How long is a piece of string

Asked on the group yesterday was the question about length of trains given loading schedules for various locomotives on a given piece of railway. Its an interesting question, but a very hard one to answer.

I think that the best way to look at it is how much space do you have on the layout. There's not much point running trains that are longer than your largest passing loop, or more importantly storage siding. In this respect we are far less limited by space than people who model in those odd larger scales.

I'll use as an example My long planned (and seemingly quite distant) Paikakakriki layout. Here the limiting factor is going to be the the loops at each end. I have figured on 3 trains for the layout when its operating, so the limit on train length has to be 1/2 of the circle. At a minimum radius of 18" this is (using some math that I have not used for a while, but then who doesn't know Pi to 7 decimal places?) 113", or 2.8m. 1/2 of this is 1.4m. Subtract a bit for the loco and we get about 1.2m. given that a 4 wheeled wagon (la) is 5cm including the couplers, we get a total train length of 24 4 wheeled wagon equivalents. This is visually quite a good sized train on a layout, and about right for one loco to pull, especially if you have a few trackside whitemetal kits in the consist. The express train that I am planning will be about 6 cars long which assuming these are about 15cm each will be 90cm long and again will be visually right.

The old Otaki/Cass layout was a bit different in that we could run a longer train than the passing loop at Cass as long as the second train would fit. This was normally a train of 2 Dc's and 7Cbs, which would do the dash between stations while the gargantuan Lc train just rumbled on in its own time.

To sum up, Space and station loop size will dictate train size, not what a loco could theoretically pull on a given stretch of railway (which is actually just like the real thing).