Sheave and Drum Ratios

Construction* Suggested
D/d Ratio**		 Minimum
D/d Ratio**
6 x 7 72 42
19 x 7 or 18 x 7 Rotation Resistant 51 34
6 x 19 S 51 34
6 x 25 B Flattened Strand 45 30
6 x 27 H Flattened Strand 45 30
6 x 30G Flattened Strand 45 30
6 x 21 FW 45 30
6 x 26 WS 45 30
6 x 25 FW 39 26
6 x 31 WS 39 26
6 x 37 SFW 39 26
6 x 36 WS 35 23
6 x 43 FWS 35 23
6 x 41 WS 32 21
6 x 41 SFW 32 21
6 X 49 SWS 32 21
6 X 43 FW (2 op) 28 18
6 x 46 SFW 28 18
6 x 46 WS 28 18
8 x 19 S 41 27
8 x 25 FW 32 21
6 x 42 Tiller 21 14

* WS - Warrington Seale
FWS - Filler Wire Seale
SFW - Seale Filler Wire
SWS - Seale Warrington Seale
S - Seale
FW - Filler Wire

**D=tread diameter of sheave
d= nominal diameter of rope
To find any tread diameter from this table, the diameter for the rope construction to be used is multiplied by its nominal diameter (d). For example, the minimum sheave tread diameter for a 1/2" 6 x 21 FW rope would be 1/2" (nominal diameter) x 30 (minimum ratio) or 15".

NOTE: These values are for reasonable service. Other values are permitted by various standards such as ANSI, API, PCSA, HMI, CMAA, etc. Smaller values affect rope life.

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