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.
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.
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
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
On 14 Aug 2006 06:56:57 -0700, email@example.com wrote:
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
Brian Whatcott Altus OK
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 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
FYI......... I finally found some good information from the
They say, "Largest Recommended Wire Rope Size - Should be no larger
than 1/8th the cable drum barrel diameter for most recovery
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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