Some of your posts have been a real asset over this last few years Hexagon. Thanks for taking the trouble to research/explain this.Up until about 1988 they were about as reliable as a normal 47/4, after that while they were maintained as well as possible I think it became known they were getting replaced and so there perhaps wasn't the same level of impetus as before.
Certainly in the late 1980s there was a booked Sunday Inverness-Aberdeen-Glasgow formed of a Mk2 air-con push-pull rake but booked for a 47/4. The Mk3 stock was all in ScotRail by 1985.
100mph was only authorised from May 1985 and only at that point on Edinburgh-Glasgow. From May 1986 it applied on Glasgow-Aberdeen as well. Until those dates the 47/7s were still 95mph machines, indeed if a 47/7 missed it 'special maintenance' as it were, it reverted to 95mph.
The 100mph sections in the 1980s are broadly as now, Dundee-Arbroath is mostly HST 100 and 47/7 push-pull sets were allowed to use these differentials at the time.
They only managed as they did in Scotland because of the care and attention they were given.
Braking. They are part of the compressor cooling system for the air brakes. Normal 47s' compressors only ran when a key was in the desk, the 47/7s were modified so they would run without a key in, when in propelling mode. The compressors were running for longer and note frequently and thus getting hotter.
They were effectively part of an aftercooler to deal with excessive moisture build up which was causing failures, these were an addition, the first batch of locos didn't have them from conversion, the later batch did.
Nevertheless, it didn't succeed in increasing reliability as I understand it.
Right, that's enough of that.