How much winch do you need?

[winkosmosis]

The consensus seems to be that you need a winch rated between 1.5x-2.0x vehicle weight. I don't really buy it and here is my reasoning:

---I'm not sure that the experts who say "you need 1.5x vehicle weight" understand the physics
Examples
http://www.ehow.com/how-does_4926305_a-winch-work.html
http://docs.google.com/gview?a=v&q=.../whichwinch.pdf+winch+pull+rating&hl=en&gl=us

They seem to be assuming that a 5000lb winch can only pull a 5000lb vehicle on a flat surface, and that any slope or rough terrain increases the effective vehicle weight. Anyone who has ever pushed a car knows that isn't true. It doesn't take much force to roll a vehicle on flat ground, and that increases with incline, up to a max of 1.0x vehicle weight when pulling
straight upward.

OK, if the vehicle is stuck behind a big rock or something, you could need more force than the weight. But wouldn't that be enough force to break things? Hell, folks break axles by applying much less force than that. Aren't you better off trying to shift the vehicle so it's not lodged behind something?


---If the vehicle were actually hung from its winch, would the winch bumper's mounts survive? On a unibody vehicle like an XJ, I'm sure the mounts would break or bend. So why would you ever apply 1.5x that force?
The same goes for a hitch-mounted winch. A class III hitch is rated to pull a 5000lb trailer, but not pull it straight up a cliff. Also, the tongue load rating is usually something like 500lb. A 5000lb winch pulling at a slight upward or downward angle should easily exceed that.
I definitely wouldn't want someone applying that much force to my independently mounted front tow hooks.



Am I missing something?

 

[off-roader]

Am I missing something?

Yes you are. The tow/snatch points may need to be reinforced or rebuilt to handle the applied stresses of a winch under full potential load (stuck behind an obstacle) when used off road.

 

[762X39]

Check out the sites that deal with vehicle recovery (tow trucks and wreckers) for more information on why your winch needs to be rated at 1.5 times vehicle weight. If you are using a winch to recover a vehicle it means a simple push on level ground won't do it. There are rules of thumb based on what percentage of the tires are buried (in the case of mud or bog), incline etc. that all come into play.I'll try and find the reference material but a quick search should get you started.Perhaps a military recovery manual might have the info as well.

 

[Scott Brady]

Your thinking is sound, it is all about mechanical advantage, but consider these additional factors.

1. Yes, a 5,000lb winch, with enough pulley blocks could extract a fully mired Land Cruiser - But.

2. Like the vehicles we choose, we buy them based on reserve capacity. A winch should have significant reserve.

3. Terrain factors: Stiction created by mud can exponentially increase the pulling force required to extract the vehicle. Even with 8 or 9,000lb. winches, I have had to use pulley blocks, even two to free a CJ-5.

4. How big are the vehicles that travel with you?

5. Limit to the amount of line and pulley blocks you carry. A typical winch will have 80-100' of line, which with one pulley, would limit your reach to about 35-45' (given the number of wraps that must remain on the winch). Add a third block, and the amount of line available puts you in the 20-30' range.

6. A winch only develops maximum power on the bottom layer, so each layer added after that point, as you spool in reduces the available force, typically 8-15% per layer.

At the end of the day, the additional pulleys and line extensions, etc. negate the cost and weight savings advantages of a smaller winch. In addition, (as an example), you can buy a Warn M8000, which is an excellent winch, for about $500 on sale. It is fast and powerful, and with synthetic line and a delrin fairlead can weight in at about 50lbs.

I typically recommend a winch rated at 1.5x GVWR. That just seems to do the trick. . .

 

[cruiseroutfit]

...Am I missing something?

Simply put, Yes. Take a closer look at those sites you linked, no where do they say you need a 5k winch to roll a 5k vehicle on flat ground? But why consider flat ground really? Rarely will a winch need be on a level flat surface free with a free-rolling rig

Lets assume your in your 5000lb (loaded) vehicle.

Surface Resistance:
1/10 LW (500lbs) to push a free wheeling rig on a hard, level surface
1/3 LW (1700lbs) to push a free wheeling rig on soft surface, grass or gravel
(add a broken rig to either of these situation and they can easily multiply the resistance and therefor the needed winch).

Damage resistance:
2/3 LW (3400lbs) to move a vehicle if the wheels cannot rotate (bound up axles, brakes, etc.)

Lets look at more common winch needs:

Stuck in mud:
Wheel Depth Mire (up to wheel hubs) = Resistance is the LW (5000 lbs)
Fender Depth Mire (top of wheels) = Resistance is 2x LW (10000 lbs)
Cab Depth Mire (over the fenders) = Resistance is 3x LW (15000 lbs)

And the above figures can increase (or decrease) based on the slope your working with:

Working with slopes:

Uphill Winch Pull (pulling up slope)
15 degrees - add 25% LW (add 1250 lbs)
30 degrees - add 50% LW (add 2500 lbs)
45 degrees - add 75% LW (add 3750 lbs)

Downhill Winch Pull (pulling down slope)
15 degrees - subtract 25% LW (minus 1250 lbs)
30 degrees - subtract 50% LW (minus 2500 lbs)
45 degrees - subtract 75% LW (minus 3750 lbs)

So lets say your 5000lb (LW) vehicle is stuck up to the top of its wheels and getting deeper as you continue to try and work it free. The nearest winch anchor is just over a 30* angle a above you. Your calculated load could easily exceed 12,500lbs. Far more than a 5k winch can even do single snatch blocked. Now remember that a winch is only capable of their rated capacity on their first layer of wrap, that which each additional layer they lose capacity. So unless you want to be re-rigging constantly to keep your winch in its optimal range (this goes for needing a snatchblock too), it makes sense to select a winch that will be capable of handling these loads. Sure you could use a complicated system of multiple snatchblocks. But the added cost of blocks and extension straps in conjunction with the limited range you would end up with (a 125' cable is good for lets figure 100' on a single line pull, yet only 50' with a snatch, start adding additional blocks and you'll end up with just a vehicles length of range each rigging). There will always be compromises, due to size, weight and mounting you can't fit the biggest winch on every rig, but I would do my best to fit the biggest I can

As far as trusting your tow hooks or unibody. Well, I'm not going to comment on trusting the setups of other vehicles, but I would have zero problems winching as needed with my vehicle setups including recovery points and frame strengths. Equipping a vehicle for recovery and winching operations doesn't stop at bolting a winch on to a bumper

Hope that helps?

 

[winkosmosis]

These explanations and breakdowns make sense, thanks. So if you're going to be winching with that much force I guess you need to be sure the vehicle can handle it, or not get into those situations

 

[ryguy]

Drag(including obstacles and terrain) as well as recovery angles play signifigant roles in calculating total resistance in terms of weight. Because no recovery is ideal, any outside resistance are important calculating factors when determining which winch can recover your vehicle. cruiseroutfit's answer is spot on and 1.5x-2x curb weight is a safe calculation.

 

[petrolhog]

Here is another great info from Pirate 4X4:

http://www.pirate4x4.com/tech/billavista/Recovery/index.html

I have a Landcruiser 80 series with a warn 15k. I guess you never have too much of a winch power........Just good to know that you have a winch to pull your rig out of troubled situation.

 

[cruiseroutfit]

Here is another great info from Pirate 4X4:

http://www.pirate4x4.com/tech/billavista/Recovery/index.html

Bill did a great job on that writeup and it has served as a reference for many including myself. I'll also add that there are US military vehicle recovery and rigging handbooks that are extremely thorough on these subject.

 

[92 red cummins]

I could see your point if you only do light wheeling. I only have a 5000 lb winch on my diesel truck but I carry a snatch block. also I don't try to get stuck and its mainly on there because it was free! (Is 10,000lb enough for A 92 dodge diesel not stuck too bad?)

 

[Fireman78]

I have a 12,000 pound winch for my 7000 pound vehicle. I would not go any smaller. When you add factors like snow, slopes, mud, crappy angles, sand, towing trailers, equipment, ect. ect., you need more winch.

 

[michaelgroves]

For smaller vehicles (with an all-up weight of up to 4 tons, say), it makes sense to go with a winch that is at least 1.5x the weight. There's only a small cost and weight penalty, and as Scott says, you'd need to carry a lot more rigging if you go smaller, which offsets the weight and the cost.

With bigger trucks, I believe the balance starts shifting towards a proportionally smaller winch. If you have a truck with an all-up weight of 7.5 tons, you'd supposedly need at least a 12 ton (25000lb) winch. That would cost BIG money, and weigh an awful lot. And cable to match. And then you'd need to find an anchor capable of holding 12 tons.

To me, it then makes sense to use a smaller winch, say a 12,000lb hydraulic, and carry lots of ropes, snatchblocks, shackles etc. Some of the kit would potentially have to be able to cope with the 10- or 20-ton loads, but most of it wouldn't.

 

[SunTzuNephew]

The type of ground you're stuck in can apply a bunch of suction, which effectively adds to your GVWR.

 

[dzzz]

For smaller vehicles (with an all-up weight of up to 4 tons, say), it makes sense to go with a winch that is at least 1.5x the weight. There's only a small cost and weight penalty, and as Scott says, you'd need to carry a lot more rigging if you go smaller, which offsets the weight and the cost.

With bigger trucks, I believe the balance starts shifting towards a proportionally smaller winch.........................

I found Michael's explanation above very true as I work thru recovery equipment for a 25K lb truck. The first winch I've purchased is a 20,000lb hydraulic. That only gives me a .8x weight factor. But as suggested I'm only putting 100' of line on the drum (I could do 150'). That gives me a winching range of 15,000 to 20,000 lbs. I expect my high flow 300lb industrial hydraulic winch has considerably more useful power than a 18K electric winch. Also, by using extensions and a snatch block I have a working range of 30-40K lbs.

I don't think I want to apply more force than that. At a point a shovel, maybe an airbag, blocking and cribbing become a safer approach compared to enormous horizontal forces.

With a 20,000lb winch the snatch block and tree saver become expensive. I'm ordering a 15 ton working rating snatch block (it really should be 20 ton). A lot of off-road gear is rated at estimated breaking strength, which is probably 3x conservative working rating.

Most winching "rules" come from wheelin'. I'm expeditionin'. As Michael points out when the numbers are run for bigger trucks the approach and equipment changes. Being able to quickly pop out a big truck mired to the axle is not a realistic expectation. Even if I purchased a 50 ton winch with 1" Amsteel Blue rope I'm not sure where I could anchor the pull. 100 ton snatch blocks exist, but require a crane to place.

 

[sjk99]

An oldie but a goodie:

FM 20-22 Vehicle Recovery Operations
http://www.archive.org/details/Fm20-22VehicleRecoveryOperations

To download the pdf I had to select the "all files" link and then right click on the pdf file & save as. Could just be the way my 'puter is configured.