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PostPosted: 03 Feb 2013, 13:15 
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Location: North Cambridgeshire, UK
A communication has been received from non-member Robin Brownlie concerning an incident in about 1958 in which a steam crane on the Edinburgh Slateford to Collinton branch line was attempting to lift or lower a barge into the Union canal from the bridge when it toppled into the canal, killing the driver. Robin is interested in learning more about the disaster.

I don't know of this particular incident but can see several possible reasons for the toppling:
# In operating on a bridge (or on a canal side) there may have been no room to fully extend the propping girders, and the driver and/or supervisor may not have been sufficiently aware of the resulting reduction in capacity and stability.
# If the rail was on an adverse cant, the driver may have let the jib and its load slew too quickly to the side. Slewing would have been via a clutch rather than direct drive, so not fully under the control of the engine. Even if the jib was braked to slow the slew, both the jib and the load would have tried to continue to swing out - and a heavy barge can provide a lot of inertia.
# Similarly if the barge caught the wind when the driver hadn't got the jib fully under control.

Enough of the suppositions! Does anyone know more about the actual incident?


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PostPosted: 03 Feb 2013, 20:24 
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Joined: 24 Jan 2011, 21:37
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Location: Stockton-on-Tees
Found this and it mainly fits but could the accident be in 1950 and not 1958?


www.railwaysarchive.co.uk/documents/MoT_Balerno1950.pdf


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PostPosted: 03 Feb 2013, 23:21 
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Well found, Dick!

Robin wasn't certain about the year, and this must surely be the incident he remembers. Thanks very much for taking the trouble to dig it out.


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PostPosted: 04 Feb 2013, 10:50 
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This is actually a fairly well-known incident, and is cited as a leading reason why the "London" type of p-way and general purpose crane fell out of use. The incident is described in Brownlie's seminal work (see pp.238/9, quoted below). Incidentally, I wonder if the original enquirer is related to the great man?

The "London" type of crane, as built in large numbers most notably by Grafton of Bedford, was characterised by having a slewing ring which was able to turn on the carriage. The idea of this was in the event of a situation which would shock-load the slewing gear; rather than risk a component failing, the slewing ring would simply rotate limited by friction and act like a shock absorber. This is a great concept and worked well on a new crane, but the reliance upon friction to provide a consistent resistance to movement between two non-adjustable surfaces proved to be its undoing. As the crane wore and the slewing ring became a looser fit, so the resistance to movement became less. If the crane were then to lift over end on a cant, or over side on a gradient, there was a very grave risk of uncontrolled slewing of the jib towards the low point since there would be insufficient friction between the slewing ring and carriage to resist the gravity-induced torque. In the Balerno incident the tragedy was that the barge exceeded the safe load of the crane, and as it slewed broadside on the crane fell into the canal with fatal consequences.

In the aftermath of the Balerno incident many "London" cranes had the slewing rings welded. In practice however they remain as safe as any other crane provided that they are used on level track only, although finding a modern crane examiner who is familiar with and happy with the system is increasingly rare (the 6-ton Grafton which is currently out-of-use at the the ESR is a victim of this - the examiner at the time of withdrawal insisting that the slewing must be locked if the crane was to be used again).

With hindsight, a better implementation of the concept would have involved the incorporation of an adjustable friction device rather than relying upon the non-adjustable fit of two very large machined components.

Brownlie's report on the incident reads as follows:-

Use of the loose race for slewing has long been a feature of cranes of the 'London' type. It was thus applied to many P.W. cranes and apparently met the conditions of working. In later years a growing awareness of the effects of cant led to a tightening up and the cessation of the practice for new cranes. Many existing cranes were converted to fixed type in Railway Workshops, although the need for this drastic step has been questioned. It is contended that internal grit was responsible for the sliding and that cleaning only was required. The alteration resulted in greater wear and tear of certain parts of the slewing gear owing to the absence of 'give' in the drive. The action was precipitated in deference to a recommendation by the Inspecting Officer at the Balerno Junction accident in February, 1950. This involved an L.N.E.R. crane which was employed to place a barge from a bogie waggon into the canal near Slateford Aqueduct, the branch being on a sharp curve at the point chosen.The line being single, the barge had to be lifted then swung round athwart the track before lowering. Those concerned were misled by the fact that, when lifting, the load was touching the inside of the waggon. When clear, it at once swung to the inside of the curve taking with it the crane jib. The engineman was unable to prevent the movement because of the sliding of the race, the crane and the load being thrown into the canal as a result and the driver drowned. The mishap was due to the cant of 4 3/4 inches, plus lack of guidance to those responsible for the operation and underlines the possible danger of work of this kind. The guying of the crane jib until the working radius was reduced might have saved the situation. (The radius was increased by having to lift the barge lengthwise or parallel to the track.) While a combination of factors was responsible, we observe once again a seemingly simple task, presenting a very difficult situation and being delegated, almost cursorily, to those in charge. The latter could hardly be expected to foresee the risk involved and were placed in a most invidious position. The pernicious effects of cant and other accidents attributable are also referred to in Chapter V. [John S Brownlie, "Railway Steam Cranes", published privately, 1973, pages 238/9.]


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PostPosted: 04 Feb 2013, 16:16 
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Location: Poole, Dorset
Here is a photo of the bridge.

http://www.railbrit.co.uk/imageenlarge/ ... p?id=29982


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PostPosted: 04 Feb 2013, 16:25 
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Joined: 23 Dec 2010, 00:07
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Location: Poole, Dorset
And another, from the canal:-

http://www.geograph.org.uk/photo/992665


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