Lamp Making

By Pat Field

The original inspiration came from an article in Model Engineer about making lamps for traction engines. The idea was to make a die the shape of the vent top and then punch shim brass into a lump of lead. This produced very inconsistent results, with more bad ones than good ones. There were problems with the lead spreading, and keeping the die upright, so I decided that the solution was a guide for the die and a mould for the lead.

A casting from an old lawnmower bolted to a steel plate made an ideal guide for the die and a mould was turned up to fit in a hole in line with the die. This worked a lot better, but gradually the die would go in deeper; the stamping would get stuck and then deform as it was levered out.

I tried various grades of lead and solder in an attempt to get better results. Eventually I noticed a lump of Plasticine on the shelf in front of me and wondered how it would work. The results are very good as long as the metal and die are a close fit in the mould to stop the Plasticine escaping.

The final breakthrough came when I could not get all the detail from a die that I wanted, and decided to try a layer of soft cardboard such as a Weetabix box on top of the Plasticine. For every new stamping the Plasticine is re-levelled and a fresh layer of cardboard inserted. This produced excellent results, with nice clear detail on the stampings and very few failures.

This system is also good for the slightly domed backs of round lamps with the boss for the red light if required, and for the tops, bottoms and sides of square lamps and many other parts. The ultimate aim was to make lamps like the originals. I recently tried a small medallion with 5 thou. shim with excellent results. If you can get the detail on the die, you can produce as many as you like which are all the same.

It was intended to put some sort of lever on the die guide to turn it into a press, but I have found it best to select the right size of hammer for the job and give it a quick sharp blow. Mostly I use annealed 10 thou. brass, and if the stamping requires a lot of forming it can be re-annealed and stamped again. The advantage of the mould being soft is that it reforms for every stamping.

Making round items, apart from the conical vents, have required a lip round the edge, so the shim is cut into disks slightly larger than required to allow for trimming. The metal is formed and then trimmed by laying a washer the same thickness as the lip inside the item as a guide, for trimming round with small tin snips. To finish off it is given another light stamping to straighten up any distortion and finally rubbed over a sheet of wet and dry paper to clean up the edges.

So far all other shapes have normally required a lip round the edges. To avoid problems at the corners, the metal is cut out at the corners and the edges bent up over a block the same size as the die, so that it fits in the mould. The item is then worked in the same way as the round ones.

This may appear to be a lot of trouble to produce a few items, but in the long run it has many advantages. You only have to make each die once; after that all the stampings are identical and as close as I can get to the full size lamps. It has also been a lot of fun.

As there appear to have been as many designs of lamps as there were carriages, whenever I see an interesting lamp in a museum I take a few photos and measurements for future use. One day I should be in a position where I am able to make most of the parts for a new design from my collection of dies. If any member wants any parts to make lamps, please ask. I may be able to help.