Friday, March 10, 2006

Fixing a Signal Instrument

Signal Instrument in bits.
Originally uploaded by Phil_Parker.
It’s amazing how problems hide themselves to pop up when you least expect it.

I recently bought a power supply indicator. The device had (apparently) come from a signal box. My plan is to use it on the Hospital Railway to indicate when we are about to run the electric loco. If this doesn’t work, because of its signalling origins I’m sure someone will give me more than the fiver I paid.

The only thing really wrong with it was that the indicator arrow was scruffy. A touch of paint would cure that, or so I naively thought.

Taking the instrument apart, the arrow is not only missing paint, it appears to have corroded as the surface is rough. I start rubbing this down very gently and bad things happen. The arrow bends. In fact it tears a little. Oh dear, or words to that effect.

A bit more sanding and I have two bits of arrow. One half of the head has fallen off as well.

In the end I had to work out how to remove the arrow (take off the top pivot support, then grip under the arrow with small pliers and unscrew the nut on top with another pair) so I had all the bits on the bench.

While I did think about making a replacement with some thin nickel silver but decided instead to stick the bits to some 10 thou plasticard, carefully arranging them so the arrow was whole. The metal is very thin and sticks to the plastic with superglue. The plastic was trimmed back so it didn’t show and the arrow filled where the original tear was.

Now painted with black paint (matt followed by a gloss coat) the arrow looks as good as new. All I have to do now is put the thing back together. It better work after this.

No comments: