drum size versus line size

I've got an old winch (10 ton) that has a 6.5" diameter drum. Does
anyone know where I can find a chart to determine the largest size of
wire rope I should install on this drum size.
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There are two issues here. First is the strength of the rope relative to the hoist capacity of 10 tons. Second is the ratio of drum diameter to rope diameter.
If the hoist does in fact have a line pull capacity of 10 tons, then the rope must be capable of pulling 10 tons with a suitable safety factor. Consider 3/4 inch diameter extra improved plow steel wire rope. It has a breaking strength of 29.4 tons (handbook value; specific manufacturers' products may vary). Thus, this size rope provides a safety factor of just under 3 at a line pull of 10 tons. Whether or not this is acceptable will depend on your proposed usage.
The ratio of diameters seems small, though. 6.5 / 0.75 = 8.67. Various crane and hoist standards (in the US) generally require that this ratio be 16 or greater, again depending on the usage.
Overall, your proposed use of this winch will dictate the safety standards with which you must comply.
Reply to
David Duerr, P.E.
you have several things to consider when picking the rope - strong enough rope that the hoist won't break it (around 80,000 lbs, min for an electric hoist) what it lifts the rope-d/Drum dia where it is lifting at what speed it lifts and how it stops
that small a drum and that big a hoist, it almost had to have been wire core (to keep the rope from flattening on the drum)
that is a very big hoist for such a small drum; it almost has to have been for extra improved plow steel (or extra-extra). I don't have that data at this desk.
thoughts -
1) Rule of thumb is 30 to one d/D, but many are designed for as low as ten to one d/D. It depends on the wire rope type and core, spooling, and a couple other things.
2) If it is a grooved drum, that diameter is the designed size for the drum. A ten-to-one almost always requires grooving.
3) Going at it another way, the winch service and connection would have a lot to do with the rope size.
4) Ten ton and 6.5" sounds a fair ways from standard - that sounds like a 5/16" rope drum, which is not ten ton. And bending a 5/8 rope around that drum is a man-sized effort A ten ton 6.5 inch dia drum will have a heavy wall - 1/2" steel or heavier.
5) Lifting persons has a different margin than lifting iron in the desert sand - a ten ton person lift would use 140,000 pound rated cable (7:1)
maybe more info later
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Hmmmm...this is an interesting question. For several choices of wire rope, 1/2 in diameter is near 10 ton breaking strain. But for cranes and other critical uses a design factor of X5 might be applied, and that suggests a one inch diameter or so. One inch diameter on a 6 1/2 in diameter drum seems way too thick to me.
Brian Whatcott Altus OK
Reply to
Brian Whatcott
The winch is used on an oilfield bed truck, i.e., horizontal load application. Someone has put 1" fiber core wire rope on the drum. This obviously explains the flattening of the cable!!! I'm just a little concerned that 1" line may actually be too large a diameter for this drum.
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check out
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Drum ratio figures into rope life
minimums are in the 15 to 18 though I've seen smaller (like 10 to 12) but the wires wear out
better ratios are in the 24+ range with rope life being greatly increased in the 40 range
a 1" rope on 6.5" dia drum is WAY too low a drum / wire ratio
cheers Bob
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FYI......... I finally found some good information from the manufacturer;
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They say, "Largest Recommended Wire Rope Size - Should be no larger than 1/8th the cable drum barrel diameter for most recovery applications."
Bob, this calculation actually works out to 9 by your formula. I think I'd better follow the OEM spec. Thanks for kick starting my mind!
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You and me both!
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Brian Whatcott

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