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How Tight Is Too Tight Part 2

Last month I examined the effects of using cheater bars when tightening tie downs, both chain and web.This time I going to try to answer the question-How tight should they be? Before I do that, I want to absolutely convince you that cheater bars have no place in the tightening tie-downs.

If you remember, I was able to reach and exceed the Work Load Limit of 3/8 Grade 7 chain using a 36” long cheater bar and minimal effort. What would happen if someone was to use considerable effort? I was able to nearly EXCEED the breaking strength of the chain. How?

When I saw the loads that were being reached with minimal effort I realized two things: it might be possible to exceed the break strength of the 3/8” Grade 7 chain (26,400 LB)in a vertical hitch, and this was becoming unsafe and I needed to rerig my test set up. I changed the chain from a vertical hitch to a basket hitch. The chain was looped around one hook of the tester, then around the other hook of the tester then hooked back to itself. The lever load binder was attached to one leg of the chain so that the load was divided between the two legs. In this configuration the test bed would read the entire load, while the chain and binder would only see half of the load.

Chain in basket hitch for load binder testing Disclaimer time: The tests are conducted with new, unused products in a controlled environment. Extreme care was used to prevent personal injury and property damage. The data presented is for informational purposes only. All load binder manufacturers, including B/A Products, state that cheater bars are NOT to be used. As always, NEVER exceed the Work Load Limit of your tie-downs.

So what load was reached? 25,803 lbs. Yes, you read that right, 25,803 lbs. Less than 1000 lbs below the breaking strength of the chain. Now, remember that in the basket set up, the chain and binder are only seeing half that load, roughly 12,901 lbs, or just shy of twice the chains WLL. Could I have broken the chain if I had stayed with a vertical hitch? I doubt it, and here is why:

In order to reach the load of 25,803 lbs I had to strain. With half that load on the binder the threads of the load binder were beginning to bind up (squeaking and resisting turning) and the body of the load binder was getting warm. The signs were evident to me that I had tightened enough. Hopefully this is evidence that cheater bars have no place on your trucks.

So this month I’m going to talk about web tie downs. How tight should they be? This should be easy, right? Well, not so much. I contacted a few people in the chain and tie down industry. I got answers like “that’s a good question”, “no one has ever asked that before”,” I don’t know”, and “as tight as you can without exceeding the Work Load limit”. At least one of these answers is useful.

I looked through my usual sources, and found very little, sometimes conflicting information. I started with the Web Sling Tie Down Associations WSTDA-T-1 “Recommended Standard Specifications for Synthetic Web Tie Downs”, chapter 4 Recommended Operating Practices. There is a large amount of information presented, including not to exceed the WLL of your tie down, how the angle of the tie downeffects the WLL, and so on, but no guide to tightening. There are two bits of information worth noting: first, you must take into consideration the anchor point of your tie down. If your anchor point, be it a D-ring, keyhole slot or rub rail is not rated the same or higher than your tie down, the tie down MUST be de-rated to match. A chain (or tie-down) is only as strong as its weakest link (or anchor point). Second, it refers to the Federal Motor Carriers Safety Administration Standard for Protection Against Shifting and Falling Cargo. Guess where I’m going next?

I went to the FMCSA web site (www.fmcsa.dot.gov), found Regulations, then cargo securement, then Drivers handbook on Cargo Securement, Chapter 9-Automobiles, light trucks and vans. This must be the place! Nope. But I did find some useful information. In brief, the chapter covers securing vehicles under 10,000 lbs. it states:

“At least two tie downs at the front and rear of the cargo to prevent movement side to side, forward and rearward, and vertically.

The sum of the working load limits from all tie-downs must be at least 50% of the weight of the cargo”

I also looked at Chapter 1, “Fundamentals of Cargo Securement”. Once again, no instructions on tightness, but I did find this:

“Each cargo securement system must be able to withstand a minimum amount of force in each direction.

Forward force: 80% of cargo weight when braking while driving straight ahead.

Rearward force: 50% of cargo weight when accelerating, shifting gears while climbing a hill, or braking in reverse.

Sideways force: 50% of cargo weight when turning, changing lanes, or braking while turning.

Upward force: 20% of cargo weight when traveling over bumps in the road or cresting a hill.”

A diagram is included showing these forces with the definition the 80% of the cargo weight is considered .8g (as in g forces).

So far, we know what we have to restrain, and how much of it we have to be able to hold, but not how tight the tie-downs should be. On to the next reference, “Practical Cargo Securement, Guidelines for Drivers, carriers & Shippers”, published by the Commercial vehicle Safety Alliance. This book as lots of useful information on the proper ways to secure many things, including vehicles. In chapter 5, section 5.4.B they discuss tie-down position and tightness. The following statement is made:

“When tightening direct tie-downs you want them snug but not over tightened. You can make them weaker by over tightening them. For example a chain with a WLL of 5000 lbs that is tightened so that it has 1000 lbs of tension will only have 4,000 lbs remaining to resist force acting against it.”

Lets step away for a minute and talk about direct vs. indirect tie-downs. A direct tie-down is one that goes from the deck of the transport vehicle to an attachment point on the cargo, a cluster strap for example where the chain on the ratchet is in a keyhole slot on the deck of a carrier and the T hook in in the frame slot of the towed vehicle.

An example of a direct tie down. The tie down is connected to the load and the transport vehicle.

An indirect tie-down attaches to the transport vehicle, goes over or through the cargo and then reattaches to the transport vehicle. A crushed car on a flat bed with chains over the hood and trunk areas would be an example of an indirect tie-down. The angle of the tie-down to the cargo has and effect of the usable WLL of the tie-down. For our purposes we are discussing direct tie-downs only.

An example of an indirect tie down. The straps hold the load in place with pressure only; they are not connected to the load.

Lets go back to the statement “…will only have 4000 lbs remaining to remaining to resist force acting against it”. This just didn’t sound right to me. If it was reversed, say the chain had a WLL of 5000 lbs and was tensioned to 4000 lbs (which we know is possible) it will only have 1000 lbs remaining to resist force acting against it, I might have accepted it and moved on.

I contacted a friend, Mike Green and posed that question to him. Mike is a Captain in the Montgomery County MD Fire Department Special Operations, has a general engineering degree, and runs his own business, Mid Atlantic Technical Rescue, which teaches rescue techniques, including how to figure loads and forces. Mike consulted with one of his instructors, Mike Johns, who is also in Special Operations with the Montgomery County Fire Department and holds an engineering degree. Their answer, in short, is that the original tension on the tie-down would have no effect on the end loading.

They explain it this way: Lets say you put 3000 lbs of force on your tie down. The only way that 3000 lbs of force would ever be increased beyond 3000 lbs is if the car were to surge forward with sufficient acceleration or deceleration to create a force greater than 3000 lbs. At that point the initial tension you placed on it is irrelevant, because the load itself has exceeded your initial force.

I asked Mike about the CVSA statement that the tie-downs must be able to restrain .8g of the load. He did some quick calculations and found the deceleration rate to achieve .8g. The rate would be going from 53 mph to 0 in 3 seconds. Short of hitting a 4’ thick concrete wall, not likely to happen, as trucks do not have the ability to brake that quickly.

What about damage cause by over tightening, is that a possibility? I called a friend at a body shop that has a frame machine and asked if he could tell me how much pressure they used when straightening frames or bodies. He answered that there are a lot of factors, but forces as low as 4000 lbs are used. If 4000 lbs can straighten a frame, I’m betting it can also bend, or damage one. I think I’m starting to get somewhere.

Lets take a little break and recap where we are at. So far, I have not found an answer to how tight a tie down should be. I have found:

The tie-down should not be tightened above its WLL. Depending on your tie-down, this could be as low as 2000 lbs. A frame machine uses 4000 lbs of force, so we definitely want to stay below 4000 lbs.

The attachment points of the tie-downs must be equal or greater to the tie-down WLL, or the tie-down must be derated.

The tie-downs need to restrain .8g of the load (defined by FMCSA as 80% of the loads weight).

I looked through several instruction manuals for car carriers and tow trucks to see if specific forces were recommended. I did not find specific forces, but saw the phrase “sufficient force” mentioned several times. In addition, I saw the statement “sufficient force has been applied if the tire sidewalls begin to bulge”. How much force does it take to bulge a side wall? Do different sizes of tires bulge at different loads? What about tire pressures? Guess what I’m going to try and find out next.

One afternoon I gathered a roll back, several vehicles with different sizes of tires, a load cell and some tie-downs and attempted to find out. The first question that came up was what if the tire pressure is low? Sure enough, the first car we put on the bed was supposed to be at 52 psi was at 35 psi. The nextquestion was what defines a bulge? There were 3 of us trying to work it out, and I could already see there were too many variables and opinions for this to be accurate. Since everything was there, I trudged on. What we found out was that whether the tire pressure was at 35 or 52 psi, it did not make much of a difference with a direct tie down. We really were not getting a noticeable bulge, and the load on the tie-down was anywhere from 300 to 600 lbs.

We switched to an over the tire strap, as used in our Roll Back Tie Down System. The loop around the tire was indenting the tire when we had between 400 and 600 lbs of force at the ratchet side of the assembly. The issue was that the three of us each had a different opinion of the indentation. Back to the drawing board.

I stepped away from this to work on another project for a customer. The customer had asked for tie-down assemblies to be labeled to a European standard, EN 12195-2. I located the standard, printed it out and among other things discovered it called for a SHF (standard hand force) and a STF (standard tension force) to be on the label. Per the Standards definitions the SHF is a “hand operating force of500N” and the STF is “residual force after release of the handle of the ratchet”. I had found a standard for tightness, but what is a N and how can I measure it?

From my other testing work I knew that N stands for Newtons, the metric measurement of force. I Googled “convert Newtons to pounds”, plugged in 500N in the Newtons box, hit enter and found that 500 Newtons is equal to 112 lbs. So the standard read that the Standard Hand Force to be applied to the ratchet is 112 lbs. Next I made a section of strap covered with Velcro, and adjusted the overlap of the until until regularly came apart at between 110 and 115 lbs. This was done by repeatedly lifting a bucket filled with a known weight and measuring the overlap.

I then attached the Velcro to the handle of a ratchet strap assembly in the test bed, and repeatedly tightened the ratchet by pulling on the Velcro strap until it came apart, and recorded the load on the test bed. The average load was 1181 lbs. Now, I’m the first to admit that this was not the most scientific method, and may not be 100 percent accurate. But, an EN 12195-2 rated tie down assembly with a 5000daN break strength (11,240 lbs) has a standard tension force of 1124 lbs, so I am not too far off.

So now we have a target load for our web tie-downs. Time to see how close some operators are, and if I can teach them to load the assembly to 1124 lbs.

I picked three employees at random to do my control tests. TJ, Andy and Keith were brought to the test bed. The only instructions they were given was to tighten the web assembly until they thought it was tight, and that there was no right or wrong way to do it. They each tightened the strap three times, and the loads were recorded. Average loads were 1442 for TJ, 872 for Andy, and 1615 for Keith. More interesting was the difference between each employees high and low: TJ was 931 lbs, Andy’s was 11 lbs and Keiths was 417 lbs. As each of them finished their turns, I asked them if they thought they tightened the strap evenly each time. Andy answered yes, TJ said the first two times yes but on the third he “put more leg into it”, which was the high load of the test at 1976 lbs. Keith thought he did it evenly all 3 times.

Now when I said I picked the employees at random, I was not completely honest. I picked one person who I was pretty sure had never used a tie-down before (Andy), someone who I knew for sure had used them (Keith) and one who I was not quite sure of (TJ). I also picked employees of varying height and weight.

I then explained the purpose of the testing to my group, and told them how I was going to try and teach them some techniques. The first thing we discussed was “Body English”. If you remember in part 1 I defined Body English as “body motions made in a usually unconscious effort to influence the progress of a propelled object”. What I wanted them to be conscious of was to not use their body or legs, but to attempt to use arm strength only. I pointed out TJ’s admission that he “put more leg into it” and the difference it made in the load applied.

I also showed them the technique I wanted them to use. I had them pull the slack out of the assembly so the strap was snug before they started tightening the ratchet. I asked them to operate the ratchet until they began to feel tension build in the assembly, and then to tighten the ratchet two more “clicks”.

Over the day we practiced four times, with each employee tightening the strap three times in each session. I did not tell them the loads until all three had completed their turn. I then reviewed the load each applied, and the difference between the high and low for each of them.

By the end of the day TJ was averaging 1046 lbs, with an 11 lb difference between the high and the low. Andy averaged 798 lbs, with a 35 lb difference between the high and low. Keith averaged 922 lbs, and had a 50 lb difference between the high and low. So far so good. TJ is pretty close to the target of 1124 lbs, Keith and Andy are a little low. I gave them a day off, then did one more test to see how much they remembered and how close they would be to the target. TJ averaged 852 lbs, 86 lb difference between high and low, Andy averaged 627 lbs, with a 55 lb difference, and Keith averaged 707 lbs, with a 90 lb difference.

So do I call this experiment a success? I would say it was marginal. While we missed the target, especially after a day off, we were able to tighten the strap more evenly. Consider that the difference between the high and low load in the first test was 1107 lbs and in the final test it was 225 lbs, all 3 operators were became much more consistent. With a little more practice, who knows?

In addition to my earlier disclaimer, I need to say that a number of factors were ignored during this testing. Operator position and stance were not taken into account. The setup of the ratchet strap assembly in the test bed does not accurately reflect how a direct tie-down acts against a cars suspension. My point of this exercise was to try and find a tightness standard, and to see how close I could get a group of employees to get to it.

I would be interested to hear from you, and get your input. Is there a standard for tightness that I was unable to find? Do you teach your employees a specific method to tighten tie-downs? What other information would you find helpful? I can be reached at Fritz@baprod.com.

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To Optimize Your Switch to Synthetic Winch Lines, Enlist the Pros

Rope Tow Truck
By Bill Putnam

On the winch drums of tow trucks nationwide, high-performance synthetic cordage is rapidly replacing wire line. It’s a change driven dually by efficiency and safety: synthetics are lighter, easier to handle, and just as strong as their steel counterparts; yet if they do fray or part, they don’t carry the same threat of bodily injury from razor-sharp kinks and some fiber choices offer less chance violent snap-backs.

But the most groundbreaking trait of synthetic ropes is their potential to be customized and optimized. Among the thousands of fiber, size, diameter, and construction combinations available today, application-specific synthetic rope manufacturers and certified distributors help users select or design the safest, best rope for the job – and train them on how to use it for maximum safety and product life.

Unitrex Vectrus
Here are just some of the specific tasks your rope rep can help you do:

Determine the right synthetic fiber for your workload, budget, and climate

Unlike wire, which is fairly synonymous with steel, the synthetic winch line category includes a vast array of fiber compositions. Environmental conditions (temperature and precipitation) and the primary workload of the winch (weight, volume, and frequency of use) largely determine which fiber will work best. Since towers need reliability in all weather conditions, high-tenacity polyester jacketing is commonly used to protect the load-bearing core of the line. The core can be made of polyester; or for heavier lifts, a high-modulus polyethylene (HMPE) or liquid crystal polymer (LCP) core can bolster breaking strength.

Choose the construction most conducive to your environment.

Weather is also a primary driver when it comes to rope construction. Rain, freezing temperatures, sand, wind, heat, and sun exposure all play in to the type of braid you need.

In environments where abrasion is less likely to occur, a 12-strand single-braid rope might be a worthy option, though any 12-strand rope should still have a protective coating to prevent premature wear. Example: Yale Cordage’s Ultrex™.

In environments where the rope is likely to come in contact with plenty of sand, dirt, salt, sunlight, and other abrasive forces, a popular choice is a balanced double-braid, wherein a polyester core is protected by a high-tenacity polyester sleeve. Even if the sleeve experiences surface abrasion or UV damage, the independent core retains its strength. Example: Yale Cordage’s Double Esterlon™.

For ropes used in all conditions and for heavier lifts, core-dependent double braid construction provides the next level of performance. A core of Spectra™ HMPE, one of the strongest fibers available, protected by a high-tenacity polyester sleeve, provides ultimate strength and optimum protection. HMPE is also lighter than polyester, offering excellent maneuverability and sheave cycling capabilities for high-stakes recovery tasks. Example: Yale Cordage’s Maxibraid Plus™.

Align the strength of your rope with the capacity of your rig.

The breaking strength you choose for a synthetic winch line typically needs to be five or more times the rated working load or lifting capacity of your truck winch. Making a correct match is essential to preventing accidental overloads out in the field. But since acceptable working load to breaking strength ratios can vary, particularly with newer rope constructions, this is an area where it can be very helpful for your rope manufacturer or certified distributor to weigh in.

Analyze your work practices to determine energy absorption needs.

A rope of any breaking strength can be compromised if asked to absorb a dynamic load beyond its energy absorption capability. A rope’s energy absorption capability is not related just to its breaking strength; rather, it is ascertained by studying a stress strain curve of load versus elongation. Rope manufacturers understand the metrics involved, and can help you determine which fiber and construction will offer the energy absorption characteristics you need for the loads you typically handle, as well as how much rope you will need to deploy to avoid shock loads.

Understand the splicing requirements of your lines.

When switching from wire, or even older synthetics, to a new synthetic fiber or construction, you may need to change your splicing protocols. Whereas the techniques for older rope styles may have been fairly straightforward, many newer constructions require product-specific techniques. Most rope manufacturers and distributors offer splicing, splice training, and technical support for these proprietary products. Take them up on it.

Custom-fit ropes keep you efficient. These five maintenance tips will keep you safe:

  • Inspect before every use – Check the working eye and the area adjacent to it for any movement. The rope should have a Whiplock® or lock stitching at the eye to prevent movement. If the locks are not intact, or you notice the eye becoming larger or smaller in service, replace the rope.
  • Use slings – Never choke back on the winch line by securing it around the load and attaching the rope back to itself with a hook or shackle. This will wear out the rope, and may create visible damage for the first four to eight feet above the eye. If you notice such damage, either replace the rope or end-for-end it, placing the new end on the drum.
  • Invest in a certified splicer – A certified splicer who is trained on your rope will ensure you get a proper splice every time, with the added benefit of each splice being tagged and recorded for you under the rope’s serial number. This data can help large tow companies effectively track the condition of their ropes and replace them on time.
  • Consider proactive replacement – Because a line’s life expectancy can be shortened by shock-loading incidents, and because it’s difficult to definitively know how much damage each incident causes, many users proactively retire their lines immediately after any shock loading occurs. Another common practice is to end-for-end all ropes every 12 months and retire them after two years.
  • Dispose of retired lines properly –It is important to properly dispose of a retired rope before it reaches the hands of a user who could overestimate its strength. All too often, used commercial lines get recycled for personal use – thrown in the back of a pickup truck as a tow line, or boat line, or to haul a moose out of the woods. To prevent resultant accidents, retired lines should be cut into short lengths and recycled or repurposed for non-critical uses.

Bill Putnam is president of Yale Cordage.

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Cutting Corners Part 2

cutting-corners-p2-chain-(9)

Let’s do a little recap from the first half. Last month, I showed the reduction in strength when loading a web tie down strap, a 2 inch lifting sling, a V strap leg and a 3/8” steel core wire rope over a 90 degree corner, and not necessarily a sharp one. The average reduction in strength was 37% when loaded over the outside corner of a piece of 2 inch angle iron.

I also showed what the same towing tools look like when they are cut, as opposed to being overloaded. In this article, I want to show how chain reacts when loaded over a corner, talk about some methods of preventing the same tools from being damaged, and, finally, what to look for when inspecting your straps, wire rope and chain.

I also need to repeat the disclaimer: Please be aware that this testing was done with new product under controlled conditions. NO product should EVER be used above its WORK LOAD LIMIT. Minimum break strengths should NEVER be used to determine the suitability of a product. Failure to follow these warnings may result in property damage, personal injury or death. The intention of this article is to show the effect of improper loading over a corner has on the product.

Time to talk about chain. While chain is arguably the most durable of the tools we are testing, it does have its limitations. When misused or abused, it can fail. Unlike web and wire rope, chain can tell a story. As our National Sales Manager Chip Kauffman has explained before, through testing, it can be shown what the highest load a piece of chain has been loaded to. When chain is made, it is proof tested to twice its Work Load Limit. This stretches the chain very slightly. For a section of 3/8” Grade 7 chain, the Work Load Limit is 6600Lbs, so proof test is 13,200 Lbs. Let’s say this same piece of chain is loaded to 19,000 Lbs, nearly three times its WLL. The chain has already been slightly stretched when it was proofed at 13,200 Lbs, so it will not stretch until the load passes 13,200 Lbs. Once the load exceeds 13,200 Lbs, the chain begins to stretch. This can be seen on the graph when the indicator line changes direction. The same effect happens when the chain is overloaded. It will not stretch until the load exceeds the point at which it was overloaded.  Once again, the indicator line on the graph will be nearly vertical until 19,000 Lbs is passed. The chain will begin to stretch, the indicator begins to move horizontally, and the point at which it does is the maximum load the chain has seen. To illustrate this, I loaded a piece of 3/8” G7 chain to 18,400 Lbs. Proof test on this pieces was 15,100 Lbs. The same piece of chain was pulled to destruction. The previous load of 18,400 Lbs is visible on the graph.

38-G7-18400-LB

38-G7-18400-LB-2

Graph on left shows 18” section of 3/8” G7 chain loaded to 18,400 Lbs. Mark 1 is proof test load of this chain, 15,100 Lbs. Graph on right shows same section of chain loaded to destruction. Mark 1 shows previous maximum load of 18,400 Lbs. Chain has a memory.

In addition, chain has what is known in the industry as a preferential failure. Chain is designed to be pulled in a straight line, end of one link against the end of the adjacent link. When a chain is loaded in other than a straight line, such as when a grab hook is hooked over a link to form a loop, the chain will fail at that point, and by as much as 20% below the minimum.

Enough talk, let’s do some testing. I set up the test bed the same way as I did for the previous tests, with a piece of 2” x 2” x 3/16” angle iron. I then attempted to load the chain so the link was pulled over the angle. For these tests, I used 5/16” grade 70 chain with a Work Load Limit of 4700 Lbs, and a minimum break of 18,800 Lbs. I pulled one chain to use as a control sample; it failed 19,875 Lb, a shear at the end of the link.

chain-over-angle-set-up

The photo shows the test set up. The links were marked showing which were in contact with the corner of the angle.

The 3 samples tested over the angle failed at 15,055 Lbs, 12,803 Lbs and 15,574 Lbs, for an average of 14,477 Lbs, an average 28% reduction in breaking strength. If you look at the links that failed, a pattern emerges.

chain-over-angle-1

chain-over-angle-2

chain-over-angle-3

All of the links failed in the middle of the link, unlike the control that sheared on the end. All three also failed where the link was in contact with the angle. While it appears to be a weld failure, the failure occurred adjacent to the weld. There are also contact marks from the adjacent links and the angle. In addition, there is no “necking down,” a reduction of the links diameter commonly seen in straight pull tests. Due to the load being concentrated on one side of the link, and the mechanical damage caused by bending the link over the angle, the chain failed below minimum.

chain-over-angle-2

A close up of one of the links, showing the weld intact.

chain-over-angle-graph-2

chain-over-angle-graph
Top: Graph of the above link. Bottom: Graph showing reduction of break strength of 5/16 G7 chainover angle

cutting-corners-p2-chain-(9)

Every now and then, I get lucky. Usually when a failure occurs, the parts go flying. In this example, a quick hand on the switch stopped the tester at point of failure, and the parts remained in place. While the load was being applied, only one leg of the link was in contact with the angle. At failure, the link rotated 90 degrees towards the camera and came to rest as you see here.

So once again, I have shown that loading over a corner can reduce the ultimate breaking strength. How do we prevent this from happening? There are some general things that can be done that apply to all the tools I have tested, and some specific things for each product.

General Precautions:

First thing is to NEVER exceed the products Work Load Limit. In all of the tests I did, the samples failed above the WLL, and in 3 out of 4, at twice the WLL. This is not to say that corners or sharp objects will not damage these tools if the WLL is not exceeded, but it will help reduce damage, and is good practice.

Watch how the strap, chain, or wire rope is routed, and avoid contact with anything they may cause wear or damage. This includes the load or cargo that is being secured or moved.

Regularly inspect and maintain your straps, wire rope and chain. I’ll go into specifics for each product, but regular inspection can prevent a small problem from becoming a large one.

Make sure your tie down or tie downs have sufficient Work Load to restrain the object being moved. If not, add tie downs until they do. In addition, make sure the tie down points you are hooking to are rated for the tie down. A strap and ratchet with a 3300 Lb WLL hooked to a D ring with a 1000 Lb WLL is only good for 1000 Lbs!

NEVER shock load any of the tie downs we are discussing.

Product specific precautions:

Web slings and tie downs:

Of all the items I tested, web is the most easily damaged. Any place that web contacts the cargo, the load being moved or the tow vehicle itself must be protected or moved. I have shown that tensioning a load over a corner, even on as seemingly innocent as the corner of a piece of angle iron, can damage the web. A hand ratchet can tension a piece of tie down web to about 1400 Lbs, well below the WLL of most tie downs. If the strap is tensioned over an edge, the vibration on the vehicle going down the road can and will wear and possibly cut the strap. In addition, when hauling a vehicle, the can be some movement, which will also accelerate wear. This can also happen with V straps. If they are under tension and in contact with the under frame or suspension, the vibration and movement will wear the web.

I did a quick test to show the effectiveness of three different sling pads on a tie down strap. I tested one sample each of a cordura sleeve, a cordura pad sewn to the strap and a rubber pad. I’ll let the results speak for themselves:

three different sling pads

sewn cordura pad over angle

cordura sleeve over angle

: rubber pad over angle

sewn cordura pad failed at 8623 Lbs

cordura sleeve failed at 8922 Lbs

cutting-corners-pt-2-(10)

pad-improvement-graph
Top: rubber pad failed at 11,319 Lbs Bottom: graph showing average increase in break strength padding provides

While the strap still failed where it contacted the angle, the average failure was 9621 Lbs, a 30% increase over the unprotected strap. While further testing is required to validate the results, I think I can predict that the protected strap will break at a higher load.

Wire Rope:

Wire rope is the second most easily damaged. Improper drum winding, which can lead to crushing and flat spotting, will quickly turn a new wire rope into a useless piece of scrap metal. This is commonly seen on roll backs. Once the wire rope crosses over itself and a load is applied, the layer underneath is irreparably damaged.

Wire rope also has a minimum bend radius. Whether the wire rope is being bent around a sheave or another object, wear, fatigue and reduction in strength is occurring.  The smaller the radius the wire rope is bent around, the greater the wear and the greater the reduction in strength. This is commonly referred to a D/d ratio, where D is the diameter of the sheave or other object the wire rope is wrapped around, and d is the diameter of the wire rope. The higher the ratio, the lower the wear, fatigue and reduction in strength, and the lower the ration the higher the wear, fatigue and reduction in strength. For example, a 3/8” wire rope being pulled around an 8” sheave has a D/d ratio of 21.3, and this rope would have about 92% of its breaking strength. The following graph shows the effect the D/d ratio has on the strength of the wire rope.

Dd-graph
Graph shows the effect of D/d ration on ultimate strength of wire rope

It is also vitally important that when wire rope is used over sheaves, such as in a snatch block or at the end of a wrecker boom, that the sheave grooves be correctly sized for the wire rope being used. Sheave grooves that are too small can pinch the rope and prevent the individual wires and strands from adjusting (necessary movement within the rope itself; grooves that are too large will not support the rope, allowing it to flatten and restrict free movement. When a change in direction is required in a run of wire rope, it should always be routed over a sheave or roller. Pulling a wire rope over an edge (such as the end of a roll back bed) will damage the rope. Yes, I have seen this done. Finally, lubrication of wire rope can increase its life. There are several lubrication products specifically for wire rope.

Chain: While chain is the most durable of the products I tested, it still requires care in its use. Chain is designed to be used in a straight line, tensioned end of link to end of link. Avoid wrapping chain over itself. Only use hooks and fittings that are sized properly for the chain (1/2” hooks on ½” chain for example). Chain should not be twisted, knotted or kinked. Avoid temperatures above 400 degrees F for grade 70, 80 and 100.

Inspection

Most inspection criteria I have seen calls for three types of inspection: Initial, Frequent and Periodic. Let’s look at each quickly:

Initial: Before any new product is put into use, it should be inspected by a designed person to verify it is correct of the application and in undamaged condition.

Frequent: Before each use, the person using the product should inspect it.

Periodic: This inspection should be conducted by a designated person. Frequency of this inspection should be based on frequency of the products use, severity of service, and experience gained in the service life of similar products.

While we can debate the need and frequency of inspections, I hope we all can agree that they are necessary. But what are you looking for? And who is this designated person? I did a little searching and came up with the following: “Designated” personnel means employees selected or assigned by the employer or the employer’s representative as being qualified to perform specific duties. The designated person should have some background or training that makes him knowledgeable about the items he is inspecting.

So what is this designated person looking for? I am going to cover out of service criteria for each group of product that was tested.

WEB SLINGS AND TIE DOWNS: A web sling or tie down shall be immediately removed from service and destroyed if any of the following are observed:

If the capacity or material identification tag is unreadable or missing

If any acid or alkalis burns are present

If any melting, charring or weld spatters are present

If any holes, cuts, snags or embedded particles are present

If there are any broken or worn stitches in the load bearing splice

If there is excessive abrasive wear

If there are knots in any part of the sling or tie down

If there is excessive pitting or corrosion, cracked, distorted or broken fittings

If there is any other visible damage that causes doubt to the strength of the sling

(Photos of these conditions can be found on our web site: www.baprod.com)

WIRE ROPE: A wire rope winch line or sling shall be removed from service immediately and destroyed if any of the following are observed:

Kinks, bird caging or popped core in the working section of the wire rope

Discoloration due to excessive heat

Corrosion with pitting of the wires

More than 11 broken wires in six diameters of length

More than three broken wires in any one strand

More than two broken wires at the end connection

CHAIN: A chain shall be removed from service immediately and destroyed if any of the following are observed:

Any links or components are worn, bent, gouged or stretched

Any links or components are cracked or distorted

Any link measures below the NACM standard thickness as shown in chart XIV found at http://www.nacm.info/welded.php

I hope you have found this article interesting and informative. It is not intended to be the be all end all discussion; rather, my goal was to make you aware of some of the common signs of misuse and abuse that can reduce the strength and useful life of web, wire rope and chain products. Cutting corners can be dangerous.  I encourage you to use the following links to gain more knowledge:

B/A Products www.baprod.com

National Association of Chain Manufacturers  www.nacm.org

Web Sling Tie Down Association  www.wstda.com

Associated Wire Rope Manufacturers  www.awrf.org

Wire Rope Technical Board  www.thewireropethenicalboard.org

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Straps and Chains

8MU50_Straps_AA04

By Simon Birch

This month, we are going to discuss straps and chains. We will cover their uses and applications, ratings and sizes, and care and maintenance.

STRAPS

7X879_Straps_AA02

Straps-and-wrecker

Nylon or Polyester straps have become the industry standard over the last decade or so. They are available in as many different shapes, sizes and configurations as you can think up, and most strap manufacturers have the ability to custom produce straps for any application.

They are being used on every size and style of towing and recovery vehicle, from the smallest wheel lift to the largest rotator. We are using straps to secure vehicles to our trucks, winch vehicles from ditches and wrap around over turned vehicles to upright them, all without incurring any further damage to the casualty.

The benefits of using straps over chains in many situations are numerous.

Since straps are lighter and easier to handle, strain on the operator is reduced. They can be used in many situations where chains would cause damage, like during recoveries when the chain would be up against the side of the vehicle, potentially cutting into the vehicle or scratching the painted surfaces. Straps can also be fed into locations that chains could never fit.

3KN78_Strap_AA01

As the design of the automobile has progressed, many manufacturers are omitting tie- down slots and replacing steel or cast suspension parts with lightweight, stamped pieces, which can be very susceptible to damage if hooked onto. In response, strap kits have been developed to secure vehicles to the transporting truck by its wheels and tires, thus eliminating any body or chain contact.

These tie-down strap kits are available in many configurations, including 4-point over the wheel, 4-point through the wheel and 8-point over the wheel. They can be paired with almost any size and style of ratchet or custom ordered to fit the operator’s specific needs and requirements. The use of these tie-down straps  has now expanded to the auto hauler industry, as operators that are transporting new cars to dealerships from factories and sea ports are being faced with the same challenges of securing the vehicles to their haulers as the towing operators are.

When it comes to vehicle recovery, few can argue the benefits of straps and web slings. For years now, heavy duty operators have been using 6, 8 or even 12 inch wide straps to support, lift and catch trucks and trailers that have overturned, run off the road or been involved in an accident. Often used in conjunction with Air Cushions, these have become an integral piece of equipment in every heavy duty recovery fleet. Now, with the increasing presence of large rotator recovery vehicles, these recovery straps are helping operators perform complicated jobs that in the past would have taken much longer, and used more trucks and operators.

The arrival of endless loops or round slings has also added to the “tool box”. These synthetic polyester, continuous loops are available in a multitude of lengths and strengths, depending on their usage, and are a perfect complement to the recovery straps already discussed. These are lightweight, washable and very flexible and are being used in all types of recovery situations, both large and small.

CHAINS

3YDJ9_Chain_AA02

Although the development of recovery straps has led to them replacing chain in many applications, chain still plays a very important role in our industry. Graded by strength and available in many sizes, there is a chain available for every task.

Grade 70 is now regarded as the minimum grade for transport and towing applications. V bridles, light duty tie down chains and safety chains are almost always Grade 70, but grade 40 is still available if preferred.

3YGF8_Chain_AS04

Recovery work should only be performed with a Grade 80 or higher chain, and, depending on the task and equipment, can be sized anywhere from 5/16 to 5/8. Most heavy towing and recovery operators are using Grade 100 or 120, in ½ inch or higher, as their standard for recovery work, with Grade 80 being used for tie downs or securing axles, drivetrains etc.

One thing to pay note to is that you should always pair your chain with the same grade hardware and hooks. Installing a Grade 70 hook on a Grade 100 chain will render that entire assembly Grade 70. The weakest link is always the item with the lowest grade.

Chain maintenance is often overlooked, and, as a result, failure can occur when you least expect it. Keep your chains clean, and inspect your chains for flat spots, cracks and link failures on a regular basis, and they will last for a very long time.

Simon Birch, Technical Support, AW Direct

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Cutting Corners, What Our Testing and Research Shows

By Fritz Dahlin
Testing Strap Research

Note: Please be aware that this testing was done with new product under controlled conditions. NO product should EVER be used above its WORK LOAD LIMIT. Minimum break strengths should NEVER be used to determine the suitably of a product. Failure to follow these warnings may result in property damage, personal injury or death.  The intention of this article is to show the effect of improper loading over a corner has on the product.

One of our salesmen called me back to his desk the other day. He said, “So and so sent me a picture of a strap that broke. Can you take a look at it and see what you think?” I said, “Sure. Pull it up.” As soon as the picture opened, I said, “It was cut.” He asked, “How do you know?”  “Easy.” I said. “Those hundreds of fibers did not all break at the same time and same place for no reason.”

Now, as much as I’d like to say I thought that up all by myself, I can’t. Credit goes to Michael Gelskey, a fellow member (and past president) of the Web Sling Tie Down Association. One of my jobs at B/A Products Co. is to attend the semi-annual WSTDA meetings. We talk about exciting stuff like the recommended pin diameter for testing 12” slings, what the minimum corner radius round slings should be loaded over, and my personal favorite, whether poly and nylon slings should be washed or not.

Mike gave a presentation about a sling his company made that failed and resulted in a fatality. As he told the story, there was a picture of the sling on the screen. The sling had been laid over the angle iron arm of a transmission tower. The sling was laid over the arm of the tower, unprotected, and loaded repeatedly. The arm of the tower contacted the same place on the sling each time it was loaded, until it wore through (cut) the sling with catastrophic results. To those of us in the web industry, the cause was obvious. To many outside the web industry or those who may not have been trained on proper use and inspection of web slings, it may not be. And I won’t limit that statement to web. Wire rope and chain, when used in a manner that they are not designed for, or are not protected from damage, will fail. They will also leave telltale signs. The goal of this article is to make you aware of the damage that a seemingly innocent corner can cause, the signs that a piece of web or wire rope was damaged or cut, and some basic inspections that must be performed on a regular basis.

TEST SET UP AND PARTICULARS

I wanted to recreate some things that I see on a fairly regular basis. Another of my jobs at B/A is to do the testing of inbound materials, as well as inspecting returns to try and determine cause of failure, so I have not only seen a lot of broken things, but I have broken my share of them, as well. I decided to try to replicate what happens when a piece of wire rope or web is pulled over a 90 degree corner.

To set up the tests, I cut several lengths of 2” x 2” x 3/16” angle iron to fit over the top edge of the carriage of one of our test beds. I then figured a way to secure a piece of tie down web, wire rope, 2” 2 ply sling and a V strap leg so it was pulled over the outside corner of the angle iron.

Test set up for tie down strap.

Test set up for tie down strap.

Let’s get to the testing. For each item, I loaded 3 samples over the angle to get a good average break, and did either a straight pull test or used test results from my files for each product to use as a control sample.

First up was a cluster tie down strap, rated at a 4000 Lb. Work Load Limit, 12,000 Lb. minimum break strength. Keep in mind that the minimum break strength (MBS) should NEVER be used as a rating or for selecting a tie-down, strap chain or wire rope.

The control sample broke at 11,664 Lbs. As you can see from the photo, the webbing shredded at the stitching. The straps were set up with the free end of the strap wound up in a ratchet, and the mini J of the cluster hooked to the underside of the test bed.  The samples that were pulled over the angle were marked where the web contacted the corner, and two inches on either side of the angle. Force was applied until the samples failed. As the force increased, the web stretched and the contact point with the angle moved about two inches. Failures occurred at 7519, 7383 and 7181 Lbs., all where the web contacted the angle.

38-100 strap control sample.

38-100 strap control sample.

38-100 strap pulled over angle iron.

38-100 strap pulled over angle iron.

Notice that the strap pulled over the corner is cut cleanly across the width of the web, and all or nearly all the fibers are the same length, with minimal fraying. Compare these with the control sample. This is the indication that the webbing was cut.  The average failure was at 7361 Lbs., for a 37% reduction in MBS. Look at it another way: Work Load Limit is based on a ratio of the MBS. In the case of this strap, the 4000 Lb. WLL is a 3 to 1 ratio of the 12,000 Lb. MBS. Since our MBS over a piece of angle iron is 7361 Lbs., divide that by 3, your WLL is now 2453 Lbs. Now, I’m not suggesting that the straps be rerated because it is being pulled over a corner, but the reality is if the strap is pulled around a corner, the strap will fail at a lower load.

Let’s put a 2” two ply sling to the same test. WSTDA ratings for this sling are a WLL of 6200 Lbs. in a vertical hitch, with a 5 to 1 design factor for a MBS of 32,000 Lbs. My control sample failed at 31,820Lbs., the webbing again shredded at the stitching.

2” sling control sample.

2” sling control sample.

graph for 2” sling control sample

graph for 2” sling control sample

The test samples were installed in the test bed with one eye over the hook, under the carriage, over the angle and to the second test bed hook. The samples were marked the same way as the cluster strap, and force applied until failure. As force increased, the strap stretched until the 2 inch mark was adjacent to the corner. During one of the test pulls, the test bed ran out of stroke. (The ram was fully retracted before failure occurred. I did the testing over several days and this sample was hooked to the test bed differently.) I took the strap out of the test bed to reset the test and noticed the damage to the strap where it had been in contact with the corner of the angle. I’ll show you that damage a little later.

2-INCH-2-PLY-SLING-OVER-ANGLE-P2

All three samples failed at the angle, with an average failure of 13,023 Lbs, less than half of the straps MBS. Using the same logic as the cluster tie down strap, the WLL has effectively been reduced from 6200 Lbs, to 2604 Lbs. Once again, I am not suggesting the strap be rerated; I am trying to illustrate how damaging loading over a corner can be. As with the cluster strap, the fibers at the cut are relatively even with minimal fraying.

2-INCH-2-PLY-SLING-OVER-ANGLE-P4

CUTTING-CORNERS-2-18-14-(20)



2 inch 2 ply slings after being pulled over angle. Arrow shows direction strap was being pulled.

Let’s switch from web to wire rope for the next test. For this round, I tested 3/8” EIPS IWRC (Extra Improved Plow Steel Independent Wire Rope Center) made into 10 foot long sections with thimbled eyes at each end. The samples were attached to one hook of the test bed, laid over the angle on the carriage, then run under the carriage and tied off to a cross member of the tester.

The wire rope test set up.

The wire rope test set up.

This resulted in the sample contacting the carriage in two places. In all three tests, the end of the wire rope attached to the movable hook of the test bed failed (the end having force applied), including one test that I inadvertently ran under the carriage to the hook (it failed on the edge of the carriage, not the angle).

The control sample failed at 16,397 Lbs., at one of the swages.

graph of 3/8” steel core wire rope control sample

graph of 3/8” steel core wire rope control sample

cutting-corners-31-2

The three samples pulled over the angle failed at an average of 9503 Lbs., a reduction of 42% from the control sample. In each case, the wire rope failed where it was contacting the corner. Four of the six strands failed on two of the samples, and two of six failed on the third. I stopped each test once the failure occurred. If I had continued to apply force, the remaining strands would have failed, but the load would have been lower that the first failure point.

damage to three samples pulled over angle.

damage to three samples pulled over angle.

detail of failure over angle. Damage to the angle is from previous wire rope tests

detail of failure over angle. Damage to the angle is from previous wire rope tests

It should also be noted that the wire rope sample contacted the carriage on the test bed in two places, and the point where failure did not occur was damaged, as well.

So far, the testing has gone pretty much as I expected. All of the samples failed where they contacted the corner of the angle iron at an average of 46% below their Minimum Break Strength, due to the damage the corner inflicted.  Next, I tested individual V strap legs, and things get very interesting. My goal was to recreate the damage you see here:

V strap returned by customer for inspection.

V strap returned by customer for inspection.

Take a look at the bottom leg. Notice how the fibers are smooth and even for the first two inches of width from the bottom. They compare very closely to the cut tie down strap and 2 inch sling shown earlier, but also take a look at the top leg. Notice the mark that mirrors the cut on the lower leg? Most likely both legs were riding against a cross member or control arms.

To simplify the testing, I had single legs of our V straps made up. Our V straps have a 4700 Lbs. Work Load Limit.

I set up the V legs so the last 3 inches or so of the strap was contacting the corner of the angle, and applied force. The first two legs I pulled got fairly high readings: 13,181 Lb and 13,272 Lb. On the third leg, I moved the contact point slightly and got 15,712 Lbs. Samples 1 and 3 were cut at the contact point with the corner, sample 2 was a cut on either side of the leg at the contact point, and then the oblong pulled through the remaining center inch or so of the eye. The control sample failed at 16,032 Lb., the oblong elongated significantly and cut through the web at the end of the eye.

Three V strap legs after being pulled over the corner of the angle.

Three V strap legs after being pulled over the corner of the angle.

V strap test set up

V strap test set up

V strap control strap after test.

V strap control strap after test.

The average reduction in break from the control sample was 14%. Why is the reduction in MBS on the V strap leg only 14%, when the average reduction of the other parts is 46%? The V strap legs have a Cordura pad sewn over the eye at the hook end. In all 3 tests, the Cordura pad was at the angle or pulled to the angle when the leg stretched. That cordura pad made the difference.  “But the control sample looks just like the other legs, the fibers are all the same length with minimal fraying. What gives?” I’m glad you have been paying attention. It’s time to talk about some of the signs of damage.

Let’s start with the V strap legs. In reality, the control sample was cut, as well. Take a look at the oblong links in the photo of the test samples then the oblong link in the control sample. The test samples elongated very little, which shows that they were not getting the 14,000 Lbs. or so average it took to break the sample. The oblong of the control sample elongated considerably, indicating it was seeing the full load applied to the sample.  As it elongated, the contact point with the eye of the web became smaller and smaller, until that point could no longer support the load and the web failed. This is a good example of why it is important to check the entire assembly during routine inspections or after a failure. The example of the green V strap shown earlier backs up this point. The side that did not fail shows that there was contact with an object.

WIRE ROPE: The samples were pulled over two 90 degree angles; one end was tied off to the frame of the tester, the other end tied off to the ram of the tester. Failure occurred at the 90 degree angle closest to the ram (even on the sample I ran incorrectly). Where the wire rope contacted the second angle, there was damage, as well.

SHOWROOM-SAMPLES

This damage creates a weak spot that can fail when a load is applied later. Also take a look at the photo of the break in the wire rope while it is over the angle. The ends of the individual strands show two different configurations. Some are flat, like a chisel or knife blade. This is an indication of mechanical damage, such as crushing or being bent around a corner. Others show a cup and cone shape. When an individual wire is overloaded, it will stretch. When it cannot stretch any more, the wire breaks. One side of a break looks like a cone, the opposite side like a cup.  Overloading will also leave signs. The thimble will stretch at roughly twice the Work Load Limit of the wire rope.

thimble that has not been subjected to overload. Bottom: Thimble used in break test.

thimble that has not been subjected to overload. Bottom: Thimble used in break test.

WEB SLING: I mentioned that during the testing I had to reset the strap and noticed damage. The strap had been pulled to 12,109 Lbs. Here’s the damage:

Damage to strap pulled over corner without failure.

Damage to strap pulled over corner without failure.

When the strap was reset and pulled again, it failed at 12,110 Lb., 1 pound over the previous pull. Do you think the damage had something to do with that? Compare the previous photo with the photo of the strap after it was pulled the second time. It failed in the same place. Still not convinced? That strap broke lower that the other two by almost 1000 Lbs. Once again, previous damage can and will weaken the assembly.

Same strap from previous photo, after being pulled over angle to failure.

Same strap from previous photo, after being pulled over angle to failure.

Also notice the wear and marks at the letter “S.” In the test set up, the sling contacted the carriage of the test bed in two places. While most of the load applied to the strap was concentrated at the angle where the strap ripped, there was enough force at the second corner to create additional damage. All of the 2 inch slings and the cluster tie downs exhibit this damage.

BA Products graph

So, how can these failures be prevented? What kind of inspections should you be doing? And what about chain? I’m going to cover those subjects next month.

One thing before I go: In the opening, I talked about going to WSTDA meetings and some of the topics of discussion. Please don’t get the wrong idea; I really do enjoy the meetings. And yes, those are really topics we discuss. The answers, in case you are interested: 12” sling testing pin diameter 4.5”, span 13”; minimum corner radius for round sling, depends on the sling, a yellow round sling is 5/16”, and no, slings should not be machine washed (or washed at all).

Fritz Dahlin is vice president of B/A Products Co., www.baprod.com

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Which Winch is Which?

Merriam – Webster defines a winch as a machine for hauling or pulling.  Specifically, a winch is a powerful machine with one or more drums on which to coil a rope, cable, or chain for hauling or hoisting.  In industry, winches stand at the heart of machines as diverse as tow trucks, large industrial cranes, heavy hauling equipment and off road vehicles requiring self-recovery.  The more elaborate designs have gear assemblies that can be powered by electric, hydraulic, pneumatic or internal combustions drives.

The two most common designs of winches used in the Industrial Marketplace are the Worm Gear Winch and the Planetary Winch. Worm gear winches, by design, provide a very rugged platform for heavy duty applications. The planetary winch design offers higher speed and higher efficiency when compared to its counterpart.  However a separate breaking system is required with the planetary design. Which type of winch is better?  It depends on the application.  This is where a winch professional comes in; to help with the specification of the proper winch.

Most US manufactures design to the Industry Standard:  SAE J706 Rating of Winches:  SAE J706 is a voluntary standard for intermittent duty winches.  Winches meeting this standard must comply with design guidelines for the free spool mechanism, brake holding force, drum diameter in relation to the cable diameter (8:1), cable anchor pocket and other design guidelines.  As part of the testing procedure, all winches must be tested to a two times load test.

Worm Gear Winch

Worm gear winches have fewer moving parts than other designs and are known for their superior endurance and high reliability.  The gear box of a Worm Gear Winch has two major parts, the worm and the main or bull gear. It is generally accepted in the industry that worm gear winches have a slower line speed and are less efficient than other designs. However, they are also generally self-braking, meaning that they stop when the driving worm gear stops and are extremely robust.  Due to some new highly efficient gearing technology, there are some worm gear winches that have line speeds that are equal to their planetary counterparts for the same line pull.  Reference:  Ramsey Winch HSW 10,000 Worm Gear Winch has the same line speed as the HD-P 10,000.

Planetary Winch

The planetary winch has gained popularity because of its compact size, smooth operation and good resistance to torque loads.  This design also allows for generally higher efficiency gear ratios than the standard Worm Gear Winch. The planetary winch gear box is made up of the sun gear surrounded by a number of planetary gears that engage the ring gear.  The planetary winch is also more efficient than its worm gear counterpart.  However this device does require a braking system to safely hold the load.

Other Major Components of the Winch:  Although the basic industrial winch design is named after the winch gearbox, there are other components that make up the total winch product.  The major ones of these are the Rope (Synthetic or Wire Rope); the Drum; the Clutch Assembly; the Braking System; and the Driving Motor (generally electric or hydraulic.)

Rope and Drum

The winch rope is stored on the drum in layers.  The published rating of the winch is the “rated line pull on the first layer of rope on the drum.”  The first layer is the layer closest to the drum.

Clutch Operation and Maintenance:  There are several defining factors in the operation of a winch.  One of the most important of these is the operation, inspection and care of the “Clutch Assembly.”  The clutch is used to engage and disengage the gear and drum assemblies of the winch.

Clutch Disengaged

When the clutch is disengaged, the cable on the drum may be pulled off by hand, commonly known as “free spooling”.  There are a number of specified ways to disengage the clutch assembly based on the type of winch, its design and the procedure for operation that is detailed in the winch owner’s manual.

To Disengage Clutch: Run the winch in the reverse direction until the load is off the cable.  Pull outward on the clutch handle, rotate counterclockwise 90 degrees and release. With other designs, the clutch handle can be moved toward the drum until the clutch disengages.   The Clutch is now locked out and the cable may be pulled off by hand. (Free Spool.)

To Re-engage the clutch, pull outward on the handle; rotate clockwise 90 degrees and release. In the other design shown, to reengage the clutch, the handle is pulled away from the drum to the, “IN” position.  The drum is then rotated until the clutch jaws engage the drum jaws.

Important Note:  The most important rule with respect to winch operation: The Clutch must be fully engaged before starting any winch operation. Failure to do so may result in the dropping of the load, with the potential for injury.

Clutch Re-Engaged

Clutch Inspection and Maintenance:  As part of the normal maintenance procedure of the winch, the clutch assembly should be inspected regularly.  These inspection procedures are detailed in the Winch Operation Manual provided by the winch manufacturer.  As an example, on the Ramsey Winch HSW-10000 model, an inspection plug is provided on the top of the clutch housing.  During the inspection procedure, this plug should be removed with the clutch engaged.

The jaw clutch must be fully engaged with the drum jaw to see if the Jaw clutch shows wear.

Drum jaws and clutch Jaw should have square edges.  If the Drum jaws are rounded, the drum must be replaced. It is important to note that the drum should not be welded or machined in an attempt to eliminate round edges.  If the drum jaws are rounded, the drum must be replaced.  This is just one example of a clutch inspection procedure.  The procedure can and will vary depending on the winch design.  See the winch operation manual for the specific winch model and design.

The important thing to remember about the Winch Clutch Assembly:

  • A fully engaged and properly maintained clutch will not release under load.  The operator is responsible for ensuring the clutch is fully engaged before starting winching operations.
  • A partial engagement of the clutch can result in a sudden loss of load and damage to the clutch mechanism, and the possibility of injury.

Summary:  An industrial winch is a robust and reliable device that is used in a variety of industrial applications e.g., towing and recovery, heavy hauling etc.  If properly maintained and operated correctly, it will provide service for a long time.

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Winch Basics and Not-so-Basics

Todd K., AWDirect Technical Product Support

Coming from a life working in (and owning) collision centers, repair shops, tire shops and now working in the marketing and technical side of the industry, my human hard drive of stories, mistakes, accomplishments and knowledge of the towing industry is reaching critical mass.

I think back to the beginning of my recovery days when it seemed fine to wrap the wire rope around the frame of an overturned casualty, attach the hook back to the wire rope, idle up and jerk the vehicle back to its correct “top-side-up” position. I compare that situation to the knowledge I have now of doing it correctly and safely, all while saving money from having to replace damaged parts. It seems as though it should be easy to teach the new guys not to make the same mistakes I made. WRONG. Now, I do not proclaim to be a psychologist or even know much about the human thought process, but 20+ years in the recovery industry has taught me that most of us have a hard time admitting we have done things wrong or do not know something recovery related.

This leads me to why I am writing this article. When we think of winches and wire rope, we assume they’re super-strong and nearly indestructible. WRONG again. That was the impression I had when I started out in the recovery field. For quite some time, I had the impression that if something broke within the winching system then it had to be a manufacturer’s defect. And…I was WRONG again. Are you seeing a pattern here?

Let’s start with wire rope. First off, we need to think of our wire rope as a running machine with moving parts. How’s that you ask? Think of a 4×4 truck on dry pavement. The truck hops and chirps when you make a really tight turn. This is because the outside wheel is traveling much farther than the inside wheel while being locked together, which wears rubber off of the outside tire. Wire rope behaves the same. When it goes around a sheave or the winch drum, the outside wire strands of the rope rub against the slower-moving inside strands. This wears on the small metal strands of the wire rope the whole time. It’s a sound practice to replace wire rope at least every six months on a regularly used recovery vehicle, even if there are no obvious signs of wear. The wear could be taking place, unseen, inside the rope where the small wire strands have worn on each other, leaving breakage to occur anytime with no warning. A six-month replacement schedule should keep you, your employees, your equipment and your customers safe.

There are a host of other damages and problems one can inflict upon wire rope. These include, but are not limited to: bending, smashing and kinking. For instance, a 3/8″ wire rope should never be run around anything less than a 4″-diameter sheave, or across sharp edges (such as the edge of your carrier bed). Plus, we all know we should never wrap the wire rope and hook around an object and attach the hook back to the wire rope itself. Most of these problems can be avoided by using a synthetic rope, but that is an article all by itself and we will leave that for a future writing.

Now on to the winch. The winch is the heart of your truck. Just like the heart that beats in your chest, you are bound to have problems with it if you neglect it long enough, and probably at the most unfortunate times. You do not have a heart attack at the hospital and your winch will not give out at the shop. So…Lubricate! Lubricate! Lubricate! Lubrication is the lifeblood of your winch. Be sure to change the lubricant at least every season to prolong the internal parts of your winch. The type and weight of lubricant can be found in your winch’s manual. (AHHH! No manual? Manuals for most common name brand winches can be found on the manufacturers’ websites).

Check for leaks at the gear and motor side of your winch. The hydraulic motor mount usually has a weep hole. If there is any fluid dripping from it, replace the seal between the motor and the mount. Check for leaks at any gear case seams and replace the gaskets as necessary. Check for loose bolts in the winch frame and for excessive play in the winch drum from side to side. Last, but certainly not least, check the clutch side of the winch. This usually has a fairly simple design—a handle hooks to a clutch fork that slides the jaw clutch’s two teeth in and out of the two teeth in the side of the drum. This allows the winch to free-spool. The simplicity of this design is also what causes the most problems with user error. That’s right, here is where a lot of us go wrong.

There’s that pattern again. Since I was one of the largest violators of the correct clutch disengagement-engagement procedures, I can explain it well! It is 18 degrees outside. We are picking up a stranded mid-size car in 15″ of snow. We pull up, hit the MICO lock, engage the PTO and idle up. We jump out, pull the clutch release and raise the bed. We shovel the snow from the front of the car, attach our V-strap and proceed up the bed to pull the winch cable out. We find ourselves sliding down the snow and ice on the bed until we stop abruptly at the snow-covered V-strap and attach the hook. Now shivering and slightly shaken from the unintended luge trip down the carrier bed, we check traffic then hurry back to the side of the carrier. We tap the clutch release lever back in and pull on the “winch in” handle until the clutch engages into the spool. WRONG again. Rounded jaw clutch teeth are the single largest repair to winches that I see and are easily the most dangerous condition to have with your winch.

It all stems from the clutch engagement method mentioned before. When we power in to engage the clutch, the pressure and speed of the drum rotation can catch the jaw clutch before it is fully engaged, leaving only a 1/4″ or less of the teeth engaged. This situation causes the teeth to round out if done repeatedly. Once rounded, it may cause the winch to disengage at any time, allowing your casualty to freely roll down the bed and over anything and anyone behind it. The correct procedure for engaging the jaw clutch is to release the clutch lever, then tug on the wire rope until the jaw clutch engages into the drum and stops the free-spooling. Then and only then should power be applied to the winch. I want to stress this: we can prevent damage to our machines and customer vehicles, or even prevent the loss of life by simply using machines the way they were designed to be used—safely and correctly.

Give someone a winch and they will pull stuff around. Teach someone recovery and they will be an asset to our industry and society.

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Does It Really Matter

Cargo Control for Tow Professionals

Cargo Control for Tow Professionals

B/A products has been manufacturing and distributing towing and recovery products since 1978. We have come a long way since our start, increasing our product line, doing more manufacturing in house, larger space and more employees. Product quality is our top priority, and to ensure quality, we do a lot of testing.

If you have been to one of our open houses, you may have seen some of the testing we do. Random samples of all inbound chain, wire rope and forgings, snatch blocks and more are tested. While we receive documentation from our manufacturers, we test to verify that documentation. Does it matter? Yes!

In the course of testing, we occasionally find product that does not meet our specifications. We received a batch of chain that was not breaking properly. While the chain made minimum break strength, there was little to no elongation, the chain was too brittle. After discussing the problem with the chain manufacturer, it was discovered the chain had been heat treated to the wrong specification. The chain was returned, annealed and reheat treated, and now met spec. Did it really matter? In this case, yes.

We also test finished product to verify that the ratings we give them are accurate. When we started making tie downs for the auto hauling industry, there was a lot of debate on what the Work Load Limit of the straps should be. One side wanted to rate it based on the weakest component. The other side said in use, the load would be distributed and it would withstand a higher load. How to settle the debate? We built a mock up of a car hauler deck to use on our Crosby National CN22 flat bed tester, strapped a tire in, and tried to pull it out from under the strap.

The result? At 15,400 lbs, the test was stopped. The tire was still under the tie down, and as you can see in the photo, we compressed the tire a few inches. The strap got the higher work load limit, and we are confident the strap is suitable for the job. Did it really matter? Once again, yes.

We also get customer driven requests. A customer asked us to document the differences in the breaking strength of ratchet type load binders depending on how far in or out the hooks were relative to the ratchet mechanism. Test parameters were set up, and the testing began.

Load Binders at the Beginning of the Test

Load Binders at the Beginning of the Test

For the first round of testing, a 5/16”-3/8” load binder with a Work Load Limit of 6600 lbs and a Minimum Break Strength of 19,800 lbs was tested. Three samples were tested: one with the hooks wound all the way in, one with the hooks 1/3rd of the way out, and one with the hooks 2/3rd of the way out.

The samples were then hooked onto a section of 3/8” grade 80 chain. Each end of the chain had a clevis grab hook, and loops were formed over the hooks of the test bed.

Load Binder and Chain in a Test Bed

Load Binder and Chain in a Test Bed

Force was applied to the point of failure, the results were graphed and photographed. So what happened? Here are the results:

Hooks all the way in: one grab hook on load binder opened at 23,275 lb

Hooks 1/3rd of the way out: one grab hook on load binder opened at 23,711 lb

Hooks 2/3rd of the way out: one grab hook on load binder opened at 21,396 lb

So did it really make a difference? In this case, no. Regardless of the hooks position, the load binders exceeded their Minimum Break Strength, and nearly four times their work load (remember: NEVER exceed a products Work Load Limit!).

Just to confirm our results, another group of load binders was tested. These were 3/8” G100 binders, with a Work load limit of 8800 lbs, and a minimum break of 26,400 lbs. The test set up was the same, using 3/8” grade 80 chain. This time the results were a little different:

Hooks all the way in: chain broke at 29,889 lbs

Hooks 1/3rd of the way out: chain broke at 22,089, where binder was hooked

Hooks 2/3rd of the way out: chain broke at 22,029 where binder was hooked

GRAPH OF TEST. CHAIN FAILED AT 22,029 LBS

Graph of initial test

Graph of initial test

So what happened? First, the Work Load Limits were mismatched. Binder Work Load Limit is 8800 lbs, 3/8 Grade 8 chain WWL is 7100 lbs. One test went above the Minimum Break Strength of the chain (28,400 lbs); two were below the MBS. In both cases, one of the links the binder was hooked to failed. This is known in the chain industry as a Preferential Failure. Because of the way force is applied to the link by the grab hook; it can fail at up to 20% below the chains MBS. Chain is designed to be pulled in a straight line, not from the side. Also remember, that an assembly is rated by its weakest component, and once again, NEVER exceed the products Work Load Limit.

So did it really matter in this test? I’ll have to say yes and no. No because the position of the load binder hooks did not affect the result of the test. Yes because the differences of the Work Load Limit of the components did affect the test, as well as the Preferential Failure.

I’ve asked the question does it really matter several times, and answered some with yes and some with no. The answer to all of them should be yes. We test to make sure you get the best product available, every time. It matters because when we ship a product, any product, we want there to be no question it will do the job for which it was designed., every time. Yes, it really does matter.

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