On Thu, 18 May 2017 13:10:48 -0500, Tim Wescott
wrote:

I use "thingie" in the title to not give anyone a false impression of
what I do or don't know.

I'm working with a client who's using one of these in his specialized
bike:

https://www.amazon.com/dp/B01KYKEP2Y...xx_P1400_1000?
tag=dradisplay-20&ascsubtag=c73ee0e485a804ac76001596b2b029f4_S

He's currently using the 250W version, but we're having problems of
insufficient torque -- this is partially due to re-purposing a board, and
we're on top of that part, but I'm thinking ahead (well, borrowing
trouble, in proper engineering fashion). So we thought -- hey! We'll
use the 350W version (that's the one in the link).

The problem is that the 350W version actually has a lower current-to-
torque constant -- it gets its higher power through pulling more current
for the torque, and delivering more speed.

So -- any thoughts on an easy way to gear the thing down? I just
recommended to the customer that they put two chain rings on the crank,
so that they can drive the pedals at one speed and the bike at another.

Is the purpose to make an electric drive vehicle or a bicycle with
electric power available?

If the first then possible a dual front crank, i,e, two sprockets,
might work - from motor to crank sprocket, from second crank sprocket
to rear wheel. Note that dual or triple cranks are pretty much the
standard on sports bicycles these days.

If the latter then I would think that there would have to be some
method of disconnecting the motor from the pedals in some manner.

Whizzer, which was a belt driven internal combustion motor design used
a separate belt drive from the motor to the wheel. See
http://tinyurl.com/n4tlr9e
--
Cheers,

John B.