The problem of speed produced by power means that speed is obtained at the expense of power expended. The relative size of the sprocket-wheels determines the relative speed of the cranks and rear wheel. To get the greatest speed with the least power possible means diminished friction and lessened weight. The band or chain complies mechanically with these requirements, permitting a certain amount of play, which lessens the danger of sudden strains and jars, and supplies the power to the rear wheel with the least possible loss by friction.
| Gear | 63 | 72 | 76 | 80 |
|---|---|---|---|---|
| 61⁄2 crank proportion | 411⁄13 to 1 | 5⁄13 to 1 | 511⁄13 to 1 | 62⁄13 to 1 |
| 8 crank proportion | 315⁄16 to 1 | 441⁄2 to 1 | 333⁄4 to 1 | 5 to 1 |
| 61⁄2 crank pressure | 4.85 | 5.54 | 5.85 | 6.15 |
| 8 crank pressure | 3.37 | 3.84 | 4.5 | 5.00 |
| 61⁄2 crank ground covered by large wheel | 16 ft. | 19 ft. | 20 ft. | 21 ft. |
| 8 crank ground covered by large wheel | 16 ft. | 19 ft. | 20 ft. | 21 ft. |
| 61⁄2 crank ground covered by pedal | 40.84 inches | |||
| 8 crank ground covered by pedal | 50.26 inches | |||
“Scientific American Supplement, No. 1025,” August 24, 1895.
Rating wheel by the amount of progression for each turn of the crank (pedal), the following table, compiled by Henry Starkweather, will be found of advantage:
| No. teeth in large Sprocket. | 26 in. wheel. | |||
|---|---|---|---|---|
| No. teeth in small sprocket. | ||||
| 6 | 7 | 8 | 9 | |
| 18 | 20 ft | 17 ft | 15 ft | 13 ft |
| 19 | 21 ft | 18 ft | 16 ft | 14 ft |
| 20 | 22 ft | 19 ft | 17 ft | 15 ft |
| 28 inch wheel. | ||||
| 18 | 22 ft | 19 ft | 16 ft | 14 ft |
| 19 | 23 ft | 20 ft | 17 ft | 15 ft |
| 20 | 24 ft | 21 ft | 18 ft | 16 ft |
The following table, from the New York Evening Post, shows the gear according to the number of teeth on large and small sprocket-wheels:
| Sprockets on pedal crank. | 28 in. wheel | |||
|---|---|---|---|---|
| Sprockets on rear wheel. | ||||
| 7 | 8 | 9 | ||
| 17 | 68 | 59 | 1⁄2 | 53 |
| 18 | 72 | 63 | 56 | |
| 19 | 76 | 66 | 1⁄2 | 59 |
| 20 | 80 | 70 | 62 | |
| 21 | 84 | 73 | 1⁄2 | 65 |
CHAPTER XIX.
Adjustment.
In bicycling, the word “adjustment” means much, for the movable parts of the bicycle must be adjusted to suit the requirements of the individual bicyclist, and the mechanical parts of the bicycle’s construction adjusted so that they will work together properly.