Saturday, 16 September 2017

September 2017 meeting

This month's group meeting, in Edinburgh, was sparsely attended. Alisdair, Andy and Graham gathered to progress the point rodding on Sauchenford.

First though Alisdair shared some of his recent modelling: the filter tank for a sewage farm (no, really) which posed an interesting problem since his chosen prototype has masonry walls with a noticeable batter. The shape needed is a slice through a cone.

Alisdair's first thought was to wing it, slapping together two plasticard discs separated by a spacer and side walls made up of flat segments. After strips of Wills stone pattern styrene were glued in place and the whole thing sanded down a bit, it would look fine, he thought. Except that it didn't; it remained lumpy and unconvincing.

So another attempt was made, this time drawing out the wall as a flat sheet before curving it into a three-dimensional shape. Alisdair explained that he was able to do this quite simply, by making a trammel, pivoting it near the edge of a sheet of plasticard, and using a scalpel fixed to the trammel to cut two lines giving the correct shape. I have no idea how he knew to do that (perhaps he was in contact with David Eveleigh, who bases whole layouts on conic sections, or perhaps he simply paid more attention in maths than I ever did). Anyway this technique worked much better. The correct name for the shape of the tank, so the Interweb tells me, is a frustrum (no wonder). Several web sites explain how to draw it out (for example, here). Alisdair found that, if he nicked the rear of the stone-sheet strips and bent them slightly (the whitish marks in the shot below), they followed the shape of the wall much better. This is how it looks even before sanding down to reduce the overscale stone courses. 

Alisdair has also been experimenting with Scalescenes downloadable brick and slate sheets to construct other buildings for the sewage works. He found he was able to change the colour cast and tile size of the sheets with a graphic editor to give the effects he wanted. We look forward to more details as his investigations proceed.

After our lunchtime bacon rolls, we got on with the task of assembling the point rodding stools (made up from Laurie Adams' etches, see last month's blog) onto small bases of black card, ready for planting on the layout. Alisdair soldered up a rodding compensator from the Association etch. The results of all this labour may need a little tweaking for straightness but are reasonably effective from normal viewing distance, even when not painted or weathered, and with the glue still wet. 

On its own this short run is not very visible, but the overall effect once all the rodding is in place should be worthwhile. It had better be, after three of us going cross-eyed all afternoon ... 😲 

1 comment:

  1. what a productive lot you are north of the border