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Winch Capacity v Snatch Block Capicity

23K views 38 replies 15 participants last post by  ChuckTheRipper 
#1 · (Edited)
I have it on good authority that winch capacity should be 1.5 times the Jeep GVW. Getting mixed info on snatch block rating/capacity. On the one hand it should equal the winch capacity and on the other hand it should be at least twice the winch capacity, so a 9000 lb winch would require an 18000 lb snatch block. Or are both rules of thumb wrong?

What is the proper rule of thumb?

P.S. Yes, I can't spell capacity twice in the heading
 
#2 ·
The proper "Rule of thumb" is that you can beat your wife with a stick no bigger around than your thumb. As for the Winch/snatch block stuff, I'll let other fellas answer that...
 
#3 ·
Sorry, I'm a smart-ass. From all I've read and the times I've used winch/snatch block, from what I understand, you basically double the pulling power of your winch with snatch block, so, you will need to make sure the snatch block can handle double the pulling power of the rope/cable on the winch. Also, you have to make sure the rope/cable on the winch can handle twice the pulling power of your winch, as well. If you have a 8000# winch, you will want a 16,000# snatch block, and the rope/cable should be rated to handle the same, if not a little more, to err on the side of caution. If I'm mistaken, I'm sure these fine folks will set us both straight! :)
 
#4 ·
Oh lord. Your answer makes more questions. Going to listen for a while though. All smart ass, dumb ass, and no ass comments welcome.
 
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#5 ·
So what snatch block or D-ring should a person buy? I have no problem buying one that is 2x the rating but I want a good quality. I have seen cables break and couldn't imagine a snatch block letting go.
 
#6 ·
Good question. Some snatch blocks described for wire ropes, others for wire or synthetic. So will synthetic of same diameter as wire still work with the blocks that say wire and don't reference synthetic?
 
#7 ·
To throw some more mud in the water:
I was always taught the sheave diameter for hoisting rope was 30 times the rope dia., but I took a 32 hour rigging basics course last year where the test answer was 20 times rope dia....but one might have been for a block and the other for the main sheave.
This is because the rope turning too tight can fatigue the line.
 
#8 ·
coilrod, where can I sign up for your Physics Class?
 
#9 ·
Dave Logan, where are you?
 
#11 ·
It depends.

Think how you want to use a winch.

A guy who is planning on pulling a jeep buried to the axles will want a different setup than a guy who needs a winch to bump him over an obstacle.

For example, I run a relatively low capacity Warn winch with only 80' of synthetic rope. We have trees or hard points every few feet here Oregon. The shorter rope allows me to not be super careful on rewind so the rope doesn't get into the drum supports. The shorter rope also gets me down to the lower wraps where there winch can pull more.

I wanted the 156:1 ratio for the high line speed. It helps prevent overrunning the rope and rewinds fast. Smaller winch is also lighter. Didn't need a big heavy brick way out front and high.

My Jeep and offroad style doesn't require any huge pulls. Just a little help to assist through the occasional low traction obstacle. I have never needed a snatch block.

So think about how you will be using your winch and go from there.

:)
 
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#16 ·
It depends.

For example, I run a relatively low capacity Warn winch with only 80' of synthetic rope. We have trees or hard points every few feet here Oregon. The shorter rope allows me to not be super careful on rewind so the rope doesn't get into the drum supports. The shorter rope also gets me down to the lower wraps where there winch can pull more. :)
Interesting. For similar reasons I chose a Warn 9.0RC winch recommended by a friend. 216:1, 54 lbs and 50 ft of rope. It's my first winch. Remains to be seen if the choice proves itself in the field. Given past experience I'm good with it.
 
#12 · (Edited)
I've been told the Snatch block should be rated for winch capacity not the doubling factor. i.e. 12K winch 12K pulley... But thats not what it looks like here.. I go see what i can dig up
 

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#18 ·
Yep! Your diagram poses more questions to me than it answers. Truly murky ground we walk.
 
#13 ·
Heres a good read from Pirate.. Pirate4x4.Com - Extreme Four Wheel Drive

An interesting paragraph from this article:

Calculating the force of a recovery operation:

This is a critical step in both the conduct of a winch recovery (because you need to be absolutely sure that EVERY single piece of equipment used in the task is strong enough and will not fail and thereby endanger life and limb), and in the selection/purchase and decision to use a piece of recovery equipment. It is a calculation where, quite frankly, the manufacturer's recommendations are woefully inadequate. Why? Simply because if they let you in on how large the forces really are, it would leave you realizing that they are unable to economically produce a winch of sufficient capacity in anything resembling a small, light, or economical enough package. They get away with it, because, as I said, there are virtually no regulations or standards governing the industry. I'm not saying all 4x4 winches are inadequate, dangerous, or useless. But I am saying that the forces involved are often much greater than the manufacturer's would have you believe, and you will be far more capable and SAFER if you approach your 4x4 recovery KNOWING THIS, and knowing the real numbers. Realize, that for reasons of practicality and economics, your 4x4 recovery equipment is almost certainly undersized.....you can still do the job, using the correct techniques, but you will be much SAFER if you keep this in mind. Enough of the pre-amble.

Most, if not all, winch manufacturers will tell you to select a winch based on 1.5 times the gross vehicle weight. This often leads to less than satisfactory results for 2 reasons:

1) Most people are terrible at actually estimating the gross weight of their rig as it sits on the trail, full of gas, tools, equipment, food, camping gear, people, the dog...everything. Heck, in some cases the real figure can actually exceed the GVWR of the vehicle. Simple advice here - either err WAY on the heavy side, or get your rig weighed in trail trim.

2) More importantly, the "effective weight" of a "stuck" 4x4 is very often FAR more than 1.5 times the GVW. The following data on how to more accurately estimate the "effective weight", is taken from the world of professional heavy recovery - the guys that recover Tractor-trailers that have flipped on their side for instance, as well as U.S., Canadian, and UK Military recovery manuals.
 
#14 ·
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#17 ·
Thanks. This is the first set of blocks I've found that clearly states which one should be used for stated winch capacities..........and that either wire or synthetic is okay. Given the other responses to my question, the overall reasoning to arrive at rated capacity of Winch v Snatch Block remains cloudy. Warn's statement is clear and I assume can be trusted?
 
#15 · (Edited)
Double post.
 
#19 · (Edited)
i don't feel like nor have tons of time to invest in thinking about it so I went & bought a couple of these ( before they redid the website but same product ) back when they were $20 and have carried them with my recovery kit every since. I use them occasionally but mostly to recover others. One of those affixed to a tree allowed my RR 10.5k to deadpull a XJ full of water out of a 9' deep hole so I think they are more than ample. I also have triple shackled a 110' poplar tree off a trail with them . :jeep2:
 
#28 · (Edited)
According to a recover tech who lives by this stuff the diagram is correct. Makes sense to me that each line is 9000# with a 9000# winch.. If you have clearer info then this please share.. I'm not too concerned about winch strength as I chose to go 12K winch and Warn Epic hook and Snatch blocks but should I have one heavier Snatchblock incase I need a third as in the diagram..?
 
#22 ·
I'm diggin' the thinkin' on a short line for trail use. Makes sense all around.

I currently run a Warn 8s with their 12K Epic snatch block and full length of line to facilitate use on numerous stumps I've been pullin'.
The bumper failed...

When I finish the job, there may be a shorter length of line left as the Jeep goes from work mode to play mode. Prolly get another snatch block, tree strap and shackle for off-line pulls on the trail, too. However, as I see the possibility to make road recoveries in snow conditions, the full length can stay as long as it's serviceable.
 
#23 ·
I don't want to subvert the thread subject, but the guy that recommended the short line winch said to add a recovery strap to the line if necessary, although he had never had to do so. Looks like I will be going to the Warn 12K also.
 
#24 ·
The snatch block should have at least double the capacity of the winch because they can be used for double lining.
Double lining is a technique where you run the winch line from the winch through a snatch block and back to the Jeep's tow point.
This technique doubles the pulling power of the winch and halves the winch line speed.
If a Jeep is heavily mired in mud or is off the trail and needs to be pulled uphill, double lining works well.
 
#26 · (Edited)
A quote from that page... but remember, you can't just grab anything before knowing how much you need as far as capacity. There must be like 10 pages or more worth of stuff on that page.

Pirate4x4.Com - Extreme Four Wheel Drive




1) Most people are terrible at actually estimating the gross weight of their rig as it sits on the trail, full of gas, tools, equipment, food, camping gear, people, the dog...everything. Heck, in some cases the real figure can actually exceed the GVWR of the vehicle. Simple advice here - either err WAY on the heavy side, or get your rig weighed in trail trim.

2) More importantly, the "effective weight" of a "stuck" 4x4 is very often FAR more than 1.5 times the GVW. The following data on how to more accurately estimate the "effective weight", is taken from the world of professional heavy recovery - the guys that recover Tractor-trailers that have flipped on their side for instance, as well as U.S., Canadian, and UK Military recovery manuals.

Once you have accurately estimated or measured the trucks loaded weight (LW) you can calculate the resistance to be overcome in any recovery situation (this is commonly known as the ROLLING resistance). There are 4 types of resistance that must be accounted for to accurately assess the resistance that must be overcome. These are surface resistance, damage resistance, mire (stuck) resistance and grade (slope) resistance. Calculate them all as follows:

Surface resistance

A pull of 1/10 LW will cause a free wheeling truck to move on a hard, level surface.

A pull of 1/3 LW will cause a free wheeling truck to move on a softer surface, such as grass or gravel,

Damage resistance:

A pull of 2/3 LW will be required to move if the wheels cannot rotate (as if the brakes were fully applied), the pull required to overcome the resistance (drag) the truck id 2/3 or 67% of the LW. Damage resistance includes surface resistance (i.e. you only use one or the other)

Stuck (mire) resistance:

A pull of 100% of LW will be required if the truck is stuck to a depth of the sidewall on the tires.

A pull of 200% of LW will be required if the truck is stuck to the hubs.

A pull of 300% of LW will be required if the truck is stuck to the frame..

Mire resistance includes damage resistance (i.e. you only use one or the other)

Grade (slope) resistance:

Upgrade (vehicle has to be recovered up a slope or grade)

15 degrees - add 25% of LW

30 degrees - add 50% of LW

45 degrees - add 75% of LW

Vehicle recovery on level ground - no correction

Downgrade (vehicle has to be recovered down a slope or grade)

15 degrees - subtract 25% of LW

30 degrees - subtract 50% of LW

45 degrees - subtract 75% of LW
 
#27 ·
The above is 100% true.

That said, it is relatively rare to have to deal with a vehicle that is unable to help in its own recovery to some extent. this greatly lessens the LW (from above) greatly.

More winch capacity equals more weight on your vehicle and (generally) slower line speed.

As with everything, its all about tradeoffs and balance.

:)
 
#29 ·
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#30 ·
Fabulous contribution. May not solve the mystery, but it does present the many variables that have to be considered, and in clear language and illustrations. FYI, I chose the ARB block rated close to 20,000 lbs. primarily because I felt, based on comments here, I wanted plenty of excess capacity. The deciding factor was it weights 5.3 lbs v the Warn Epic block 18,000 capacity which weighs in at over 16 lbs.
 
#31 ·
The Epic Snatchblock is rated by winch size rather then total capacity so if the mid size Epic is rated for the 12k winch it's total capacity would be at least 24k. I will contact Warn for clarification.


Jeff
 
#32 ·
Nice catch. I remember that now. This would explain the robust difference in size and weight, but muddles capacity ratings across brands. Their 12K would have to be 24K for a two line pull and 36K for a three line, as I understand things. So we are left with conjecture at this point.:wink2: Look forward to your findings.
 
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