The Night Mail

[Hroth]

30 minutes ago, Compound2632 said:

But the Castle represented the culmination of a period of design development on the GWR, with no significant improvement until the 1950s, whereas the A1 was the start of a period or remarkable design development on the LNER. the first step was to increase the boiler pressure to 220 psi.

 

And the adoption by the LNER of a number of engineering precepts employed by Swindon.

 

[Dave Hunt]

5 hours ago, newbryford said:

Even The Great Bear looks the same, but with an extra pair of wheels........

 

Last time I met Bear he didn't have any wheels.

 

Dave

[newbryford]

Just now, Dave Hunt said:

 

Last time I met Bear he didn't have any wheels.

 

Dave

 

In which case, it would be Bear Castle.......

[Hroth]

Can't think of anything more terrifying than a Bear on roller skates...

 

[Dave Hunt]

Saw the spinal consultant and had a long chat about my trouble. He said that injections wouldn't work and showed me the CT scan, in which even I could see that there are three intervertebral discs that are impinging on the spinal cord plus bony overgrowths on the insides of the vertebrae themselves so the affected nerves are creating a fuss. There are actually four but he said that by the time the fourth starts giving me problems it will be up to a higher authority to fix it. He has therefore put me on his list for something called a spinal decompression and even though it carries with it a risk of some highly unpleasant collateral damage I've agreed to go for it as the condition is already affecting my quality of life and if left will only get worse. My next door neighbour has recently had the same operation and he is now quite fit and mobile so I can but hope for the same outcome. Unfortunately because it is not an emergency and is unlikely in the short term to result in permanent disability I'm not near the top of the list and it will probably be another six months before it's my turn but at least I know that eventually it will get sorted. He is also writing to my GP suggesting some different pain relief drugs as he thinks that the ones I am on at present do not really offer relief from neurological pain.

 

It's a rich, full life ain't it?

 

Dave

[MrWolf]

16 minutes ago, Hroth said:

Can't think of anything more terrifying than a Bear on roller skates...

 

 

No?

 

[34theletterbetweenB&D]

1 hour ago, Compound2632 said:

Which it was, objectively, in terms of the standard tractive effort formula, irrespective of the outcome of the exchanges.

False. The tractive effort formula estimates the potential force that can be exerted from a stand, and has no fixed relation to power output. Ask any physicist. Because the A1 was necessarily much heavier than the Castle it will regularly have developed greater engine power while working.

 

What the pacific format offered in exchange for the penalty of extra weight compared to the 4-6-0 was development potential, which within ten years would relegate all UK 4-6-0 express designs to the second rank of express power; with no penalty in coal consumption and reduced water consumption per unit power output.

[Winslow Boy]

56 minutes ago, MrWolf said:

 

No?

 

Don't won't to worry anyone but I believe Bear has been out on his wheels.

[DenysW]

7 minutes ago, 34theletterbetweenB&D said:

False. The tractive effort formula estimates the potential force that can be exerted from a stand, and has no fixed relation to power output.

Mostly true, I fear. Yes the tractive effort formula is 'starting' not 'running'. The fiddle factors (or application of reality) comes in what you set the effective pressure to  - before checking whether your boiler can output that power. See: Diamond EL. The Development of Locomotive Power at Speed. Proceedings of the Institution of Mechanical Engineers. 1947;156(1):404-443.  Diamond points out that developments like long-lap and poppet valves reduced the effective pressure drop between the boiler and the cylinders. But you still can't develop more power than the total cylinder volume * actuations/sec * pressure drop, the latter between the effective pressure at the cylinder inlet and the back-pressure from the blast system.

[Compound2632]

26 minutes ago, 34theletterbetweenB&D said:

False. The tractive effort formula estimates the potential force that can be exerted from a stand, and has no fixed relation to power output. Ask any physicist. Because the A1 was necessarily much heavier than the Castle it will regularly have developed greater engine power while working.

 

As it happens, I am a physicist. It is false to say that the tractive effort formula does not give a larger result for the Castle than the A1; it does - that's the objective fact I was stating. You are right, though, to say that it's not the whole story. One could apply the formula used by the Midland / LMS / BR to determine power class, which took into account an emprically-determined factor related to piston speed at 50 mph (for passenger engines); however, since both engines had cylinders with 26" stroke and driving wheels of only a nominal 0.5" difference in diameter, the outcome in terms of the relative tractive effort of the two designs would be much the same as for nominal tractive effort.

 

26 minutes ago, 34theletterbetweenB&D said:

Because the A1 was necessarily much heavier than the Castle it will regularly have developed greater engine power while working.

 

But I'm afraid this statement is false. The weight of the locomotive has no bearing on the power it can generate (as any student of the 4-6-0s of Dugald Drummond could tell you), although it will have some bearing on its ability not to slip.

 

The power a locomotive can generate is determined simply by the energy content of the steam (which depends on pressure and temperature) and the rate at which that energy is transferred to the kinetic energy of the pistons (pressure and volume swept out). Of course the detailed design has an effect on the efficiency of this process (design and setting of valves and valve gear, design of steam passages, etc.) with the result that engines with the same key parameters (cylinder dimensions, boiler pressure, and driving wheel diameter) were not in practice equal.

 

Edit: @DenysW posted as I typed.

Edited October 5, 2023 by Compound2632

[newbryford]

1 hour ago, Dave Hunt said:

He is also writing to my GP suggesting some different pain relief drugs as he thinks that the ones I am on at present do not really offer relief from neurological pain.

 

It's a rich, full life ain't it?

 

Dave

 

Glad to hear there is some progress - albeit slow.

 

Gabepentin/Neurontin worked for me when the pain was bad.

I ended up on 6 per day.

One of those drugs where the dosage is increased/decreased at one tablet per week................

I'm now down to one every 2-3 days and zero at the best times.

[Compound2632]

33 minutes ago, 34theletterbetweenB&D said:

with no penalty in coal consumption and reduced water consumption per unit power output.

 

I should hope not. If your big engine is consuming more coal than your small engine to do the same work there's something sadly wrong with your grate and boiler design. (See Dugald Drummond again.) As to water consumption for a given power output, that's down to boiler pressure and gas temperature after the superheater; you could get to the same energy content in the steam with a 4-6-0 as with a 4-6-2.

 

What the big engine with its big boiler does give you is the ability to produce a given power output for longer, as steam can be generated at a greater rate - you don't run out of puff. The 19th century locomotive engineers preferred small boilers and big cylinders, as peak power could be generated for a short while when required but the engine couldn't be thrashed - the idea was to encourage efficient working at short cut-off.

Edited October 5, 2023 by Compound2632

[DenysW]

2 minutes ago, Compound2632 said:

I should hope not. If your big engine is consuming more coal than your small engine to do the same work there's something sadly wrong with your grate and boiler design

This is a nitpick, but all reciprocating steam engines have a maximum-efficiency point, so asking a 6P locomotive to do a 2P's work (as Bulleid on the Southern I have seen it asserted) will consume more coal and water per ton-mile shifted.

[Compound2632]

1 minute ago, DenysW said:

This is a nitpick, but all reciprocating steam engines have a maximum-efficiency point, so asking a 6P locomotive to do a 2P's work (as Bulleid on the Southern I have seen it asserted) will consume more coal and water per ton-mile shifted.

 

Quite. The fair comparison is between a 4-4-0 with 6' 6" drivers, two 18" x 26" cylinders, and 160 psi boiler pressure and a 4-6-0 with the same vital statistics, working a 200 ton train over the same route. 

[jamie92208]

4 hours ago, Hroth said:

 

A proposed answer to the LNER streamlined B17s?

 

However the nose shape looks more like Cock o the North!

 

Probably because they were both designed by the same person.  Bullied did the development work on streamlining and liaised with Bugatti and was present for the tests at Vitry Sur Seine.  

 

Jamie

[BoD]

1 hour ago, Dave Hunt said:

Saw the spinal consultant and had a long chat about my trouble. He said that injections wouldn't work and showed me the CT scan, in which even I could see that there are three intervertebral discs that are impinging on the spinal cord plus bony overgrowths on the insides of the vertebrae themselves so the affected nerves are creating a fuss. There are actually four but he said that by the time the fourth starts giving me problems it will be up to a higher authority to fix it. He has therefore put me on his list for something called a spinal decompression and even though it carries with it a risk of some highly unpleasant collateral damage I've agreed to go for it as the condition is already affecting my quality of life and if left will only get worse. My next door neighbour has recently had the same operation and he is now quite fit and mobile so I can but hope for the same outcome. Unfortunately because it is not an emergency and is unlikely in the short term to result in permanent disability I'm not near the top of the list and it will probably be another six months before it's my turn but at least I know that eventually it will get sorted. He is also writing to my GP suggesting some different pain relief drugs as he thinks that the ones I am on at present do not really offer relief from neurological pain.

 

It's a rich, full life ain't it?

 

Dave

Of course you will let us know when it actually happens so we can all keep our fingers crossed (or whatever we do) at the time.  In the meantime I hope that they can do something positive to alleviate the pain.

[34theletterbetweenB&D]

41 minutes ago, Compound2632 said:

But I'm afraid this statement is false. The weight of the locomotive has no bearing on the power it can generate (as any student of the 4-6-0s of Dugald Drummond could tell you), although it will have some bearing on its ability not to slip.

You misinterpret what I suggest: the greater all up weight of the train with the heavier locomotive requires more power output to move it. Put two extra coaches behind the Castle (for equivalent train mass) and see what happens...

[Happy Hippo]

The A1/3 pacific  and subsequently the A4 were designed differently to the GWR fleet of various 4-6-0 locos. The Pacific locos were designed for high speed running along straight and undulating lines whereas the GWR were after surefooted locos capable of flogging up and down the steep and sharply  curved west country banks.

 

Completely different requirements.

 

Gresley designed his locos with wide and shallow fireboxes which gave a large surface area, and were ideal for burning  hard Yorkshire coal.  The Western engines all had narrow and deep  firebox using Welsh steam coal.

 

Different designs for different tasks, all of which performed admirably for the job they were designed to do.

[Compound2632]

24 minutes ago, 34theletterbetweenB&D said:

You misinterpret what I suggest: the greater all up weight of the train with the heavier locomotive requires more power output to move it. Put two extra coaches behind the Castle (for equivalent train mass) and see what happens...

 

Yes, of course, a heavier train requires more power to move it; but that's not function of the weight of the locomotive. You said:

 

1 hour ago, 34theletterbetweenB&D said:

Because the A1 was necessarily much heavier than the Castle it will regularly have developed greater engine power while working.

 

Which I think you can see is most naturally understood as referring to the weight of the engine alone.

 

Of course a 4-6-2 generating the same power as a lighter 4-6-0 is inefficient: it is having to move its own excess weight as well as the weight of the train.

Edited October 5, 2023 by Compound2632

[Compound2632]

5 minutes ago, Happy Hippo said:

Different designs for different tasks, all of which performed admirably for the job they were designed to do.

 

Of course, but the point in question was the truth of the statement made at the British Empire Exhibition that the Castle was the more powerful of the two, and with the proviso that the A1 did in fact require further development to "perform admirably".

 

(As indeed did the Castle, but that had to wait until the 1950s.)

[iL Dottore]

9 hours ago, Dave Hunt said:

I’ve seen a film of the Coronation Scot taken from an aircraft during its record run but not one of a King . Mind you, I have a porn filter on my computer anyway.

 

Dave

I never took you to be a prude, Dave.

 

Does this mean you've never Hump Shunted, had a loose caboose, took possession or enjoyed a multiple working?

 

So much for Dionysian and urbane sophistication....

[Happy Hippo]

4 minutes ago, Compound2632 said:

 

Of course, but the point in question was the truth of the statement made at the British Empire Exhibition that the Castle was the more powerful of the two, and with the proviso that the A1 did in fact require further development to "perform admirably".

 

(As indeed did the Castle, but that had to wait until the 1950s.)

Thanks Stephen,

 

I was pointing this out in the vain hope of preventing Mick from blowing his turbocharger up with the thought of panniers suddenly able to cruise at 130 mph down Penrhos Bank.

[polybear]

2 hours ago, Hroth said:

Can't think of anything more terrifying than a Bear on roller skates...

 

 

A Hippo on Roller Skates.....twirling.....

[jamie92208]

58 minutes ago, BoD said:

Of course you will let us know when it actually happens so we can all keep our fingers crossed (or whatever we do) at the time.  In the meantime I hope that they can do something positive to alleviate the pain.

I believe that Dave has already started taking a self prescribed medicine from Scotland and even Wales. 

 

Jamie

[BoD]

27 minutes ago, jamie92208 said:

I believe that Dave has already started taking a self prescribed medicine from Scotland and even Wales. 

 

Jamie

You mean it’s not available on prescription?