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unns_boy
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Electric Winch

12/10/2012 8:33 AM

Recently, I came across a catalog regarding electric winch. What I don't understand is that why its lifting capacity is much lower than its pulling capacity, for a particular model, it can lift 2200kg but can pull 6500kg (incline 11 degree in angle). I just don't understand the theory behind it. Gravity? Please help.
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redfred
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#1

Re: Electric winch

12/10/2012 8:45 AM

Cable weight?

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TerraMan
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#15
In reply to #1

Re: Electric winch

12/10/2012 9:23 PM

What??...4300 kg of cable?...seriously?

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redfred
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#25
In reply to #15

Re: Electric winch

12/11/2012 11:32 AM

No, I'm not serious. But since our OP cannot explain what baffles them I do not feel obligated to explain myself either.

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lyn
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#2

Re: Electric winch

12/10/2012 8:49 AM

Yes.

Winches will lift more weight with all the cable spooled off the drum, too.

Notwithstand the added cable weigth in this instance.
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Fredski
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#3

Re: Electric Winch

12/10/2012 8:59 AM

dragging or pushing something is different than lifting it.you might be able to push a 200 lbs. car for a long distance, doesn't mean you can bench press it an inch
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redfred
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#4

Re: Electric Winch

12/10/2012 9:04 AM

There's also a safety margin issue. An accidentally released item being dragged will likely remain in place. A lifted item accidentally released can cause some considerable damage.

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rakesh_semwal
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#5

Re: Electric Winch

12/10/2012 9:37 AM

6500 x sin11 +friction due to drag (assumed by supplier)=2200

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rakesh_semwal
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#10
In reply to #5

Re: Electric Winch

12/10/2012 11:16 AM

Add- if you can manage to reduce friction to zero than your winch can pull about 11900Kg at 11Deg slope.

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phoenix911
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#11
In reply to #10

Re: Electric Winch

12/10/2012 11:21 AM

11900? ....... I believe you have a typo and that it should be 11500.

See post #7

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rakesh_semwal
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#12
In reply to #11

Re: Electric Winch

12/10/2012 12:51 PM

You are correct I was texting on my cell without /00/

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#13
In reply to #12

Re: Electric Winch

12/10/2012 12:53 PM

thought so, .........

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MUKULMAHANT
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#23
In reply to #5

Re: Electric Winch

12/11/2012 7:06 AM

Like Stunt Men pulling loaded trucks with his hair on his skull .
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PWSlack
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#6

Re: Electric Winch

12/10/2012 9:41 AM

It may be a motor rating or supply capability thing, perhaps? Sin(11°) = 0.1908, so the pull up an 11° slope at the same drum speed uses energy at 19% of the rate of lifting the object vertically.

What was the outcome of the telephone discussion with the equipment supplier's hotline on this topic?

[Edit - simultaneous posting with reply 5↑.]

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phoenix911
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#7

Re: Electric Winch

12/10/2012 10:37 AM

I did a force diagram of it, it doesn't quite work out, probably due to the coefficient of friction. but I it does have to do with leverage and mechanical advantage.

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Fredski
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#8
In reply to #7

Re: Electric Winch

12/10/2012 10:40 AM

what program did you use to produce the drawing?
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phoenix911
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#9
In reply to #8

Re: Electric Winch

12/10/2012 10:42 AM

just a sketch in autodesk

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durtieduck
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#14

Re: Electric Winch

12/10/2012 4:55 PM

lifting or pulling a higher load when the cable is spooled out has to do with the cable being closer to the spool. i'ld never trust a truck wench to lift a load because of the braking system.
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roy hammy
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#16

Re: Electric Winch

12/10/2012 10:35 PM

It is a safety issue, winches are not designed to lift only pull or drag. If they are designed to lift they are called a hoist and have a brake or worm drive to prevent uncontrolled lowering also very few companies get into hoisting due to regulations. I found a nice unit years ago from Taiwan that suited my purposes at that time. 8000 lbs pull and 2000 lbs lifting.

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bandership
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#17

Re: Electric Winch

12/10/2012 11:22 PM

I suspect it means you can pull with a max force of 2200 KG. And, you can pull a 6500 kg boat up onto its transport trailer when it is on a launching ramp built with an 11 deg slope.

Boat trailer winches often have two ratings, one for reel empty and another for reel full.

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HiTekRedNek
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#18

Re: Electric Winch

12/10/2012 11:57 PM

Allow me to explain this as I would to a new engineering student, without formulas or graphs,etc.

Pull a 6500kg load on rollers on perfectly level ground and measure the amount of force required to pull it.

Increase the incline by 1 degree and measure the force.It will be higher.Naturally.

Increase by 1 degree and measure each time and you will see that the force required increases with the angle of the slope.

At 11 degrees incline, the force required is 2200kg.

If you increase the angle any more, the winch cannot pull the load because the power required is greater than can be provided by the winch.

Now, for the sake of illustration, increase the angle to 90 degrees.It will require 6500kg of force to lift the load (ignoring friction,etc).

It is obvious that a hoist capable of lifting 2200kg straight up (90degrees) is capable of pulling a much higher load on a slanted or level surface.

A ramp is a form of gearing, and in effect acts as a reducer to the torque required to lift the load, at the sacrifice of speed.For instance, if a ramp slopes up from 0 to 4 feet over a distance of 40 feet, the ratio is 10 to 1; that is 10 feet of pull provides 1 foot of lift.

Suppose the winch has a 1 to 100 ratio on the drum.That is, 100 revolutions of the motor will give 1 revolution of the drum.Whatever torque is available from the motor is amplified by the gearing by a factor of 100.

Suppose that when the drum is evenly wound with a single layer of cable,it has 40 feet of cable on the drum.This required 100 X40(4000) revolutions of the motor to move the load 40 feet.If the drum rotates at the rate of 1 revolution per second,it required 40 seconds to lift the load 4 feet,using the ramp.

Now, lift the load straight up.It only requires 4 revolutions of the drum.Much faster,(4 seconds) but much more torque is required.But the amount of power is the same (ignoring friction,etc.)

Simple,eh?

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JIMRAT
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#21
In reply to #18

Re: Electric Winch

12/11/2012 5:46 AM

A GA from me. Did this in high school, didn't everyone? Guess not, maybe it's the age group.

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HiTekRedNek
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#22
In reply to #21

Re: Electric Winch

12/11/2012 6:30 AM

I agree.No one seems to teach the basics anymore, they simply plug in the question and get the answer from a calculator or computer,and never even try to understand the "Why" of the solution.

IMHO, society is being dumbed-down slowly to the point of total dependence on a select few that have, what once was considered an average, education.

(Even a one eyed man can be king in the world of the blind.)

Put a token in the machine, push a button or two, out pops your snack.No need to know how to make the machine from scratch,or how it works.

Plug a question into Google, up comes your answer.Most do not dig any deeper as to the origin of the answer,they simply accept it as Hoyle.

That is a sad indicator of a trend to convert the huddled masses into simply consumers, like cattle.

They will be managed like a commodity.If you are beyond a certain age, medical treatment will not give a good ROI,so you will be sent to the back of the line,and told"Wait your turn." The wait will turn out to be terminal.Forget about a knee transplant if you are over 50 years old.Not worth the investment.Go to the back of the line and wait till you are called.

It will not be as blatantly obvious to everyone as it is to me, but the handwriting is on the wall, and it is writ in blood.

The sad part is, like cattle or sheep the people will have the illusion of freedom and never know how they were used.

Sorry for the long rant, so I will mark it off topic.

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JIMRAT
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#28
In reply to #22

Re: Electric Winch

12/15/2012 7:48 AM

It is often said that we here in OZ are about 20 yrs behind the US. I hope we never catch up with your health care system/woes. Sadly, i feel it is inevitable.

You have yourself a nice day now!!!

Jim

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#19

Re: Electric Winch

12/11/2012 2:46 AM

may be a higher coef of safety for lifting ? If load falls damage can be higher than when on ground where the only problem is that it does not slide/move further ?
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TripppleP
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#20

Re: Electric Winch

12/11/2012 2:54 AM

Hello you there..., I think the most plausible answer so far is the brake rated capacity and its safety factor. (gravity acceleration time mass from full speed to stop).

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#24

Re: Electric Winch

12/11/2012 11:26 AM

I do not understand fully the spec in your question: does it mean that you can lift 2200 kg and exerce a pulling force of 6500 kg or that you can move a load of 6500kg mass on a slope 11° ? The difference is important since either this means that the pulling force is limited to 22000 N or that it can go as high as 65000 N if the winch is not used for lifting

Please make it clear.
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#26

Re: Electric Winch

12/14/2012 9:56 PM

You've got 2 good answers here, the rest are so over-thought they miss the obvious.
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TripppleP
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#29
In reply to #26

Re: Electric Winch

12/16/2012 11:33 PM

What is your explanation, Mister i know the thrut...

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TripppleP
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#30
In reply to #26

Re: Electric Winch

12/21/2012 1:23 AM

I am still waiting for the thrut...

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#27

Re: Electric Winch

12/15/2012 5:04 AM

In fact depending on the sliding friction coefficient the mass/weight one can pull on the ground differs from the 6500 lg. A simple computation shows that at 11° slope and with teflon pads (as usual for such operation) or on grease lubricated steel slides up to 9300 kg could be moved. This to show that mi question was not unnecessary. The friction coef. to pull with 2200 kg a mass of 6500 kg is around 0.15. No professional will let such a mass slide on non lubricated guides! This being the friction for steel on steel almost without any grease in between.

If the friction is dry steel on steel then the mass to be pulled with same 2200 kg would be 5600 kg a lot under the given value.
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