Boniface Christmas QUIZ

ANSWERS

If any one who reads this is interested in more recovery theory contact us and we will invite you to Thetford for a tour of the factory and spend a little time winching a vehicle on various surfaces and gradients to test the theory, remember we are the people to deal with when it comes to heavy recovery

 

For those of you daunted by the questions set in our Christmas quiz but interested on some of the theory behind the questions here is a summary.

Questions 1 and 2. If you attended an Institute of Vehicle Recovery course you would have been taught that on arrival at the recovery scene an assessment of the job should be done and that maybe these factors should be taken into consideration.

ROLLING RESISTANCE

GRADIENT RESISTANCE

DAMAGE RESISTANCE

Various organizations have developed factors that when applied to the weight of the casualty aid the operator to estimate how much pull is required.

Q1 YOU ARE CALLED TO WINCH A TIPPER, WHICH IS UNDAMAGED, OFF A BUILDING SITE, THE GROUND IS LEVEL AND SOFT CLAY, THE TRUCK WEIGHS 24 TONNES, HOW MUCH WINCHING POWER WILL YOU NEED?

A1 In question 1, we know that the ground is level and that the truck which weighs 24 tonnes is undamaged, so we can forget GRADIENT and DAMAGE RESISTANCE.  The only two things we need to consider is the 24 tonnes weight and the fact that this is stuck on soft clay, the recognized factor for this type of ground is a dividing factor of 2. The answer then is 24 divided by 2 = 12 tonnes

Q2 THE NEXT JOB YOU GET IS TO RECOVER A TRACTOR/TRAILER, WITH ALL ITS WHEELS INTACT AND WEIGHING 44 TONNES, UP A MOTORWAY EMBANKMENT THE SLOPE IS 20 DEGREES AND HAS A SURFACE OF SOFT GRASS, HOW MUCH WINCHING POWER DO YOU NEED TO PULL THE CASUALTY UP THE SLOPE?

A2 In question 2, we know the casualty weighs 44 tonnes and in this instance it is also undamaged, so we can disregard DAMAGE RESISTANCE, however we have a slope to pull it up of 20 degrees and the surface is soft grass. The calculation for the winching effort to overcome the GRADIENT RESISTANCE is WEIGHT OF CASUALTY DIVIDED BY 60 MULTIPLIED BY THE SLOPE IN DEGREES hence 44 tonnes divided by 60 multiplied by the 20 degree slope equals 14.6 tonnes, you have to add to this the fact that the truck sits on soft grass, it is more difficult to pull something over soft grass than hard standing. The factor to use for soft grass is 4, hence 44 divided by 4 equals 11 tonnes, this must be added to the GRADIENT RESISTANCE, so the total winching effort required is 14.6 + 11, the answer being 25.6 tonnes.