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Pacific231G

bullhead rail on the Central Line

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I was watching the second part of Channel 5's surprisingly interesting programme Inside the Tube: Going Underground which focussed on the Central Line and noticed in the section about relaying track on a tightly curved section that the rail appeared to be bullhead though with a short foot. I use the Central Line quite often and know that there used to be some bullhead at White City now replaced but didn't know it was still being used in the tube section. Is there something about BH that makes it particularly suitable for tightly curved section or is this use just because this section hasn't yet changed to Vignoles (FB) rail?

Edited by Pacific231G

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May be easier to form into tight curves?  Flat bottom is likely to be stiffer in the foot than in the head, so prone to twist if bent. 

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May be easier to form into tight curves?  Flat bottom is likely to be stiffer in the foot than in the head, so prone to twist if bent. 

 

I would say that it would be easier to bend it to fit in the chairs and then key it, than try and get it into position and hold it whilst fitting the clips, especially as speed is of the essence.

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May be easier to form into tight curves?  Flat bottom is likely to be stiffer in the foot than in the head, so prone to twist if bent. 

 

Bullhead is much quicker and easier to change in an emergency! :-)

Edited by Horizontal

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Remember the tight dimensions of the Central London Railway tunnels. It may be a clearance issue - the positive rail is higher in the old tunnel sections meaning trains using the section need high lift shoegear.

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Remember the tight dimensions of the Central London Railway tunnels. It may be a clearance issue - the positive rail is higher in the old tunnel sections meaning trains using the section need high lift shoegear.

I'm not sure why the height of the conductor rail would advantage bullhead but if its easier to bend that might well explain it as the Central Line is notoriously sinuous (to avoid wayleaves by going under the streets) 

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The conductor rail height isn't connected to the use of bullhead I was merely using it as an example of the small nature of the CLR tunnels. You may be correct about the curvature of the tunnels (especially around the City) but bullhead rail has a lower profile than flat bottom rail so may be a combination of the two. I must ask my mate on LUL the reasons....

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Curve radius is probably the biggest factor - I think flat bottom rail needs to be pre-formed below a certain radius, which would make it more difficult to store spare rail in the four foot. The taller flat bottom rail would cause issues as the passing clearances are around 25mm, but I'm sure that low profile rail fixings are now available to counteract this.

 

Regards,

 

Dan

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I would believe that the use of Bullhead is just a strait replacement of the existing rail rather than a full relay!

 

Mark Saunders

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It's most likely to be due to the sharp curvature - BH rail is quite 'floppy', so is easier to manoeuver into position in the tunnel section and get it fixed down than FB - this was effectively demoed on a LU self-improvement P-Way course I did some years ago which showed footage of 60' lengths of BH and FB rail being craned from the centre - the BH still had its ends on terra firma with the centre some 4 or 5 feet up while the FB lifted it's ends with the centre only 6" up.

 

We are also told on the same course that BH is only drawn by the steelworks occasionally nowadays for LU and NR 'legacy' use and for the preservation market, FB production outstrips BH by easily 50:1 or more.

 

Much of the tube network, open and tunnel section is now laid with FB rail.

Edited by CloggyDog

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There is plenty of Flat bottom rail on the Central line, including in the sharp curved sections in the City, in the last few days I have waited on the platforms at Oxford Circus and at Bank which both have FB rail and Bank has very tight curves. On the other hand the straight track through the platforms at Stratford is bullhead. I think its just a matter of when the full relay programme reaches the area.

Regards

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