So say we could add 100 watts to my 100 watts, for 200 watts total.  If 200W
is the output that a real athlete could produce, then I'd be able to keep up
with them at least.

I can average about 12-14 MPH on my bike, a good rider can average 18MPH
given all flat terrain.  So my estimate of 150% speed for double the power
isn't too far off.  In town, I can only average 6MPH because of traffic,
stoplights and so on.  In heavy traffic I can still beat the cars!

In a lot of situations, I just want a boost up the hills, which would
seriously increase my average speed.  There was a fuel cell unit that would
produce 12 volts, 2 amps for $214, signifigantly less than my first estimate
of $2000 smackeroonnies. Maybe my estimate is going to be revised to nearer
$400 clams.   That's only 24 watts, but at 20% duty cycle it's approx 100
watts.  Still have to lug around a battery plus a hydrogen tank, and we are
still not doing any better than a battery charger.  OTOH it would be really
cool.

--Lawrence



----- Original Message -----
From: "Russell McMahon" <apptech@PARADISE.NET.NZ>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Thursday, July 18, 2002 10:09 PM
Subject: Re: [OT]: Hydrogen Powered Cars


> > How much power is developed by a [overwieght middle aged and balding]
> human
> > on a bicycle?  I am thinking about 25 watts, but my memory is as bad as
my
> > hair.
>
> Based on the exercise equipment that I have built, 25 watts is an
extremely
> modest load, 100 watts is getting stiffish and 200 watts plus is for
serious
> in anything  less than short bursts. I can burst to around 500 watts but
> only very briefly (then I burst :-) ).
>
> Depending on how zippy you want to be a 100 to 200 watt motor is probably
> the reasonable minimum.
>
> A good starting point for determining power needed to maintain a given
speed
> for a given vehicle is to run it (or a facsimile) at say 10% above this
then
> coast and see how long it takes to reduce speed to say 10% below target.
> Some energy calculations (0.5 m V^2) will give you some clues as to how
much
> losses you are getting. This would be very easy with a bicycle.
>
> Windage energy losses incrse with speed cubed and it takes about 30 HP to
> get a motorbike to "ton" (onld style imperial ton = 100 mph).(Note where
> this V^3 term comes from - Drag = F is proportional to V^2 as below and
work
> = FV )
>
> Frontal drag forces are about 0.5 x Rho x V^2 x A x Cd.
> Cd = coefficient of drag = 1 to start with (~=flat plate)
> Rho = air density in consistent units (1.3 kg/m^3 etc)
> A = frontal area.
> V = Velocity
>
>
>
>         Russell McMahon
>
> --
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> ways.  See http://www.piclist.com/#archives for details.
>
>

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