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Railway signalling discussion

Bransty

Current and future British signalling (UK except Northern Ireland)

Re: Bransty

Unread postby John White » Sun May 29, 2016 11:29 am

Hmm this might be difficult to describe, but I'll have a go..

The method of lifting the hook rack changed several times in LNWR days and they finally settled on the well known tumbler arrangement back in the late 1800's. However, the tumbler, which is really a small rocker attached to the lever, become worn on the pivot pin, which in turn allows enough free movement to permit the lever to be operated even when the interlocking is in a locked state.

During the 1950's Crewe Drawing Office developed a new method of actuating the hook rack - which became known as the Cam and Sleeve lever - and was employed throughout Manchester and Crewe divisions. I don't know if it was used 'Down South', though I would suspect so, as all our LNW levers were serviced at Crewe, and routinely changed to the C&S type by the workshops. There were very few original 'Tumbler' levers left in service by the 1980's.

The tumbler is removed from the lever and replaced with a box section (the sleeve) which wraps around the lever, and is free to slide up and down it. The lower end of the sleeve is attached to the original adjusting link that lifts the hook rack. Rivetted to the right hand side of the sleeve are two bronze dogs which follow a cam race, which is attached to the left side of the quadrant. (Each lever being on the left of its own quadrant).

The cam race is roughly akin to the letter Z turned 90 degrees, and flattened out a bit. The central portion of the Z is a shallow arc, concentric with the lever axle. Moving the lever out of normal from N to A the sleeve rises up the first part of the cam, which develops the locking motion. No motion is transmitted for the central part of the lever travel until the E position is reached, when the sleeve rises up the last part of the cam to R, giving the release movement.

After 25+ years testing and examining the brutes, I'm ashamed to say I can't find a photo of one - just another day at the office.

Surely someone on here has a pic. of a cam and sleeve lever?
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John White.
John White
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