What is winch capacity by layer?

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What is winch capacity by layer?

Post by RealNick » 06 Dec 2016, 9:37 am

Saw this for the first time on a spec sheet and I don't get it.

Winch specs and it had different pulling capacity "by layer".

It was a 9,500 lb winch but was rated something like

Layer 1 - 9,500 lbs

Layer 2 - 8,000 lbs

Layer 3 - 6,500 lbs

I made the numbers up but you understand. What am I missing?
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Re: What is winch capacity by layer?

Post by Blackened » 06 Dec 2016, 11:17 am

Think of the winch drum like a gear.

You can't run a winch without a layer of rope because the locator screw which holds the rope to the drum is just to get it started, it's not load bearing, so you need to have 1 layer down and bound to the drum with friction to start using it.

With the first layer of rope on, it's a short gear.

After you've spooled the second layer on the gear has become taller.

When you spool the 3rd layer on, it's onto the now taller gear so the winch has less torque, less capacity.

Every layer you add increases the length of the gear thereby decreasing the capacity of the winch.

It depends on the size of your drum and thickness of your line how fast the layers build, but it's very significant as by the time you're 3 or 4 layers up you will have reduced your winch capacity by something like 40-50%.

A 9,500lb winch is not a 9,500lb winch all the time. Less often than more in fact.
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Re: What is winch capacity by layer?

Post by AusTac » 06 Dec 2016, 11:35 am

As blackened said, the winch rope grips the drum which transfers the pulling power via the drum, less rope = less " clamp " which in turn is less strength, for this reason you can't just hand feed in the rope for the first few layers, it must be tensioned ie hooked to a car and wound in under slight brake pressure
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Re: What is winch capacity by layer?

Post by brett1868 » 06 Dec 2016, 12:16 pm

Nothing to do with clamping, the mechanical advantage decreases as the drum diameter increases.

Image

Distance is radius to cable layer and you know from everyday experience it takes more force to torque a bolt with a short wrench than with a long one. So just reverse that - same torque pulls harder on a short radius arm than a long one. Changing the radius from 48 inches to 18 inches almost triples the pull , 48/18 = 22/3
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Re: What is winch capacity by layer?

Post by Bourt » 06 Dec 2016, 1:25 pm

AusTac wrote:you can't just hand feed in the rope for the first few layers, it must be tensioned ie hooked to a car and wound in under slight brake pressure


If you don't pretension rope and just free-hand it on you risk spinning the whole spool on the drum under load and snapping off the locator screw, unravelling the whole thing.

Definitely a must to pretension your rope :thumbsup:
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Re: What is winch capacity by layer?

Post by Chronos » 06 Dec 2016, 3:10 pm

Bourt wrote:
AusTac wrote:you can't just hand feed in the rope for the first few layers, it must be tensioned ie hooked to a car and wound in under slight brake pressure


If you don't pretension rope and just free-hand it on you risk spinning the whole spool on the drum under load and snapping off the locator screw, unravelling the whole thing.

Definitely a must to pretension your rope :thumbsup:


It's also about packing the layers tightly enough that when you do load up the winch the cable doesn't cut down into the lower layers and bind in there

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Re: What is winch capacity by layer?

Post by <<Genesis93>> » 06 Dec 2016, 4:38 pm

I had an idea some of you blokes didnt pay attention to my posts / rantings. :lol: :huh: ...at least I know this character^ doesnt, (indfact he cant even see them) :D

I described the torque and the 'most pull with unwound winch' in the other winch thread... :thumbsup:
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Re: What is winch capacity by layer?

Post by BBJ » 07 Dec 2016, 12:58 pm

Maybe mods can tell you how many people have you on their FOE list to filter out :lol:

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Re: What is winch capacity by layer?

Post by RealNick » 07 Dec 2016, 2:50 pm

Got it, thanks guys
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Re: What is winch capacity by layer?

Post by <<Genesis93>> » 07 Dec 2016, 3:17 pm

BBJ wrote:Maybe mods can tell you how many people have you on their FOE list to filter out :lol:

:friends:

Yeah nah.
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Re: What is winch capacity by layer?

Post by Lorgar » 10 Dec 2016, 8:28 pm

Blackened wrote:It depends on the size of your drum and thickness of your line how fast the layers build, but it's very significant as by the time you're 3 or 4 layers up you will have reduced your winch capacity by something like 40-50%.

A 9,500lb winch is not a 9,500lb winch all the time. Less often than more in fact.


I have my "11 thousand pound" winch book in front of me here as it happens. Figures for you Nick are:

Layer 1 - 11,000 lbs

Layer 2 - 8,634 lbs

Layer 3 - 7,106 lbs

Layer 4 - 6,038 lbs

Layer 5 - 5,248 lbs
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