Recovery Straps and Kinetic Ropes
by Alain Hoffmann
We are luckily a long way from those
days you used chains and cables to recover a stuck vehicle. Oh, I still
remember those days 'bout 20 years ago. We used to get stuck fairly often
as tyres at that time weren't what they are today. But mud holes were
as deep as they are still meaning you could get a real good stuck after
only a couple of minutes.
So we used to grab a length of cable, swing it around a suitable looking place and tried to pull the stuck vehicle out after tightening the cable. Of course in 90% of the cases this gentle approach didn't work, so we tried with just "a bit" more slack in the cable. This continued until
A) the stuck vehicle got out, about 50% of the time or
B) a PART of the vehicle got unstuck, about 30% of the time or
C) the cable broke in about 20% of the time so we had to use another cable and restart the whole process.
Especially the B) and C) variants weren't too popular; we tore all possible things off our 4x4s, from bumpers to hooks to trailer balls, even a window wiper but that's a different story...
Those method had the disadvantage that there were often parts flying at one or the other vehicle. The pic on top is the result of a winch cable breaking loose under load. Luckily no one was hurt. The pic left shows what a strap without any metal part but soaked with water does.
Today the most common method of getting unstuck is by using a recovery strap or a kinetic rope.
Straps are commonly used since about 20 years. They are made of heavy nylon and get their elasticity from an x-webbing, allowing it to stretch for about 30%. Do NOT confuse them with those straps for fastening down loads- those are not elastic and will act like cables!
Getting unstuck is easy. You put the second vehicle about 80% of the length of the strap from the stuck. You should really try to pull FORWARD as the forward gears are much stronger than the reverse gear.
This means with the standard length of 10 m/30 feet you give 1,5-2m freeplay. Now the recovering vehicle pulls away with a steady speed, usually 1st or second low box. As soon as the slack is taken up the force is "stored" in the strap.
Now 2 things may happen: At one point the force needed to pull the strap longer is higher than what the vehicle can produce= the forward motion stops and, if you're good you will just in time push the clutch and the brake. Now back up again and repeat the process with a BIT more vigour. The other thing that can happen is that the stuck vehicle comes out. In any case it normally doesn't hurt if the stuck vehicle tries to help. As soon as the vehicle is unstuck it's driver should operate the horn and stomp on the brakes. Ideally it should stop the other vehicle. Than any of the 2 vehicles has to back up a bit to relieve the tension.
Kinetic energy recovery ropes work in a similar way but are even softer in working. They are also easier to stow away. Kinetic ropes were initially designed to recover stuck armoured vehicles so they are available up to 100 tons rating. They were so successful they are now widely used on ships of every size.
Kerrs a more expensive than recovery straps. In any case you will need at least an 10 ton rated strap or Kerr. If you go for a higher rating it will not flex! A lower rating will be unsafe.
Straps and ropes are UV sensitive. This means they will decay when you leave them in sunlight.
They also hate to be stored wet and dirty. If you use them and make them dirty try to find a small stream on your way home and wash them quickly out. Afterwards just throw them in the back of your car. At home you should wash them with a good pressure cleaner and hang them up for drying. Don't put them in the washing machine as the remaining mud and small nylon pieces will clog the filters. Also they don't like high temperatures or the detergents in modern soaps.
They should feel smooth to the touch. Any cuts reduce the load capacity but if about 10% of the wide is cut at any place you MUST discard it. A strap braking under load has a tremendous force. A good way to ruin a perfectly good strap is to sling it around a sharp edge. It will be cut under load! Another good way is to spill oil or grease on it. Both destroy Nylon and stay in the webbing. If a strap has such stains it MUST be cleaned with a good soap. You can use shower soap with good results.
The shell life of a strap is limited. After 4 or 5 years you should no longer use it even if it looks like new. Load carrying capacity may be reduced.