BR 4MT tanks on Parcels & Goods ?

[The Stationmaster]

As a matter of interest and. going back to the 9F on 'The Red Dragon'  it might be illuminating to note that the following classes of steam engines were all allowed the same load (485 tons) when working unassisted on passenger trains between Patchway and Badminton - 10XX (4-6-0 'Country'), 4073 ('Castle'), 47XX. 70XXX ( 'Britannia'), 92XXX (9F - yes they did have quoted passenger load but were restricted to 60mph as were the 47XX).  

 

The maximum permitted unassisted load for all (except the prohibited 47XX) between Severn Tunnel Jcn and Patchway was 455 tons.  BTW these are the maximum permitted loads in order to maintain booked running times, If a heavier load was taken then it was obvious that time would legitimately be lost in running.

 

For comparison and the interest of those of a GWR persuasion 'Stars' were allowed 420 tons unassisted between Severn Tunnel Jcn and Swindon while 'Saints' were allowed 406 tons unassisted.

[The Stationmaster]

On 20/07/2019 at 23:29, Nearholmer said:

I wonder how long Evening Star would have lasted on express passenger work before one of its many bearing surfaces overheated, or some vital pin sheared, causing a spectacular failure at high speed? Probably a good job that a it was spotted at Paddington!

And note my post above - 9Fs were subsequently permitted to work passenger trains on the WR but their speed was (officially) restricted to 60mph.  In other words for passenger train working they were mre or less regarded as being the equivalent of a GW 47XX.   There is somewhere a published photo of a black liveried 9F which had just worked a passenger train into Paddington.

 

And casting the conversation a bit wider the July edition of 'Bylines' will open more than a few eyes with some pictures of freight tank engines (N15 0-6-2Ts), complete with three link couplings and no vacuum fittings, painted in lined mixed traffic black livery in both early and late emblem condition.  Never say never!

[Nearholmer]

Even 60mph is a tribute to the design, given the wheel diameter and other factors, implying good control of lubrication, rotating masses, fits, etc.

[Siberian Snooper]

ISTR reading about a 9f being used on a test train of 25 Mk 1s running to Swindon or beyond, I can't remember the start location, but probably in the London area, I belive it was supposed to run at 60mph, but I believe it comfortably exceeded that. Due to it's length it was allowed two block sections.

 

 

[The Johnster]

4 hours ago, Nearholmer said:

Even 60mph is a tribute to the design, given the wheel diameter and other factors, implying good control of lubrication, rotating masses, fits, etc.

I think you're underestimating the ability of small wheeled engines to run at speed, not that is is a practice I would recommend in daily use.  An LBSCR Terrier exhibited at the Paris Exhibition ran from Dieppe under it's own power light engine and is said to have averaged 60mph; the wheels and motion must have been an invisible blur!  It had it's own crew and a French route conductor.  60mph average was something of a shibboleth on the Brighton for many years as they wanted to be able to advertise a sub-1 hour service from Brighton to Victoria, 59 miles in 59 minutes.

 

I'm not seriously suggesting that Terriers would have been used for this, mind, but it shows what can be done with a well set up loco lubricated properly.  And the lubricants had improved exponentially by the time of the 9Fs, as had bearing materials, piston rings, and other factors.  And the 9Fs had 5' diameter driving wheels, large by British freight standards and more akin to a Victorian 'goods' loco, which were in reality mixed traffic machines.

[Nearholmer]

I’m not saying that small wheeled locos couldn’t run nippily; clearly some could.

 

But there is often a world of difference between what can be done and what it is wise to do on a regular basis.

 

Express passenger steam locos had biggish wheels for very good reasons.

 

TBH, I think that all this “very fast 9F” stuff involves concentrating on the exceptional, sometimes even the mildly exaggerated, to a degree that obscures mundane engineering truths.

 

 

 

[pH]

4 hours ago, Siberian Snooper said:

ISTR reading about a 9f being used on a test train of 25 Mk 1s running to Swindon or beyond, I can't remember the start location, but probably in the London area, I belive it was supposed to run at 60mph, but I believe it comfortably exceeded that. Due to it's length it was allowed two block sections.

 

You may be referring to the runs with the first 9F to be fitted with a double chimney - 92178. In early 1958, it was tested between Reading and Stoke Gifford with trains of passenger stock, and a dynamometer car, weighing up to 650 tons. There's a picture of this engine, without deflectors, at Hullavington on a train of 14 coaches during these tests. 

 

(Information from 'Loco Profile 33 - BR Class 9 2-10-0')

[pH]

'Steam Days' for September 2007 has an article "BR Standard '9F' 2-10-0s on Passenger Trains". In it, the author states that he estimates that at least 80% of the class worked a passenger train while in BR service. He gives detailed accounts of these engines being used as a result of failures, and also being rostered to scheduled and test trains in all BR regions. Many examples of 9Fs running faster than 60 mph are described.

[TheSignalEngineer]

On 22/07/2019 at 13:12, jim.snowdon said:

To get authority to build 36 Coronations late in the 1930s on a railway that was still a private company needed a sound business case and support from the operators.

6245-6252 were built between June 1943 and June 1944, so would also have needed Government sign-off as essential to the war effort. Given the severely restricted maximum speeds at the time this had to be for haulage capacity over the hills.

Around the same period two Jubilees were rebuilt and rebuilding of the Royal Scots commenced, hardly anything other than an express passenger type, so again the Government must have agreed that they were needed for the war effort. The Scots were rebuilds in name only as they had completely new boilers and new frames. 

[keefer]

can't remember where I've read it, but wasn't there the issue of 9Fs wheels lifting when used above a certain speed? Smaller wheels = higher rotational speed = higher vertical forces than, say, a proper 'passenger' loco with larger wheels

[pH]

39 minutes ago, keefer said:

can't remember where I've read it, but wasn't there the issue of 9Fs wheels lifting when used above a certain speed? Smaller wheels = higher rotational speed = higher vertical forces than, say, a proper 'passenger' loco with larger wheels

 

I believe that happened with many more classes. I've read of Stanier Fives' wheels lifting above 90 mph - once every revolution, so several times a second. 

[Nearholmer]

Back to mundane engineering truths: a lot of mass, in the form of coupling and connecting rods, is flying up and down (and, to and fro) on the outside of a typical steam loco and, if the design speed is exceeded significantly, it will cause wheel-unloading, which can be very dangerous even short of the wheels actually lifting from the rails.

 

 

Edited July 24, 2019 by Nearholmer

[The Johnster]

2 hours ago, keefer said:

can't remember where I've read it, but wasn't there the issue of 9Fs wheels lifting when used above a certain speed? Smaller wheels = higher rotational speed = higher vertical forces than, say, a proper 'passenger' loco with larger wheels

I'm not an engineer, so I'm probably missing something, but surely once a wheel is properly balanced it shouldn't lift off the track no matter how fast it is rotating.  The upward 'lifting' vertical force imparted by the rear of the rotating wheel is balanced by the downward vertical force of the front of the same wheel.   This does not of course prevent hammer blow, which is as I understand it the result of reciprocating movement which cannot be balanced and the effect of which increases with speed; the greater piston speed of a smaller wheeled loco comes into play here.

[Phil Bullock]

4 hours ago, The Johnster said:

I'm not an engineer, so I'm probably missing something, but surely once a wheel is properly balanced it shouldn't lift off the track no matter how fast it is rotating.  The upward 'lifting' vertical force imparted by the rear of the rotating wheel is balanced by the downward vertical force of the front of the same wheel.   This does not of course prevent hammer blow, which is as I understand it the result of reciprocating movement which cannot be balanced and the effect of which increases with speed; the greater piston speed of a smaller wheeled loco comes into play here.

 

Theres a relevant thread here...

 

https://www.model-engineer.co.uk/forums/postings.asp?th=136906&p=1

 

Phil

[LMS2968]

Several points:

 

You need to be careful in saying they had 'new frames'. Not all received them, but generally, these consisted of the frame plates only and all the cross stretchers, horn guides, etc., were reused. These are the expensive bits which must be carefully machined to size, and so eliminate most of the work and cost in assembling the frames.

 

The classic example of wheel lift was experienced in tests with three Black Fives with different increments of reciprocating balance. They were run up to high rotational speed on greased track, so linear speed was only about 5 mph. The one with maximum balance, 66%, was measured at rpm equivalent to 102 mph to give a wheel lift clear of the rails of 2.4 inches. Details in Eric Langridge's book: 'Under Ten CMEs'.

 

You cannot achieve perfect balance with a two cylinder reciprocating steam engine; the same applies to a two-cylinder motorbike engine. You can balance all the rotational masses - crankpins, coupling rods, etc. - but not the reciprocating masses - pistons, piston rods, crossheads and part of the connecting rods. This is because these move only longitudinally - backwards and forwards. The balance weights in the wheel are rotational, so also have a vertical component - go up and down. These balancing forces are cancelled out (loosely applied term) by the reciprocating masses in the fore and aft direction but there is no opposing force for the vertical component, hence hammerblow and, in extreme cases, wheel lift. The imbalance rises with the square of rpm, so the smaller the wheel, the greater the hammer blow at a given high speed.

[Compound2632]

On 20/07/2019 at 19:54, LMS2968 said:

Would you care to explain that please? Why would it make more sense to employ two sets of men, use two lots of coal and incur two lots of maintenance instead of using one larger engine and the economies that brings, or should the LMS / LMR reverted to Midland Railway ideology from pre-1923?

 

Sorry, what?

 

 

 

[LMS2968]

It isn't always realised that the Midland wasn't the only Railway that commonly used double heading; so did the LNWR, although in that case it wasn't policy.

 

Francis Webb had a theory that an engine was at its most efficient when working flat out, and there is some justification to this. So when he designed his engines, they were just about capable of working trains at the loadings and timings then in force. If, afterwards, either the timing was reduced or the load increased, the engines could not meet the new standards and (slightly) bigger engines had to be built to meet the new standards, Of course, next year... And so on. So until the new engines appeared the Traffic people had to resort to double heading simply to meet the new timings. The Running Superintendent was George Whale, who suffered under this for years and it came to a head at the turn of the century when much heavier bogie stock was introduced, and he struggled to find enough engines. It caused great bitterness within him, and when he succeeded F.W.W. as CME, he began designs on much bigger engines, notably the Precursors and Experiments at the cost of the Compounds.

 

Basically, double heading was forced on to the LNWR by Webb's intransigence but, unlike on the Midland, it wasn't official policy.

[Compound2632]

20 minutes ago, LMS2968 said:

It isn't always realised that the Midland wasn't the only Railway that commonly used double heading; so did the LNWR, although in that case it wasn't policy.

 

Francis Webb had a theory that an engine was at its most efficient when working flat out, and there is some justification to this. So when he designed his engines, they were just about capable of working trains at the loadings and timings then in force. If, afterwards, either the timing was reduced or the load increased, the engines could not meet the new standards and (slightly) bigger engines had to be built to meet the new standards, Of course, next year... And so on. So until the new engines appeared the Traffic people had to resort to double heading simply to meet the new timings. The Running Superintendent was George Whale, who suffered under this for years and it came to a head at the turn of the century when much heavier bogie stock was introduced, and he struggled to find enough engines. It caused great bitterness within him, and when he succeeded F.W.W. as CME, he began designs on much bigger engines, notably the Precursors and Experiments at the cost of the Compounds.

 

Basically, double heading was forced on to the LNWR by Webb's intransigence but, unlike on the Midland, it wasn't official policy.

 

Unfortunately I couldn't find a post-able photo of a pair of Claughtons on a west coast express... Webb's approach to locomotive design certainly wasn't responsible for that! On the Midland in Webb's day (i.e. the last three decades of the 19th century), engines were big enough for the job - bigger than Webb's engines, certainly - without being thrashed, and there was very little double heading. That only came in with, as you say, the Edwardian inflation of the train weight per passenger ratio, with heavier, wider, corridor carriages and dining carriages. The Midland was hampered in adopting larger engines by civil engineering limitations. Plus, of course, Guy Granet's control system, which set out to optimise the efficiency with which the railway as a whole was run. Unfortunately the Midland did have some lines which didn't fit the mold, hence the Hawes Junction and Aisgill tragedies.

 

On topic, the BR Standard 4MT was the ultimate flowering of the Derby LDO's half-century of work on big tank engines but were turned out in LNWR livery, so honours even.

Edited July 24, 2019 by Compound2632

[LMS2968]

26 minutes ago, Compound2632 said:

Unfortunately I couldn't find a post-able photo of a pair of Claughtons on a west coast express... Webb's approach to locomotive design certainly wasn't responsible for that!

Remember that there is more than one reason for double heading a train, and that one engine alone couldn't manage isn't always the case. Returning a surplus engine following an unbalanced working was quite common, witness 5637 piloting 6202 in the Harrow collision. The 5X was simply working back to its home shed of Edge Hill but got caught up in the tragedy.

 

The LMS / LMR specifically banned two Pacifics from working a train, and in what circumstances that sort of power would be needed is difficult to imagine. But I have seen photos of a Pacific piloted by a Scot, and again it is hard to imaginable that that sort of power output could be usefully employed in steam days.

[TheSignalEngineer]

2 hours ago, LMS2968 said:

The imbalance rises with the square of rpm.......................

Yes, double the speed, quadruple the problems, which would mean that the speed component of the hammer blow effect for a 9F would rise by 230% between 60mph and 90mph.  No wonder the authorities didn't like them going fast. 

[jim.snowdon]

It depends which authorities. From what has been written (in other places), the principal concern seems to have been in respect of the locomotive itself, in particular the linear speeds of its reciprocating components. The effects of hammer blow are more the concern of the Civil Engineer, in terms of load plus/minus hammer blow. For all the debate on here, does anyone know what the hammer blow figures are for the 9F?

 

Jim

[The Stationmaster]

1 hour ago, jim.snowdon said:

It depends which authorities. From what has been written (in other places), the principal concern seems to have been in respect of the locomotive itself, in particular the linear speeds of its reciprocating components. The effects of hammer blow are more the concern of the Civil Engineer, in terms of load plus/minus hammer blow. For all the debate on here, does anyone know what the hammer blow figures are for the 9F?

 

Jim

I think that's more a consequence of who drew attention to that fact rather than any balancing of potential damage between that to the loco and that to the track.  If more civil engineers of that era had been into writing I suspect we would have heard far more about hammer blow and overweight engines than we have from loco engineering and operating persons.

[keefer]

1 hour ago, LMS2968 said:

 

The LMS / LMR specifically banned two Pacifics from working a train, and in what circumstances that sort of power would be needed is difficult to imagine. But I have seen photos of a Pacific piloted by a Scot, and again it is hard to imaginable that that sort of power output could be usefully employed in steam days.

 

I used to have an LNER Sectional Appendix which had a section listing which types of loco could be coupled together (and in which order). It must've been a common enough occurrence (and potentially cause problems) to warrant it being set down in 'the rules'

[LMS2968]

49 minutes ago, The Stationmaster said:

I think that's more a consequence of who drew attention to that fact rather than any balancing of potential damage between that to the loco and that to the track.  If more civil engineers of that era had been into writing I suspect we would have heard far more about hammer blow and overweight engines than we have from loco engineering and operating persons.

When 6200 emerged from Crew Works in 1933 with a designed weight of 104T 5cwt and maximum axle load of 22.5T, she was sent to be weighed. There was a bit of concern that the pointers for the driving axles went hard up to the stops at 24T, and the total weight was 109T 18cwt. She went back into works to be lightened as much as possible and the weight reduced, I believe, to 106T. But to the Chief Civil Engineer, the figure given was always 104T 5cwt!

[keefer]

Was still happening into the diesel age - the Baby Deltics and Kestrel are ones that come most easily to mind