Having had the Twitter Display v1 photos on my portfolio and being that Google is spartan of any useful results several people have contacted me over the years regarding my display, looking for help making their own, to name a few:
I originally got in touch with someone at Network Rail (Tom Chaffin) about their old units back in 2009 but even then there was nothing about, too late I guess, however he did have some photos for me but I can’t find them any more, he did have a interesting little bit of information about the recent history of the units within the UK rail industry:
The split-flap indicators where widely used for customer information systems on the railway, but the final installations have now gone on National Rail – the last I was aware of was the large main departure board at Liverpool Street and some small displays in the ticket office at Lewis; I forget the exact date, but I think Liverpool Street has been replaced by LED panels for over a year now. I know for sure that there are none left in service as the Network Rail maintenance standard to maintain them has now been withdrawn – the standard no longer has any use.
The majority of the flap indicators where supplied by an Italian company, Solari SPA and as such these indicators were often called ‘Solaris’ by railwaymen in much the same way as vacuum cleaners are called ‘Hoovers’ whomever the manufacturer is. However, some flaps indicators were also supplied from a company, I think German, called Krone.
The newest indicators consisted of a number of modules, each module having 80 flaps – each module therefore being able to display 80 different sets of information, though inevitably there would be at least one blank in that set of 80. Earlier modules had just 40 flaps. The flaps were printed both sides with sets of information – this varied from a set of a group of stations split over the two flap sides to final destination split over two flap sides – i.e. the two together would show “Victoria” or similar. The flap spindle was driven by stepper motors with electrical contacts or I think in some cases optical sensors being used to ascertain the position of the spindle and hence stop the motor once the module was displaying the correct thing. One of the major disadvantages of flap displays was that every time the timetable changed altering train service calling points or final destinations changed or even for a train company name/branding change, new flaps had to be silk-screen printed and then inserted into the indicators ideally the night of the timetable change. The new main departure boards such as those at Liverpool Street, Victoria and Charing Cross had the columns of flap modules pivoted top and bottom, so to change the flaps it was possible to turn the column through 180 degrees and change the flaps from the inside. With older displays a tower or ladder was required to work from the outside. The displays were built up of a number of modules, from typically just two for a single-sided platform next train indicator to many rows and columns of modules for a large departure board at major terminal station. We never used flaps where one module was used for individual letters – hence this problem with having to change the flaps when the stations changed would not exist, albeit with the drawback of a far more complex and expensive display required, but airports did (and may even still do somewhere) have displays formed in this way.
One of the great advantages of flap indicators, which other alternatives have not fully addressed, though they are now getting close, is their readability under all lighting conditions and viewing angles. There disadvantages was the need to change flaps, as above and the ongoing maintenance cost for something which is electro-mechanical.