Reducing ground pressure

With the work that we carry out on the moors and on agricultural land it is important that the vehicles we use are designed to minimise ground pressure to reduce compaction.

Compacted soils contain fewer larger pores, which have greater volume for water filtration and drainage.  This results in surface water standing on the surface rather than penetrating and draining away.  If on a hillside or moor, this water becomes run-off, causing erosion.  The potential for moorland to counter-act global warming is great, with its ability to lock up thousands of tons of carbon in its peat.  It is vital to preserve and restore our moorlands and prevent the the peat being washed away.  On farmland, flooding not only causes crop damage, but forces water straight into streams and rivers which can cause them to flood their banks, as we have seen in recent weeks in Cumbria.

Ground pressure is measured in Pascal’s (Pa) which is then corresponded to PSI.  Average ground pressure can be calculated by: average pressure = Net force/Area (p=FA)

Increasing the size of the contact area of the machine to the ground (footprint) reduces the ground pressure and therefore reduces compaction and makes traveling on unstable ground less risky.

Below is some examples of ground pressures:

Human male stood (1.8m tall, medium built)       55kpa (8psi)
Human male walking (1.8m tall, medium built)   110kpa (16psi)
Horse weighing 550kg    170kpa (25psi)
Horse weighing 550kg galloping        3.5mpa (500psi)
Mountain Bike     245kpa (40psi)
DTMS Alpine tractor and flail     33kpa (4.7psi)
ATV (wheeled)            13.8kpa(2psi)
ATV (rubber tracked)    5.165kpa (0.75psi)
Hover craft          0.7kpa (0.1psi)
                           

When we designed our flail rear wheel attachment, the aim was to reduce ground pressure, to reduce compaction and to increase traction.

Adding large floatation wheels to the alpine tractors and manufacturing bespoke axles for the flails to facilitate floatation tyres that has reduced the ground pressure by 6.5 psi.

Reducing the air pressure in the tyres also reduces ground pressure.  The flatter the tyre, the greater the amount of rubber is in contact with the surface.  This reduces the overall ground pressure of the vehicle.