GRADIENTS WITHOUT RATIOS!

I suspect that like everyone else I’ve been brought up on gradient ratios – 1-in-40, 1-in-60 and suchlike. We’ve traditionally had gentle gradients for main lines and considered steeper ones best for short trains. To me, that’s always been a generalisation, without applying much logic.

I’ve been helping my friend Peter Salmon build his layout for quite a few years now and, back when we started, he needed to find out what would travel up a potential gradient to his high-level branch line terminus. As with every complex layout idea, I suggested we make a mock-up on which we could undertake a series of experiments to define gradients and stock performance.

Initial tests showed that identical classes from different manufacturers and identical locomotives from the same manufacturer performed differently. In testing Peter’s locomotive collection there were some surprises, with smaller locomotives occasionally outperforming larger contemporaries. Additionally, it depends on the train. Varied stock length and weight will all have an impact, as will added detail, particularly if, like Peter for example, you add real coal into mineral wagons.

From the results of our experiments, we found that we could rise approximately 3in, enough to clear stock on a track below, over a distance of 56½in, a ratio of approximately 1-in-19.

Viewed side-on, it’s a tough-looking climb, restricted by factors at both ends and yet, at normal three-quarter viewing angles, it looks perfectly acceptable. I know there are only five mineral wagons and a brake van behind the ‘9F’, but that was for the purposes of a photograph. The 2-10-0 would comfortably haul ten wagons and a 2-6-4T could pull three coaches up the grade.

Even when you’ve factored in variables already mentioned, two of the most important considerations still outstanding are: l Resistance against movement is always going to be greater when your train either commences from a standing start at the bottom of a gradient or stops partway up and then has to restart. l Transition in track as it changes from on the level at the top or bottom of a gradient – at its worst it will cause driving wheels to lift off the rails. On the immediate right you can see the different degrees of success; the lower level has a track joint right at the point of change and, as a result, there is a slight kink. Fortunately this hasn’t affected performance, whereas the upper level is a very smooth transition from level, right, to the gradient, left of the point.

A possible effective option (though one I’ve not tested) might be to have plateaus spaced so that only half or part of a train, particularly a long one, is on the gradient at any one time. In this way the locomotive and front end stock will be on a flat section before it picks up the full resistance of the rear section onto the grade.