I'm not arguing that point. When used properly, yes, I agree 100% that there should be no shock load applied to a chain. However, if you cannot use the vehicle's momentum to generate the force, you're limited to what the vehicle can put to the ground through the tires. If you bury an F-150 in soft, loose sand right down to the frame rails, no other F-150 shod with street tires will be able to pull it out of those holes without a tug. It's not possible for the tires to generate enough force to drag the vehicle, but that type of recovery hardly merits a dozer to pull you out.

I'm talking about force and energy, not strictly force. 50,000 lbs is 50,000 lbs of force regardless. However, take a 7000 lb truck, and get it moving at any speed, and now we're talking about energy. The stretch of the strap occurs over a certain time period. The stretching of the strap is disippating that energy the moving of the truck generated, however it's still converting that energy back into force at the other end of the strap. My point is that some materials, like shackles and tow hooks, can sustain the greater forces when those forces are applied to them more slowly (or in other words, applied over a longer time period). The increased distance has nothing to do with the force applied to the vehicle. I can apply the same force with a 4 foot chain as I can with a 30 foot chain or a 50 foot strap if I pull slowly. However, if I tug on it, the force spikes much more rapidly (and much more uncontrollably) on a chain than it does on a strap.

Look at it another way. Take the slack out of a chain and gas-it to pull on a stuck vehicle. Whether you use chain, cable, barge rope, or strap, you're only going to apply as much force as your tires can generate traction. Now, tug on that same stuck vehicle. Your end force on a chain spikes much more rapidly than it does with a strap. The force on a strap spikes much more slowly (relatively speaking) as the strap stretches, absorbing and dissipating that kinetic energy generated by the momentum of the vehicle. It's that momentum that allows you to generate a higher pulling force.


Agreed 100%. As I said, you cannot shock-load a chain. It's easy to exceed the chain's capacity with the slightest tug. If you have to tug on a vehicle, recovery straps (not hoisting straps) are designed to absorb that energy and reduce the shock-load.

Think graphically. Say a strap and a chain are going to both break at 50,000 lbs. The chain will stretch .5 inches before it breaks, but the strap will stretch 5 feet before it snaps. Get the truck moving at 5mph. Which medium (chain or strap) is going to reach the force peak of 50,000 lbs sooner? Sure, at their stretch limits they're both putting 50,000 lbs of force on the vehicles, but one has applied that force over a much longer time, reducing the shock load on the equipment.

I almost think we're saying the same thing....

 

chester,

From your SIG, I assume you are in the same line of work as my father (heavy equipment operator, truck driver, diesel repair). He thinks of everything in these terms, and has also told me (back in my off-road mudding days) that chains are the best tool for getting a truck unstuck. BUT, he knows I know how to use a chain! MOST PLP DO NOT. While a chain may be the strongest "device", what happens when a chain or a link is 'kinked'? The only chain I have ever seen fail, occured during one such "mudding" excursion. I assure it was a hardened steel chain (having grown up having to lug huge lengths around flatbed to lock down equipment) however, they had a hook locked into the inside of a link, and there was some twist in the setup once it drew taught (me taking cover behind another truck, there were drunken idioits everywhere).(proper method is capture both spans of a link, no twist)

I would say, tow straps are the safest method, only because they are more forgiving for an average drunken fool in the mud to get a vehicle out of the hole...

 

I disagree with that, too. Using techniques explained in detail in the Army FM for wheeled vehicle operators & the one for field-expedient vehicle recovery, it's possible to apply more force to a stuck vehicle than the recovery vehicle's traction, withOUT using a winch or pulley. And more importantly: it's possible to direct even a small recovery vehicle's force in a specific way to extract a larger vehicle. Given the proper rigging, it's even safe to ****** with chain, but ONLY if you know exactly what you're doing.

That's not the "increased distance" I was talking about. I mean the distance "added" by the stretch of the strap. The distance over which the recovery vehicle's momentum/inertia/impact is converted to force/energy at the stuck vehicle.

 

You have my attention. Please elaborate.

Again, please enlighten us.

I think I was trying to describe the same thing... I just wasn't as eloquent about it....

 

I didn't, intentionally. I don't want to do a half-@$$3D job of it & get someone hurt. If you don't know how, DON'T TRY IT. Call a professional recovery service & pay them whatever they charge. If you want to know how, take the time to read those manuals a FEW times. You can find them through Al's BroncoLinks, or Google. Then practice with light loads, & work your way up to an F350 buried to the frame.

But I'm not saying that using a light vehicle for recovery or snatching with chain is the BEST way - I'm just saying it CAN be done safely & effectively. It's always the last resort (even for someone who knows how), so you'll probably never need to do it anyway. A $30 come-along will do a lot more than most people think, if it's used right.

 

I didn't see anything there... I think I missed the page you're referring to... Where do I go from that link?

Edit: I found the one field manual, but nowhere in there does it explain what you described. It focuses on winch recovery, as well as alternative recoveries, but makes no mention of pulling a large vehicle out with a stuck vehicle at all. Winching is an entirely different art form, and that section of the manual explains only the most basic techniques.

I want to see the part where they explain how to apply more force to a stuck vehicle than the recovery vehicle's traction alone can provide without using a winch or pulley.

 

The field-expedient recovery techniques are explained in detail; the physics behind them aren't. But using the log A-frame or the rim rope winch, you can apply more force than the recovery vehicle's traction due to the mechanical advantage of the lever, or the rim's smaller diameter than the tire.

 

Regardless of what you use, if you're pulling some douche out in a Dodge with a **** on Ford sticker on his back window make him peel it off and wad it up before you pull him out. That's what I did down here on McFaddin beach, it was worth more than $100 to see the look on his face when I told him I wouldn't help him until he took that sticker off, with the tide lapping at his sidewalls. I agree with the steady pressure posts regardless of what Item is used, snatching is for drunk rednecks. Also Chevrolet tow hooks will kill you, stay away.

 

OK, yeah, I understand what you're saying... Using those materials as a fulcrum, but in doing so, that force is no longer directed forwards, it's redirected upwards at an angle. Your forward-pulling component of the tension force on the chain may actually be reduced, depending on the relative lengths of the two legs of the chain, the angle upward the two are pulling, and the location of the fulcrum. *technically* you are correct.

However, even with that type of setup, your maximum forward-pulling force is NOT increased. If you draw the system as a free body diagram, your forward-pulling vector cannot, under any circumstances, be any greater than the tractive force the vehicle can apply to it. It can only be less. If I get time later, I'll draw up a sketch and show the equations that govern those forces.

Also, all those techniques use chain to attach the winch cable to a solid anchor point on the vehicle. As I've already stated, you don't tug on a chain. EVER.

Furthermore, even in the a-frame case, you still cannot tug the stuck vehicle with that setup. It simply uses the a-frame to redirect the force of the WINCH cable upwards instead of forwards. Doing so can help lift the rig out of a hole or ditch when pulling forward gets you nowhere.

Motivating military 5-ton that's stuck in a big hole requires a whole different set of hardware and techniques than recovering a 5500lb pickup stuck in a snowdrift. It's like the difference between hoisting an engine out of a car with a chainfall and hoisting a progressive die out of a stamping press with a gantry crane..... Even though the concept is similar and the same principles apply, it's not at all the same job..

 

...except when you use the recovery vehicle's momentum in addition to its traction, or when you anchor the recovery vehicle, or when you increase the recovery vehicle's normal traction by adding sand/gravel/tire chains...As I've already stated, I do. SOMETIMES.Yes, you can, and I have. With that setup, it's possible to jerk without applying a significant impact to the chain because the stuck vehicle can rise off its own suspension, just like a ****** strap loading up.Of course not, but we're just talking principles here.

 

I agree that they are MUCH more forgiving than chains, but that's what makes them dangerous.... A pickup CAN produce enough momentum to break a ****** strap. That's why you should use a big chain. You CANNOT ****** a big chain. If you do, it will tear your reciever hitch off or twist the frame. But it won't break the chain, and THAT'S what hurts people.

When a ****** rope comes loose, or breaks, it's bad. When a chain comes loose, it just falls and hits the ground. If you rip your reciever hitch off, with a chain, oh well. Shouldn't have been jerking. But think what would have happened if it had a ****** rope hooked to it. It would have launched the hitch 200mph.

Use a STRONG chain and NEVER ******. That's the safest way. If you can't pull somebody out without snatching, then you MUST go get a bigger vehicle. Please.

 

...or a winch, or a come-along, or throw some sand/gravel under the tires, or jack up the stuck vehicle & fill in the holes under it, or build an A-frame out of logs, or use a log as a lifting lever, or...

 

You know, I've been reading this thread and I gotta say, there's a lot of bad information here.

There is a lot of reasons PROFESSIONAL wheelers use straps instead of chains. Weight is one, you can get a strap that is as strong as a chain with about 10% of the weight. Mechanical advantage of a strap is the major reason. I have safely snatched semis with a full size pick up - it depends on the stuck.

Here's the key - most trucks are not properly set up for any type of pull, never mind a ******. For a ******, minimum 2 grade 8 bolts. Welds can and do break, bolts will typically elongate and rarely break 2 at once. You need equipment rated for the job. I use a 4" strap in the Jeep and 6" in any full size - why? I've seen 2 and 3" straps snap. Use equipment that is in good condition - frayed straps can and will break.

Few if any off roaders carry the equipment they need to use chains for recovery. Typically, they buy chain because it is cheap. Recommending chain to the average joe is dangerous, he can't tell good chain from bad at a glance. At least with a strap average joe stands a pretty good chance of being safe.

I think GIJoeCam did a great job of explaining the physics of recovery using both. He has obviously done his share of wheeling where big equipment recoverys are almost impossible - or ridiculously expensive. When $200 of recovery equipment (strap and hardware) has almost never let me down I paid the extra $1000 for a winch (wanna start talking about dangers?). I've been stuck in places where heavy equipment would have wanted that much just to get to me.

All that said, education is still the key! Learn to use all types of recovery equipment in safe manners. That way you can be safe no matter what needs to be done.

 

You said it! I have some 1/4-20 Gr.8 bolts here. Can I ****** my 3-ton Bronco if I use both of them to attach a 6" strap to another fullsize truck?

 

I'd recommend 3/8's. And just remember, your connection is only as strong as your weakest link. If you use a POS strap and it snaps while connected to a chain, your chain will be on it's way as well. Which happened to me while pulling out a buddy's stuck Blazer, he was on his frame. I have this on video and will be putting it in my next video, it's wicked. Broke the back window (vertical power sliding), damaged the hell out of the tailgate and nearly hit the passenger up front.