Sunday, 22 September 2013

Lighting our Meccano world

Meccano building has not changed an awful lot in the hundred years plus that it has been with us. The size of the parts, thread and hole specifications have remained unchanged. Yes there have been deviations (Series-X) over the years but the basic concept has remained unchanged. It is the world around Meccano that has changed and no more so than in that associated with electricity.

Today in the developed world we accept our utility services without a second thought. Electric is just there, available as a stable (well, relatively!) supply whenever we want it. It was a very different matter a hundred years ago. Here in the UK domestic use was originally very limited until local authorities used an assisted wiring scheme to encouraged people to connect their houses.  To quote a line from the History of public supply in the UK:

"The scheme began in 1930, and by 1936 over 12,000 premises had been connected"

Meccano Accumulator
(Photo: John Thorpe)
Even by the late 1930s domestic supply was very limited. Meccano attempted to keep pace with the technology by producing motors that ran on all sorts of voltages and lethal looking contraptions to convert the 'supply' to something that would run their motors. There were no batteries as we know them today.  Accumulators were the only source of portable power and you took it to the local garage or cycle shop to have it charged! Meccano sold an accumulator under their brand (now an expensive collectors item) in an effort to standardise the supply. In the early days, supply varied from area to area, not only the actual voltage but whether it was supplied as alternating current (AC) or direct current (DC).

All this played havoc with Meccano's plans to introduce the new technology to their system. While all this was going on Meccano introduced a lighting kit to add lighting to their models. The bulbs supplied were small grain-of-wheat (GOW) style filament bulbs. Today any of these bulbs that still exist are precious and although will probably still work today, they have a relatively short life expectancy and using them in our models for every-day use is not something most of us would want to do. In order that Sue could use her table lamp from her lighting kit (that I would not dare hint we use!), I suggested we used a modern alternative, instead of a modern replacement GOW bulb.

Sue's lighting kit
This is its normal state - closed!

Light Emitting Diodes are not new and have been with us for decades. it is only in recent years that the technology has moved on to produce useful colours and at a price that is affordable. They have several other advantages including developing hardly any heat and just sip power so they will run on very little supply current, usually 20mA. I won't bore you with the maths but it is very easy to match a led to any low voltage supply just by adding a current limiting resister in series with the LED - they also have to be connected up the correct way to a DC supply. If you want more detailed information on using LEDs, and the formula to work out what value of resister to use for a given supply voltage, go to THIS post on my workshop blog - you will have to scroll down a bit, past the frog - you'll see! For now, if you want to run a standard brightness LED from a 12V supply you will need a 470 Ohm ¼W resister.

Sue's Lamp

Sue wanted to used her table lamp from the lighting kit but did not want to use the original lamps for fear of damaging them so we came up with a modern solution to the problem!

Old meets new

The cast lamp base that Sue wanted to use in her model  has a hole just the right size to accept a 3mm led clip. Into this a 5mm LED will sit with its leads just making a good grip and insulating them from the casting.

Parts required - you only need one resistor!
The leads of the components are shortened and the resistor is soldiered in place.  The wires are soldered to the ends and heat-shrink tubing is used to insulate the wiring from each other and the casting.

Resistor soldered in place
Heat-shrink tube insulation - great stuff!
The wires are pulled through the small hole in the side of the base and twisted together to simulate the twisted, cotton-covered electrical 'flex' of the day. After the flex has been twisted together, heat is applied to 'set' it. works fine and the lampshade from the kit sits happily on top without any risk of it getting hot.

The leads emerge from the base and are twisted together.
The photograph above shows the bottom of the base, although it feels sound it is covered in cracks. I wonder if this is age - it must be over 80 years old now - or if it is a maufacturing fault and it has always been like that.  I think the final model is a demonstration of old and new working together in complete harmony!

Ralph.

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