Chain and strap working/ load limits

[Foxx]

After buying a couple of new ratchet straps today, I have a technical question for y'all. When I have to haul forklifts at work, we just chain them to the truck with Grade 70 chains or secure them with 2" ratchet straps and go. But after looking at the weight limits/ working limits on my new straps, I wondered how the math works out on this.

I plan on hauling my OBS truck about 200 miles soon. I'll estimate the truck weighs 7500 pounds. I have some 2" ratchet straps with a working load limit of 3,325 pounds and a breaking limit of 10K. If I were to put one strap on each corner of the truck, would the weight of the truck be evenly split between all four straps, making the load on each strap 1875 pounds, thus within the safe working load? I looked, just for kicks, and cant even find any straps with a high enough working load limit to hold down 7500 pounds. I believe a 4" is only rated for about 5,000 pounds.

So am I right on my math, or is there more to this?

[NateHolmes]

Yes you would split the weight of the truck between the four straps if you did it that way. Obviously the weight distribution would not be equal if you had three on say the back and one on the front. But with one on each corner the weight would be divided between all four (probably not exactly perfectly, but close enough) leaving plenty of safety room on each strap.

Those are the kind of straps I use for hauling a lot of stuff. I have recently moved to wheel straps that are of the same working load and they are much easier for hauling vehicles.

[olddieseldude]

I would suggest this...

The only time all 4 are sharing the load is when you've hit a bump and the load is trying to bounce into the air. When you turn left only the two on the left side are carrying weight (centrifugal force is trying to throw the load off the trailer). When you turn right only the two on the right are carrying weight. When you brake only the two on the rear are carrying weight and when you accelarate only the two on the front are carrying weight.

What the straps see depends on how many G's the tow rig can put into the trailer; start up; stopping; turning. I would think that emergency stops would impart the most tension in a strap, especially if you hit something that isn't moving. High speed in a turn would probably turn the trailer over (depending on it's weight) before the straps see anything close to the trucks weight. You'd have to have a hell of a truck to accelarate fast enough to hurt a strap but you could back into something solid and put a good sized load into them. Friction between your truck's tires and the trailers going to carry some of the load.

When I carry a vehicle, nothing as heavy as yours so far, I use two 3/8" grade 70 chains (6600# ea) at the rear and two ratchet straps (3300# ea) on the front.

[DezRacer]

Olddieseldude is on to something. Ever seen a flatbed semi hauling rolled steel? Two chains in the back and one on the front.

[Albin]

DOT rules, from memory, are .7xload for forward loads, .5xload for rear and side loads. Hence 7500 x .7 = 5250 lbs/2 = 2625 lbs; which, *theoretically*, means that two straps at 3300 lbs (i.e. 2") *should* work.

And you will see a lot of people use 2" straps to tie this type of load down - but not me. As Oldie suggested, I use two Grade 70 3/8" chains with binders on the rear; chains and straps up front (8 total), I want my vehicle tied down. Mine weighs 4775 +/- ('85 Toy 4runner).

Want to start a 4 page scream-fest? Post this question over at the Pirate4x4.com tow forum.

For a good discussion on how the military ties down their rolling stock for road transport, see the PAM 55-20 *.pdf at this link: http://www.tea.army.mil/pubs/nr/depl.../PAM_55-20.pdf

Good luck.

Al

[Foxx]

That's pretty interesting. I'd consider the wheel straps, but this is really a one- time trip. I'm taking the truck back home for my parents to drive.

I'd prefer to go with chains and ratchet binders, but I cant figure out how to attach chains to the truck's frame and be able to run it down to the trailer without hitting or damaging the lower body or bumpers, or even really find a great place to attach it to the truck's frame. I'm not entirely sure how I'll do it yet, because my buddy is loaning me his trailer (complete with chains and binders) to haul it, and I'm not picking it up until right before Labor Day weekend.

Any ideas on how to attach the chains to the truck without damaging anything?

Thanks!

[Albin]

Lots of ways:

- Chain to frame using links and existing frame holes: http://awdirect.com/finditem.cfm?itemid=9253

- Chain to axle using axle straps http://www.awdirect.com/finditem.cfm?itemid=20140

- Strap to frame using existing holes.

When going around axles, make sure you're strap won't cut or damage any brake lines etc. I chain to the axle and strap to the frame. My axles have u-bolt tiedowns already welded on, so the chain end slips right on.

Don't tie to steering assemblies like tie rods etc.

Good luck.

Al

[Foxx]

I've looked at the transport hooks, but I really dont want to invest a whole lot of money in what's basically a one time trip. By the same token, I want to be safe about the deal and not have a rolling road hazard. I was planning on using flat- hook straps hooked over the top of the frame rails; one on each corner of the truck going out to the trailer. I'd prefer not to strap to the axles because I just feel more comfortable with the entire load (truck and trailer) moving as one without the truck's suspension in the picture.

[olddieseldude]

I find that crossing the tie-downs makes it easier to get to a spot on the frame without quarter panel damage (left side of trailer to right side of truck frame and vice-versa). Crossing the tie-downs has the added advantage of creating smaller angles with respect to the trailer deck that will in turn minimize the slack if and when the truck's springs compress on a hard bump. Keep in mind that the truck's suspension will compress on a hard bump momentarily loosening all the tie-downs if fastened to the frame. If you do use the frame be sure to compress the springs significantly with the tie-downs before you stop cranking. I would consider tieing to the trucks axles instead (don't crush brake lines) close to spring or shock mounts. Be careful, you can hurt an axle tieing to the differential.

[arisley]

[ QUOTE ]
I find that crossing the tie-downs makes it easier to get to a spot on the frame without quarter panel damage (left side of trailer to right side of truck frame and vice-versa). Crossing the tie-downs has the added advantage of creating smaller angles with respect to the trailer deck that will in turn minimize the slack if and when the truck's springs compress on a hard bump. Keep in mind that the truck's suspension will compress on a hard bump momentarily loosening all the tie-downs if fastened to the frame. If you do use the frame be sure to compress the springs significantly with the tie-downs before you stop cranking. I would consider tieing to the trucks axles instead (don't crush brake lines) close to spring or shock mounts. Be careful, you can hurt an axle tieing to the differential.

[/ QUOTE ]

That is why I always tie to the axle.

[Jrod13]

I use 3/8's grade 70 as well.

1) I chain around the rear axle
2) drive forward
3) attach chain around front axle, tighted binders with pipe
4) tighten rear binders with pipe.

I've pulled through 5 different states, and 1000's of miles with that procedure, and have never had a vehicle move a fraction of an inch.

[mudguppy]

agreed w/ above statements: secure by axles.

i have found that it's easier on the load, the rigging, and the trailer. and even though the truck may rock a little on the trailer, it never, ever actually moves.

[KVOM]

olddieseldude has the correct info. The only time you would come close to the straps' breaking strength is in a highspeed collision, where the rear straps will keep the towed vehicle out of your truck's bed. Otherwise the loads are pretty light.

I always attach to the axles using slings with ratchet straps, and cross the slings over the diff.

[larry_minn]

I also like using chains for tractors/trucks/equipment. For "rolling stock" (like theat term) [img]/ubbthreads/images/graemlins/smile.gif[/img] I set up chain infront with it just a little too far forward. Then back up to snug chain. Then hook up rear chain with load binder.
THEN I put on pair of straps as safety. Drive short distance (say to just before interstate) and pull over/check chains/binder/straps. Retighten if needed and hit the road.
I have had dealers comment that the trailer could be lifted upside down with crane, raised up 50' and dropped to 15' above ground (shock stop) and the load likely wouldn't shift a inch.

[Dualie]

The reason there is a "Working Load Limit" on straps and chains is for shock loading during a wreck or a high G force incident. I would be more worried about the truck coming forward than I would the truck being sent backwards. The only Real time your going to have a high amount of force trying to push the truck off of the back of the trailer is if you were rear ended. And at that moment you have much bigger problems than cargo securement.

Your not so much holding the truck to the trailer as you are the trailer to the truck.

THE FMCA and USDOT cargo securement laws Dictate a Full Four corner tie down on any vehicle being transported on a flatbed truck or trailer. that means one strap or chain at each corner of the vehicle. the working load limit of all 4 tie downs added up must be grater than the vehicle load. And using the winch on the front as a tie down does not count.

I also prefer to keep the straps or chains crossed from one side to another. this helps keep the load much more stable and helps the chain or straps avoid contact with body panels. Personally I ONLY use lever binders or ratchet straps. I hate ratchet binders but for a novice the ratchet binder is the much better way to go.

Make sure that if you use ratchet straps you keep the webbing away from anything that resembles a sharp edge. even if you think that its a "pretty rounded edge" put something between the strap and the edge. In a pinch a cut up plastic soda bottle, cut up mud flap, rag, cloth baby diaper or small length of fire hose will protect it. also if you have a long strait run of strap put a twist in it. That will keep it from vibrating in the wind and basically sonically cutting the strap as it vibrates in the wind.

Its nice to see some one doing there home work before undertaking an equipment move.

And I personally don't put much merit into the work of "professional" drivers. I see plenty of 20K+ steel coil being transported with out coil bunks and just two chains keeping it on the trailer. Or my favorite two 15K coils loaded dead center on a 53' aluminum flatbed. I'm often more scared of what Cant see that's going on inside of dry van freight trailers.