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Post by afarlie on Mar 28, 2008 12:40:18 GMT
Hi,
A Specfic question for once.
In terms of the Northern Hieghts plans at Finsbury Park,
What would the clearance between the track on viaduct level of the Northern City and the surrounding infrastructure including the have been?
Also what would this viaducts height have been in relation to later works in 1975 concerning the Northern City?
I ask because in routing the Beck Line north of Euston I've hit the problem of how to bring it into Finsbury Park from the Nags Head direction, such that I can bring it up-to the level of The ParkLand Walk...
My current plan should the clearances work is to effectivly do
a south-eastward turn coming out of Nags Head, and attempt
to surface it Alongside the Emirates Stadium onto the Viaduct
that existed for the Northern Heights Plans. Getting it onto the Parkland walk is then a matter of relative ease..
I am also trying to track down 2 technical drawings from the late 70's, which gave detailed measurements in respect of 'tube' tunnel sizes and infrastructure clearances...
Thanks
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mrfs42
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Post by mrfs42 on Mar 28, 2008 13:18:46 GMT
I am also trying to track down 2 technical drawings from the late 70's, which gave detailed measurements in respect of 'tube' tunnel sizes and infrastructure clearances... Try John Polley's site: Metromodels, there are two machine-readable drawings there that fit your description. |
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Post by stanmorek on Mar 29, 2008 1:37:21 GMT
Can't really go wrong with mrfs' suggestion for clearances in tube tunnels. But sorry can't help you regarding specific info on Northern Heights!
I have an 1980s structure gauge diagram for tube stock in open sections (sorry again hard copy only). It says minimum overhead clearance from top of rail level to be 3200mm and the absolute minimum 3047mm. Lateral clearances are 150mm from load gauge up to 914mm above rail level.
Above 914mm, required lateral clearance is 930mm minimum measured from the load gauge, 775mm absolute min and 670mm min from isolated structures less than 2m long e.g. signal posts. From memory, the current structure gauge diagrams used by LU show clearance relative to the running rail and also shows kinematic envelope of a train and not the static load gauge.
Clearances for platform structures are also different. For curved track additional clearance (added to figures above) is required for car centre throw and end throw. This is calculated on the basis of the radius of curvature of the inner or outer curved rail and the dimensions of the train carriage.
In case anyone is interested the formulae are:
Centre Throw = B2 x 1000/BR
End Throw = (L2 - B2) x 1000/BR
Where B = Distance between bogies, L = Overall carriage length, and R = Radius of curvature of the rail
Radius of curvature of the rail at any particular point can be simply calculated by measuring the versine over a 10m chord. This is a simple measurement to take having done this type of survey as a site engineer on a bridge refurbishment job though this wasn't for calculating structure clearances. The design engineer called over a weekend possession requiring the information to calculate the centrifugal forces exerted on the bridge structure which was carrying curved track as trains pass over it.
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mrfs42
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Post by mrfs42 on Mar 29, 2008 1:54:07 GMT
10m or 100m?
Interested.
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Post by stanmorek on Mar 29, 2008 14:00:58 GMT
It was a simple string line survey with 10m chord as we were interested with what the track was doing over a 25m span bridge and not carrying out major realignment of a curve. Besides it was an impromptu thing as the delivered components due to be installed on the weekend were wrongly fabricated and I could only get two helpers to assist!
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mrfs42
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Post by mrfs42 on Mar 29, 2008 14:22:59 GMT
Aha! All the versine work I've been involved in used 100m chords - hence the interest  |
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Post by stanmorek on Mar 29, 2008 15:05:24 GMT
My experience with Track is in maintenance I've not worked in the survey section or a track design office. How do you achieve the 100m chord? I'm not sure if a chain would give the desired accuracy and I suppose the corrections needed for a steel tape would be a lot for 100m. Or did you splash the cash with an EDM survey instrument with optical prism  As a general rule I try to avoid theodolite work - I can just about cope the booking for levelling! |
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mrfs42
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Post by mrfs42 on Mar 29, 2008 15:58:29 GMT
I don't know to be honest - I was merely asked to check over the calculations for someone: my knowledge of this is only based on the figures I was given, the mechanics of getting those figures is a black art to me. |
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