On 6/8/2020 12:02 AM, Jeff Liebermann wrote:
On Mon, 8 Jun 2020 11:34:47 +1000, James
wrote:

Possibly a year ago a mate and I had a conversation about the
possibility of making an electronic gear change actuator that could
effectively replace down tube shifters and operate on regular Bowden
cable operated derailleurs. I even looked up some small linear
actuators that I thought would have an appropriate motion range and pull
force.

A couple of days ago my mate sent me this link.

https://cell-cycling.com/

Very close to what we had discussed!

So, improve on the basic design by adding a microprocessor to do self
calibration. Add a tachometer or shaft encoder to the rear wheel to
detect rotational speed or when it shifts. It can be temporarily
attached as it's only needed to calibrate the shifter. Life the rear
end off the ground, spin the crank by hand, and punch the self
calibrate button. The bicycle will go up and down the various
freewheel gears to set the optimum shift point. Then, do it again for
the each chainring gear since the freewheel shift points are slightly
different for each chainring gear. Control everything via Bluetooth
from a smart phone.

Extra credit for replacing the cable and rear derailleur with a 2 axis
linear and rotary actuator. While the existing cable and derailleur
parallelogram is probably the minimum cost and weight solution, it has
the disadvantage of only working for one size freewheel (for both
number of gears and spacing). When both the extension length (linear
actuator) and angle relative to the rear axle (rotary actuator) are
adjustable, then any size freewheel can be accommodated.

So will that will be Di3?


--
- Frank Krygowski