Imaginary Locomotives

[Compound2632]

1 minute ago, 313201 said:

Absolute beast of a loco but I think it woild need an 8 wheel tender with coal and water capacity like the A3 & A4 locomotives had on the Kings Cross to Edinburgh non stop runs

.

 

The tender needs to be shorter by as much as the loco is longer, to fit on GE turntables. So a 4-wheel tender?

Edited December 12, 2022 by Compound2632

[tythatguy1312]

9 minutes ago, Compound2632 said:

 

The tender needs to be shorter by as much as the loco is longer, to fit on GE turntables. So a 4-wheel tender?

I'm not gonna attempt to picture that but the mental image of a tender so hilariously small that it makes the one behind the TGOJ M3t look like a Gresley Corridor tender is possibly the funniest idea discussed.


Speaking of the most successful of the turbines, could the LNER have built a turbine-mechanical? Not saying it has to work but it could be a fun idea. Actually, thinking about this further, steam turbines are the perfect locomotives for the LNER's numerous long distance runs, though the idea of the Flying Scotsman whirring along emitting the noise of 1,000 vacuum cleaners is... peculiar.

Edited December 12, 2022 by tythatguy1312

[PhilJ W]

1 hour ago, tythatguy1312 said:

you know what, just for fun, considering that the B12's are an evolution of the Clauds most prominent for their lengthening, imagine if that was taken to its logical conclusion

The freight version of the B12 was the J20, using the same boiler. Until Bullied brought out his Q class the most powerful 0-6-0 on British rails. It was used on duties for which other railways used 0-8-0's. An 0-8-0 version of the J20 perhaps?

[62613]

1 hour ago, tythatguy1312 said:

you know what, just for fun, considering that the B12's are an evolution of the Clauds most prominent for their lengthening, imagine if that was taken to its logical conclusion

Really wouldn't want to be the fireman with a firebox that long, even with the special longer - handled shovels supplied for this class. Make the wheels 6 foot, or even 5 foot 8 (a G.E. mixed traffic 4-4-0 with that size wheels reached the G.A. stage - it was reproduced in Backtrack many years ago); shortens the firebox and/or boiler.

[Jeremy Cumberland]

Regarding the GER S69 / LNER B12, how common was it to have the firebox directly over the middle coupled axle? It looks like the primary purpose of this arrangement was to reduce axle loading rather than to increase power, and it cannot have been much more powerful than another railway's large 4-4-0 (a Midland 990 class, perhaps). It gives the appearance of an evolutionary dead end; the future was surely outside cylinders and shifting the coupled wheels forwards, although perhaps this was not obvious at the time.

[DenysW]

12 hours ago, Compound2632 said:

to fit on GE turntables. So a 4-wheel tender?

Could you do two 4-wheel tenders, one coal (attached) and one water (not attached during turning)? Same idea as adding a wagon to tank engines to give extra coal capacity.

[Compound2632]

34 minutes ago, DenysW said:

Could you do two 4-wheel tenders, one coal (attached) and one water (not attached during turning)? Same idea as adding a wagon to tank engines to give extra coal capacity.

 

Nah, side tanks would do the job. In fact the whole thing could be a 4-8-4T and save the bother of turning at all. 

[tythatguy1312]

2 hours ago, Compound2632 said:

 

Nah, side tanks would do the job. In fact the whole thing could be a 4-8-4T and save the bother of turning at all. 

Ah, the Derry solution

[62613]

21 hours ago, Jeremy C said:

Regarding the GER S69 / LNER B12, how common was it to have the firebox directly over the middle coupled axle? It looks like the primary purpose of this arrangement was to reduce axle loading rather than to increase power, and it cannot have been much more powerful than another railway's large 4-4-0 (a Midland 990 class, perhaps). It gives the appearance of an evolutionary dead end; the future was surely outside cylinders and shifting the coupled wheels forwards, although perhaps this was not obvious at the time.

You're correct; for the design department had axle load informing every decision (Nominally, it was designed by S.D. Holden of course, but it was the drawing office that was entirely responsible). The GE needed a loco more powerful than the Claud, as they were becoming overloaded on the hardest turns. After the modifications in the 1930s (slightly larger boiler, long - travel valves) they became quite good locos, not that they weren't before. BR put them in class 4P3F

[62613]

7 hours ago, tythatguy1312 said:

Ah, the Derry solution

The RCTS "green book"* says that when the LNER were looking at a more powerful design for the GE section than the B12s, they considered a tank engine, but the Sevenoaks derailment dealt the idea of express passenger tank engines a mortal blow

 

* RCTS Locomotives of the LNER Part 2B: Tender engines classes B1 to B19, in the part about class B17

[toby_tl10]

22 hours ago, PhilJ W said:

An 0-8-0 version of the J20 perhaps?

I agree. The J20 had a wheelbase of 18 ft 10 in, whereas the Raven Q6 0-8-0 has a wheelbase of 17 ft 2 in - shows how long the J20 is.

[The Johnster]

Not disputing this, but an example of the culprits, the Maunsell River class, was tested at speed on the LNER, specifically the GN main line, with Gresley on the footplate (which must have taken some nerve given how the class was behaving on the Eastern Section of the Southern.  The loco was run up to 80mph, a very respectable speed for any tank engine, and found to be stable on the GN, and the real cause of the Sevenoaks accident was poor ballasting; Dungeness shingle was used because it was available to the Eastern Section at very low cost.

 

So, Gresley was aware that big express tank locos were viable and safe.  The LMS used them without issue, as did the GW.  A tank engine replacement for the B12s on the GE section would have had to have been a big 'un, though; the LBSCR had used them successfully on the 60-mile Victoria-Brighton service, but Norwich from Liverpool Street is a bit further, so larger tanks and probably a larger bunker would have been needed if non-stop workings were being considered.  The B17 now makes sense, a more powerful version of the B12 with 3-cylinders and a much bigger boiler.  I have no idea why this engine was not the success it should have been on paper, but it is interesting that the LMS had early troubles with their comparable 3-cylinder 4-6-0, the Jubilee. 

 

In fact, I can't offhand think of any British 3-cylinder 4-6-0 that particularly covered itself in glory until the time of the Ivatt rebuilt Patriots and Royal Scots, which had much better boilers and presumably more attention paid to the draughting.  The rebuilt Royal Scots apparently had a reputation for bad riding, by the way.

[tythatguy1312]

15 minutes ago, The Johnster said:

So, Gresley was aware that big express tank locos were viable and safe.  The LMS used them without issue, as did the GW.  A tank engine replacement for the B12s on the GE section would have had to have been a big 'un, though; the LBSCR had used them successfully on the 60-mile Victoria-Brighton service, but Norwich from Liverpool Street is a bit further, so larger tanks and probably a larger bunker would have been needed if non-stop workings were being considered.  The B17 now makes sense, a more powerful version of the B12 with 3-cylinders and a much bigger boiler.  I have no idea why this engine was not the success it should have been on paper, but it is interesting that the LMS had early troubles with their comparable 3-cylinder 4-6-0, the Jubilee. 

Well I suspect we've just found a use-case for a 4-8-4t in the UK, though it would've been an absolute titan (the closest equivalent, the Derry Northerns, were merely equivalent to 2-6-4t's). I'd suggest some flavour of Garratt but I'm unaware as to any successful passenger garratts.

I did successfully find a passenger garratt in the form of the TGR M Class, though I'm inclined to discount them as they had 8 cylinders yet only had the tractive effort of the LBSC Marsh H2 Atlantics post-1938.

Edited December 13, 2022 by tythatguy1312

[rodent279]

13 minutes ago, tythatguy1312 said:

Well I suspect we've just found a use-case for a 4-8-4t in the UK, though it would've been an absolute titan (the closest equivalent, the Derry Northerns, were merely equivalent to 2-6-4t's). I'd suggest some flavour of Garratt but I'm unaware as to any successful passenger garratts.

I did successfully find a passenger garratt in the form of the TGR M Class, though I'm inclined to discount them as they had 8 cylinders yet only had the tractive effort of the LBSC Marsh H2 Atlantics post-1938.

There were some very successful Algerian passenger Garrets, semi-streamlined, some with Cossart valve gear. Passage below from Wikipedia:-

 

Algeria

In Algeria, 29 4-6-2+2-6-4 Garratts, constructed between 1936 and 1941 by the Société Franco-Belge de Matériel de Chemins de Fer at Raismes in Northern France, operated until the Algerian independence war caused their withdrawal in 1951. This class, designated 231-132BT, was streamlined and featured Cossart motion gear, mechanical stokers and 1.8 m (5 ft 11 in) driving wheels, the largest of any Garratt class. On a test in France, one of these achieved a speed of 132 kilometres per hour (82 mph)—a record for any Garratt class (and indeed any articulated class).[5]

[rodent279]

Handsome beasts as well:-

 

[tythatguy1312]

4 minutes ago, rodent279 said:

Handsome beasts as well:-

 

I never want to see anyone complain about the aesthetics of the Thompson pacifics ever again after laying my eyes upon that

[rodent279]

40 minutes ago, tythatguy1312 said:

I never want to see anyone complain about the aesthetics of the Thompson pacifics ever again after laying my eyes upon that

Well, each to their own! I think it's a beaut, and I don't have a problem with Thompson pacifics either-they may not be quite as easy on the eye as his predecessors or of Peppercorns machines, but they certainly look like they mean business. 

Edited December 13, 2022 by rodent279

[DenysW]

40 minutes ago, tythatguy1312 said:

I did successfully find a passenger garratt ...

Probably my favourite Garratt is the 1915 2-4-0+0-4-2 (short-haul) passenger design for the Sao Paolo railway at 14 tons axle loading. It lacks the odd gap under the boiler normally required to comply with the patents, improving the aesthetics quite a bit. Don't you look at most Garratt designs and want to push the wheelsets together to remove/reduce the gap?

 

The same railway also had express 4-6-0+0-6-4 Garratts (as rebuilt in 1931). Together with @tythatguy1312's and @rodent279's cited Algerian Garratts I think that covers the full range of duties from weak to mega-strong!

Edited December 13, 2022 by DenysW
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[AlfaZagato]

Articulating a thought not bound to the UK traffic.   Possibility for a double K-27 for the D&RGW.   Mallett-style articulateds on NG weren't unheard-of in the US.   I am also fairly certain I have seen K-27's double-headed, though that may be a preservation thing.

 

I also want to see some bulky outside-framed 2-8-8-2 in full Baldwin splendor.

[billbedford]

1 hour ago, The Johnster said:

The B17 now makes sense, a more powerful version of the B12 with 3-cylinders and a much bigger boiler.  I have no idea why this engine was not the success it should have been on paper, but it is interesting that the LMS had early troubles with their comparable 3-cylinder 4-6-0, the Jubilee.

 

Simple:  The spec was impossible. The traffic department wanted a loco with a low axle weight and Gresley wanted to use 3 cylinders. This resulted in a loco where the max axle weight was 2 tons over spec and one where Doncaster DO couldn't get the middle cylinder to fit into the space for it. The end result was that the design was passed over to NBL who used the same cylinder layout as they'd used for the Royal Scots. In an effort to keep the weight down the frames of the first batch were lighter than they should have been and all those frames crack badly enough for the locos to be given new heavier frames within a year of entering service. 

[DavidB-AU]

6 hours ago, rodent279 said:

Handsome beasts as well:-

 

 

They weren't designed to be pretty but were designed to keep the sand out. They did their job and were very reliable, until WW2 stopped the flow of spare parts.

[Yarravalleymodeller]

9 hours ago, tythatguy1312 said:

I'm inclined to discount them as they had 8 cylinders yet only had the tractive effort of the LBSC Marsh H2 Atlantics post-1938.

What is a tractive effort and why does one matter?

 

* stands back *

[rodent279]

27 minutes ago, Yarravalleymodeller said:

What is a tractive effort and why does one matter?

 

* stands back *

It is the ability of a loco to "pull", the ability to start a train; the force exerted by a locomotive,  in the case of a steam locomotive,  usually quoted at 85% of maximum boiler pressure,  and with part-worn tyres. It is a function of cylinder dia & stroke, boiler pressure,  wheel dia, no. of coupled wheels.

The ability of a loco to use its tractive effort is dependent on its adhesive weight ( the weight on the driving wheels) and the amount of friction between the wheels & rails. Too little adhesive weight, or a slippery rail, and the wheels will slip.

Tractive effort is at a maximum when just starting to move, and tails off as speed increases. In Imperial units, T.E. is quoted in lb force, in SI units it is given in Newtons (N or kN), occasionally in kg.

Not to be confused with power. Power is force x speed, i. e.  The power at a given speed is given by the tractive effort x the speed. If TE is in N, speed in metres/second, power will be in Watts. Power at starting is 0 (as speed =0, so force x speed =0), and usually increases with speed up to a point, at which it will tail off.

Edited December 14, 2022 by rodent279

[Yarravalleymodeller]

25 minutes ago, rodent279 said:

It is the ability of a loco to "pull", the ability to start a train; the force exerted by a locomotive,  in the case of a steam locomotive,  usually quoted at 85% of maximum boiler pressure,  and with part-worn tyres. It is a function of cylinder dia & stroke, boiler pressure,  wheel dia, no. of coupled wheels.

The ability of a loco to use its tractive effort is dependent on its adhesive weight ( the weight on the driving wheels) and the amount of friction between the wheels & rails. Too little adhesive weight, or a slippery rail, and the wheels will slip.

Tractive effort is at a maximum when just starting to move, and tails off as speed increases. In Imperial units, T.E. is quoted in lb force, in SI units it is given in Newtons (N or kN), occasionally in kg.

Not to be confused with power. Power is force x speed, i. e.  The power at a given speed is given by the tractive effort x the speed. If TE is in N, speed in metres/second, power will be in Watts. Power at starting is 0 (as speed =0, so force x speed =0), and usually increases with speed up to a point, at which it will tail off.

This is good. 

 

Now given that as we've learned we start with maxium tractive effort and we descend on a curve as our speed increases let us ask what effect our maximum line speed would have on our requirements for tractive effort and ponder weather low tractive effort in the case of the M class is in fact an indicator of lacklustre design or failiure given the maxium line speed is 60 compared with the maxium line speed of (guessing) 80? London to Brighton etc. Let us also ask, by how much would we have to change the specifications to reach equilibrium with the atlantic mentioned. This will be a fun bit of number crunching. 

[rodent279]

22 minutes ago, Yarravalleymodeller said:

This is good. 

 

Now given that as we've learned we start with maxium tractive effort and we descend on a curve as our speed increases let us ask what effect our maximum line speed would have on our requirements for tractive effort and ponder weather low tractive effort in the case of the M class is in fact an indicator of lacklustre design or failiure given the maxium line speed is 60 compared with the maxium line speed of (guessing) 80? London to Brighton etc. Let us also ask, by how much would we have to change the specifications to reach equilibrium with the atlantic mentioned. This will be a fun bit of number crunching. 

Churchward aimed for a drawbar pull of 2tons at 70mph in the design of his 4-6-0's.

2 tons = 2000kg

2000kg x 9.81 = 19.62kN

(70mph x 1609)/3600 = 31.286m/s

31.286m/s x 19.62kN = 613.8kW

613.8 / 0.746 = 822.8hp at 70mph

 

He comfortably exceeded his target, Stars were capable of around 2.5t at 70mph.