I would like to point out Frink, which can do unit-based calculations=20
very easily.

http://futureboy.us/frinkdocs/#SampleCalculations

For example I can put "100 amps * 48 volts" into the "from" field,  And=20
"hp" into the "to" field, to see (in an ideal world) how many horsepower=20
that battery can produce.

Better yet, try  "100 Amps * 48 Volts * 1 hour"  ->  "km * 100kg * gravity"

Joe




On 2011-02-15 09:07, RussellMc wrote:
> The original post does seem to have enough data to support many of the
> writer's observations, other comments notwithstanding. This doesn't mean
> that they make sense, as he says. The uphill slowing description is
> incalculable as the distance is not given. Over 1 metre its very easy. Ov=
er
> 10 km it's not etc.
>
> Method 1:
>
> A motorcycle  with fairing takes about 30 HP to ton *(100 mph)
> Power needed is proportional to V^3.
>
> So power needed to do 95 kph ~~~~=3D
>      (95/160)^3 x 30 =3D
>
> Method 2
>
> Energy due to drag =3D 1.3 x Cd x A x V^3
>
>       Cd =3D drag coefficient
>       A =3D area m^2
>       V =3D velocity m/s
>
> At 95 kph V =3D 26.4 m/s
>
> To get 2200 Watt [[watt]] you need a Cd x A product of 0.15
> eg 1 m^2 area and Cd=3D0.15 (about impossible)
> or A - 0.5 m^2 and Cd=3D0.3 etc.
>
> A picture would be good, but I'd say  a reclining seated position would
> allow under 0.5 m^2 frontal area. Add wheels to that and some body drag.
> Body drag gets significant as length to area grows. Idf you can add some
> "base bleed - air fed out tail to reduce base drag (maybe it stops the
> airflow separating prior to the base  but that's getting speculative.
>
> So - I'd say that the very very very best designs going MIGHT approach th=
at
> speed.
>
> I haven't tried to look at the rolling while loaded with N people stuff. =
You
> can easily enough decide whether the laws of physics and perfect bearings
> allow what you are seeing. If not
>
> Quick glance. If the motors are off ypou can decide. If the motors are on
> it's called throttle up :-).
>
>
>          Russell
--=20
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