Pulling Force

Assuming all have about equal traction, pulling force would be fairly proportional to the pulling vehicle's weight. Make a guess of the ground's coefficient of friction (0 - 1 is typical) and multiply by the vehicle's weight for a pulling force. A dozer would probably be the best with the crawler tracks increasing the traction over pneumatic tires.

you can move the moon with a long enough cable and a small force if you can get a good connection point - here's why -

as to breaking - doubling the cable gets you 80,000 lbs - doubling that,

160,000 pounds, etc..

as to applied force - run the cable from a capable anchor to the truck, and push across the cable, and the trigonometric advantage will pull the truck out

- or rather, more likely pull it apart.

ratings are not very big, compared to the force needed to pull a loaded semi up yo its axles thru mud -

The tow bars on the road vehicles have ratings by class - class III and IV are as big as they get for pickups and SUVs. In low range, they can pull a lot

- but not tow it. ( I have pulled 40 foot spruce trees buried half-deep in the sand in the lake in the spring with my big jeep in low range, but I wouldn't want to have that load on the towbar at 50. Hey, it's a jeep, with a class IV bar and the vehicle is rated for class III towing) Tractors come from old Farmall utility A's to huge 4-grouped-wheel monsters used in bottomland tilling - towbar force accordingly Dozers come from cute little scoops to D-9 cats - or maybe bigger these days

- pull a wagon to cut and push tons of stuff

bottom line - a lot of range in pulling force.

As to the truck in the mud - Big truck = big forces = big problem when cable breaks = cuts the cab off the pulling vehicle like it is a can of salmon under a grizzly claw - people are less resistance - even a 5/16 cable breaking at

10,000 pounds can cut a man nearly in half.

However, it is just that the load and the mud just makes it potentially deadly dangerous - you could do it with a block and tackle if the truck could take it and you have a place to hook it. Do you sled it out on a wide 1/4 inch plate of steel with a nose curled up like a toboggan put under the axles and haul the truck and the sleds with a trace of cables? Or do you get it out of the mud and onto a temporary mat track so the wheels can roll? Depends on the place and the mud.

Some ideas and approaches - USE WITH CARE - ONE SIZE DOES NOT FIT ALL

1) So you have the capacity of the cable as a limit- whose capacity is cut in half or worse if you do not use proper shackles, thimbles, and other tackle (that keeps the bends to connect, etc., from losing more than 20% of rated strength)

2) you have the connections of the cable at the ends as a limit - the anchor point and attachment point on the truck - which goes all the way to the dirt if you are trying to pull it out with a truck. You need a big frame on the semi to pull out a loaded semi in mud - so where to connect to it...... need a place that can take the load and not destroy the frame - and that load is at the other end, too Look up tank retrievers on the net and see the arms and cables they use to pull those big 100 ton SOBs out of mud up to the top of their treads - more lift than pull.

3) you have the resistance of the mud and truck as a limit .

This one is probably the best place to save some grief - but the solution may depend on how thick the mud is, and if it flows, and if the truck is up or down, or halfway -

--------- If the truck is not upright, decide if you want to right it so it can roll out, or leave it on its side and sled it out - (hell of a sled to move a truck, BTW), or leave it and make ramp and tire-road and then right it onto the temp tire-road and pull it out

a) To stay alive, right the truck or lay it all the way down and stay it off using cables so when it moves in the goo it CANNOT - not "won't" -cannot - flip - and remember, once it starts moving to right itself, it will just keep going onto its other side unless a soft restraint is used on the rising side - like a cross-stay halfway along the stay to limit the stay rise as it moves up

- and the truck tops are pretty flimsy when talking about holding it, BTW. Anchoring the stays in mud means trenching cable-holding-timbers crossways at least twice the distance from the truck as the truck is high - both sides -- large spade-cable ground anchors, logs or 6 x 6 timbers crossways trenched in the ground, etc.

maybe you want to lay it down or keep it in place until the trenches are in place before righting it, and then right it onto the temp road. depends on the conditions, etc. b) it is easier to roll a truck than drag a truck, and it is easier to drag a truck on top of the mud rather thna thru the mud.. make a ramp for the wheels and move the mud out from under the axles or move the axles out of the mud - idea is, you want a clear run in front of the axles so they won't catch. Which first- the ramp or the axles? depends on the mud type as to which is safer to do first. Dig a ramp in front of the wheels and then line it and a path far enough to reach solid ground - (the stuff we used to use for running tires on was marsden matting - kind of a long steel plate with holes to grip the ground used for portable airstrips and roads across swamp) then clear the axles so the truck can move forward and up above the mud without draggin axles on the mud - and check the stays a lot - the anchors can slowly move in mud

- so now the truck can roll up and out so you loosen the stays so it can move a few feet but not fall over, and use the wrecker winch to draw it up - or - if this is in a swamp or the like and the ramp will fill with mud as fast as you empty it, make a long box out of plywood/timbers to sit in the ramp and hold the mud back - water is not a problem, mud is.

nuff said - good luck

Again - If the axles are in the mud, get them out of the mud - let them sit in water if need be, but not thick mud.

Rules of thumb: PTO horsepower is about 86% of engine horsepower. Drawbar horsepower is about 86% of PTO horsepower. I think this is for 2WD tractors in average conditions. One horsepower = 33,000 Ft.Lb./min

There isn't a good answer to your question without more information. How big are the tractors? 100 HP? This won't help you much since traction difference will probably be a big factor. The tractors should easily out pull the pickup and probably the semi in dirt or mud. The dozer should out pull everything on dirt. My guess is the dozer wouldn't do too well on concrete. Wheel slippage for tractors is usually in the 10% -15% range in good conditions. That's considered the most efficient for field work. You might be able to get some information on drawbar pull from the University of Nebraska Tractor Test Lab. I don't know if they have a website.

Dean

a good size track dozer and you wont even know the trailer is there. just tell the driver of the rig to leave her in neutral unless she needs a bump start as well ;-)

be careful not to peel the tires off the rim...

I do not know the answer to an equation to solve your problem.I do know my uncle owns a Year : 1985 Make : CAT Model: D6D Bulldowser. It is a big machine. Pulling a Fully Loaded Semi even stuck up to the axles is a piece of cake. I have seen him pull a Cat Backhoe out of a revine approximately 80 feet down. The Backhoe was not even upright.It dragged it up on it's side like a Tonka toy.

Doug

The usual word of caution ... my buddy thought he'd be a smart ass and took his cat into the soggy field to pull out the tractor ... you guessed it ... it sank.

With our Jeeps and 4x4's we generally figure we can pull something that is half the rated pull of the winch out of the mud.

So for my 9,000 lb winch, I can drag a 4500 lb vehicle out of the mud 'if' my vehicle is anchored because my CJ7 only weighs in at 3000 lb or so and I can drag my mud tires.

I also can use a pulley block to up my winch's pull to 18,000 lb.

HP of the engine or winch motor doesn't really come into it. The winches are rated in lb they can pull.

If you are taking just a straight strap pull, then the best traction and biggest engine wins hands down.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

g3_josh wrote:

Personally I've seen a grain wagon (unloaded) stuck so deep in mud that it took 2 large 4wd tractors, a Cat 6 wheel road grader, and a Cat Dozer (not to mention 300 ft of cable) to pull it out (5ft floatation tires and all).

Anyway, yes I realize there are many complicating variables but...

I guess I need to be a little more specific - I've been doing an independent engineering analysis of a device called the Safe-T-Pull for a company here in North Dakota. The device is essentially a 10 foot 6"X6" section of square tubing with a tounge hitch at one end and a large pin at the other. The Safe-T-Pull is sold with a large half ring hitch that is attached to the frame of your truck(custom designed for many different makes and models). Without going into too much detail, the Safe-T-Hitch is attached to the drawbar of a tractor, when a truck gets stuck the tractor is backed up to the front of the truck, the Safe-T-Pull is set in place via hydraulic cylinders from inside the tractor. The idea here is: the operator doesn't need to leave the cab of the tractor to crawl through knee high mud to hook up a chain, in fact many farmers just leave the Safe-T-Pull attached to the tractor throughout harvest. Secondly the Safe-T-Pull is much safer than cable or chain because it won't break in a violent manner (it doesn't store energy). Moving along, following my engineering analysis I found that most of the Safe-T-Pull can pull up to

100,000lbs without yielding, however a chain is only as strong as it's weakest link, the weakest link can handle perhaps 58,000 lbs pull. Somebody is going to ask me what kind of GVW (gross vehicle weight) can this device pull? And under what conditions? Any suggestions?

That was great help Dean. UNTTL has a site it's,

Josh

My 6000lb. warn winch on a single line pull can just bearly budge my

4000lb 4 runner up a slight grade buried to the frame in bog, assisting it by slowly driving the wheels and it can do it no problem. Sounds like the device he's talking about is more likely to break frames and hitches than to break itself.

I had a similar experience buried to the axles in deep, snow. 9000# winch, 4500 lb. 4Runner, straight pull did nothing except stall the winch motor, put the truck in gear and let the wheels turn and it popped out of the hole with ease.