Imaginary Locomotives

[DenysW]

11 hours ago, The Johnster said:

 It looks to me as if the LMS engines would probably not have been considered if Derby had built a 2-8-0;

Writing in 1969 in "The Garratt Locomotive" A.E. Durrant agrees with you:

 

"... the size of boiler plus the tractive effort could have been easily built into a large 2-8-0 with a 21 ton axle load."

 

The engines on the LMS Garratts were capable of delivering about 3,000 hp, but the boiler was only at about 1700 hp. In both cases very close to twice a Fowler 4F, what a surprise.

[Compound2632]

19 minutes ago, DenysW said:

Writing in 1969 in "The Garratt Locomotive" A.E. Durrant agrees with you:

 

"... the size of boiler plus the tractive effort could have been easily built into a large 2-8-0 with a 21 ton axle load."

 

The engines on the LMS Garratts were capable of delivering about 3,000 hp, but the boiler was only at about 1700 hp. In both cases very close to twice a Fowler 4F, what a surprise.

 

Were the goods lines between Toton and Brent cleared for 21 ton axle load by 1930?

[DenysW]

14 minutes ago, Compound2632 said:

Were the goods lines between Toton and Brent cleared for 21 ton axle load by 1930?

Presumably, because the LMS Garratts were at 21 tons/axle - from the same book, which commented these were the heaviest axle loading of any Garratt, ever. I'd say a couple of decades of the 20 tons/axle of the 4P Compounds, and the outcome of the bridges report allowed this to get by the committees.

 

It looks to me that both the LMS Garratts and 4Fs were designed to start heavy loads and get them up to about 10 mph, after which the boiler became limiting, but the train was rolling by that time.

Edited November 5, 2022 by DenysW

[Compound2632]

36 minutes ago, DenysW said:

It looks to me that both the LMS Garratts and 4Fs were designed to start heavy loads and get them up to about 10 mph, after which the boiler became limiting, but the train was rolling by that time.

 

One wouldn't want to design a locomotive that could too easily get its train up to an unsafe speed.

[DenysW]

1 hour ago, Compound2632 said:

One wouldn't want to design a locomotive that could too easily get its train up to an unsafe speed.

I'm fairly sure I'm failing to understand you. For the avoidance of doubt, the LMS Garratts and (two) 4Fs seem designed to start 150 tons of locomotive(s) plus 1450 tons of loaded wagons and get them easily up to about 10 mph against a 1:100 ruling gradient. By the time you are asking the same load on the same slope to do 25 mph, there isn't enough power from the boiler, and the train will slow down, probably ending up at about 15-17 mph, depending on how much rolling resistance you assume. That doesn't seem an unsafe speed.  

 

The timings given in the book "The LMS Garratts" imply a Toton-Brent speed of 13 mph if you ignore the fact there were a couple of scheduled stops, and 20-25 mph when the loaded train was moving.

 

In all horsepower calculations I'm using the effective pressure curves developed by Lancs & Yorks, and (re)-posted by @Crimson Rambler in the Midland Railway thread.

[Compound2632]

16 minutes ago, DenysW said:

I'm fairly sure I'm failing to understand you.

 

All I was saying was that I was agreeing with you that the starting tractive effort was key; once you've got the train rumbling along at a speed from which it can be safely brought to a halt, that's as much as you need the engine to do.

 

The S&DJR 2-8-0s and the Lickey Banker were tried on the Toton-Brent trains as an experiment; both failed because although they were designed for high starting tractive effort, they failed at the rumbling along part of the exercise.

[tythatguy1312]

40 minutes ago, Compound2632 said:

 

All I was saying was that I was agreeing with you that the starting tractive effort was key; once you've got the train rumbling along at a speed from which it can be safely brought to a halt, that's as much as you need the engine to do.

 

The S&DJR 2-8-0s and the Lickey Banker were tried on the Toton-Brent trains as an experiment; both failed because although they were designed for high starting tractive effort, they failed at the rumbling along part of the exercise.

That has me failing to see why the Midland 0-10-0 was tried at all. It's clear from a design standpoint that Big Bertha was designed to maintain an absurd tractive effort for 2 miles at the expense of all other abilities, meaning that she'd be awful at continuous running for more than those few miles. The 4f's, though pathetic as far as tractive effort was concerned in comparison to a 2-8-0 or the 0-10-0, were damn good when it comes to rolling under mostly momentum.

[Michael Edge]

Much the same happened on the one occasion the LNER Garratt was tried on a train over Woodhead - it stopped short of steam at Crowden, some way from the top.

[billbedford]

Here we go again...

22 hours ago, AlfaZagato said:

LNER's U1 had six cylinders at Gresley's insistence.    Compounded, too.  Offhand, I'm not aware of any locomotive that was able to reliably feed six cylinders to any great effect, the U1 included.   Basically restricted to banking, as it was built for.

21 hours ago, DenysW said:

I believe that this is simply Gresley looking at two 37,000 lbf Tractive effort engines (associated with the one boiler) and saying that he couldn't fit this into the UK loading gauge with 2 x 2 cylinders, he'd have to go to 2 x 3 cylinders. The same logic as the 3-cylinder Pacifics, in fact. And he can't have liked 2 x 4 cylinders (i.e. 2 x the GWR choice) to try it, for whatever reason.

The inspiration a for this loco was work done by Robinson on the GCR to provide a suitable loco for moving coal trains from Wath concentration yard. By 1921/2 this had coalesced into a design for a Beyer Garratt utilising the GC's class 8K frames and cylinders and a new boiler that was to be designed and built by Beyer Peacock. Two such locos were ordered in 1922. After the Grouping, Gresley became responsible for the design work and "modernised" the cylinders and motion with that used on the GNR class O2, which was being built at Doncaster at the time. 

 

The Boiler BP designed had a grate area of 56.5 sq ft, which is somewhat more that the usually accepted limit for one man to fire comfortably. which means the loco would likely to have been steam-shy however many cylinders it had. The answer may be that Robinson was thinking of using mechanical stoking, in particular the system of burning pulverised coal that he had been working on for the previous five years. 

 

 

[DenysW]

57 minutes ago, tythatguy1312 said:

That has me failing to see why the Midland 0-10-0 was tried at all.

If you've built Big Bertha and are successfully operating it in its design duty, it's cheaper and easier to shut up the "can't we just ... " brigade (in meetings) by actually trying it out, rather than by using reason. Same goes for trying the S&DJR 7Fs, that were tasked with a real roller coaster of a line, much more up-and-down than Toton-Brent.

[Northmoor]

2 hours ago, Compound2632 said:

 

All I was saying was that I was agreeing with you that the starting tractive effort was key; once you've got the train rumbling along at a speed from which it can be safely brought to a halt, that's as much as you need the engine to do.

 

The S&DJR 2-8-0s and the Lickey Banker were tried on the Toton-Brent trains as an experiment; both failed because although they were designed for high starting tractive effort, they failed at the rumbling along part of the exercise.

This also relates to the earlier discussion about the ability of steam to produce excess power for short period while a diesel cannot exceed what the diesel engine is governed to deliver (and the electric transmission able to accept for more than a few minutes before overheating).  Early diesels too often had to run at full power all the time, which wasn't sufficient to cope with the severely graded sections of line.

 

The HST used to demonstrate how it was fit for purpose.  Accelerating out of Reading for example, it would be beaten up to 50mph by one of the 2nd Gen DMUs, but above this it would just start to pull away at an increasing rate.  By 125mph it was running on about Notch 5/6 out of 8, as there was so much power in reserve.

[toby_tl10]

Imagine if the LMS Garratts were built under Stanier reign instead of Fowler reign (either they were built later or Stanier came earlier), what would be the differences? Would it have better axleboxes, so the main issue is gone?

 

On the other hand, I would like to mention the proposed GWR Garratts of 1931. The 2-8-0+0-8-2 was intended to replace 2-8-0, 0-6-2T, 2-8-0T and 2-8-2T on South Wales coal trains, I believe. Does anyone have an idea what jobs would be suitable for the 4-6-0+0-6-4?

[tythatguy1312]

12 minutes ago, toby_tl10 said:

Imagine if the LMS Garratts were built under Stanier reign instead of Fowler

the issue is... they weren't built under Fowler or Hughes. They were ordered by James Anderson (locomotive superintendent) behind Fowler's back, as Anderson was capable of enough doublethink to call the Garratts 2 small engines that just so happened to be permanently coupled together. If they'd been ordered with the supervision of anyone who wasn't as stubborn and conservative as Anderson, they may have been spectacular machines.

[rodent279]

In all this, the message I'm getting is that Garrats only made sense in the UK where they could be used to eliminate regular double heading on lengthy freight turns. Is that right?

Were there any freight turns that required double headed 2-8-0's on a regular basis (wartime excepted)?

[Compound2632]

2 minutes ago, tythatguy1312 said:

the issue is... they weren't built under Fowler or Hughes. They were ordered by James Anderson (locomotive superintendent) behind Fowler's back, 

 

Anderson didn't have that authority - it was the LMS Board who authorised the ordering of the locomotives. Fowler, as CME, would have been perfectly well aware of, and would have consented to, that decision.

 

The relationship between the various departments responsible for locomotive design, procurement, and operation under the LMS' management structure is, I would say, now better understood, if one can be bothered to find out, rather than relying on the self-serving myth-peddling of certain much-read writers. I would thoroughly recommend reading D. Hunt, J. Jennison and R.J. Essery, LMS Locomotive Profiles No. 15 The ‘Royal Scots’ (Wild Swan, 2019) and J. Jennison, A detailed history of the Patriot Class 4-6-0s (RCTS, 2018).

[DenysW]

3 hours ago, billbedford said:

the usually accepted limit for one man to fire comfortably. which means the loco would likely to have been steam-shy however many cylinders it had.

I've also seen it commented (in general) that banking is the worst possible duty for a steam locomotive. You try and prepare the fire, you then thrash it as hard as it can possibly go for the 10-20 minutes it takes you to get up a 3 mile bank, meaning a deep, vigorous firebed with everything HOT, then you coast back downhill with any energy supplied by gravity, whilst hoping the brakes still work. Then you wait for the next iteration. And on the Worsborough Bank there was routinely the extra dips/rises caused by mining subsidence.  Not a surprise there were some negative comments on the sole U1.

[Michael Edge]

The usual and obvious complaint was that the U1’s fireman was doing the work of two for the same pay.

[TheSignalEngineer]

5 hours ago, Northmoor said:

 

The HST used to demonstrate how it was fit for purpose.  Accelerating out of Reading for example, it would be beaten up to 50mph by one of the 2nd Gen DMUs, but above this it would just start to pull away at an increasing rate.

The same sort of comparison was true amongst the 2nd gen DMUs. For journeys less than about 15 miles between stops a 150 could outrun a 158 despite the difference in top speed.

[Compound2632]

12 minutes ago, TheSignalEngineer said:

The same sort of comparison was true amongst the 2nd gen DMUs. For journeys less than about 15 miles between stops a 150 could outrun a 158 despite the difference in top speed.

 

Ah, but at Reading you could make the comparison in the flesh, as it where, with simultaneous departures on the main and relief. There's something of the same sort now, with up departures from Twickenham - the train from the Kingston loop making a brisker start than the up Reading train. (I'm afraid I'm not up on what these units are called, other than ugly.)

[toby_tl10]

11 hours ago, rodent279 said:

In all this, the message I'm getting is that Garrats only made sense in the UK where they could be used to eliminate regular double heading on lengthy freight turns. Is that right?

If a single 2-8-0 can do the job, what's the point of the Garratt? But I wouldn't expect a Garratt to equal two 2-8-0s, as it still has to be within the shovelling capability of one fireman.

[DenysW]

4 hours ago, toby_tl10 said:

as it still has to be within the shovelling capability of one fireman.

The UK chose to make that statement true, but it was a choice. The grade (size) of coal for mechanical stokers is different from shovelling coal, so there's a direct cost of having two coaling stations, and a botheration factor of keeping the two separate. There was a trial of a 9F fitted with a mechanical stoker, but it generated the circular logic that a boiler sized for one man's capability doesn't increase in power when automation delivers the same amount of coal.

 

Australian and African (we tend to forget the Kenya Ugandan Railway and focus on South Africa) Garratts used automated stoking to Go Large successfully.

 

It comes back to the UK infrastructure needing a major rework (passing loops, signalling blocks) that was regarded as uneconomic in order to transition from 60-wagon unfitted trains to 90 wagon unfitteds.

 

Even if some routes had generated the need, mostly it could have been met by extra tracks not longer trains.

[Compound2632]

6 minutes ago, DenysW said:

There was a trial of a 9F fitted with a mechanical stoker, but it generated the circular logic that a boiler sized for one man's capability doesn't increase in power when automation delivers the same amount of coal.

 

Three, I think all allocated to Saltley and intended for the Birmingham - Carlisle freights, via the Midland route. For an account of the effort required by the fireman when the mechanical stoker failed, see Terry Essery's Firing Days at Saltley.

[DenysW]

3 hours ago, Compound2632 said:

the effort required by the fireman when the mechanical stoker failed

If this account is unavailable to you, think of driving a car with failed power steering. Not good news at all.

[rockershovel]

How much work would a fireman actually do, when banking? How much coal would a loco like the U1 actually use? 

[DenysW]

1 hour ago, rockershovel said:

How much work would a fireman actually do, when banking?

What motivation are you giving him?* The L&Y R graphs have a sanity check for a maximum of 40 hp/sq-ft of grate superheated, 32 hp/sq-ft saturated. However, I have seen assertions of 50 hp/ft-sq when the team were striving for a record. And I note the "Same pay, twice the £$%^& work" remark above - that I've not yet seen for the LMS Garratts.

 

It's conventional wisdom that superheating was only really effective at steady state, which banking isn't.

 

Opening the door to shovel fuel in also degrades the airflow by moving it away from under the fire to over it. More shovelling isn't linearly better.

 

Too complex to call, even before you get onto (Welsh) GWR coal having a better heat content than the (Yorks/Lancs) coal used by LMS/LNER. Hence the much-maligned post-Nationalisation 'trials' specifying the coal to be used, probably to the detriment of GWR as forced to use higher-ash coal.

 

*Her only a modern possibility, sadly.