Up: Table of Contents Reverse-engineering calculations for this hub
Sachs Torpedo 7-speeds[1]
  Number of gear teeth Drive path Ratios  
Shifter Position Sun Gear 1 Pinion meshing with sun  Pinion meshing with ring Ring gear 1=R to P, 2=Direct, 3=P to R Drive ratio as fraction Drive ratio from Sheldon Brown Ratio incre- ment
1 33 13 17 63 1  273/460 0.593 0.594  
2 30 17 17 63 1   21/31 0.677 0.677 1.141
3 21 25 17 63 1   75/92 0.815 0.814 1.203
4 21 25 17 63 2 1        1.000 1.000 1.227
5 21 25 17 63 3 1  17/75 1.227 1.227 1.227
6 30 17 17 63 3 1  10/21 1.476 1.476 1.203
7 33 13 17 63 3 1 187/273 1.685 1.684 1.141
[1]
John Allen:
Ratios are calculated but are necessarily correct, as the sun-gear tooth counts are given in the parts list, and the sum of tooth counts of each sun gear and the planet gear meshing with it must be about the same. Discrepancies with Sheldon Brown's gear calculator reflect rounding errors. See the next page for an example of how tooth counts are derived from ratios.