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String Transport or Yunitskiy String Transport is an elevated transportation system using two "strings" or tracks with a wheeled vehicle riding on them. It is proposed for both freight and passengers designed by Russian inventor Anatoly Yunitskiy.
The string transport is a transport system design not yet built nor planned. Only small scale models exist.
The way design is based upon the use of strings built with high-tensioned steel wires inserted into a concrete/resin core and enveloped within a steel shell. It differs from traditional cable ropeways by using a perfectly flat rolling way to limit the wear, rolling resistance and noise. The functions dedicated to rope tension and rolling way are handled by separate parts. Low span intervals (~50m) coupled with tension much higher than common ropeway allow for low sag, permitting high speed operation.
The string attachments are fixed and there is no tensioning system. The steel thermal expansion over the seasons is absorbed by the modification of the tension stress in the string. As such there are no junction gaps in the rail except for switches, which are built similarly to railway switches. In principle, the system can utilize the most direct possible route, but it is possible to create curves by using intermediate supports which locally replace the string with steel structures.
Requiring minimal ground clearance, the vehicles are streamlined, creating very low aerodynamic drag, resulting in low power consumption. The absence of any standardized gauge permits wider gauge and wheel position less intrusive in vehicles than for an ordinary railway. While some recent concept drawings show electric motors being used, the system was originally proposed using internal combustion engines for power.
Proof of concept
No complete full scale prototype has been built or tested.
- The test model built in 2001, which was created with a tube supported with a wire rope and spreaders, unlike the monolithic string as proposed now, have proven that there is no loss of traction, even under icy conditions.
- Miscellaneous models were built either with one or two strings. The dynamic and wind behaviour was tested by using a single-string 1/10 scale model in 2006.
- Fatigue handling of the rail, which is an integral part of the string is being studied. As for pre- or post-tensioned beams mixing steel and concrete, fatigue studies are also being carried out. The designer proposes low overall fatigue, considering that the variation of the string tension due to vehicle weight is relatively low.
- The use of internal combustion engines on an elevated travel-way that lacks a means to immediately evacuate potential passengers raises safety concerns. Electric traction, while more costly, should be safer.
Notes and references