Traction Engine Lamp Lenses

by John

My Fowler 3R, 1:4 scale traction engine had nice little lamp bodies, but they looked a bit odd because they had no glass lenses.

Old photographs suggested that the lenses were convex, not flat, so cutting out some circles in flat glass or perspex was not appropriate.

But in my junk store, I had been saving some perspex balls which had originally been part of a desk lamp.


The perspex (?Lexan) balls were 50-60mm diameter


With a 12mm hole

I needed the lens to be 22mm diameter, and I could not figure a method of holding the balls in a lathe chuck without damaging the Lexan surface.

So I milled the outside diameters.


Holding the Lexan ball in the mill vice, and milling the 22mm outside diameter (CNC of course).  Then it was easy to hold the machined cylinder in the lathe chuck (collet chuck actually), and part off an 8mm thick lens.

The parted off Lexan lens was too opaque on its parted off surface, so I spent some time with 400 grit, then 600 grit wet and dry paper to remove the parting marks.   Surprisingly, it became fairly transparent.  If I had some 1000 grit paper on hand I expect that it would have been quite transparent.

Then I pushed the lenses into the lamp bodies, and this is the final appearance.


They look like they have a squint, but that is a photographic illusion.  They are pointing straight ahead.


Not bad Eh?  The side aperture needs glass or perspex.  I have some LED’s on order to provide lumens.  Not sure how I will arrange the batteries.