Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering
Transport Technology

T.J. Boeschoten en N.R.J. Langenkamp Negatieve kruip op tractieschijf met halfronde groef.
Laboratory experiment, Report 94.3.TT.4367, Transport Engineering and Logistics.

The application of more elastic materials and the increasing need to know the effects of relative displacements of cables on traction sheaves on the cable life, make it necessary to examine besides the forces also the displacements.
So far this had been done by using Eytelwein's theory, but technical developments increase the gap between theory and reality, and are the reason that Eytelwein's theory has become less reliable.

By using a built-in endoscope with a video-camera and a frame-grabber computer programme, the behaviour of the cable on a traction sheave and especially the displacements, were examined. This was done for traction-ratio's 1.25 and 1.35, while releasing the cable. A strain gauge was used to measure the stress at the surface of the cable, on the same location as where the displacements were measured.

The experiments showed that, while driving the traction sheave, the position of the cable on the sheave hardly changes, except for a location at about two thirds of the area where the cable lies on the sheave. On that location the creep-direction suddenly turns to negative.

The negative creep is an effect of small elements of the cable, caused by a varying internal friction and a change of shape of the other cable-elements. These effects have much influence on cable behaviour because of the relatively low cable load, when compared to the maximal cable load.

Reports on Transport Engineering and Logistics (in Dutch)
Modified: 2008.05.13; , TU Delft / 3mE / TT / LT.