Try not to edit inside quotes. It makes it difficult to reply to the points.
jeromedynamics said:
Why do you need to calculate rolling resistance?
=> to have an estimation about autonomy of a vehicle
Autonomy or economy? Travelling at speed over sand will be very inefficient.
jeromedynamics said:
What range of tyre pressure, wheel loading, driven or lazy axle?
The 4 wheels of a 4X4
All-wheel-drive will reduce rolling resistance because it will help prevent the tyres digging holes, bogging down, and the vehicle sinking.
To lower rolling resistance over sand, maximise the wheel diameter and tyre width, (but you have fixed those parameters as 37/12.5 R37), so you must use a low tyre pressure to increase the area of the contact patch. The tyres will be destroyed if you then travel fast over rocky ground without increasing the pressure. Reduce the total weight of the vehicle. Improve the suspension to reduce ground impact.
jeromedynamics said:
What type of sand, stability angle, moisture content?
=>I don't know = The vehicle will be used in the South America desert
You will need to investigate the sand. Windblown sand will be a problem.
To experiment, get some rounded bedding sand that flows, to compare with some sharp sand used for mortar. Test the slope before they flow when dry, then when wet.
jeromedynamics said:
Vehicle velocity?
=>95 km/h (max 180 km/h)
There are dynamic effects. At high speed you may float over the sand before it has time to flow, but if you slow down, the sand will move and rolling resistance may be greatly increased. The tuning of the suspension will be very important.
If you cannot characterise the sand, you will be unable to estimate rolling resistance, and so must assume it to be 1.00 while the vehicle still moving, before it bogs.
