Imaginary Locomotives

[melmerby]

How about a UK version of this beauty?

https://en.wikipedia.org/wiki/SNCF_240P

 

20t axle load, 4000HP.

[Dr Gerbil-Fritters]

15 hours ago, melmerby said:

How about a UK version of this beauty?

https://en.wikipedia.org/wiki/SNCF_240P

 

20t axle load, 4000HP.

 

I had a go at it a while back in this thread...

 

 

not very good photoshop work.

 

 

[Corbs]

I tried something similar too

 

[melmerby]

18 minutes ago, Dr Gerbil-Fritters said:

 

I had a go at it a while back in this thread...

 

 

not very good photoshop work.

 

 

 

4 minutes ago, Corbs said:

I tried something similar too

 

But are they compounded and built based on Chapelon's ideas?

[Dr Gerbil-Fritters]

58 minutes ago, melmerby said:

 

But are they compounded and built based on Chapelon's ideas?

 

Well, no because they are imaginary.  But also yes, because they are imaginary.

 

I certainly knocked mine up as a response to the Chapelon 240P with compounding, which is why it has small wheels and Walschaerts valve gear

 

[Traintresta]

On 09/05/2019 at 20:13, Niels said:

There is another phantasy way.

WD locomotives came around  850 as 2-8-0 and 150 as 2-10-0.

They were built without reproci etc balancing and that is good on lousy tracks and tolerable at speeds below say 25 mph.

Coming home they were not really liked.

The distance between center of leading wheel and second driver was 13 feet and11inches.

On a B16 (made by my Hero mr Raven) the distance between front boggie wheel and driver is 14 feet.

Take the austerities and remove the first driver  and leading wheels.

Put in a three-cylinder compound machine over a boggie and drive unto the now first driver.

It will now have balance and riding like an A4 and better fuel economy.

After say 100 years of experiments the swedes found their ideal locomotive.

Twenty of these three-cylindered beauties:

 

Best Swedish lokomotive

 

UK could have had almost 1000 for nothing.

UK loading gauge makes drive unto first set of driver nessecary and connecting rods will be as short on A2/2s

Photoshopping anyones?

This is certainly an interesting proposal, I wonder if you could provide larger drivers to make them a more mixed traffic loco. 

[LNWR18901910]

I've finally completed two locomotives within one week - an LNWR 19" Goods in original condition during the LNWR days and my GWR 71XX 2-6-4T!

 

I've finally completed my GWR 7100 Class 2-6-4T. I haven't put the numbers on, but I will at some point.

 

Edited May 15, 2019 by LNWR18901910

[Niels]

7 hours ago, Traintresta said:

This is certainly an interesting proposal, I wonder if you could provide larger drivers to make them a more mixed traffic loco. 

 

 

 

Larger drivers are counterproductive when three-cylindered.

The Schools class for example  will be a  better locomotive if rebuilt with five feet wheels and wide firebox.

After Chapelon and mr Diamond it was common knowledge that power and speed was limited by valve area more than anything else.

Just like car engines

It is the poor balancing of two cylindered engines that made it nessecary to employ big wheels for going fast.

Try to look at the power curve of the very succesfull SNCF 2-8-2

 

30 years small wheeled high power.

 

And step 13 pages backwards

 

Higher power at speed than any UK locomotive and 1550mm wheels and two cylinders.

This was possible due to big Cossart valves and the two funny looking connecting rod look alikes.

Try this link instead

Caso masterpiece

Edited May 11, 2019 by Niels

[Traintresta]

5 hours ago, Niels said:

 

 

Larger drivers are counterproductive when three-cylindered.

The Schools class for example  will be a  better locomotive if rebuilt with five feet wheels and wide firebox.

After Chapelon and mr Diamond it was common knowledge that power and speed was limited by valve area more than anything else.

Just like car engines

It is the poor balancing of two cylindered engines that made it nessecary to employ big wheels for going fast.

Try to look at the power curve of the very succesfull SNCF 2-8-2

 

30 years small wheeled high power.

 

And step 13 pages backwards

 

Higher power at speed than any UK locomotive and 1550mm wheels and two cylinders.

This was possible due to big Cossart valves and the two funny looking connecting rod look alikes.

Try this link instead

Caso masterpiece

I wasn’t aware of those factors. I know the 9f’s we’re capable of a good turn of speed but I always laboured under the misapprehension that larger wheels equalled speed. 

[34theletterbetweenB&D]

2 hours ago, Traintresta said:

... I know the 9f’s we’re capable of a good turn of speed but I always laboured under the misapprehension that larger wheels equalled speed. 

Because it is fixed gear, for any given stroke rate, the larger the wheel the faster the loco will go if adequate power is available.

 

What is true is that a wheel diameter of 2m/6'6" +, once thought essential for express speed (typically in the range of  110 - 140 km/h or 70 to 90mph in the steam traction era) can be achieved with smaller diameter wheels with superior valve arrangements. But this knowledge arrived rather late in steam development, as it was about to be displaced from its position as principal power for rail traction.

[melmerby]

And nobody mentions hammer blow!

[The Johnster]

Hammer blow; don't knock it...

 

It was realised early on that you could employ a large driving wheel in order to make a loco go faster while keeping piston speeds low; it also gave a better ride on the footplate and encouraged the more nervous drivers to have a go.  Trevithick Jr's 'Cornwall' had a 10'6" diameter driving wheel with the boiler beneath the axle in it's original form, and Harrison's failed broad gauge attempts 'Thunderer' and 'Hurricane' were also designed with this in mind.  In the 1840s and 50s, if you wanted to go fast you built a single driver with a big wheel, and it did the work for the next 20 years.  Loads were within the loco's capacity and the relatively poor lubricants and bearing materials you had to work with encouraged low piston speeds.  McConnell, he of the Bloomers, claimed at the Gauge Commission Inquiry that his locos could run at 100mph on good track; it is probably as well nobody called him out on it but 80mph+ was certainly achievable while not killing everybody involved...  

 

Heavier loads and timetable improvements demanded 4 and eventually 6 coupled locos, multiple cylinders, compounding, and, as better lubricants and bearings became available, it became possible to reduce the size of the drivers but maintain speeds by allowing piston speeds to rise, but, particularly in the UK, the small c conservatism prevalent among designers led them to continue to use the biggest drivers they could get under the ever bigger boilers and fireboxes.  As soon as steam sanding became available in the 1890s, the GW, Midland, and GN all reverted immediately and enthusiastically to big wheeled singles for the fastest trains, a regression to the practice of 30 or 40 years before.  The LNW, which never liked throwing anything away, continued to use it's old singles as pilots, and the Midland simply refused to play the big engine game at all. coping with increased traffic by running more frequent but shorter trains and double heading.

 

In France, they were more accepting of new ideas, and smaller wheeled compounds that could develop a lot of power and still go quickly without compressing the footplate crews' spines as a 9F did at 90mph (!) were used on fast heavy freight and very heavy passenger work.  This may be because there was a greater distinction in the UK between heavy express passenger work demanding big locos with big boilers, and the heaviest freight work which was loose coupled 25mph mineral long hauls within the capacity of 2-8-0s comparable in size to mixed traffic 4-6-0s.  The GW, Midland, and GN all used special block instructions to run 90 or 100 wagon coal trains to London, but none of these were vacuum fitted and ran very slowly.  Mixed traffic locos sufficed for fast freight work, along with the odd pacific on the ECML fish trains.  There was no real demand for a long haul fast heavy freight loco; Churchward had a go with the 47xx, but route availability ultimately sank it in favour of Halls which could efficiently be used on all sorts of other work as well.  

 

The 9F was something of a revelation, a loco that could make decent speed with a thousand ton train.  The heaviest job in the country in the 50s and early 60s was reckoned to be the overnight Birmingham-Glasgow fully fitted freight, with 60mph timings running via Leeds and the S & C, and a brace of mechanical stoker 9Fs were provided for it.  

 

It is interesting that many of our proposals here for neverwazzas are precisely for this sort of work, fast fitted freight, understandable as some of the express passenger locos are adaptable to this.  They would not have ever been needed in large number in reality; no 4-8-0s based on Kings, or 2-10-4s based on Duchesses.  Such locos could have transformed UK general merchandise freight, but would have needed 75mph fully fitted bogie or at least long wheelbased continental type freight stock to be taken full advantage of, and we were firmly wedded to the 9' wheelbase and thought of 10' as modern until the 30s.  Insufficient vehicles were vacuum fitted, and few suitable for fast running, and the railways did not perceive a demand for it until road transport was already beginning to make inroads; the response was fast overnight guaranteed delivery services like the Birmingham-Glasgow and the ill-fated Condor, which spectacularly failed to guarantee anything but late arrival with replacement steam haulage after diesel failure (should have been a 9F job from the outset), the train that built the motorway network (ok, that's a bit simplified, but it did the railway no favours at the very time that the hauliers were lobbying heavily for the traffic and for road building schemes)...

 

This sort of abject failure was the root cause of the Beeching era concentration on block loads and containers/Freightliners, which the railway could not fail to do well at and make money.  The railway seemed to give up on other freight almost overnight in 1963, handing wagon load and part load traffic to the road hauliers on a plate.  There was still a thriving NCL based network of it 15 years later, which suggests that there was more traffic for a longer time than the Beechingites reckoned and despite their discouragement (companies asking for private sidings were refused unless they could supply traffic in daily block train quantity), and BR made a belated response with 'Railfreight', very much on the continental long wheelbased air braked model, but diesels had replaced steam by then and there was no need for specialist locos.  But wagon load, and the likes of livestock, horsebox, and eventually even milk, were given up without much of a fight because they didn't fit the 'modern image'.  

 

There is another reason for large driving wheels, though, that of water consumption, vital on non stop services.  A loco with big wheels will go further on the same amount of water than an otherwise identical one with smaller wheels and the same crew and load over the same route (we are talking about steam engines so this can only be measured in general terms; the small wheeled loco will have less water in it's tender and hence a lighter load when it gets to the bottom of the bank for example) with the same driving wheel rotation speed, because the rate at which their boilers produces steam is the same, as are the pistons, but a cylinder full of steam will take the big wheeled engine further along the line than it will the smaller wheeled alternative.  UK railways (Southern excepted) used water troughs to replenish tender tanks without stopping, though slowing down was sometimes necessary; this does not seem to have been done on the continent where bigger tenders were the norm.  

 

Likes a bit of a Saturday afternoon musing session, I does!

 

 

[Niels]

5 hours ago, 34theletterbetweenB&D said:

Because it is fixed gear, for any given stroke rate, the larger the wheel the faster the loco will go if adequate power is available.

 

What is true is that a wheel diameter of 2m/6'6" +, once thought essential for express speed (typically in the range of  110 - 140 km/h or 70 to 90mph in the steam traction era) can be achieved with smaller diameter wheels with superior valve arrangements. But this knowledge arrived rather late in steam development, as it was about to be displaced from its position as principal power for rail traction.

Nope

Dutchmen in Indonesia rebalanced and revalved a class of 2-8-0 gauge 1067mm  with 1105mm drivers sustaining 90 km/h earning money and doing 105 on test run before ww2 and after Chapelon.

Edited May 11, 2019 by Niels

[Niels]

7 hours ago, melmerby said:

And nobody mentions hammer blow!

 Hammerblow is not nessecary on  three cylinder engines.

Bulleid proved it by modifying a Schools

Edited May 11, 2019 by Niels

[Compound2632]

2 hours ago, The Johnster said:

Heavier loads and timetable improvements demanded 4 and eventually 6 coupled locos, multiple cylinders, compounding, and, as better lubricants and bearings became available, it became possible to reduce the size of the drivers but maintain speeds by allowing piston speeds to rise, but, particularly in the UK, the small c conservatism prevalent among designers led them to continue to use the biggest drivers they could get under the ever bigger boilers and fireboxes.  As soon as steam sanding became available in the 1890s, the GW, Midland, and GN all reverted immediately and enthusiastically to big wheeled singles for the fastest trains, a regression to the practice of 30 or 40 years before.  The LNW, which never liked throwing anything away, continued to use it's old singles as pilots, and the Midland simply refused to play the big engine game at all. coping with increased traffic by running more frequent but shorter trains and double heading.

 

There is another reason for large driving wheels, though, that of water consumption, vital on non stop services.  A loco with big wheels will go further on the same amount of water than an otherwise identical one with smaller wheels and the same crew and load over the same route (we are talking about steam engines so this can only be measured in general terms; the small wheeled loco will have less water in it's tender and hence a lighter load when it gets to the bottom of the bank for example) with the same driving wheel rotation speed, because the rate at which their boilers produces steam is the same, as are the pistons, but a cylinder full of steam will take the big wheeled engine further along the line than it will the smaller wheeled alternative.  UK railways (Southern excepted) used water troughs to replenish tender tanks without stopping, though slowing down was sometimes necessary; this does not seem to have been done on the continent where bigger tenders were the norm.  

 

Likes a bit of a Saturday afternoon musing session, I does!

 

 

 

The 19th century objection to coupled locomotives for fast express passenger engines was chiefly that the coupling rods were an additional source of friction - given the manufacturing tolerances to which locomotive components could then be built - and also a component subject to high and not fully understood stresses, leading to concern about the risk of failure.. That's why, with the advent of steam sanding*, S.W. Johnson and others leaped at the chance to revert to singles for fast work over reasonably flat routes**. The driving wheels of late 19th-century singles were not really very much greater than the coupled engines - Johnson in common with many others was building 6'6" and 7'0" 4-4-0s; most of his singles had 7'6" drivers, with only the 115 Class and 2601 Class having 7'9" drivers - a 10% reduction in piston speed at a given speed. Various explanations have been offered for F.W. Webb's 3-cylinder compounds having uncoupled driving wheels; freer running is certainly one good reason but also, the uncoupled axles could be on a greater wheelbase than most engineers were confident of using - 9'8" for the Teutonics, against 8'3" for the Precedents - giving room for a much larger firebox. Johnson progressed cautiously from 8'6" to 9'0" and eventually 9'6" for the 60 Class of 1898 and the Belpaires of 1900. (It is simply untrue that the Midland did not play the big engine game - Midland engines were big for their day from Kirtley's time right up to the Compounds. The 20th century policy of frequent, lighter trains was surely driven by commercial considerations rather than by limitations of its locomotives.)

 

I don't buy the water consumption argument, at least as stated. Given a single and a coupled engine of otherwise similar characteristics (say, same boiler, valves, cylinders and motion - for example Johnson's 115 and 60 Classes) working the same train over the same route, the energy required must be the same; that means the same amount of work done in the cylinders, i.e. the same volume of steam (at the same pressure). Hence there should be no difference in water consumption. In fact there was because of the greater rolling resistance of the coupled engine.

 

*In the first experiments, compressed air sanding, applied to air-braked engines, until the Westinghouse Co. got wind of what was going on and objected to any tampering with their system that might reduce its effectiveness.

** Not that the southern end of the Midland main line, with Sharnbrook's 1:200, was particularly easy.

[The Johnster]

A better illustration of what I was getting at might be arrived at by comparing, say, a Hall and a 28xx, or, better because they used the same tenders, a Black 5 and an 8F.  Given exactly the same job with the same crew and in general trying to ensure that other things are equal, the Black 5 will go further than the 8F before it runs out of water.  It's an oversimplification, things are never that equal, and a gross generalisation, but still holds.  

 

In South Wales, 56xx 0-6-2s were used to replace pregrouping types, but only came in one wheel size, 4'7".  This was the sort of size used by the Taff Vale, Rhymney, and Barry for 'goods' engines; something like 4'1" was favoured for 'mineral' and shunting work and 5'3" or thereabouts for passenger work.  The 56xx (effectively a Rhymney R built out of Swindon standard bits and given vacuum brakes) proved capable of performing well in all 3 roles, helped by the fact that no great distances were involved and speeds were generally low (line speed on the Barry and on the Taff Vale north of Radyr was 50mph, which the 56xx could manage.  But TVR 'A' class or Rhymney 'P'' class locos with 5'3" wheels were preferred for passenger work until their demise because of their greater range on a tank full of water, despite the As having smaller tanks (they had a smaller boiler as well, even as Swindon rebuilds). 

 

So, the replacement for these locos in the late 40s and early 50s were 41xx series large prairie and BR Standard 3MT 2-6-2Ts, which held the fort until the dmus took over.  They were reckoned less powerful than the 56xx, and certainly couldn't accelerate from a stand like those locos, but were preferred for turns where longer distances were involved, such as Barry-Treherbert, or Cardiff (Clarence Road) to Bridgend via the Vale of Glamorgan line.  The extra range of these locos, despite their lesser tankage compared to the 56xx which had the same boiler and similar sized cylinders to the GW large prairies and a very similar boiler to the 3MT, which in the interests of BR standardisation had smaller cylinders hence the drop in power rating compared to the 4MT of the GW prairies and 5MT of the 56xx, was the reason for their allocation to Barry, Cathays, Merthyr, and Rhymney in the late 40s and early 50s; all those sheds had plenty of 56xx but for some work they were out of their depth on in terms of water consumption.

 

Bigger wheeled engines could go faster as well, but only the Rhymney main line below Ystrad Mynach was rated for any more than 50mph.

Edited May 11, 2019 by The Johnster

[Compound2632]

2 hours ago, The Johnster said:

A better illustration of what I was getting at might be arrived at by comparing, say, a Hall and a 28xx, or, better because they used the same tenders, a Black 5 and an 8F.  Given exactly the same job with the same crew and in general trying to ensure that other things are equal, the Black 5 will go further than the 8F before it runs out of water.  It's an oversimplification, things are never that equal, and a gross generalisation, but still holds.  

 

 

The 5MT / 8F comparison is a better one than the Johnson 115 Class 4-2-2 / 60 Class 4-4-0, since forty years' advances in metallurgy and improved manufacturing tolerances had greatly reduced the additional friction due to an additional coupled axle. So I stand by my argument from physics: the same work done by a locomotives operating at the same boiler pressure and with the same front end design must necessarily require the same volume of steam, and hence the same water consumption. 

 

I imagine that by the 1930s, with the establishment of the LMS Scientific Research Laboratory at Derby, there might be some published results of tests on this point?

 

Under normal operating conditions, one would never get a fair comparison, since the two classes were employed on different types of work; I would not be surprised if the sort of low-speed mineral work with a lot of hanging around, compared to faster long-distance fitted or semi-fitted freight work, might give the impression that the 8F had an intrinsically greater water consumption than the 5MT. But that has nothing to do with the mechanical details of the design, such as wheel diameter and number of coupled axles, except insofar as those are linked to the type of work undertaken.

[RLBH]

On 11/05/2019 at 15:26, The Johnster said:

 

There is another reason for large driving wheels, though, that of water consumption, vital on non stop services.

There is a third reason, one which explains the American preference for relatively large drivers even on what they call 'drag' freight - balancing. When you have large reciprocating masses, as is inevitable on a large two-cylinder locomotive, you need large balancing weights even at relatively low speeds. Small wheels simply don't have space for the required wheel weights to balance the reciprocating weight on a really big locomotive!

[The Johnster]

This is true, but any rotating mass on a wheel any size can be balanced, perfectly in theory.  The problem of balancing reciprocating mass, hammer blow, is lessened by larger wheels to the extent that the reciprocating parts move more slowly; it isn't predicated on the size of the balance weights on the wheels.  These weights look bigger on smaller wheels as the occupy more percentage of the wheel area inside the tyre, and are larger where long piston travel and large crank throws are used, an American trait copied on the GW by Churchward.  Look at the balance weights on a 28xx, 42xx, or 56xx.  It is probably true that the size of weights required on some of the bigger American locos precluded the use of driving wheels below a certain size!

 

Again, heavy freight operation in the US, with the benefit of Janney couplers that could take the loads, bogie vehicles and air brakes throughout, generally took place at much higher speeds, typically 2 or 3 times faster than ours, especially where long single track sections required heavy loads to be cleared quickly to supply paths for the required traffic.  The 'Highball' freight never really happened in the UK in steam days, so the big boilered 2-8-4s with 6 foot wheels were never needed here.  American axle loads and loading gauge facilitated this; 100lb rail is considered light there.

[RLBH]

18 hours ago, The Johnster said:

 

Again, heavy freight operation in the US, with the benefit of Janney couplers that could take the loads, bogie vehicles and air brakes throughout, generally took place at much higher speeds, typically 2 or 3 times faster than ours, especially where long single track sections required heavy loads to be cleared quickly to supply paths for the required traffic.  The 'Highball' freight never really happened in the UK in steam days, so the big boilered 2-8-4s with 6 foot wheels were never needed here.  American axle loads and loading gauge facilitated this; 100lb rail is considered light there.

A (very rough) rule of thumb I've come up with for comparing British and American tender locomotives is this: equivalent roles warrant an extra driving axle and trailing axle on the American locomotive, and the American locomotive has an axle load about 50% higher.

 

By way of example: The British equivalent of the big-boilered 2-8-4s with 6-foot wheels is then a big-boilered 2-6-2 with 6-foot wheels. Or in other words, an LNER V2.  Their ultimate passenger locomotive was a 4-8-4, whilst ours was a 4-6-2; exactly which ones is of course rather contentious!

[melmerby]

2 hours ago, RLBH said:

 

By way of example: The British equivalent of the big-boilered 2-8-4s with 6-foot wheels is then a big-boilered 2-6-2 with 6-foot wheels. Or in other words, an LNER V2.  Their ultimate passenger locomotive was a 4-8-4, whilst ours was a 4-6-2; exactly which ones is of course rather contentious!

Apart from the LNER, big 2-6-2s were oddball in the UK where a leading bogie was preferred (so more 4-6-0s instead) or in later times with the Britannia a 4-6-2

[RedGemAlchemist]

12 minutes ago, melmerby said:

Apart from the LNER, big 2-6-2s were oddball in the UK where a leading bogie was preferred (so more 4-6-0s instead) or in later times with the Britannia a 4-6-2

Agreed. Generally 2-6-2 is more common as a tank engine arrangement from my knowledge.

[RLBH]

13 minutes ago, melmerby said:

Apart from the LNER, big 2-6-2s were oddball in the UK where a leading bogie was preferred (so more 4-6-0s instead) or in later times with the Britannia a 4-6-2

I believe there was some interest from the LMS in a big 2-6-2, but that never came to pass; the point is, though, that the rule-of-thumb indicates that a big British 2-6-2 tender locomotive would probably be appropriate for the type of work a 2-8-4 was used for in North America. Just as 2-8-2s didn't really take off, nor did 2-6-2s, due to operational conditions on our railways. 

 

The equivalent to our mixed traffic 4-6-0s would, then, be a 4-8-2 - which were indeed used extensively as mixed traffic and fast freight locomotives in the United States; the Britannia perhaps equates to some of the smaller-drivered American 4-8-4s that were intended for similar heavy mixed traffic work. It's a rule of thumb, rather than a law of nature, but one that I think helps with making fairer comparisons between the state of the art in locomotive design and in traffic conditions.

 

Comparing British and American 2-8-2s (say) isn't terribly informative, because on this side of the Atlantic they were some of the biggest and most powerful locomotives, whilst the American ones were a smallish, go-anywhere, do-anything type of locomotive. Similarly, a British 2-6-2T would be completely lost on an American railroad - they'd probably use a 2-8-4T for similar work, except that such locomotives were't built. They use tender locomotives instead.

[PhilJ W]

The reason for using tender locomotives rather than tank locomotives in the US was probably the greater distances between service points for coal and in particular water.

[Zomboid]

https://images.app.goo.gl/bBtA42NG9bVNYEPS6

 

They did go in for large tank engines in some situations...