons.

						Marc
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