I have to study several industrial pulleys made for lifting heavy weights.
It is important to select one which has a low coefficient of friction because the system is based in a hoist and several corner angle transmissions under heavy load. So that there is lots of strength lost by friction. I also have many other constraints of course. I'm not searching for pulley brand but for a test mechanism I could use to check the already selected candidate pulleys' coefficient of friction.
I could test the static coefficient of friction quite easily using a weight at one side and a dynamometer at the other side.
However my application wile involve several lifts a day with up to 20 meters of rope running under heavy load (1~2 metric tons per pulley). The speed is relatively low. 1m/s in the rope would be the absolute maximum.
I don't know if the static coefficient of friction will be enough to make a relevant selection. What do you think about it ?
I had several ideas to build a testing machine. All seems to be quite complicated :
I firstly imagined 2 big hydraulic jacks with a dynamometer at each side. I'm not sure of the minimum length of the jacks but I had in the idea that 2m would be a minimum to get something representative.
I then imagined a relatively compact system with an endless rope running under load between a motor and pulley. I would measure the torque between the motor axis and the wheel actuator. I'm not sure of what I would exactly be measuring here but I could make some comparisons.
I also imagined a system with 2 opposite pulleys under tension. I would measure the strength needed to move the rope with a dynamometer. I'm quite sure I should not do it manually but with a constant speed or constant strength system. I'm afraid to build a labyrinthine system.
Do you have better ideas or insights on how to do it ?