Buffer Stops at Bradford Interchange

[alexl92]

Can anyone tell me why the newer buffer stops at Bradford Interchange are so far forward from the originals? I know the originals are out of use but it seems really wasteful to have the new ones so far down.

 

[swt_passenger]

Can anyone tell me why the newer buffer stops at Bradford Interchange are so far forward from the originals? I know the originals are out of use but it seems really wasteful to have the new ones so far down.

It's normally because new buffer stops provide a gradual increase in retardation over a relatively significant distance compared to older designs, you normally see various pairs of friction clamps on the railhead behind them, and as the buffer moves along more clamps come into play and gradually increase the retardation.

An example from the German company Rawie (used in various applications in this country) is shown here, the image shows the friction clamps as grey lumps on the railhead behind the buffer itself:

http://www.rawie.de/index.php/gb/bahntechnik/vollbahn/personenverkehr/bremsprellboecke/typ4zeb6

 

[Joseph_Locke]

It's normally because new buffer stops provide a gradual increase in retardation over a relatively significant distance compared to older designs, you normally see various pairs of friction clamps on the railhead behind them, and as the buffer moves along more clamps come into play and gradually increase the retardation.

An example from the German company Rawie (used in various applications in this country) is shown here, the image shows the friction clamps as grey lumps on the railhead behind the buffer itself:

http://www.rawie.de/index.php/gb/bahntechnik/vollbahn/personenverkehr/bremsprellboecke/typ4zeb6

To amplify this there is a maximum rate of deceleration allowed for a friction retarder buffer stop on a passenger line, but it has to be designed for the lightest train (in this case probably a Pacer) but also the heaviest train (which is the scrap train running round), in which case it has to have a long enough slideway to pick up all the brakes and slide to a stop.

Typical slideways on passenger only lines are as short as 4 or 5m, a worst-case mixed railway one might be 20m+

The "main line" platforms at Euston are quite an eye opener in this regard, and since the station was built before TPWS the concourse deck plays a part in the management of a serious buffer stop collision.

 

[civ-eng-jim]

On a couple of schemes I've worked on, for a 2 car DMU travelling at 15kph, the sliding length was a mere 4.5m. This equates to approximately 2m/s/s deceleration

This UK company provide buffer stop sliding length calculations:

http://www.hjskelton.co.uk/home.htm...tm_medium=referral&utm_source=applegate.co.uk

A buffer stop risk assessment is a little more complex and involves a mixture of parameters including total mass of train, envisaged approach speed, signalling which protect the end of the line, track gradient et cetera.

 

[Ploughman]

If there is a structure behind the stops then the stops may need to be moved further away.
I had to do this at Bradford F Sq during the electrification for Leeds NW.
The structure was a new OHLE mast.