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Swing-bridge bolt

British signalling of the past (UK, excepting Northern Ireland)

Swing-bridge bolt

Unread postby Chris Osment » Mon May 29, 2017 10:20 am

When the Barnstaple to Ilfracombe line was opened in 1874, the new swing-bridge at Pottington was controlled by the signal-box at the new Barnstaple Quay station. In a subsequent re-inspection for the BoT, Lt Col Hutchinson commented that that bridge bolt 'did not work very well' - presumably they fixed that! In an 1881 diagram the bridge bolt was shown as lever 4 in Barnstaple Quay box. In the instructions accompanying Fig 154 in Raynar Wilson (applicable to the pre-1898 period, by which time the Quay box had been re-named Town) 4 is described specifically as the bridge bolt lever.

But....the swing-bridge was approximately 450 yards from the Quay/Town box, so how did it work that bolt? Not rodding all that way, surely? Yet nothing to suggest any form of key or intermediate GF etc....

Any thoughts please?
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Re: Swing-bridge bolt

Unread postby Ashley Hill » Mon May 29, 2017 11:09 am

There is a photo of Pottington swing bridge on the Cornish Railway Society website taken in 1975. It shows a small box on the town side of the bridge together with a lever of sorts in the 4ft on the bridge. In his book Light Relief Jack Warburton gives a brief account of opening the bridge and the perils of getting it wrong ie stranded on the wrong side. He describes opening the small box after obtaining permission from adjacent boxes and undoing various pins and bolts. Do the far side first otherwise the wind could blow and cause embarrassment.
http://www.cornwallrailwaysociety.org.u ... 5_orig.jpg
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Re: Swing-bridge bolt

Unread postby Ashley Hill » Mon May 29, 2017 11:20 am

That Light Relief book was by Jack Warland. Always read what spellcheck corrects! Also there appears to be an article on the bridge (described as Pill bridge) in the May 1907 edition of Railway Magazine.
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Re: Swing-bridge bolt

Unread postby Chris Osment » Mon May 29, 2017 12:14 pm

Ashley Hill wrote:There is a photo of Pottington swing bridge on the Cornish Railway Society website taken in 1975. It shows a small box on the town side of the bridge together with a lever of sorts in the 4ft on the bridge. In his book Light Relief Jack Warburton gives a brief account of opening the bridge and the perils of getting it wrong ie stranded on the wrong side. He describes opening the small box after obtaining permission from adjacent boxes and undoing various pins and bolts. Do the far side first otherwise the wind could blow and cause embarrassment.
http://www.cornwallrailwaysociety.org.u ... 5_orig.jpg


That lever was for winding the bridge around - nothing to do with the signalling interlocking. The 'small box' was Ground-Frame 'B', opened in 1898 i/c/w the new Barnstaple Town station and signal-box. My query related specifically to the pre-1898 period and the former Barnstaple Quay box :-)
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Re: Swing-bridge bolt

Unread postby davidwoodcock » Mon May 29, 2017 1:07 pm

I actually don't see why a 450 yard rodding run for a bridge bolt wouldn't work, at least in theory, because a bridge bolt is basically a hefty piece of metal, almost certainly tapered, being pushed into, and pulled out of, a large hole. The tolerances involved are nothing like as tight as with a facing point.
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Re: Swing-bridge bolt

Unread postby JRB » Mon May 29, 2017 2:36 pm

I mostly agree but don't think it would be tapered. The status is much like that of an FPL and I remember the fallout when a little taper was put on one of them on the XXXXXXX Railway.
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Re: Swing-bridge bolt

Unread postby Mike Hodgson » Mon May 29, 2017 11:12 pm

Chris Osment wrote:
That lever was for winding the bridge around - nothing to do with the signalling interlocking.


Interesting photo but it raises more questions in my mind than answers.
That lever looks a very awkward shape for winding the bridge, even if below deck gearing gave it plenty of mechanical advantage. I would have thought that it would have been easy to produce a more user-friendly design of winding handle without significant increase in cost.
As it's in the four foot it presumably just lifts off when not in use and normally resides in the box rather like a crank handle for motor points.
I don't see any signals to interlock with that bridge, nor a bridge bolt, are those upright plates in the right foreground part of the bolting arrangements?

Would the BoT regulation on maximum run for point rodding apply to a bridge bolt?
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Re: Swing-bridge bolt

Unread postby Ashley Hill » Tue May 30, 2017 1:18 am

The SRS diagram for Pottington shows that end of the bridge is bolted from that box,the other by the ground frame. Town's signal controlling down traffic over the bridge is slotted with Pottington Though this is probably outside of Chris's timeline.
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Re: Swing-bridge bolt

Unread postby John Hinson » Tue May 30, 2017 3:17 am

Mike Hodgson wrote:Would the BoT regulation on maximum run for point rodding apply to a bridge bolt?

I don't think so, as far as I know the limit specifically applied to points. If it didn't, the benefits of having bolt-released ground frames for pointwork too far from a box to be directly controlled would be negated.

Nevertheless, a direct bolt to a bridge (rather than to a ground frame locally controlling it) at the distance described here sounds to me as if it would be fraught with both reliablility and operational efficiency problems. Longer distance ground frames were often interlocked by a "mid-way bolt" (thus doubling the practical operational distance) but that wouldn't be possible with a direct bolt.

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Re: Swing-bridge bolt

Unread postby Mike Hodgson » Tue May 30, 2017 8:20 am

John Hinson wrote:
Mike Hodgson wrote:Would the BoT regulation on maximum run for point rodding apply to a bridge bolt?

I don't think so, as far as I know the limit specifically applied to points. If it didn't, the benefits of having bolt-released ground frames for pointwork too far from a box to be directly controlled would be negated.


Yes, that does sound right. I think the requirement only applies to points according to the letter of the rules, but it could reasonably have been construed as contrary to the spirit, since points are moveable rails, and so is a swing bridge.

We seem in the UK to have been a lot more paranoid about the risk of open bridges than other countries, with Lock & Block commonly having been seen as a necessary safeguard on routes that did not otherwise warrant it. Perhaps I am just more relaxed about these bridges than the Victorian authorities, having been brought up close to several of the Manchester Ship Canal's road swing bridges - I saw more sunken vessels than people driving into the gap!
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Re: Swing-bridge bolt

Unread postby Frank » Wed May 31, 2017 7:14 pm

Hello MIke,

not a Railway-Bridge, but simply locked
http://www.mathias-essen.de/scot/kanal/framemitte.htm
Picture
http://www.mathias-essen.de/scot/kanal/ ... /keil1.jpg
http://www.mathias-essen.de/scot/kanal/ ... raulik.jpg


Open Bridges overall a security issue and from simply to High Tec Equipment is in use to protect that.

Here in Schleswig-Holstein at the River Schlei this Bridge
http://www.kappeln-eschmidt.de/seiten/2 ... 0_16-2.htm

would be replaced with a new one and the Signal man there has then the smallest electronic Signal Box in the german net 8)
(Controlling only the Line Eckernförde - Flensburg ).

regards

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