As you can see in the attached doc, we have two winches on the same shaft of motor M1, two moving pulleys ( 3 and 4 ) and a fixed pulley (5). The load is 130 Tons, and we can measure that with a load cell at pulley 5 ( 32,5 Tons) when we stop the lifting of the load. But when the load is rising we measure only 30 tons! Note that we have a cable of steel with 30mm diam. and the rising speed is about 1m/min. When we lower the load, the load cell measures 36,2 Tons. Can someone explain this? This is a real case and my problem is to adjust the safety relay to 110% of nominal load, which is impossible with this beahviour of the system!!