Selective compression is a term frequently used by model builders. It’s the process by which the modeller reduces or eliminates elements of a given prototype, in order to build a model that is smaller than a true scale model of the real thing. My friend Jim Providenza recently asked how much compression of the track and structures I was forced to do in Port Rowan.
The short answer is, “not much”. For the long answer, keep reading…
Here’s an example of selective compression – one I’m not going to pursue:
The Port Rowan station has six dormers in the roofline on the trackside of the structure. One could make the station two-thirds actual length and model it with four dormers. Or one could reduce the size of each dormer – and, by the same amount, the space between the dormers – and perhaps make a model that was only 80% as long as the real thing.
I do not plan to do this with the Port Rowan station. My mock-up is full-size – for a few reasons, including:
– I have the space.
– It’s a signature structure.
– It’s adjacent to the railroad so its size will be compared to things I can’t compress – namely, the trains themselves:
Now here’s an example where selective compression can be used – and I will:
I’m going to build a row of tobacco kilns near St. Williams. When I measured these prototypes (in Scotland, Ontario) I learned that they’re perfect layout-sized structures: They’re just 24′ x 22′:
But the kilns in the group I measured were spaced 55′ apart. If I did that on my layout, I’d only be able to model three of the kilns, and that didn’t seem like a big enough grouping. So, as suggested by my mock-ups of the kilns, I’ve selectively compressed the clear space between them to 25′:
On my layout, all structures are being modelled full-size. Many of them are small and my layout plan is so simple that there’s plenty of room for structures around the tracks, so I really don’t feel I need to compress them.
As for track arrangements, St. Williams suffers from some liberties. Most notably, I’ve had to build part of the double-ended siding on a curve, whereas it was straight on the prototype.
In Port Rowan, I am compressing the yard, but not too badly. Using the CNR survey map I have, and knowing that the trackside wall of the station is 80′ long, I’ve worked out the prototype yard to be about 1,700 feet long from the first switch to end of track. On my layout, the distance from first switch to end of track is almost 1,100 scale feet (17 actual feet). That works out to approximately 2/3 full size – which I think is pretty good for a layout.
The turntable actually goes the other way – it’s five feet longer than the prototype. Selective Expansion?
(Thanks for asking the question, Jim!)