Friday, March 18, 2016

Mt Lowe observatory's telescope room

Late last summer I started work on an N scale model of the observatory on the Mount Lowe Railway. The project was almost immediately side-tracked by preparations to see the E. L. Moore collections in North Carolina. Recently, I decided to see if I could complete the telescope room, because if I could, then it would give me confidence that the rest of the project wouldn't be too difficult.

First off, this project is more a caricature of the Mt. Lowe observatory than an exact replica. I've guessed at most dimensions, approximated shapes, made windows a bit larger, and added doors where I thought they might be needed. I think it'll look close to the prototype and capture its essence, but it's not a one-to-one representation.
The telescope room is a 16-sided cylinder. I laid out its walls in one continuous strip on a piece of 140 lb, rough surface watercolour paper. I won't go into the high-school trig on how to compute the length of a wall strip to support a semi-spherical roof of a given diameter, but if you're curious, this is the equation,

total length of strip = 32 x radius of the roof x 0.19509

For this model, I computed the strip to wrap around the perimeter of the roof, and the strip length worked out to be 102 N-scale feet after a little fudging for the folds between each wall panel.

I used graphical division to layout each of the 16 wall panels on the strip. Just take any ruler you have on hand - scale and units don't matter - place it on the drawing as shown until there are 16 equal divisions on the ruler between one end of the strip and the other, then tick off the divisions on the drawing.
Draw the lines according to the ticks on the paper. 
I then drew on the window and door openings and cut them out prior to cutting the strip from the paper. The doors on the telescope room are internal. Each of the panel divisions was scored for easy folding. 
As a test I wrapped the scored strip around the roof. The fit is not too bad. Ok, well, to tell the truth, the first strip I cut I bungled the measurements and had to cut a second. All the photos I've shown are for the second try!
I was finally happy with the wall strip so I joined the two ends with a glued piece of thin graph paper.
The floor was tricky. The first thing I did was try to cut a 16-sided floor from 1/16 inch sheet balsa. After around 3 attempts I gave up. The problem I had was that any small over or under sizing on any side causes the whole piece not to fit properly. For a large scale I don't think this would be a problem, but I couldn't get the precision I needed at this scale. I can hear a few friends in the background saying, "If you would just use a laser cutter these problems wouldn't happen" :-) 
What did work was to cut a circular disk of 1/16 inch sheet, glue some support ledges to the bottoms of the walls, and then glue the disk to the supports. 
The inside walls were panelled with pieces of 1/32 inch balsa. I plan on making the interior viewable, so this both stiffened the walls and provides the basis for a decent little scene.
The last thing was to frame the windows with the thinnest strip wood I had in my scrap box. It's a little oversize, but since the entire outer surface will be painted white, I don't think it will be too noticeable.


  1. "If you would just use a laser cutter these problems wouldn't happen" -- haha, exactly what I was thinking! Looking good though, nice wee building, and I like the ruler trick.

    1. Thanks Michael! One day I'll get one of those cutters, but I'll need to make sure I'm well stocked with spare blades until then :-)