For most trucks what this means is there are 5 or 6 (depending on gears) maximum descent speeds a truck can maintain.
Retard/brake performance curves determine the speed that can be maintained when the truck is descending a grade with retarder applied. If no grade lines are available calculate the rimpull by multiplying the effective grade by the vehicle weight. Drawing left to the rimpull graph (~320,000N rimpull, 2nd gear) Manually reading a rimpull graph involves If you wish to enter your own data, it is important to note that scales and units on rimpull charts range from linear to logarithmic and can use kg force, kN or lb force.Įxample: If a fully loaded (324t) Caterpillar 789D travels up a 10% effective grade, there are two ways to determine the maximum speed attainable. Spry has a truck database which includes over 100 common mining truck/engine combinations. Rimpull curves are used to determine the maximum speed attainable, gear range and available rimpull when machine weight and effective grade are known. Rimpull is the force available between the tyre and the ground to propel the machine (limited by traction) and it is measured at the wheel so includes all transmission losses. The following details what parameters of truck performance are used in Spry. Once your haul environment has been determined, the next stage is to choose which truck fleet options you wish to simulate. Your static force will be around 1% less than this, if you’re interested in static force calculations please visit as a starting point. Please note: This isn’t quite the maths, this has been simplified to avoid learning too much physics. Taking a loaded truck of 376t (GVM) as an example, on a uphill ramp of 8% grade and a rolling resistance of 2%, the effective grade will be 10% and the static force on the truck will be 376 x 0.1 = 37.6tf (or 37,600 kgf). In up-hill calculations, the effective grade (resistance) % = grade % + rolling resistance %, and conversely for down-hill calculations the effective grade % = grade % – rolling resistance.
Rolling resistance is combined with the grade of a slope to determine the effective grade (or static force applied to the truck). (1993): Mechanical Engineer’s Data Handbook Effective Grade (or Static Force) The table below (Carvill, 1989) shows example rolling resistances for pneumatic tyres on various road surfaces. Generally expressed as a percentage of truck’s weight, rolling resistance is the force that resists the rolling of a wheel or other circular object along a surface caused by deformations in the object and/or the surface. Rolling ResistanceĬentral to the cost of truck hauling is the concept of rolling resistance. The setup includes providing an input schedule, relevant equipment/truck specifications, road specifications (speed restrictions and segment codes), and the creation of road networks. Running haulage simulation and analysis requires both a multi-step setup and the use of Spry’s Logic controls. This section is designed to introduce the fundamental concepts of haulage simulation both in and out of Spry, in order to best meet the individual requirements of your projects. Haulage simulation plays an important role in identifying opportunities for improvements, testing the viability of haulage plans and managing considerable financial assets. As such, under-performance or poor planning can impact strongly on the mine’s productivity and the bottom line.
Truck haulage and haulage related costs can account for up to 50% of the total operating costs incurred by an open-cut mine.
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