Pinion development chart mystery?
No, that cannot be!
Simple example:
A gear down ratio of 0,25 means, if the crank does one turn, the backwheel will do a quarter turn.
The circumference of a 26 inch wheel is ~ 2 meters.
A quarter of 2 meters is 0,5 meters, not 1,30 m!
Below the calculation for the 18th gear (gear up 1,59):
26 x 0,0254 x number Pi x 1,59 = 3,29 m and not 8,28 meters!
Somebody might shout now: “You did not consider the secondary gear ratio of the (front 24 t and back 21 t) chain drive!”
(Note: The pinion drive is the primary drive).
Why should I?
In the (German) part of pdf and website it is written clearly:
“Gesamt” = entire, gross, overall, complete, as a whole
“Übersetzung” = conversion, gear ratio, transmission ratio
But ok, here it is:
1st gear:
26 x 0,0254 x number Pi x 0,25 x 1,14285 = 0,59 m
18th gear:
26 x 0,0254 x number Pi x 1,59 x 1,14285 = 3,77 m
Calculated for front 24 t and back 21 the inverse value of 0,875 (rounded 1,14285) must be used, because that’s gear up.
Did they mean front 21 t and back 24 t?
Let’s try:
1st gear:
26 x 0,0254 x number Pi x 0,25 x 0,875 = 0,45 m
18th gear:
26 x 0,0254 x number Pi x 1,59 x 0,875 = 2,88 m
Hmmm, what next?
Supposed we had a wheel size of 65 (sixtyfive) inch:
(Secondary gear ratio 1:1)
1st gear:
65 x 0,0254 x number Pi x 0,25 = 1,30 m
18th gear:
65 x 0,0254 x number Pi x 1,59 = 8,25 m
Please calculate yourself, i. e. here:
http://www.schlumpf.ch/hp/berechnungen/engl_berechnen_nabenschaltung.htm
and help me, I need your voice.
I know that I am leaning far out of the window…
(Hint: The Rohloff hub has similar gear ratios.
1st gear 0,28
14th gear 1,47)
Naturally, I wrote to the Pinion Support Team (twice).
Six days ago, there was sadly no reply.
