Towing Safety (Please Read)

[rmgill]

The crossing doesn't weaken the chain. Tighter angles increases the force depending on what the vectors of that force are.

TAke a rope, spread it across a wide angle, pull down in the middle. the forces pulling inwards are FAR higher than the force pulling down. It's a sort of leverage. Rock/Mountainclimbing rigging manuals warn against this as a method.

Now, crossing chains up between sides of a vehicle CAN be just fine. It just depends on which way the force vectors are when the load tries to keep moving after the truck has stopped.

 

[kendelrio]

Safety towing

The crossing doesn't weaken the chain. Tighter angles increases the force depending on what the vectors of that force are.

Sorry, but that is incorrect.

As a rigging supervisor and certified rigging inspector, I feel I have the knowledge to at least point ya'll in the right direction.

While "Catching the bar" is a good reason, that is not the purpose of the chains. The purpose of the chains is to ensure the towed vehicle does not break loose from the towing vehicle. If your tow bar should break/become disconnected for any reason, without chains, the towed vehicle is now a rolling missle. The chains provide some degree of control over said vehicle until it can be safely stopped.

Now the rigging part.

The highest rated lifting angle on rigging (whether it be wire sling, nylon strap or chain) is 90 degrees. Lowering the angle lowers your capacity. If your tow bar should break, you will have "shock load" on your chains. This is a directional pull much greater than the weight being lifted (or towed). If rigging is in a less than optimal configuration, your rigging will fail. Take for instace heavy lift crane operations. Often times you will see a "spreader bar" in use. This is used to reduce the angle of the rigging above the load in order to ensure angles as close to 90 as possible.

Crossing your chains reduces the capacity of your chains. It's simple physics (if there is such a thing).

Here is a quote from "Hoisting and Rigging safety":

Number of Legs and Angle with the Horizontal – The smaller the angle between the sling legs and the horizontal, the greater the stress on the individual sling legs. This increased stress effectively decreases the weight that can be safely lifted with any given sling size. Large (heavy) loads can be safely moved by keeping this angle as large as possible and, when necessary, distributing the weight of the load among more sling legs.


I can send you the actual numbers (angle of rigging=loss of capacity) if any of you like. Feel free to PM me.

 

[beaubeau]

I was taught the main reason for Cross Chains is to keep the Lost Vehicle,{ whether it's a Trl, or a Towed vehicle with Tow bar, or Wrecker,} in behind the Tow vehicle. Cross Chains will pull towed vehicle into Center of other vehicle and prevent it fomm Straying to the sides. It is also the Law to have 2 individual Safety chains, and Chain binders Must be tied off with Wire when traveling across State lines. The size of a Safety chains was never mentioned. I have seen Safety chains on towed from Kids Swing Set used as Safety chains!!?? This is a good topic to spread around. Good luck all, Phil

 

[kendelrio]

I was taught the main reason for Cross Chains is to keep the Lost Vehicle,{ whether it's a Trl, or a Towed vehicle with Tow bar, or Wrecker,} in behind the Tow vehicle. Cross Chains will pull towed vehicle into Center of other vehicle and prevent it fomm Straying to the sides.

I can see the logic in that.......
I guess the main difference is the end use of the chains. Are they being used to secure (or lift) or used as a control device? If securing a load I would go with the method I mentioned. I would still use straight chains for pulling though, because if your tow bar breaks, you are in a world of trouble anyhow and I would want maximum rating on my rigging.

 

[davidkroberts]

Tennessee DOT regs require the chains to be crossed but they also think floating the gears is unsafe so who knows. Ive done it both ways and never had a problem.

 

[rmgill]

Re: Safety towing

The crossing doesn't weaken the chain. Tighter angles increases the force depending on what the vectors of that force are.

Sorry, but that is incorrect.

I was being specific on the physics. With a good attachment point and good chains, the same load suspended perpendicularly will exert MORE force on two chains strung between the load to the side (ie a very tight angle between the support point and the load vector).

Practically, the load you can support with the chains is reduced, but so are the attachment points on the support point. I was just trying to be specific over the difference of wrapping a chain or a rope over a corner or a rope with a knot because the knot itself or sharp redirect weakens the chain or rope itself.

I do agree however that a big vector angle IS going to have a larger pull.

 

[MilitaryRestoration]

RE: Re: Safety towing

beaubeau - well put...thats how i have always been taught and trained... crossing keeps load to center regardless if you lose on the other should not ever pull it off what it is sitting on...

 

[clinto]

Thanks for the tips. Here is a picture of how I do it. Any suggestions for improvement appreciated.

How long is that chain? From hoop to hoop?

Thanks

C

 

[Jones]

All good advice.
But I'm still waiting for the attachment to open... after 5 minutes I'm still just seeing the clock icon.

 

[Keith_J]

Crossed chains in pairs provide resistance to lateral loads in addition to the primary. And always under the tow bar. Towing without is asking for trouble as the bar always breaks at the pintle eye. Then it wants to function as a pole vaulter's pole, usually taking out the frame rails. Seen it, back in the 1980s, chains were hardly used. Remember, regulations in the military are usually written in blood.

 

[BEASTMASTER]

it is a dot regulation that the chains be crossed. ask any dot cop.

 

[dmetalmiki]

All interesting stuff ..I have the chains straight, one each side wrapped round each leg of the tow bar secured individually at each end to the towed vehicle and to the wrecker. both air lines service and emg. connected. I will post pics at next outing. P,S. even the M.B. jeep has individual straight chains safety chains on its towbar secured at chassis /srings and rear of towed load. (yep..train.)

 

[nhdiesel]

For towing, chains crossed is the way to go (and law, as Beaubeau and others have said). However, a load on a trailer the chains should be uncrossed, and pulling towards each corner a bit. Pulling towards the corners keeps the load from moving laterally, the same way you run the chains out to the front and rear to stabilize forward/back movement.

With crossed chains, 2 things are working against you- the strength of the chains is reduced, the amount depends on the angle they are at; but what I haven't seen mentioned yet, is the stability of the load. If the load is free floating, such as hauling a vehicle with suspension, crossed chains allow a pivot point where the chains cross that allows the load to float more. A car or truck can actually lean in corners from the pull of the opposing chains.

Funny thing is, I have seen articles in magazines (usually 4x4/Jeep mags) showing the "proper" way to secure a vehicle, and they usually show crossed chains. Then again, the articles are usually full of other misinformation as well.

Jim

 

[duncan]

When I went to pick up my truck, I went to a local hauling company that moves a lot of agricultural equipment. Had them explain me how to tie down a moving load this size... they said crossed chains, even though the vehicles will float on its suspension... so thats what I did.

 

[196thprober]

A great thread! Thanks for all the information and discussion.

 

[nhdiesel]

I just typed up a nice explanation of chain attachment, and the damn browser froze and lost it all. Anyway...

One thing I haven't seen mentioned is proper chain attachment. Most amateurs, and many pros, attach the chains wrong. You ALWAYS want the open end of the chain DOWN so the hook won't come detached if you get slack in the chain. For the load, this is usually easy, the chain naturally wants to be that way. But on the trailer end, you have to position the hook so you get it right. Here are a few pics I just ran out and snapped:

CORRECT:


If you get slack its still hooked:


Another proper attachment:


INCORRECT:


If you get slack:


And another good idea is to double check the weld job of the tie points on your trailer, even if its a genuine store-bought, professionally-built trailer. This is what happened to one of my tie points:



And thats a prime example of why you ALWAYS use more than one tie at each end of the load, and ALWAYS use separate chains (or a long chain attached in a way that both ties won't get slack if one end comes unhooked)

Jim

 

[SMOKEWAGON66]

I see so many different opinions on crossing chains, DOT laws etc....just for the fun of it, i go by what i was taught. Crossed safety chains is a must, i dont always cross load chains, but that depends on the type of load, the weight of the load, and where im able to latch onto it. I play by ear on that one. And if im ever in doubt, i consult my " Tie Down procedures manual" specifically for trucks..has all the answers...usually lol. When i was a young soldier, I was told by a very experienced and very knowledgeable driver "when in doubt...use more chains and binders" always makes me laugha little.

 

[Castle Bravo]

Amusingly enough, here is another crossed chains opinion -

I was always told that the reason for crossing towing chains is so the "outside" one gets longer during a turn rather than shorter.

 

[Tlauden]

Wow lots of good info in this thread, glad it resurfaced! I never crossed chains on a load. Always cross them pulling a trailer. That's the way I was told. Seems like 4 chains would end the debate though on a tow bar issue, cross two, and have two not crossed, best of both worlds right? In the event of a detach the parallel ones would be better for the shock the chains will have while the crossed ones will keep the truck somewhat centered behind the pulling vehicle

 

[steve6x6x6]

In your pic this is not DOT compliant, the new laws require all connections must be inside a rail, protected. When out of control the trailer swips a large pole it will rake all these chain connections off.