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bridge tie spacing has been converted from the pre-July 2008 WW&F Discussion Forum.
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Bill Reidy wrote:I noticed in the photos of the new bridges on the Welsh Highland that the bridge ties are placed tight up against each other, as seen in the recent pictures of the Pont Croesor bridge. I would think that without gaps between the ties they would rot quicker, since rain water and debris would collect on the ties and they would be slower to dry out after wet weather. This also requires at least twice as many ties as if they were spaced out. What is the purpose in spacing the ties tightly together?
Curious,
Bill
Wayne Laepple replied:Two thoughts come to mind concerning bridge tie spacing on the Welsh Highland Railway. They may have the ties tightly spaced to keep ashes and other debris from falling on vehicles below or into a stream, whichever the case may be. I encountered a few bridges during my railroad career that had the timbers placed in that manner. I also saw bridges with sheet iron nailed to the timbers to catch embers. (Come to think of it, though, the WHR locomotives are all oil-fired, aren't they?)
Another possibility is that the "solid" timber deck was done to keep the timbers from moving or skewing as the rails expand and contract as the temperature fluctuates. In the U.S., it's common to install spacer blocks between the timbers or use perforated flat steel bars lag-bolted to the ties for that purpose.
Dave Crow replied:Wayne,
Not all of the locomotives are oil fired; in fact, I believe they are converting some of the NGG16s to coal firing, due to the cost of oil.
Dave Crow
Phil Raynes replied:While Wayne is usually correct, in this case the answer is much more mundane! I contacted Barrie Hughes (owner of one of the websites, http://www.isengard.co.uk ) and got this reply:
"The solid sleeper deck is a H&SAW legislation to give a firm footing to trackworkers or upon evacuation of a train. The bridges are inclined so they drain to one end."
In case you were wondering, "H&SAW" stands for: "Health & Safety At Work". In case you wonder what that means, can you say "OSHA"?! Hopefully that explains everything! The Brits are just as bound by regulations as we are!
Phil
Wayne Laepple replied:Hmmmm. Interesting. I guess I wonder why they didn't simply lag-screw grating, such as used on the walkways on the bridge, to the ties, including in the gauge. That would have permitted drainage and still protected anyone walking from injury.
Phil Raynes replied:Not sure; but if you look closely, they are only attached to the rails at every third tie, so it does seem like a waste of ties.
Phil
Bill Reidy replied:Thanks for the replies! The idea of safe footing did cross my mind, but with the walkways to the sides, I had dismissed that idea.
- Bill
jlancasterd replied:Hmmmm. Interesting. I guess I wonder why they didn't simply lag-screw grating, such as used on the walkways on the bridge, to the ties, including in the gauge. That would have permitted drainage and still protected anyone walking from injury.
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From my experience in helping to paint one of the bridges on WHR Phase 3 (we had to paint the whole structure on the bank before the bridge was placed as a unit using a large crane), I suspect that there is also an environmental reason for the closed deck. The Snowdonia National Park authorities are very protective of the quality of river water (the Glaslyn is a salmon river and also hosts a lot of other wildlife) and the closed deck will help prevent oil and other debris falling from trains into the river.
John Dobson
