On Thursday, May 18, 2017 at 2:10:55 PM UTC-4, 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.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I think I'm missing the problem - looking at your question, you refer to driving the pedals. Looking at the picture on Amazon, they are driving a separate sprocket on the rear wheel. What's the problem with changing that driven sprocket (on the wheel) to a larger size?

But do like the idea of the Sturmey-Archer 3-speed. Just get that mounted in the middle of the drive train, and you're good to go.