(at least) Two dumb questions.

thegoonden · Post by **thegoonden** » Sun Apr 22, 2007 3:24 am

Two things have been bugging me for months, if not years......

1. I noticed something on the Bangor-Belfast line that I assumed was a NI thing, until I saw the self same thing on all the mainline stations on the mainland.....
Platforms seem to have a little placque thing every few meters, it is a little white thing with what looks like a red "slider" in a slot on it, with a row of numbers alongside.
Ermmm wassat then?

2. How are thermal issues handled on continuous rail with no fishplates?

Much appreciation for any wisdom you can offer.

mattvince · Post by **mattvince** » Sun Apr 22, 2007 10:09 am

1. Is a track geometry plate. The red slider is set at a level which is in line with the top of both rails - this gives the correct amount of cant/superelevation (how much the track leans over in corners) and the correct track height relative to whatever the plaque is attached to. The numbers relate to how far the rails are from the plaque.

2. The rails are 'stressed' - put under tension by stretching them then welding them together whilst stretched. When the rail expands due to the heat, all it is doing is relieving the tension, not lengthening the rail.

southcoasttrains · Post by **southcoasttrains** » Sun Apr 22, 2007 10:11 am

thegoonden wrote:1. I noticed something on the Bangor-Belfast line that I assumed was a NI thing, until I saw the self same thing on all the mainline stations on the mainland.....
Platforms seem to have a little placque thing every few meters, it is a little white thing with what looks like a red "slider" in a slot on it, with a row of numbers alongside.
Ermmm wassat then?

Sounds like something to do with the guage and what rolling stock is allowed on that line, I might be wrong here.

jamesinbolton · Post by **jamesinbolton** » Sun Apr 22, 2007 10:20 am

mattvince wrote:1. Is a track geometry plate. The red slider is set at a level which is in line with the top of both rails - this gives the correct amount of cant/superelevation (how much the track leans over in corners) and the correct track height relative to whatever the plaque is attached to. The numbers relate to how far the rails are from the plaque.

2. The rails are 'stressed' - put under tension by stretching them then welding them together whilst stretched. When the rail expands due to the heat, all it is doing is relieving the tension, not lengthening the rail.

Correct,

Also known more commonly as a Datum Plate.

They are attached to most trackside structures.

danielw2599 · Post by **danielw2599** » Sun Apr 22, 2007 11:50 am

You will also see expansion joints in some areas too.

johncard · Post by **johncard** » Sun Apr 22, 2007 11:50 am

mattvince wrote:2. The rails are 'stressed' - put under tension by stretching them then welding them together whilst stretched. When the rail expands due to the heat, all it is doing is relieving the tension, not lengthening the rail.

If we had a particularly long and intense heat wave would it be possible for the rails to deform once all the tension is relieved?

John

BR7MT · Post by **BR7MT** » Sun Apr 22, 2007 4:43 pm

johncard wrote:If we had a particularly long and intense heat wave would it be possible for the rails to deform once all the tension is relieved?

Yes, and they frequently do in the summer as the British climate is so variable.

Regards,

Dan

thegoonden · Post by **thegoonden** » Sun Apr 22, 2007 7:51 pm

Gentlemen, I am endebted.

I'd sort of half worked out the second one, but found it hard to believe it could cope with a climate as insane as the UK's. Must have more faith in future

Are the geometry plates used by or related to the track geometry vehicles or are they there for human linesmen inspecting the track to reference, and to give workmen a baseline/datum?

Atomic Systems

(at least) Two dumb questions.

(at least) Two dumb questions.

Re: (at least) Two dumb questions.