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I'm stuck in a ditch - what's the best way to get recovered?

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waveydavey:

--- Quote from: squaddie_fox on November 07, 2009, 02:08:42 ---before doing any type of recovery, get people out of any danger, work out an estimated pull (the force in tonnes would be sufficient and dont forget about a 25% safety factor)

--- End quote ---

I would be interested to know how many people can sensibly do that and put a number to it? Other than when your winch reaches its limit how do you estimate the force on it?

Out of interest I am currently operating a  winch that can pull 350 tonnes - that would get it out!

squaddie_fox:
the easiest way to do it, is thus:

establish the type of ground you are in, then apply the appropriate 'ground factor' (GF).

       hard standing = 25
                    grass = 7
      hard wet sand = 6
       soft wet sand
               or gravel = 5
      loose dry sand = 4
               light mud
              or shingle = 3
             deep mud,
            bog or clay = 2

then work out the weight of the vehicle, round up to the nearest tonne, so a rangie or a disco would work out to around 3 tonne.

last thing is to work out the degree of the slope that you will be pulling the vehicle up. for this example i will put it at 25 degrees.

once you have all this information you need to use it to find the rolling resistance (RR), gradient resistance (GR), damage resistance (DR) and a safety factor (SF).

use these simple equations: RR = WOV/GF
                                              GR = WOV x DEGREE of SLOPE
                                                                                60
                                              DR = two locked wheels = 1/3 weight of vehicle, four locked wheels = 2/3 weight of vehicle
                                              SF = RR + GR + DR
                                                                    4
 once you have all these worked out, add them all together (RR + GR + DR + SF) and this will give you the estimated pull (EP) required to extricate a vehicle safely.

then in tonnes, work out the maximum cut out of the winch (WCO) being used so you can work out the mechanical advantage (MA).

MA = EP
           WCO

so, a disco stuck in deep mud with an incline of 30 degrees with no damage works out something like this:

RR = WOV/GF = 3t / 2 = 1.5t

GR = WOV x DoS = 3t x 30 = 1.5t
                    60                     60

DR = none

SF = RR + GR + DR = 1.5t + 1.5t + 0t = 3t / 4 = 0.75 t
                      4                                     4

EP = RR + GR + DR + SF = 1.5t + 1.5t + 0t + 0.75t = 3.75t (round up to the nearest ton) = 4t

MA = EP = 4t =  1:1 or single line (if EP had been more than 4.3t it would have been 2:1 or a double line pull)
           WCO           4.3t (4.3t average 9500lbs winch on the bottom layer of wire on the drum)

so, any questions?

Saffy:

--- Quote from: squaddie_fox on November 07, 2009, 17:10:05 ---the easiest way to do it, is thus:



--- End quote ---

could have just linked to the full REME recovery manual instead

squaddie_fox:
i could of, that was off the top of my head.





(recovery mechanic by the way...)

littlepow:
Chinnok - might be over kill and expensive, but will look good and have some really big bragging rights!

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