From: harry@cv.hp.com (Harry Phinney)
Subject: Re: Automatic transmissions for bikes
Organization: Hewlett-Packard Company, Corvallis, Oregon USA
X-Newsreader: Tin 1.1 PL4
Date: Thu, 31 Dec 1992 22:03:43 GMT

marc@gauss.math.mcgill.ca (Marc Sokolowski) 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?
:
: 	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.

The human body, from mouth and nose to ass and legs is the equivalent of
the auto's engine.  After your touting of the abilities of the
Tiptronic, I am quite surprised to hear you believe the ideal
transmission is a simple thing.  Do you not think the Tiptronic has
knowledge of the throttle position and rate of change of the throttle
opening?  This is roughly equivalent to knowing the VO2/VO2max of the
rider and the rate of change of the VO2.

: 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.

Which means what?  If I press harder on the pedals, does the
transmission shift up or down?

: 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!!").

I don't understand.  First you say that the rider should decrease their
RPMs to 50, and then you state that the transmission will not make you
decrease your RPMs.  Which is it?  Does the transmission try to maintain
a constant RPM, or a constant pedaling torque, a constant bike speed or
what?  Any of these choices will be wrong much of the time.  A rider
does not always wish to maintain a constant torque, a constant RPM, a
constant speed, or even a constant power output.

: A tach for the wheels vs tach for the
: pedals vs variation in rpm on the pedals is all it takes.

Please explain the algorithm to me.  You were earlier talking about
maintaining a constant torque.  You will need force/torque sensors to
accomplish this.  Your "tachs" will not be sufficient.  I already have
the "tachs" you describe, in the form of a bike computer.  It tells me
my speed (wheel tach) and my pedaling cadence (crank tach).  It cannot
tell me how hard I am working - i.e.  how much power I am producing, nor
how much torque I am applying through the cranks.  It has insufficient
information to do so.

: 	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.

A single-speed bike will "keep you accelerating at a pace proportional
to this torque" as well as any other bike.  If I start pedaling harder,
does your ideal transmission shift into a bigger gear, or a smaller
gear?  Hint:  Either answer will be wrong about half the time.

: 	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).

All of which is fine, and as I pointed out is a direction the derailleur
manufacturers are already heading.  I also already noted that mechanisms
other than the traditional derailleur may indeed become common place.
My skepticism centers on the notion of an optimal automatic
transmission.

: 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.

There is no loss of energy in the single-speed case.  You do not need
any multi-speed transmission to "get the acceleration you deserve for
your energetical investment."

: 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...

I take it you've done a lot of bicycle racing.  Tell me, just prior to
launching an attack what do you do:  A) Nothing.  B) Shift into a lower
gear for more road torque and thus better acceleration.  C) Shift into a
higher gear.  D) What's "an attack"?

Again, I'm interested to know what your transmission will do when I
start pedaling harder - does it shift up or down?

: 	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).

Right.  Diablos and F40s are the height of practicality.  You never did
tell me what you meant by "an equivalent car engine".

: >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.

To exactly which laws of physics are you referring?  Take a case of two
riders riding at the same constant speed side-by-side down the same
road.  One is pedaling at 80 RPM, the other at 95 RPM (they are of
course using different gear ratios).  Are they applying the same torque
to the pedal cranks?  Are they producing the same amount of mechanical
power?  Can you predict which one will be able to maintain the given
speed the longest?

: 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).

Power/mass ratio is interesting when going up hill.  Power/drag is
interesting on relatively flat ground.  In neither case is torque by
itself a particularly interesting factor, assuming you are referring to
the pedal torque produced by the rider.  The torque at the rear wheel is
simply proportional to the speed of the bike/rider and the power being
expended.

: >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).

So what?  We can't lift that much weight over and over continuously for
an hour.  This is due to the limits of the power converting metabolisms
of our bodies.  Again, the limiting factor in cycling is the sustainable
power output of the rider.  This is true for every event from the 1000m
match sprint to stage racing.  The different length events stress
different metabolic mechanisms, but they are each limited by the body's
ability to convert stored chemical potential energy into mechanical work
continuously over some distance and period of time.

: Of course, Gorillas are a little better, but I have yet to see an
: elephant transport 25 tons.

Neither have I ever seen an elephant attempt a squat or deadlift, nor
have I seen a power or Olympic lifter attempt to "transport" the weight.

Harry Phinney   harry@hp-pcd.cv.hp.com