If you are my age, you might be able to remember ... just ... the bicycle lamps that were around in the 1960s. The photos below show such a lamp (note the metal construction) and an Ever Ready number 800 battery (photo courtesy of Michael Gerrish). These were discontinued in the very early 1970s but if you ever saw one, you wont forget it - two large zinc canisters in a cardboard wrapper with brass terminals on the top and the side. The cycle lamp had a hole in the bottom to allow you to push the battery up and out of the lamp. The canisters were pure zinc - not plated with steel as they were subsequently - and they were very prone to corroding.
- Cycle Lamp - photo David Gibson
- cyclelamp-h200.jpg (9.9 KiB) Viewed 7685 times
- Every Ready #800 battery - photo Michael Gerrish
- battery800_gerrish-h200.jpg (10.41 KiB) Viewed 7685 times
My thought is that given the lamp characteristics, and the battery data, it should be possible to come up with a numerical comparison between the performance of this bicycle lamp and a modern LED head torch, as found in many retail outlets. You dont even need to go to a caving shop to get a lamp that is perfectly acceptable for caving usage these days, such are the advances in battery and lighting technology over the last few years. Given these advances, just how much "better" is an LED head-torch than a bicycle lamp from the 1960s? Well, if I get around to making the measurements, I'll let you know. I recall that these bicycle lamps were a) not very bright and b) didnt last very long.
The two cells in the #800 battery had, I believe, the Ever Ready part number "60" and were almost exactly the size of today's "F" cells. The 1973 Ever Ready catalogue that I located in my father's garden shed recently doesnt list the #800, which ties in with my memory that it was discontinued in the early 70s, making way for cycle lamps using HP2 batteries (the modern D cell). However the catalogue does list the PJ996 battery, which was constructed out of four #60 cells, and it gives its discharge characteristics. Unfortunately, I cannot find my old "International Lamps" catalogue (I think I must have sent it for recycling, thinking I was never going to need it again) but I have a vague memory that the output of the 2.4V 300mA torch bulb was about 1 lumen. I suppose it would not be too difficult to measure it (shine it on a white surface, photograph it, and crunch the image data in Matlab). So... combining the battery data and some measurements of the lamp brightness will give us the information we need.
