Questions about bullhead rail, what is the pros and cons?

[Gostav]

Is today British suppliers still supplying new bullhead track? If flat rail were more batter than bullhead rail (by Wiki), why British Rail/ Britain's railways still keep a lot of bullhead rail before this century? l found the underground stations of Mersey Rail still bullhead rail with wood keys. Does the wood key need often be maintain to keep on the chair?

 

[Pigeon]

Bullhead rail is easier to manufacture. A major difficulty with manufacturing rails is the newly-rolled hot rail warping as it cools, due to differential contraction between the head and foot. With bullhead rail the head and foot are much more nearly the same section, so the cooling is more even and the warping is less. The degree of process control necessary to minimise warping and to effectively straighten the rails afterward was not developed until well into the 20th century, and the widespread use of flat-bottom rail is a comparatively recent development.

At one time it was thought that bullhead rail could be made to last twice as long by turning a worn rail upside down, but when they actually tried this it turned out that the original foot side got dented by the chairs and it caused very rough running.

Replacing bullhead rail with flat-bottom means also replacing all the sleepers and chairs. Flat-bottom rail is most advantageous for high-speed heavy-duty applications. On lines which are lightly used, which only ever see low speeds, or which are maintained only to a minimal standard, there basically isn't any point going to all the trouble of changing it just for the sake of it, so bullhead can persist for ages.

Yes, the keys do fall out, and people have to go along with a hammer every so often to put them back in and knock back the ones which are only half-way out. Me, I'd make bullhead chairs with lugs on the ends to put a retaining pin through to make sure the key couldn't fall out, but nobody else seems to have had this idea.

 

[Steptoe]

Yes, the keys do fall out, and people have to go along with a hammer every so often to put them back in and knock back the ones which are only half-way out. Me, I'd make bullhead chairs with lugs on the ends to put a retaining pin through to make sure the key couldn't fall out, but nobody else seems to have had this idea.

Wouldn't it be easier to use Panlock keys? Sorry I don't also have a chair & bit of rail at home to photograph it in situ but the gap in the key goes against the rail web and it is located centrally in the chair.

As a 'hammer man' I can assure you they never come out (but are a pain to install and remove)

 

[Pigeon]

That's interesting - shame you don't have a chair and bit of rail, because just from looking at the key on its own I can't figure out what actually stops it from gradually ratcheting its way out just like the wooden ones do, although perhaps more slowly. (Generally I'd expect anything performing a function vaguely similar to a rail key to wiggle itself loose over time unless it was positively retained, because the friction effects are never perfectly symmetrical and tend to get less so the further the thing comes loose.)

 

[InOban]

They relayed some bullhead rail on the Far North line last year, and I think they had to import it (?Austria) because it isn't made in the UK. Came by ship to Scrabster.

 

[Ploughman]

In the last 2 years we have bought in new BH rail for use on the NYMR from Scunthorpe as per normal.
A few years back it was supplied from Workington.

As an aside the regular haulier for all rail delivery to us, is generally a Workington based haulier.