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Wire Rope Stretch | |
QPL-83420 Reference | |
Jacket Tolerances | |
Standard Points Of Measure |
Cable Diameter Related to Pulley or Sheave Diameter
The service life of Cable and Wire Rope can be increased if (1) it operates over the largest possible pulley or sheave diameter, and (2) it is properly supported in the pulley or sheave groove. The Working life of the individual wire strands is greatly reduced as the pulley or sheave diameter is diminished. The chart below shows minimum tread diameters
over which various sizes and constructions of cable should operate.
Minimum Tread Diameter for Pulleys or Sheaves
Ratio of cable diameter to pulley diameter
Desirable Minimum |
Critical Minimum |
|||||||
| 42:1 | 24:1 | 12:1 | 28:1 | 18:1 | 10:1 | |||
Cable Diameterin Inches |
6x7or7x7 |
6x19or7x19 |
6x317x316x37 |
6x7or7x7 |
6x19or7x19 |
6x317x316x37 |
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| 1/16 | 2-5/8 | ---- | ---- | 1-3/4 | ---- | ---- | ||
| 3/32 | 2-15/16 | 2-1/4 | ---- | 2-5/8 | 1-11/16 | ---- | ||
| 1/8 | 5-1/4 | 3 | ---- | 3-1/2 | 2-1/4 | ---- | ||
| 5/32 | 6-9/16 | 3-3/4 | ---- | 4-3/8 | 2-7/8 | ---- | ||
| 3/16 | 7-7/8 | 4-1/2 | ---- | 5-1/4 | 3-3/8 | ---- | ||
| 7/32 | 9-13/16 | 5-1/4 | ---- | 6-1/8 | 4 | ---- | ||
| 1/4 | 10-1/2 | 6 | 3 | 7 | 4-1/2 | 2-1/2 | ||
| 5/16 | 13-1/8 | 7-1/2 | 3-3/4 | 8-3/4 | 5-5/8 | 3-1/8 | ||
| 3/8 | 15-3/4 | 9 | 4-1/2 | 10-1/2 | 6-3/4 | 3-3/4 | ||
| 7/16 | 18-3/8 | 10-1/2 | 5-1/4 | 12-1/4 | 7-7/8 | 4-3/8 | ||
| 1/2 | 21 | 12 | 6 | 14 | 9 | 5 | ||
**When designing Aircraft Control Cable Systems, minimum ratio of cable diameter to pulley diameter is 35:1
Pulley Grooves
When designing a pulley groove, the groove should be 150% the maximum tolerance of the wire rope.
Example:
A 1/8" 7x19 aircraft cable has a minimum tolerance of .014" (.125" minimum, .139" maximum). Multiplying the .014" maximum tolerance by 150% = .021". Adding .021" to the .139" maximum diameter = .160", which should be the pulley groove dimension.
