No Hall class likely to appear here

I think the [platform clearance is quite tight, (Bitton)

 

What LMS/BR loco is that?

 

46447

 

I don't mean Bitton do I.....Cranmore

 

Ivatt 2mt Then...............

 

yep that's what 46447 is.

 

I checked the clearance of the motion bracket to the platform edge on running into Cranmore with 46447 today and minimum separation was about 4 inches.

 

Interesting thought actually, do preserved lines work to a common structure gauge (or target one) or is it a case of what the line used under BR? Is there such a thing as a composite structure gauge that encompasses all preserved steam? Is the GWR structure gauge same or larger in every respect than that used by others of the big 4, or is it more complicated?

 

In answer to the first: surely the answer is that a preserved line has to work within the constraints of what it has, particularly around stations and bridges. For example, on the Bluebell we have a section with a platform face both sides of a single line on a curve: without massive rebuilding of the station, we couldn't increase the allowable width through that road even if we wished to. Not surprisingly, a number of engines are banned through there even if allowed elsewhere, notably visiting outside-cylinder GWR engines. Even on a standard double-track passing station, moving a platform road a few inches away from a platform to increase clearance would inevitably reduce clearance in the 6 foot between roads, possibly below acceptable limits.

On the second point: I suspect the picture is complex, at least in pre-grouping days. For example, on the SR, the LSWR had a wider gauge than the the other constituents, whereas the the LBSCR's was higher. The SECR was smaller all round than the others. The SR did do some work to get a composite loading gauge, which helps explain why Maunsell updates of Urie designs (such as the King Arthurs, S15s etc) had redesigned cabs to allow them to fit on the major ex-SECR mainlines. Similarly, one difference between the Fairburn 2-6-4T and BR Standard 4 tanks is that the latter had raised boiler pressure and reduced cylinder diameter, so as to give similar tractive effort within a slightly narrower width with concomitant greater route availability.

Tom

 

you'll be Ok then provided no one decides to flatten a penny on the offside line.....

 

Tom,

I would guess that clearances on the Bluebell, platforms 4/5 at HK excepted, are probably more generous than the NR route from East Grinstead to South Croydon. Obviously, for any guest engines arriving by low-loader, this won't be an issue, but any engine arriving via the Network Rail link, one would assume, would probably not cause too many worries about gauging on the Bluebell.

 

Whilst that's obviously true, every time you rebuild or move something you must have to bear in mind a structure gauge mustn't you?
To take an extreme example that surely won't happen, supposing you ever had to face the horrendous task of replacing all the coping stones on platforms 4/5. Would you replace them with identical stones, or would you consider taking them back an inch nearer the brickwork? Whilst there's no justification for trimming them as they are, if they were being replaced anyway...
With IT, when making plans for infrastructure changes, I always like to bear in mind what we ought to have as well as what we do have. If, at marginal cost, I can make allowances for a future expansion I like to do so.

So supposing a preserved line took care whenever it did work on structures that it complied with the largest possible UK structure gauge unless there were really compelling reasons not to then in 30 or 40 years time they might find that the amount of work needed to permit an increased loading gauge on their line had diminished to manageable proportions.

One is reminded of the GWR situation where Churchward and Inglis persuaded the GWR Engineering committee in about 1904 to have all new structures designed for 22 tons axle load. In 1926 the GWR was able to introduce the KIng class on the London to Plymouth route with only 4 bridges having to be rebuilt. In his book Pole, as a financial manager, bemoans the fact that they had been investing money in strengthened bridges for 22 years without return, but most engineers will tell you that they'd stand little chance of getting a mass upgrade past the bean counters, and the approach taken was the only one that would work.

Sadly this sort of long term thinking is even more out of fashion than its ever been with non specialist executives, who are only interested in high profile stuff that looks good on a CV. Thus an HS2 style project that costs billions is actually far easier to get approved than a whole tranche of small unspectacular improvements that might deliver more gain, viewed as a whole, for less money.

 

In practical terms that does happen. An obvious Bluebell example is that when Kingscote was restored (in the 1990s) and when East Grinstead was built (in the 2010s) the platforms were extended / built to 7 coaches + loco long, even though it may be many years before SP is extended to allow routine operation of seven coach trains. A less obvious example is that - I suspect in common with many lines - as track is replaced, it is upgraded to a heavier profile and with a more substantial formation to gradually allow heavier trains.

Of course, such things aren't entirely uncontentious: you start to run into the tensions between "preserving" a line as it was, and creating an infrastructure that is suitable for the very different operating patterns of the 21st century. But we have been over that ground before many times - <voice character="Bea Clissold">many, many times</voice>.

Tom

 

In the early days, railways built to their own standards. In 1950 the Ministry of Transport published 'Railway Construction and Operation Requirements for Passenger Lines and Recommendations for Goods Lines ' (the Blue Book) which specified the structural clearances that are to be provided on new lines, and on existing railways where new structures are built or where existing structures are modified or where clearances are otherwise altered. This essentially applied until recently when superseded by Railway Safety Principles and Guidance', Section H of which applies to 'Minor Railways'. The prsent reference documentation is ORR Railway Safety Publication No.5 'Guidance for Minor Railways' which you can read at:
http://orr.gov.uk/__data/assets/pdf_file/0015/2634/rsp005-minorrail.pdf
The standard structure gauge was effectively unchanged and mandatory for all new works until recently and would have allowed steam locos to operate with no problem. However, it is no longer a requirement and the structure gauge only has to cater for the rolling stock that normally uses it. Such things as platform clearances are now less important than stepping distances from platform to vehicle.

 

On the GCR I do recall that 6990 was used to gauge the platform at Leicester North when it was built. There is a slight 'wiggle' in the platform edge adjacent to the run-round points to allow for it swinging out.


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In light of recent events should the thread title be revised to say No Hall class likely to appear anywhere on the mainline..

Seriously though, are we seeing the end of 2 cylinder GWR locomotives on the mainline as the routes they can run along seem to be diminishing by the day, I just cannot see any owner going to the expense of mainline certification as things stand?

Also where does this leave the GWS who are presently building a Saint and County to mainline standard - when they are finished will there actually be any lines that they will fit upon?

 

Gloucester-Newport-Cardiff and the Welsh Marches line.

 

For now..... at the rate the network seems to be shrinking I suspect that we cannot guarantee that next week let alone next year!

 

There are Network Rail standards for platform clearances. If NR actually stuck to them, there should be no problem for GWR 2-cylinder 4-6-0s.

 

Is the problem with the GWR Hall class it is not the size of the cylinders, but the centre spacing of them is wider than other engines, as the LMS Black Five, 8F, LNER A4, V2, K4, SR Lord Nelson all have the same 18 1/2" diameter cylinders as the Hall's. Some classes have larger diameter cylinders such as Britannia 20" LNER A1/A2 19", B1 20", SR King Arthur 20 1/2", LMS Crab 21" and some of these do come on the main line.