Compensation For Gradients in Tunnels
See also: Table of turn tunnelsTunnels on steep gradients can present problems for air-breathing locomotives, such as steam locomotives and diesel locomotives. Poor ventilation in long or narrow tunnels can starve the locomotive of power. The solution is analogous to compensation for curvature and requires the gradient in the tunnel and for some distance on either side to be greatly reduced compared to the ruling grade. Unfortunately, the necessary compensation for gradient is not a simple equation, but is rather a trial and error process. Since one cannot build several tunnels to find out which one is best, it is useful to study existing tunnels with steep gradients.
Moisture from exhausts and springs can also make the rails slippery, and allowance may need to be taken for that as well.
Read more about this topic: Ruling Gradient
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