Imaginary Locomotives

[Gibbo675]

22 minutes ago, PenrithBeacon said:

Very nice! The projected Class 4 4-6-0 would have used Black Five frames with the Class 4 boiler and wheels/motion. The boiler would probably have had to have an extension along the parallel bit.

Cheers

Hi David,

 

The front ring of a black five boiler is parallel in any case, the cladding is not wholly representative of the shape of the boiler.

 

Gibbo.

[PenrithBeacon]

4 hours ago, Gibbo675 said:

Hi David,

 

The front ring of a black five boiler is parallel in any case, the cladding is not wholly representative of the shape of the boiler.

 

Gibbo.

As though I didn't know .

All Stanier boilers were only partially tapered, the cladding was arranged as it was to tidy up the appearance.

The point that I was making is that the Class 4 boiler would probably need to be extended to suit ,as was the later Standard 4 boiler for the Standard 4-6-0

Edited August 25, 2020 by PenrithBeacon

[Ben Alder]

10 hours ago, PenrithBeacon said:

The projected Class 4 4-6-0 would have used Black Five frames with the Class 4 boiler and wheels/motion. The boiler would probably have had to have an extension along the parallel bit.

 

Yes, I know - that is why it is plonked in the Imaginary locomotives topic..... I did look at doing it with a "proper" Five as a basis  but what with one thing and another decided to base it on the drawing in ES Cox's book  and as such it is a bit long, which is a pity as it won't fit on my terminus's 50' turntable, but the smaller Hornby model suited this better.

[sir douglas]

would the axle load be too high for a tank 4F?

 

bertha 4-8-0 or 9f 4-8-0?

 

 

[Joseph the L&YR lover]

The 4f looks nice but it seems to have little coal space.

[rodent279]

55 minutes ago, Joseph the L&YR lover said:

The 4f looks nice but it seems to have little coal space.

Might work as an 0-6-2, GWR 56xx style.

[AlfaZagato]

4F hump shunter?  I could see it.

[chris251]

Would the view from the cab work? I think the 4F cab is full width up to the roof, but that 0-6-0 tank (is it a Jinty - I'm more Great Western) your using the cab, tanks, and chassis from, the cab narrows halfway up, so presumably the windows are narrower or closer together, not so good for seeing round the larger smokebox, but I may be wrong - I sold my model J83 so I can't compare it to a 4F body.

 

The 0-6-2 is a nice suggestion, but would be a lot more work to build and difficult to get the carrying wheels to corner correctly on tight curves (I found on freelance narrow gauge models that the pivot for carrying bogie needs be between the treads of the outer coupled axle, which would be awkward if you plan to use a commercially made 0-6-0 chassis).

Good idea though - the 4F tank, if you've got the bodyshells lying around to cut and paste together... I've wondered for a few years whether to do a Hawksworth pacific (a design which never went into production), or a single car 101, or single car 158.

Edited August 27, 2020 by chris251

[chris251]

I think you'd probably be OK for weight - unless you plan to run your model on a lightly-laid branch line (for example, the Cambrian line), both engines weigh about 50 tons (according to wikipedia), effectively you're adding 5.5 tons of water in the tanks and 2 tons of coal to the weight of a 4F engine, so you're looking maybe at 56 tons, which should still fit within the same route availability of 5 when spread across 3 axles, unless the load is not spread evenly.

[sir douglas]

running with that then, there is also maybe 2 tons of metal for the tank, bunker and rear frame extension might bring the loco up to 58-59 its not far off the compound at 61 tons which i assume was intentionally the biggest the midland could do with the weight restriction

[chris251]

That sounds reasonable logic - I hadn't thought of checking the weight of the heaviest midland engine.  The weight calculations are only a rough guess, but as you point out, a midland compound is heavier, though it does have 4 load-bearing axles (I think carrying axles normally carry almost the same load as driving ones?)

[AlfaZagato]

Depends on the suspension.    I believe multiple bogie designs used on locomotives were balanced or braced to force weight onto the drivers. 

[Compound2632]

For an unsuperheated Deeley compound, 20 t 16 c on the bogie (so 10 t 8 c on each bogie axle); 19 t 15 c on the driving axle and 19 t 7 c on the trailing coupled axle. Not allowed west of Derby before further post-Grouping bridge strengthening, IIRC. For comparison, the 483 Class superheated bogie four-coupled engines were 18 t 18 c - 17 t 10 c - 16 t 19 c, while the Class 4 superheater goods was 17 t 2 c - 18 t 0 c - 13 t 12 c - more weight on the driven axle than for the 483. Big Bertha was a relative lightweight with not more than 15 t on any axle.

 

 

[sir douglas]

comparitive size is the Peckett OQ at 55 tons which is about 18 tons per axle, ive heard that it was known to break sleepers in its earlier days of preservation (cant remember where this was before moving to Elsecar)

[rockershovel]

Wasn’t Big Bertha assessed, and found wanting for any sort of regular traffic? I’m sure I’ve read that the steam chests and related passages are significantly compromised to get the cylinders within the loading gauge? 

 

 

[Compound2632]

1 minute ago, rockershovel said:

Wasn’t Big Bertha assessed, and found wanting for any sort of regular traffic? I’m sure I’ve read that the steam chests and related passages are significantly compromised to get the cylinders within the loading gauge? 

 

 

 

Like the S&DJR 2-8-0s, well-designed for short bursts of hard work but poor for the long slog - not the answer for Toton-Brent mineral traffic.

[rockershovel]

I’ve been looking at large to super-large US designs in recent months and one thing which does become increasingly obvious, is that the maximum length of the boiler barrel is a clear limitation. The super-large, high-speed, last-generation 4-6-4 and 4-8-4 designs had boilers not exceeding 21’ between tube plates, but fireboxes and combustion chambers of unprecedented size

 

 

 

this enabled them to burn, and make effective use of unprecedented quantities of coal (the NYC 4-6-4s would consume 52-54 US tons of coal in 984 miles, hauling the Twentieth Century Ltd, compared to the Gresley Pacifics’ 9 long tons in 380 miles London to Edinburgh). Given that 70% of steam is generated by the crown sheet, massively enlarged fireboxes relative to boiler length is clearly the best engineering design. 

 

 

 

 

Edited August 29, 2020 by rockershovel

[Signal Box Cat]

Standardisation à la Bulleid......

http://rue-d-etropal.com/3D-printing/3d_printed_sg-trains-q1-variations.htm

 

The Signal Box Cat

[Gibbo675]

23 minutes ago, Signal Box Cat said:

Standardisation à la Bulleid......

http://rue-d-etropal.com/3D-printing/3d_printed_sg-trains-q1-variations.htm

 

The Signal Box Cat

Hi Mr Cat,

 

I like them, they remind me of my own contraptions:

 

Bulleid WC/BB with austerity casing based uon a model I saw in the NRM some years back.

 

Imaginary Bulleid 2-8-2, the paint bloomed and I still haven't sorted it out yet.

 

Gibbo.

[The Johnster]

I like the idea of an 0-6-2T 4F LMS loco for South Wales work; Abergavenny-Merthyr, Tredegar valley, Swansea Vale, Central Wales line southern end.  It would have made the 56xx feel a lot better about itself as it pounded it's axleboxes to destruction on the banks, and it might, with the larger driving wheels, have been as good as a Taff A on passenger work.   Where else?  The requirements of South Wales mean it is good country of 0-6-2T locos, but I can't see the loco being significantly better than what was already there anywhere else, and arguably not enough of an improvement over the Webb 0-6-2T Coal Tanks even in South Wales to be worth the bother.  The Fowler 4F was fine for Lemon's LMS as things were, and continued to be built into the war, by which time they really were a bit long in the tooth as a concept.  

 

Then again, the LMR found work for them into the early 60s, and everybody seemed to find ways of working with their shortcomings.  You really can't have many LMS layouts without them.

[brack]

On 29/08/2020 at 20:04, rockershovel said:

I’ve been looking at large to super-large US designs in recent months and one thing which does become increasingly obvious, is that the maximum length of the boiler barrel is a clear limitation.

Absolutely - look at the boiler for a big boy:

 

Long firebox, then a combustion chamber, fairly short boiler barrel proper, then a very long smokebox.

Look how constrained the grate/lower firebox is in depth due to the rear coupled wheels - the firebox isn't really much bigger in cross section than the boiler barrel.

 

This is rather more optimally proportioned:

(Albeit no smokebox fitted yet). About 2' smaller in diameter (no US loading gauge to play with in Australia), but the two photos very elegantly show how conventional or mallet type articulated loco boilers constrain the firebox, particularly as loco size increases relative to loading gauge. The second boiler is of course from a NSWGR AD60 Beyer Garratt.

 

 

[rockershovel]

... which also demonstrates why the optimum number of coupled axles for maximum power, proved to be four. The Americans, with their experience of ten and even twelve-coupled designs, and 2-6-6-2 and 4-8-8-4 articulated types, opted for the 2-8-4 and 4-8-4 types for last-generation, high speed, high power locos.

 

The British, having already demonstrated that the 2-8-2 configuration could pull trains that exceeded the capacity of the network, opted for a 2-10-0 as maximum final design due to minor advantages within the range of standard components for the limited loading gauge. Hence the non-appearance of  4-8-2 types in the U.K. - they offered no real useful advantages and excessively long boilers relative to the firebox.

 

European design development had already stopped, due to the advance of electrification. The Germans also settled on the  2-10-0 as the ultimate standard design, within the relatively constrained loading gauge; Australia and South Africa, able to accommodate locos of unlimited length, opted for the 4-8-2+2-8-4 Garratt. 

Edited August 31, 2020 by rockershovel

[The Johnster]

I sometimes imagine a 4-8-4 development of Duke of Gloucester with 6' drivers, all disc brakes, all roller bearings, BFB or Boxpoc wheels, cast bed frame, British Caprotti valve gear, triple Giesel ejectors one for each cylinder, mechanical stoking perhaps oil fired, bogie tender, full Chapelon/Porta, and headcode panel between the smoke deflectors.  Class of 10 built 1960 as a result of the failure of class 40 to increase loads and reduce timings between Crewe and Glasgow non stop without needing troughs, another 20 with light fuel oil firing allowing single manning in 1969, and train air brake when Weaver-Motherwell electrification put back in 1966 instead of 50s, reckoned unecomomic as double headers for WCML use but used on Paddington-Plymouth service instead of double headed Warships.  Capable of timetable service 15 bogies at 110mph, and clearing the tops of Shap and Beattock at 80+ with 600 tons trailing.  Actual top speed between 115 and 120mph with 300 ton test train.  All bar 4 scrapped 1974 oil crisis, 1 at Crewe North, 2 Carlisle Upperby, 1 Polamadie as emergency reserve for snowplough and rescue duty on WCML if wires are down; the first dedicated Thunderbirds!

 

Then I wake up...

[AlfaZagato]

All that assumes Swindon doesn't bolt in double blastpipes anyways, like they did with the Duke.

[PenrithBeacon]

Riddles and team did think about cast bed chassis for the Britannia class but it came out too heavy and there were other risks too. There was no chance of another generation of steam the Treasury wouldn't have financed it