Hi Mark, Have you thought of using a series of star droppers.
I have six 1 metre long star droppers that I take in case I cannot find a tree. On my last experiment out in the Wyperfield desert park, I had the SWB Patrol ( about 2.2 tonnes loaded ) on a slight uphill incline, on softish sand, and the handbrake fully on.
I must preface what follows with saying that I have had no formal training in recovery techniques, or the use of star droppers to retrieve a vehicle. So I am taking some risks with these experiments. You, or anyone else reading this, would need to talk to some-one who has been trained, or better still a qualified trainer, before taking any risks yourself!
I was testing out my new high lift jack in winch mode. I used a small sledge hammer and pounded in 5 of the droppers until only about 10 cm or so was left showing above the sand. In the soft sand this was quite easy to do! I made sure, for safety reasons, that I hammered them in at an angle, leaning backwards from the truck at about 15 degrees from the vertical. I just put them all in a line, about 70 cm apart, in front of the vehicle. I used four long lengths of strong rope to bind the top of each dropper to the next, using a suitable bolt and nut at the top of each dropper to stop the ropes from slipping off the top. The ropes were long enough to wrap each pair of droppers together with 4 or 5 loops, hence magnifying the breaking strain by about eight or ten times the breaking strain of the rope itself. ( But with maybe a certain percentage loss due to the sharp bends around the droppers.)
In future I think I would use a length of chain between the front two droppers, since the front dropper actually bent a little towards the truck. This dropper takes the maximum strain, and so a chain would transfer more of that strain, compared to a rope binding, along to the second dropper. The second dropper did not bend at all, but it did move forward a little in the sand. So maybe another piece of chain could be used between the second and third as well.
Anyway, apart from being b...dy hard work, and finding out that I needed to spray the mechanism of the jack with CRC ( WD40) to let the mechanism slide freely under the strain, and sand grit, it all worked quite well. I eventually moved the truck about two metres forwards.
I think another solution to the front dropper bending, would be to split the strain from the vehicle into two ‘halves’ with another length of chain. This length would be used to make a V and so have two lines of droppers, maybe four in each line. Depending on the amount of pull required, maybe only three droppers in each line would be adequate. The angle should be as small as possible, maybe 20 degrees maximum if possible. This is going to depend on the length of the ‘V chain’. The longer the better in this respect., otherwise to keep the angle small the two lines of droppers will be too close to each other. The larger the angle of the V, then there is a magnification effect on the strain taken to each side, and this magnification will also get larger. At 60 degrees both halves of the V will be pulling on the droppers with the same force as if there were no V at all!
I think the main thing to remember would be that since the droppers can bend, it would be important to knock them into the sand, or dirt, as far as possible. Then when the rope or chain connectors are added, they should be as close to the ground as possible. This allows more strain to be transferred back to the next dropper in the line, rather just bend them.
And as far as safety is concerned, I did feel quite vulnerable. By having to stand right next to the highly stressed chain, if anything were to let go in a sudden ‘snap’, you would be hoping that no projectile would also be launched! So think about how much force you are applying with your winch, and what shackles, or other parts, might let go. They could become a projectile that might come your way.
Not sure I would be wanting to pull a 4 tonne truck out of a bog using just star droppers though! But I think this method could be useful if you have lost traction on a firmish base of slippery clay. Then with the combined pull from the winch, and maybe a little help from the trucks own traction, progress could be made bit by bit. I would think packing bits of foliage under the front of the wheels might be quicker and easier. But if you cannot find any suitable foliage . . .
