The 14 gears inside

The gear unit consists of three planetary stages in series: (1), (2) and (3). The sprocket drives the ring gear of stage (1); stages (1) and (2) sit mirror-image on a shared planet carrier and together give seven gears. Stage (3), as a reduction, doubles the number of gears to 14; its output is the (3) planet carrier, which drives the hub shell through the drive pins. How one stage gives three different ratios is shown in Planetary gearing.

How it shifts

The shift shaft turning inside the axle stops at each gear with a ball detent. Pawls lock the relevant sun gear to the axle, and clutch rings put a stage into direct drive (1:1).

• The shift shaft’s first turn selects gears 1–7: the ring gear of stage (3) is locked to the axle, and its planet carrier reduces by 0.409.
• At the 7–8 shift, clutch ring 3 puts stage (3) into direct drive.
• The second turn selects gears 8–14, with the same (1)–(2) combinations as the first.

Stage (1) reduces (0.682 or 0.774), stage (2) increases (1.292 or 1.467), or each passes on 1:1.

Gear by gear

Gear	Stage (1)	Stage (2)	Stage (3)	Hub turns per sprocket turn
1	0.682	1 : 1	0.409	0.279
2	0.774	1 : 1	0.409	0.316
3	0.682	1.292	0.409	0.360
4	1 : 1	1 : 1	0.409	0.409
5	0.774	1.467	0.409	0.464
6	1 : 1	1.292	0.409	0.528
7	1 : 1	1.467	0.409	0.600
8	0.682	1 : 1	1 : 1	0.682
9	0.774	1 : 1	1 : 1	0.774
10	0.682	1.292	1 : 1	0.881
11	1 : 1	1 : 1	1 : 1	1.000
12	0.774	1.467	1 : 1	1.135
13	1 : 1	1.292	1 : 1	1.292
14	1 : 1	1.467	1 : 1	1.467

The hub’s turn is the product of the three ratios — in gear 5, for example, 0.774 × 1.467 × 0.409 = 0.464. That is why the gears step evenly, each by about 13.6%.