Abstract :
[en] A death-ride is a long cable anchored between two dead ends, allowing the crossing of wide valleys. Besides these mobility purposes, it is also operated in rescue operations, or simply for leisure.
From a serviceability viewpoint, a death-ride design should offer a comfortable and/or enjoyable journey to the riders, which is typically expressed in terms of maximum velocity.
From a strength viewpoint, a death-ride should be designed in order to safely withstand the cable self-weight, wind forces, the rider’s load and at last but not least, the initial tension in the cable. Actually, the tensioning operation is usually subtle. Indeed, in case of a loose cable, the rider may be stopped in the in-span sagging area. Conversely a too tight cable will generate large stresses but also large outlet velocity at the end of the ride. The design of a death-ride is a tradeoff between all these aspects.
The paper presents the dynamic model that was used for the design of a 1.2km long death-ride, with an only 10-mm diameter, a constraint fixed in the very first stages of this project for compatibility reasons, with the existing equipment. This death-ride, built and used in May 2010 in a Grimp competition [1], has a world record of the longest death-ride in urban area.
The structural part of the dynamic model is rather common, with a co-rotational description of the cable by means of a chain-like model [2]. An interesting feature, however, concerns the interaction between the rider and the cable. In fact, because the pulley is rolling on the cable, the position of the force acting on the cable, resulting from the ride, depends on the rider’s velocity, which itself depends on the cable inclination. This coupling is solved in a staggered manner, and the details of the algorithm are given in the full paper.
In some limiting cases, a comparison with analytical solutions is also provided, where these analytical solutions are available [3]. Experimental validation and observation of the operated death-ride will also be presented.
