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How to use it
Describe the machine with its mass and the height of its centre of gravity, then the lifted load with its outreach and the overhanging structures (crane booms, platform) with their centre of gravity. Add the cant of the track, the wind and the required stability factor. The calculator compares the moments about the rail on the load side, in the unfavourable condition in which that side is also the lower one.
Formulas used
b is the half distance between supports, r the outreach from the track centre line, φ the dynamic factor. The maximum load is the one that brings S to the required value.
Limits
This is a rigid-body check on fixed supports. It does not consider the deflection of the suspension, which moves the centre of gravity towards the load, nor stabilisers, suspension locking or the test load. The dynamic factors, the load combinations and the required factor depend on the standard applicable to the machine and to the equipment. For the complete verification there is the service on the stability of track machines.
FAQ
Why does cant matter?
On canted track the weight of the machine has a component pushing towards the low rail and the stabilising arm becomes shorter. When working towards the inside of the curve both effects add to the load.
What stability factor is needed?
It depends on the applicable standard and on the condition verified: in service, with wind, in a test with overload. The calculator leaves it as an input, to be taken from the standard or the specification.
Why does the suspension make the result worse?
Under the overhanging load the body rolls on its suspension and the centre of gravity moves towards the load. That is why many machines lock the suspension in the working configuration.