Imaginary Locomotives

[rodent279]

22 minutes ago, AlfaZagato said:

Long boilers only add to overall capacity, to my knowledge.   Shorter, broader boilers are superior for steaming.    Larger diameter allows for more tubes, which results in more surface area to heat water.

 

Has been brought up before, but how much broader could a Garratt boiler get with the American loading gauge?

How much larger could it have been with Brunel's broad gauge?

Well we are talking about Imaginary locomotives!

[62613]

27 minutes ago, AlfaZagato said:

Long boilers only add to overall capacity, to my knowledge.   Shorter, broader boilers are superior for steaming.    Larger diameter allows for more tubes, which results in more surface area to heat water.

 

Has been brought up before, but how much broader could a Garratt boiler get with the American loading gauge?

Yes, but what you really need is a short fat boiler, which is what the Garratt design did.

[62613]

7 minutes ago, Compound2632 said:

 

Exactly so. The technical term is turbulence but I like "swirl".

Sorry; rememebring from my marine engineering days! Angled inlet ports to give swirl to the inlet air.

 

[rodent279]

And I'm guessing that the better steaming if the Garrett boiler offset the slightly higher losses incurred through longer, more torturous steam passages?

[Compound2632]

1 minute ago, rodent279 said:

And I'm guessing that the better steaming if the Garrett boiler offset the slightly higher losses incurred through longer, more torturous steam passages?

 

Loss of pressure, which is fatal to tractive effort; I've never really understood that aspect of the Garratt design. 

[rodent279]

14 minutes ago, Compound2632 said:

 

Loss of pressure, which is fatal to tractive effort; I've never really understood that aspect of the Garratt design. 

Wide steam passages and gentle, large radius bends. Which with the Garrett arrangement might be easier than it sounds.

[rockershovel]

9 minutes ago, rodent279 said:

Wide steam passages and gentle, large radius bends. Which with the Garrett arrangement might be easier than it sounds.

I think that's a general comment on most articulated types. The Fairlie is pretty much unique in that it doesn't need to pipe steam from one end to the other, but otherwise all articulated types need to do this, one way or another. Presumably the sheer volume and pressure produced offset it? 

[JimC]

24 minutes ago, rodent279 said:

How much larger could it have been with Brunel's broad gauge?

Well we are talking about Imaginary locomotives!

A 10ft diameter boiler would I think be capable of fitting on a broad gauge garratt, 11ft perhaps a bit iffy. On the basis of a 30 second sketch I suspect there wouldn't be as much gauging advantage on the broad gauge as on the narrow - I think a 9ft 6in diameter boiler would be practical above 6'8 wheels on the broad gauge. However as its probably fair to assume weight limits on the broad gauge would be much the same as on the narrow the practical max size would probably be much less. I imagine a Mallett style chassis would be practical on broad gauge though.

[rockershovel]

1 hour ago, AlfaZagato said:

Long boilers only add to overall capacity, to my knowledge.   Shorter, broader boilers are superior for steaming.    Larger diameter allows for more tubes, which results in more surface area to heat water.

 

Has been brought up before, but how much broader could a Garratt boiler get with the American loading gauge?

I'd guess that the extra height meant that it was possible to build boilers of maximum diameter on Mallet type, or even non-articulated chassis. So, not much. 

 

There are also the quite colossal grates and combustion chambers featured on last-generation 4-8-8-4, 4-6-6-4 and 2-6-6-6 types

 

I'd also suspect that if sheer size and gross TE was the goal, the Mallet (or Mallet-style simple semi-articulated) was the way to go. It also allows the limitations of hand-firing to be left far behind, with tenders holding 25 tons plus of coal being emptied on nonstop runs.

 

It's difficult to envisage Garratts entering such realms 

Edited December 3, 2021 by rockershovel

[Miss Prism]

Brunel's effort was half-baked:

https://didcotrailwaycentre.org.uk/shopimages/1. Thunderer 2 1800.jpg

[rodent279]

1 minute ago, Miss Prism said:

Brunel's effort was half-baked:

https://didcotrailwaycentre.org.uk/shopimages/1. Thunderer 2 1800.jpg

Yeah. Close, but no cigar!

[melmerby]

7 minutes ago, Miss Prism said:

Brunel's effort was half-baked:

https://didcotrailwaycentre.org.uk/shopimages/1. Thunderer 2 1800.jpg

I though all Brunel's locos were rubbish. Daniel Gooch saved the GWR loco department's embarassment.

[Miss Prism]

Just now, melmerby said:

I though all Brunel's locos were rubbish.

 

They were.

[DenysW]

Speaking as a non-GWR person, Brunel at least had the nous to employ Daniel Gooch, and to support him through the bad times when the initial manure hit the windmill. Brunel comes across as a great civil engineer who tried to meddle in mechanical engineering and was, err, less iconic.

[JimC]

Of course Brunel didn't design them: the locomotive builders did that. Brunel put together a wildly ambitious set of specifications which a number of builders followed to a greater or lesser extent. Its perhaps interesting that none were from Stephensons - perhaps they looked at the spec and declined to tender.

[Compound2632]

43 minutes ago, JimC said:

Of course Brunel didn't design them: the locomotive builders did that. Brunel put together a wildly ambitious set of specifications which a number of builders followed to a greater or lesser extent. Its perhaps interesting that none were from Stephensons - perhaps they looked at the spec and declined to tender.

 

Whereas Hawthorns looked at the spec and said "let's have a laugh"!

[AlfaZagato]

I never saw such before, but I love that Thunderer is geared, on top of the rest of the nonsense.

[John Besley]

Doubt it would pull the skin off a rice pudding... great big wheels and no weight above them...

[Zomboid]

That thing is so ridiculous that no one would accept it as fictional...

 

And it wasn't a success? Well I never.

[Mike 84C]

Interesting thread, but nobody has mentioned that the brick arch and deflector, also known as the flame scoop, provided protection to the tubeplate from the direct passage of cold air. Another combustion device was the flap plate which sat in the firehole when the doors were open. One could observe the flame change shape when the flap was in position, tending to "stand up". On LMS engines easy enough to fire over the top of the flap for that sudden puff of smoke that=ignition!  Not so on GW engines  they had a big flap to control the secondary air but a good smoke effect could  be made with a good shovel full of slack and let the blast suck it off the shovel. Been there done all that when I was a yoof back in the 60's,

[melmerby]

Another of Brunel's Beasties:

 

Built to a Brunel spec by Haigh foundry, it too was a geared loco and guess what? It wasn't a success!

It and it's sister "Viper" were rebuilt with different cylinders and no gearing and ran until 1851

 

There was another Hawthorn geared articulated loco "Hurricane" a sister to "Thunderer" (posted by Miss P) which had a 2-2-2 engine section rather than a 0-4-0

[Miss Prism]

31 minutes ago, melmerby said:

There was another Hawthorn geared articulated loco "Hurricane" a sister to "Thunderer" (posted by Miss P) which had a 2-2-2 engine section rather than a 0-4-0

 

https://didcotrailwaycentre.org.uk/shopimages/2. Hurricane 2 crop 1800.jpg

 

(as explored in October 2021 Going loco blog)

 

[Compound2632]

6 hours ago, melmerby said:

Another of Brunel's Beasties:

 

Built to a Brunel spec by Haigh foundry, it too was a geared loco and guess what? It wasn't a success!

It and it's sister "Viper" were rebuilt with different cylinders and no gearing and ran until 1851

 

The photo shows the later Snake, a 2-2-2ST of a type introduced in 1849, some of which ran until 1876, I presume this one is a nominal rebuild of the Haigh Foundry Snake?

[John Besley]

7 hours ago, Mike 84C said:

Interesting thread, but nobody has mentioned that the brick arch and deflector, also known as the flame scoop, provided protection to the tubeplate from the direct passage of cold air. Another combustion device was the flap plate which sat in the firehole when the doors were open. One could observe the flame change shape when the flap was in position, tending to "stand up". On LMS engines easy enough to fire over the top of the flap for that sudden puff of smoke that=ignition!  Not so on GW engines  they had a big flap to control the secondary air but a good smoke effect could  be made with a good shovel full of slack and let the blast suck it off the shovel. Been there done all that when I was a yoof back in the 60's,

 

GWR  engines had a chain attached to the flap so you could leave the doors open and the flap up. Simple matter to fire and flick the flap down with your left hand before swinging over with the shovel.

 

One point on tender engines like 7827 running tender first it was usefull to cut down the amount of cold air entering the box instead of firing and closing the doors every shovel full. But never have the flap up and the doors shut as over time you would burn a hole in the flap and or distort it.

 

When we had Welsh steam coal you only ever got a slight grey tinge to the smoke as Welsh coal was a clean burning fuel - great stuff in the day huge lumps that where very light and broke up easierly along the grain with a coal pick.

 

They also seemed to swell up as they burnt initially like a cauliflower - and the sweet smell of Welsh coal never to be forgotten.... ahh

[John Besley]

Wonder what would induce the mainstream model providers to introduce locos etc from this era.1850's onwards... make for some fascinating models ... remember Mike Sharmans 'The Works'

Edited December 4, 2021 by John Besley