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Structure clearances other than for passenger platforms


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I have a raft of material providing guidance on the clearances & dimensions for passenger platforms, but not so much for other structures.  For example, if I have a siding which passes alongside a loco shed, how much space should I allow between the centreline of the siding and the wall of the loco shed?  This diagram:

 

1548856844_OOGaugeStandardDimensions.jpg.ebf4a65555f33d93e0fb1dbb9d255e27.jpg

 

would seem to indicate 30mm if you treat the loco shed wall as a bridge pier, or 20mm if you treat it as just a wall.  But which would be correct?

 

And what about a coaling stage - the type from which coal would be shovelled by hand in to a loco's tender or bunker.  Could/should that be located as close to the track as a passenger platform, or would it be more prototypical to have a slightly larger gap between the coaling stage and the loco?  I guess you would still want to minimise the risk of the workies falling between the stage and the loco so maybe not.

 

Similarly with a goods loading dock: I'm aware that these tend to be a bit higher than passenger platforms, to allow more level access to wagons, but would the gap (ideally) be the same as for a passenger platform, or do you need more room for some reason?

 

I'm aware of all the caveats about curved track needing greater clearances etc.  For the purposes of these questions I'm assuming that all the tracks involved are straight.

Edited by ejstubbs
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I suggest you try to find a “minimum structure gauge” drawing for your chosen railway company and period. That was the specification that engineers used when designing lineside infrastructure.

 

For instance, Atkins’ book “GWR Goods Train Working, Vol 2” shows several structure gauge drawings, which include details of goods platforms. (3 to 4 inches higher than passenger platforms, exactly the same distance to the rails.)

 

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18 hours ago, ejstubbs said:

I have a siding which passes alongside a loco shed, how much space should I allow between the centreline of the siding and the wall of the loco shed?  This diagram:

 

1548856844_OOGaugeStandardDimensions.jpg.ebf4a65555f33d93e0fb1dbb9d255e27.jpg

 

would seem to indicate 30mm if you treat the loco shed wall as a bridge pier, or 20mm if you treat it as just a wall.  But which would be correct?

 

I don't know the answer to this specific question, but I think it's fair to point out that these are MINIMUM dimensions.  Therefore, where there is perceived ambiguity, if you go with the larger figure, you won't be wrong, whereas if you go with the lower figure, you might be.

 

Thinking of first principles, the minimum distances were specified for reasons of both safety and economics.  In the case of the parapet on a viaduct, there is a need to minimise the cost of the structure, so keeping the wall as close to the track as possible to minimise the deck width makes sense.  What are the hazards of using 20 mm?  Where is the space for a track worker to stand clear of a passing train?  What is the risk of a passenger putting their head out of the window and being decapitated by said wall?  In the case of viaducts, the lack of lateral clearance necessitated the introduction of small recesses above the piers where it was possible for someone to stand.  In the case of passenger's heads, that wouldn't be an issue if the top of the wall is below window height. 

 

If the wall was higher, then it would likely be higher for a reason, usually to retain an earthworks slope in cutting and the diagram you posted shows a larger distance in this case - ie 27 mm.  This should be enough to remove the risk of decapitated heads, as that distance is measured at the bottom of the wall and retaining walls slope backwards, so at window height you probably have closer to 30 mm, which is the quoted distance for bridge piers.  As well as removing the risk of decapitating people leaning out of the train, that would probably also be enough to allow a track operative to stand with their back against the wall, albeit I wouldn't want to stand that close to a high speed train.  It probably won't be allowed these days, but probably was in Victorian times.

 

Therefore, I'd probably go with the 30 mm distance between the centreline of the track and the wall of the loco shed on the basis that:

  1. Even if your railway company permitted a lower figure, allowing more than the minimum would not be wrong;
  2. It allows space for the driver or fireman to look outside the locomotive clear of the loco shed wall; and
  3. it provides some space between the locomotive and shed wall in the event of someone on the track needing to step out of the way.

As for coaling stages and goods platforms, I see no reason why they would be any further from the track than a passenger platform, although the sides of the loading gauge are not vertical, so if the platform is higher, then arguably, the goods platform may be very slightly further away, but we're probably talking about less than 1/2 mm in model form, so not worth bothering about.

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12 minutes ago, Dungrange said:

It allows space for the driver or fireman to look outside the locomotive clear of the loco shed wall

 

Just for clarity, the siding is for wagons, it's not related to the loco shed per se.  But I assume your point would still stand e.g. it allows space for the shunter to work alongside the wagons.

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It's does not always work extrapolating prototype dimensions to Ready to Run models.  Your models need to clear the coaling stage or wall. In OO the max width of stock should be 9ft 6" or 38mm but some RTR is 40mm wide,  The Hornby 9F is one.   The clearances should be 2ft or 8mm to walls for new build but in previous eras this was significantly less.  If your coal stage clears the stock and was built about 1880 than no one will worry util a loco demolishes the edge of it with its cylinder cover.   RTR buffer height is also variable, but should be a couple of mm above the platform surface as a minimum.

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1 hour ago, ejstubbs said:

Just for clarity, the siding is for wagons, it's not related to the loco shed per se.  But I assume your point would still stand e.g. it allows space for the shunter to work alongside the wagons.

 

Yes, the shunter will be the person on the track.  When wagons are being propelled into the siding, there will be a need for him (or her) to step to one or other side of the line.  That's why although an up and down line may be separated by the 'six foot', there will normally be 'ten foot' between the running lines and the sidings and whilst two sidings may only have 'six foot' between them, they were, I understand, normally arranged in pairs so that for each siding, there was a 'ten foot' spacing on one or other side of the siding.  This means that the shunter would be expected to step into the 'ten foot' rather than the 'six foot'.

 

In the case of a siding that is adjacent to a locomotive shed, the requirement for the shunter to be able to step aside would still exist.  If you only have one siding, then arguably, he could step away from the locomotive shed (in which case you could perhaps move the siding closer to the shed) - ie treat it as a wall and use a minimum of 20 mm.  However, if you have two parallel sidings at standard track spacing, then clearly the shunter would be expected to step towards the shed and there would need to be enough space for him to do so safely.  The problem is that the definition of being able to do so safely will have changed over time.  Giving someone two foot in which to stand was probably considered more than adequate (maybe even generous) by some of the early railway companies, but accidents would result in changes in health and safety practises and as such more space would be demanded nowadays - I believe that the current requirements are online at www.rssb.co.uk.  Therefore as @Harlequin has stated above, you really need to look at requirements for the company that built your line and would apply to the period in which you are modelling if absolute accuracy matters to you.  However, for most people, the typical dimensions given in the diagram you posted are probably good enough to allow most people to build a plausible layout.  At the end of the day, we don't really need to consider the safety of 1:76 scale plastic people.

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With a three foot platform height (maximum for passenger platforms I believe) the buffers should be no more than six inches above the platform. Goods platforms could be higher, possibly at wagon floor level (why the LNER and LMS favoured sliding doors). Hinged doors would need lower platforms to enable the doors to open.

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2 hours ago, Dungrange said:

if absolute accuracy matters to you

 

Ha, if absolute accuracy mattered to me, I wouldn't be modelling in OO :wink_mini:  (Reference recurring comments on multiple RMWeb threads re verisimilitude or otherwise of OO vs EM vs lovingly hand made by a wizened, octogenarian anchorite living in a cave somewhere in the wilds of Dartmoor etc etc...)

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Posted (edited)

Going to the source documents isn't just about accuracy - it's also about confirming whether other people's guesses, opinions and maths are correct and not committing the cardinal sin of modelling a model.

:smile_mini2:

Edited by Harlequin
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