Smoke Deflector design and theory

More details here

http://en.wikipedia.org/wiki/Milton_rail_crash

 

The "Polar Star" incident happened around 1955 at Milton, just west of Didcot where an Up train took a crossover from the Main to the Slow lines too fast, derailed and went down an embankment. Lack of driver visibilityof signals was claimed as one of the reasons, hence the modification.

 

Further evidence that the fitting of smoke deflectors is a compromise: its either smoke obscuring forward vision or the smoke deflector itself! However, I find it slightly strange that the Western and Midland region crews found forward visibility difficult on a 'Brit', when the Southern, Scottish and Eastern regions kept the deflectors as constructed. Were there any reports of similar visibility problems on the latter regions?

 

As I'm sure just about all of you know on the Western visibility was compromised because the Brit had the driver on the "wrong" side...

 

... Or the "right" side, as signals were generally still on the left on the Western region, depending on direction of travel. That should have improved visibility, if anything.

 

If you look at Converted to Unconverted Bulleids. Isn't the smoke drawn further up into the air? Is this because the Smoke Defelctors stuck out alot more? I'm not a scientist by any stretch of the imagination!

 

As opposed to Chapelon who tried to keep his steam passages as straight and uncluttered as possible.

 

IIRC there was little problem with 2001 when first built as the sharper blast with the poppet valves threw the exhaust higher. It was the piston valve variety that had the problems and resulted in the A4 style wedge nose.