The theory and practice of steam loco smoke deflectors. . . . . . .
Those of us trainspotting in the last days of steam will know these as ‘smoke deflectors’; for everyone else you are probably thinking of horses’ eyes harnessed to blank off distractions in the field of view.
Curious things, ‘blinkers’. The idea, of course, is to defect exhaust smoke upwards to avoid obscuring the field of vision for footplate crews. As locomotives got progressively bigger and faster, the need to prevent smoke getting into the field of vision became more pressing. Logically (?) goods engines didn’t really need them – but then, neither did the Great Western (taper boilers, perhaps?). Interesting. I’m sure if I had the time and a smaller in tray I might come up with the various equations that support the use of ‘blinkers’ – how the deflection of smoke was better than the sight restrictions due to the deflectors themselves and, perhaps, the drag caused by resistance to the wind. But somehow, I rather think locomotive designers were interested in the aesthetics of smoke deflectors as much as the performance of the locomotive. As a result, various designs appeared.
Conventionally, smoke deflectors would be flat metal plates attached to the running board on either side of the smokebox, probably with bracing struts against the smokebox itself. But, then, you could play around with the flat metal shape with various cut outs (see LNER A1 class), and angling inwards to the smokebox (see Southern Railway S15 class.) The problem of grab handles protruding into the line of sight was addressed on the BR Standard ‘Britannia’ Class with handles removed and replaced with small cut outs containing struts for locomotive crews to grab hold of. Other forms of ‘blinkers’ included German style Windleitbleche (wind deflecting plates) or Witte-type half plates, as fitted to Flying Scotsman, small plates on either side of the chimney (LNER A2/2 Class) and curved ‘blinkers’ as fitted to LMS ‘Royal Scot’ rebuilds (although 46106 stubbornly refused to give up its straight deflectors to the very end).
What did footplate crews really think? I put the thought to several of them in the course of recording their memories. Most hadn’t really given it much thought, assuming that locomotive engineers knew what they were doing (not something footplate men willing accepted when it came to things like firebox arrangements, for example). Dave, though, didn’t think they did much.We used to get the fire up on the down (GCR route) through
Leicestershire with a 9F. Smoke did get in the way then but it also used to drift across the new M1 and upset the cars’ views.’ (The newly built M1 ran alongside the GCR route from Lutterworth towards Leicester). We had one, can’t remember the number, where the ‘blinkers’ weren’t screwed on tight and they used to flex and rattle around. The fitters said they’d done their best, but it didn’t feel good.’
Sometimes smoke did get in your eyes, deflectors or no deflectors. Jimmy recalled approaching the vast signal gantry at the south end of Rugby Midland. ‘I always tried to leave the fire a bit until we were past Rugby. I knew my driver could have trouble picking out the gantry signals at speed though most of the time, we either stopped at Midland station or were on a signal check on the up fast.’
And that point about aesthetics? Stanier helps us by rebuilding his Royal Scots originally without smoke deflectors but with a taper boiler and double chimney. I think they looked good but, then, they did with those curved blinkers too. A favourite pastime was to scribble and erase images of locomotives in my book to see what they would have looked like without ‘blinkers’ and then to draw some onto an image of an unsuspecting ‘Black 5’. No, not quite right. I think I’ll leave it to Stanier to decide.
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