Beam compass or - as we used to call them - 'trammels', but I think 'beam compass' is a better description - as the man said, does exactly what it says on the tin. You may be wondering what use this old fashion drawing and marking out instrument has in this modern age of computers. Well, the answer to that is quite simple. In order to model the valve gear of the 5 inch gauge locomotive I'm building I needed to draw large arcs and my lap top is just too small to be able to see what's going on at the intersections. Moreover, my pension just doesn't run to buying a large monitor, so its good old pen and paper to the rescue (photo 1).
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