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Clearance Bar

 
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4rail



Joined: 15 Jan 2004
Posts: 4
Location: Cairns - Great Barrier Reef

PostPosted: Fri Mar 26, 2004 4:49 pm    Post subject: Clearance Bar Reply with quote

Hi

Can any body tell me what a clearance bar is and is it anthing like a facing points lock? i'v seen it on English signal diagrams but I dont know what it is.
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signalman
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Joined: 24 Mar 2004
Posts: 16
Location: Port Macquarie, Australia

PostPosted: Fri Mar 26, 2004 6:29 pm    Post subject: Clearance bars Reply with quote

In regards to '4rail's' question on clearance bars, I belive the device operates similar or in conjunction with an FPL. If its what I'm thinking of, the bar consists of a length of point rodding U-channel that sits adjacent to one rail head and is pivoted up or down along its axis, generally operated by point rodding. If the bar is up against the railhead, if a train or wagon were to roll onto it, it would force a derailment.

If anyone can either correct me or provide any more info, please do.

Cheers,

Ian
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DownMain



Joined: 06 Jun 2005
Posts: 3
Location: Scotland

PostPosted: Mon Jun 06, 2005 1:31 am    Post subject: Clearance bars Reply with quote

I'm new to the website/forum, so just spotted this query.

My understanding (UK) is that the bar - usually called a 'fouling' or 'locking' bar - is part of the point FPL mechanism and is mounted as mentioned by 'signalman', usually on the immediate approach to the point (facing). Its purpose is to prevent the movement of the FPL when the bar is fouled by the flange/s of a vehicle, thus preventing movement of the point blades whilst a vehicle is on, or approaching, a facing point.

Their use has been largely superseded by modern electrical detection and locking.

Examples are still in use on some UK preserved lines.
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struck
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PostPosted: Thu Jun 09, 2005 12:16 pm    Post subject: clearance bars Reply with quote

As far as I'm aware, clearance bars and facing point locking bars perform a similar function, to reduce the risk of points being changed under a train, but they work quite differently.

Facing point locking bars are generally placed on the approach to the point blades, and are normally in the lowered position. When a facing point lock is changed from locked to unlocked, the locking bar will rise to rail level and then fall. If a vehicle is on top of the locking bar, when a signalman attempts to change the lever, the locking bar will contact the flanges and prevent the points from being unlocked. One is installed in Canberra.

Clearance bars work the other way round, they are generally located between the point blades and V crossing. The are normally raised and held up by springs. When a train passes over them, they are depressed and engage the facing point lock, again preventing the points from being unlocked when a vehicle is on the points. There are two sets at the Up end of Stockinbinbal yard in NSW.

Many have been removed as power signalling has been installed.

In New South Wales, locking bars are generally 40 foot (12 metres long). Until around 1960, this was longer than the distance between wheels on any vehicle. Since then, many vehicles have been introduced with gaps between wheels exceeding this distance, so that points can be unlocked even when a train is on them. As a result, most have been replaced with electric locking.

Happy to email some pics if anyone is interested email s_truck@hotmail.com
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