Being old and feeble (50ish, overweight, with bad heart and lungs, high blood pressure etc.), the only way I could get back into cycling was with an eBike.
In PAS (Pedal Assist System) mode, my weak input was amplified to a very comfortable 12mph.
I was mobile again, carousing along the back streets and trails.
Able to go along with the grandkids on little adventure rides.
If they got too far ahead I could twist the throttle, a little, and herd them back into line.
As I got used to this modest exercise all aspects of my health seemed to be improving. I found myself inputting a larger percentage of my motorvation, spending a large percentage of my cycling at beyond the eBike speed of 16mph.
Becoming loyal to my physical therapist (my eBike) I decided to help build up my buddy. 1st step was to help "him" keep up with me, so I found a compatible freewheel and regeared for a 25% speed increase, moving PAS mode from 12 to 16mph and TAG (Twist And Go) mode from 16 to 20mph.
$20 for 25% speed increase
Next I was able to recycle "bad" notebook batteries into light weight, high capacity battery packs. Improved our range, from about 15, to +50 miles, (per 10¢ recharge). 24 to 25.9V improved also (22mph motor only w/some assist to 25mph)
Homemade Battery Packs
We've been able to spend years ... and thousands of miles together, complementing each other nicely. Completing multiple "Centuries", rocketing ahead of cars from stoplights, slipping effortlessly through gridlock traffic etc.
Sadly ... lately ... I've found my buddy lagging behind, not being able to keep up.
My, near 30mph, sprints are telling of an outgrown "pal".
... not yet!!!
I could bump up my buddies speed by "juicing" him.
The equivalent of steroids - higher voltage!
No, we shall remain a team!
Respecting each other!
I will endow him with longer legs, regearing for even higher speed.
After decreasing the motor freewheel to the smallest possible, the only possible improvement will be to increase the motors drive sprocket, stock of 9T increased to 11 or 12T, possibly higher, tough to find compatible, but am building 11T's using 2 different methods now.
EZip Drive Sprocket Upgrade
My buddy will lose low speed acceleration, but gain high speed cruising assist. He will have to depend more on me, getting up to speed, and I can depend more on him pushing to and maintaining 30mph. (25mph (some assist speed) / 9T x 11T = 30.5mph.)
Bicycle Safety - The Math of Speed
Oops! - Forgot to mention that I upgraded from a 14T to 11T rear sprocket! (90 crank rpm = +28mph)
Sprocket Ratio = Pedal Assist MPH