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3 minutes ago, Compound2632 said:

 

I doubt that!

I appreciate your vote of confidence. 

 

I was trying to figure out the power class of a 4-6-2 pacific with two 20" x 28" cylinders, a 220 psi boiler, and 80" drivers. The nominal TE is a decent 26,180, but that tells nary a thing for power class.

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32 minutes ago, GWRSwindon said:

I appreciate your vote of confidence. 

 

I just suspected you were not unique in being failed by the system...

 

32 minutes ago, GWRSwindon said:

I was trying to figure out the power class of a 4-6-2 pacific with two 20" x 28" cylinders, a 220 psi boiler, and 80" drivers. The nominal TE is a decent 26,180, but that tells nary a thing for power class.

 

Step 1:

 

Average piston speed at 50 mph = [(2 x 28 in) / (pi x 80 in)] x 50 x 88 ft/min = 980 ft/min

 

Step 2:

 

Use Mr. Gass' curve to calculate mean effective pressure.

Reading off the graph, 980 ft/min => 27 % of boiler pressure

Therefore: mean effective pressure = 0.27 x 220 lbf/in^2 = 59.4 lbf/in^2

 

Step 3:

 

Calculate total cylinder volume (including the factor 2 for double-acting cylinders and the factor 2 for two cylinders)

 

Total cylinder volume = 2 x 2 x pi x (diameter/2)^2 x stroke = 4 x pi x (10 in)^2 x 28 in = 35,186 in^3

 

Step 4:

 

Distance travelled per revolution = pi x driving wheel diameter = pi x 80 in = 251 in

Therefore

Tractive effort  at 50 mph = total cylinder volume x mean effective pressure / distance travelled

= 35,186 in^3 x 59.4 lbf/in^2 / 251 in

= 8,326 lbf

= 3.7 tons force (imperial ton =2240 lb)

 

Step 5:

 

Use LMS table to read off power class (column 2):

TE at 50 mph = 3.7 tons force => 5P

 

That's assuming the boiler power calculation gives greater than 1045 hp at 50 mph. At 40 hp/sq ft of grate for a superheated engine, that means a minimum grate area of just over 26 sq ft, which shouldn't be too challenging for a pacific.

 

 

 

Edited by Compound2632
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1 minute ago, Compound2632 said:

 

I just suspected you were not unique in being failed by the system...

 

 

Step 1:

 

Average piston speed at 50 mph = [(2 x 28 in) / (pi x 80 in)] x 50 x 88 ft/min = 980 ft/min

 

Step 2:

 

Use Mr. Gass' curve to calculate mean effective pressure.

Reading off the graph, 980 ft/min => 27 % of boiler pressure

Therefore: mean effective pressure = 0.27 x 220 lbf/in^2 = 59.4 lbf/in^2

 

Step 3:

 

Calculate total cylinder volume (including the factor 2 for double-acting cylinders and the factor 2 for two cylinders)

 

Total cylinder volume = 2 x 2 x pi x (diameter/2)^2 x stroke = 4 x pi x (10 in)^2 x 28 in = 35,186 in^3

 

Step 4:

 

Distance travelled per revolution = pi x driving wheel diameter = pi x 80 in = 251 in

Therefore

Tractive effort  at 50 mph = total cylinder volume x mean effective pressure / distance travelled

= 35,186 in^3 x 59.4 lbf/in^2 / 251 in

= 8,326 lbf

= 3.7 tons force (imperial ton =2240 lb)

 

Step 5:

 

Use LMS table to read off power class (column 2):

TE at 50 mph = 3.7 tons force => 5P

 

Ah, thank you! This was what I managed to get, glad to see I wasn't too far off.

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1 minute ago, GWRSwindon said:

Ah, thank you! This was what I managed to get, glad to see I wasn't too far off.

 

I've just edited the post to add the boiler power / grate area calculation. You want to tell your drawing office to add a third cylinder, automatically bumping you up to 5.6 tons force which is off the scale in the original scheme!

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7 minutes ago, Compound2632 said:

 

I've just edited the post to add the boiler power / grate area calculation. You want to tell your drawing office to add a third cylinder, automatically bumping you up to 5.6 tons force which is off the scale in the original scheme!

We've no money for that, we're on a budget!

Edited by GWRSwindon
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One of the reasons the Midland introduced its power classification was to reduce loco maintenance - particularly boilers, which are apt to suffer if an engine is overloaded. Hence the introduction of train weight limits associated with the different power classes. The idea being any example of particular power class could be relied on to haul a train of weight appropriate to its class limit. 

 

When the Midland devised this scheme all of its engines were saturated - it didn't really start superheating until 1912 with the 483 class 4-4-0. Consequently any Class 2 engine had to be able to take a class 2 load - furthermore saturated or superheated they all had H or G7 boilers These had the same grate area so in effect the limit was the 32HP per sq ft of the saturated engine or, for a H/G7 boiler of 675 horsepower i.e. a class 2.

 

I don't know when the power classification scheme was refined to include superheated engines. My suspicion, and it is only that, is that it was not altered until just before the Grouping. Maybe if the Midland needed more Class 3 engines it could have upgraded the '483's, but an advantage of them (and the LMS Class 2) staying in the lower classification was an even lower maintenance cost and something in reserve in service as the ex-G&SWR enginemen found.

 

Crimson Rambler

 

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Just now, Crimson Rambler said:

I don't know when the power classification scheme was refined to include superheated engines. My suspicion, and it is only that, is that it was not altered until just before the Grouping. Maybe if the Midland needed more Class 3 engines it could have upgraded the '483's, but an advantage of them (and the LMS Class 2) staying in the lower classification was an even lower maintenance cost and something in reserve in service as the ex-G&SWR enginemen found.

 

Aha! So the 2P is secretly a 3P! That'll really upset the LNWR types! 

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1 hour ago, Compound2632 said:

 

Aha! So the 2P is secretly a 3P! That'll really upset the LNWR types! 

Not really, it has already been stated that George V was all but a class 4, and given the LNWR engine men’s approach to working an engine hard, very much a class 4!

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Well, look what happens; it's been a few days since I visited this forum and it seems that doing hard sums has become the norm! I'm glad that my mate The Rambler has added to the power class discussion in his usual erudite way and tidied things up to everyone's satisfaction. In the good old days the two of us spent many an hour over a cigar or two chatting about such things and I very much hope that those times can one day return.

 

On the modelling front I'm progressing with getting the topography established on the layout but the whole thing is presently in such a state that photographs would only serve to show: a.) What a messy worker I am. b.) I have amassed more bits of foamboard, plywood, balsa, card, plastikard, cereal boxes, kitchen roll, tubs of PVA glue and plaster than I knew existed until now. c.) What a messy worker I am, and d.) What a messy worker I am. Hence pictorial evidence of what I'm up to will have to wait until a visit from cleaners R us has been arranged and a skip obtained to get rid of the piles of accumulated rubbish under which the trackwork has all but disappeared.

 

TTFN

 

Dave

Edited by Dave Hunt
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11 hours ago, Compound2632 said:

 

Aha! So the 2P is secretly a 3P! That'll really upset the LNWR types! 

Most amusing! The truth is that the calculation for tractive effort was a lot more crude than the expositions earlier and the 2P was a 2P always. I believe, but I'm not entirely sure, that the LNW superheated 4-4-0s (Georges or Precursors) were in 1923 Class 4 but the centre bearing was taken out to reduce maintenance costs and the engines became Class 3. As I say not sure about that, the reference is one of OS Nock's books.

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A point that is missed by those who bewail the LMS's treatment of the big LNWR passenger engines is that, by the grouping, they were already inadequate for the LMS Western Division's operating needs. That's not to say the 4P Compounds came much closer to meeting those needs; the LMS inherited an express passenger problem that only began to be solved in 1927. 

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38 minutes ago, Compound2632 said:

A point that is missed by those who bewail the LMS's treatment of the big LNWR passenger engines is that, by the grouping, they were already inadequate for the LMS Western Division's operating needs. That's not to say the 4P Compounds came much closer to meeting those needs; the LMS inherited an express passenger problem that only began to be solved in 1927. 

 

OK, here's a dissenting set of comments, that doesn't believe that it's merely a case of the LNWR, being hard done by! Nor was it a case of not liking the 'Midland' way, because Crewe didn't want 'red engines'.

 

Agreed that much of the LNWR fleet was no longer (if ever it really was) adequate for the job. I don't believe that the LNWR, EVER did provide adequate power for it's express services - by that I mean sufficient power to make up for lost time etc. Yes, plenty of stories with lots of thrashing and sparks being thrown all over the lineside, by generations of performance compilers in The Railway Magazine, but was it the ideal, needing loco crews, signalmen & station staff to get everything exactly right to recover late running?

 

The GWR & LNER, carried on using the best practices of their constituent companies, which meant that in practice, it was a continual improvement process. The Southern was a little different, in that it's priority was sorting out it's electrification variety (I believe they made the wrong choice, the overhead system, ought to have been the group standard - but I digress) and only new steam classes where essential.

 

Regarding the 'Midlandisation' of the loco fleet, post 1923, realistically what advantage was there in replacing the LNWR locos with another large fleet of locos, that equally weren't really modern designs either?

 

Some of the complex calculations previously, indicate that were either Class 2 or 3  (2 1/2) or either Class 3 or 4 (3 1/2). The concept of taking the centre bearing out of an LNWR 4-4-0, to save maintenance costs and in doing so reduce it's power output, is plain ridiculous.

 

The sole reason for introducing huge numbers of 4F, 2P and Compounds, was that the accountants were able to 'prove' that these locos were cheaper to maintain. While cheaper operation is great, that isn't the only factor. Very important is, can the trains run to time, with the loads needed for the service?

The case for large numbers of 3F 0-6-0Ts made a lot of sense, because they replaced a multitude of pre-group versions, with a reasonable replacement. BTW, can someone explain why some improvements to the Midland 1F 0-6-0T, cause them to skip the 2F classification? Without me doing calculations I don't understand, were the 1F's close to being 2F's and the 3F's, 2F's? Always a weakness with 'bands'.

 

Midland sheds, presumably were very good at common repairs, such as the axle boxes of various classes of their locos, but realistically why were they doing this? Surely money can be saved by designing better lubrication systems in the first place? Obviously, the Midland had long ago decided that it was an acceptable practice and enforced the practice onto other parts of the system.

 

Change came later, as Stanier locos rarely had such problems.

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6 minutes ago, kevinlms said:

The case for large numbers of 3F 0-6-0Ts made a lot of sense, because they replaced a multitude of pre-group versions, with a reasonable replacement. BTW, can someone explain why some improvements to the Midland 1F 0-6-0T, cause them to skip the 2F classification? Without me doing calculations I don't understand, were the 1F's close to being 2F's and the 3F's, 2F's? Always a weakness with 'bands'.

 

The 3F / 2441 Class 0-6-0Ts were substantially bigger machines than the 1F / 1102, 1377, and 1121 Classes:

Cylinders: 18" x 26" vs 17" x 24" (21% bigger)

Boiler pressure: 160 psi vs 140 psi (some of the 1121 Class had 150 psi; also this is for the original boilers, haven't checked the Belpaire replacements but the LMS Standard 3Fs had 160 psi)

Grate area: 16.0 sq ft vs 14.5 sq ft.

 

Doing the calculation:

 

Piston speed at 25 mph (2,200 ft/min) with 4'6½" drivers (171 in travelled per revolution):

3F: 669 ft/min 

1F: 617 ft/min

 

Using Mr Gass' graph for mean effective pressure:

3F: 0.38 x 160 psi = 60.8 psi

1F: 0.42 x 145 psi = 60.9 psi

Interestingly, nearly the same.

 

Tractive effort at 25 mph:

3F: (4 x pi x (9 in)^2 x 26 in x 60.8 psi) / 171 in = 9,410 lbf = 4.20 tons force (top end of Class 2)

1F: (4 x pi x (8.5 in)^2 x 24 in x 60.9 psi) / 171 in = 7,760 lbf = 3.46 tons force (top end of Class 1)

 

Boiler power, both engines saturated:

3F: 16.0 sq ft x 32 hp/sq ft = 512 hp

1F: 14.5 sq ft x 32 hp/sq ft = 464 hp

 

Both in the Class 1 range!

 

The 2241 Class weren't initially intended as simply shunting engines but for working goods and mineral trains between Brent and the Midland's South London coal depots via the steeply-graded switchback of the Metropolitan Widened Lines. Very early on, five of the class were sent to Bromsgrove for banking on the Lickey incline. In LMS days, the Standard 3Fs largely replaced the ex-NLR fleet at Bow, working passenger services.

 

 

 

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In Midland days the company's tank engines were not given formal power classifications, so the anomalies Stephen has found strictly apply to LMS and its application. It's possible the LMS may have used a modified curve but I don't have any details. It certainly extended it to encompass more powerful engines higher powers - maybe it altered the power boundaries?

 

I do have somewhere the BR curve which it applied post 1948 to engines from the other three companies. Essentially I seem to recall the method was largely similar save that the free area through the boiler was included as this is an indicator of steaming capability. I will try and find it. 

 

Turning to another matter recently raised, the Midland knew a great deal about lubrication and bearings - arguably more than the LMS or Churchward. Deeley with his brother-in-law wrote perhaps the then definitive book on the subject - it was in print for a generation and went through several editions. He also served on an important lubrication committee during the First World War and invented a machine for measuring the 'oilyness' of an oil - an important property necessary for axlebox lubricants. The cheap oil used by the LMS which was deficient in oilyness, was one of the major causes of the axlebox heating that the LMS experienced with the likes of the 4F and other inside cylinder classes - another was substituting a cheaper whitemetal. 

 

The Stanier axlebox - despite what Cox might try and have you believe - only lasted longer between repairs because it was bigger - you have more space on an outside cylinder engine for longer bearings. The greater length meant there was more bearing area to wear away before the 'box needed repair.

 

Deeley stated that longer bearings can cause problems on curved lines - interestingly when Cox had his way and gave the Britannia 4-6-2 class a stiff frame, he came unstuck on the Derby-Machester line. The Britannias on that ex-Midland line suffered from broken broken smokebox saddles and loosened frame stretchers.

 

 

Crimson Rambler

 

 

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Victorian engines had their oil supplied from a hole in the top of the axle box. The problem here was twofold one was that having a hole there effectively reduced the length of the journal while the engine was standing and it took several revolutions of the axle for the oil to be distributed along the length of the journal. During this time the axle box was effectively unlubricated so this was when most of the wear took place. Midland engines were no different in this respect than any other railway for the period.

Churchward introduced, on GWR, the underkeep method of supplying oil to axleboxes. This method had been successfully used in the USA and France for a number of years and it took the form of a worsted pad running the width of the journal which was soaked in oil. Churchward did tests and found that oil was supplied to the entire diameter of the journal in less than one revolution of the axle. Stanier, I understand, but I'm not entirely sure, modified this so that oil was supplied to both sides of the journal at 45° to the top, further reducing the time the journal was at risk. I'd be grateful for confirmation of this BTW.

Back to the Midland. Johnson's introduction of a wide range of standard components in the Midland ( no difference here between all the larger railway companies ) which included axleboxes. These did the MR proud but they became an issue with the introduction of the 4F. Now I find this interesting, because the MR, unusually, actually prototyped the 4 before putting it into production which implies that either there wasn't a problem with the 4F axleboxes or it wasn't reported or reports were ignored. Don't know, but Eric Langridge, who designed the 7F 0-8-0, says in his books (Oakwood Press) that the axle box is the 4F was a success, so he used them in the 7F. Something went wrong here, but I don't know what, they're a number of possibilities.

When Maunsell came to design the 4F Q Class in the later 30s he used the same size of journal as the Midland 4F but he used underkeep lubrication as did Collett and Hawksworth on the GWR in 30s-40s period. They really hadn't much choice, there is a limit to the length of a journal in an inside cylinder engine with inside Stephenson's valve gear.

It should be noted that the LMS was going to redesign the axleboxes of the 7F 0-8-0 but WW2 intervened and Beames had changed to lubrication to the LNW 0-8-0s as they became due for reboilering to 6 or 7F so making them much more reliable machines.

Think that's it.

Cheers

 

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What year did Churchward introduce the underkeep oiler. I'm interested  as I had to design and build such a system on the 1898 built horse tram that I helped to restore. They were obviously standard equipment on trams from at least 1890. As an aside, the sprung worsted pads that we used were supplied by Armstrong Oilers who are a subsidiary  of the North York Moors Railway and design and manufacture the oilers from scratch buying in only spring steel, wool and wire.

 

Jamie

Edited by jamie92208
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Langridge did comment that poorer quality oil and whitemetal had affected axlebox performance. I don't know when Churchward adopted them but an underpad was tested by Beauchamp Tower when he carried out his famous series of bearing lubrication tests in the 1870s, so they pre-date GJC. Incidentally he found it returned no better bearing performance than top oil entry.

 

Stanier did introduce the oil between about 35 and 40 degrees down from the crown via a pair of grooves. It worked well enough with outside cylinder engines but wasn't so good on inside cylinder engines as their bearing load profile is different. In its last design the Midland introduced the oil at the crown via an elliptical groove with the intention oil could enter while the journal was stationary.

 

The LNER also suffered from hot boxes on some important inside cylinder classes during the Second World War - from memory two were the J38 & J39 . The company prompted the development of a special oil that in effect replicated the older oils used pre-Grouping. Adopted and applied by the LMS to the G1, G2, 7F and 4F it resulted in a noticeable drop in hot boxes. For example in 1942 the G1 and G2 classes a hot box per engine every 8-9 months.  By 1946 this had extended to 29 (G1) and 36 months (G2) respectively.

 

But it has to be said this was really a partial return to previous practice because the poor quality whitemetal remained.

 

 

Crimson Rambler

 

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In short, LMS cheapskate ways sabotaged the effectiveness of ex-Midland engines just as much as it did ex-LNWR engines?

 

3 hours ago, Crimson Rambler said:

his brother-in-law

 

Leonard Archbutt. I dare say Miss Archbutt jumped at the chance to become Mrs Deeley.

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The threads here are fascinating and informative but I just want to point out that it is an indisputable fact that notwithstanding any evidence to the contrary the Midland was the finest railway on planet earth. In stating this I am completely unbiased in any way.

 

Dave Hunt

Chairman, Midland Railway Society.

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4 minutes ago, Dave Hunt said:

notwithstanding any evidence to the contrary

Ah, so you accept that it exists, eh?

Quote

 

the Midland was the finest railway on planet earth. In stating this I am completely unbiased in any way.

 

Dave Hunt

Chairman, Midland Railway Society.

 

If nothing else, at least you are consistent...

 

More seriously, this discussion has been an eye-opener into the importance of such things as materials science and detailed design, features which are often overlooked and yet the combination of poorer oils and poorer bearings can have a dramatic effect on the repair frequency, the haulage capacity and ultimately the economic survival of a railway company. 
After all, they were created via huge injections of capital, and existed to provide returns on that investment: not to run trains except in service of those objectives.

Strict control of loadings might require more engines to be deployed on occasion, but it also means those engines will spend more time in service between major overhauls and have fewer breakdowns.
 

My respect for the Midland has been increased by this conversation.

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  It's also interesting to look at the lines that different companies built and how they were engineered. I'm no expert but the LNWR's line up the Spen valley, in part, built around 1900 had gradients as steepmasx1 in 70 and required double heading till the end of steam.  The Midland's proposed line of 1897 up the same valley had a ruling gradient of 1 in 200. Thus imposing much cheaper working expenses than the LNWR's one.  One solution had lower capital costs but imposed higher running costs for years to come. The other had higher capital costs but left a much lower running cost.

 

As to cheap parts causing problems, that hasn't stopped.  I believe that the major problem with overheating HST engines in the late 80's, was down to someone in BR specifying cheaper gaskets. Those were the days when there used to be 4 wheeled trolleys on station platforms with tanks on marked HST coolant, so they could top them up between journeys.

 

Jamie

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2 hours ago, jamie92208 said:

  It's also interesting to look at the lines that different companies built and how they were engineered. I'm no expert but the LNWR's line up the Spen valley, in part, built around 1900 had gradients as steep as 1 in 70 and required double heading till the end of steam.  The Midland's proposed line of 1897 up the same valley had a ruling gradient of 1 in 200. 

 

The Stephensons, Father and Son, were wedded to the idea of keeping gradients down even at the expense of longer routes and missing out major traffic centres - e.g. Sheffield not on the North Midland. Their lines usually have a significant summit tunnel - Kilsby, Clay Cross.

 

Locke started out as George Stephenson's pupil but following something of a palace revolution on the Grand Junction took over the engineering of that line. He displayed his independence and confidence in the development of the locomotive - overconfidence, perhaps - with less fear of gradients. His lines are characterised by a gradient profile that looks like the roof of a house, eschewing the summit tunnel - Grand Junction, Lancaster & Carlisle, Caledonian - there is no tunnel on the WCML north of Stafford! Undoubtedly cheaper to build - which goes a long way to explain the success of the partnership of Locke & Errington - but more expensive to work. Brunel started out with the Stephensonian philosophy but his inventiveness led him towards a Lockian approach, which, he realised, would work if the source of power was fixed, with power being transmitted to the train by some means. Unfortunately his engineering materials weren't up to the task and his system was also fatally flawed by the power limitation of a pressure difference of less than one atmosphere available. From this perspective, it's hardly surprising that the WCML was electrified long before the ECML.

 

After the crash of 1846, money was tight, so the Lockian approach ruled by necessity - right down to the 1860s. By the 1890s, ideas had changed again - maybe more capital was sloshing around, certainly tunnelling techniques were more advanced. Studying a list of long railway tunnels, it's notable that they fall into two main groups by date: 1830s/40s and 1890s/1900s with rather fewer in the intervening years.

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