Imaginary Locomotives

[JimC]

5 hours ago, The Johnster said:

and spare boilers of all types needed are kept on hand in the boiler shop 

That's certainly best practice by the twentieth C, but rarely an option for smaller pregrouping lines, especially those with rag bag of different locomotives.  Even the GWR had its oddities which couldn't have exchange boilers, usually in Cheshire. 

[The Johnster]

True, but the smaller pregrouping companies, and more than a few of the fairly large ones for that matter, bought in their ragbags of locomotives off the shelf from the big manufacturers; Stephensons, Sharp Stewart, Beyer Peacock and the rest, and those people did have spare boilers for most of their 'standard' classes.  Even the smallest had workshops capable of pretty much any work required short of complete rebuilds, and had boilersmiths on hand to look after their boilers.

 

Some tended to favour a particular manufacturers' products, such as the Barry with it's Sharp Stewarts, and the availability of spares and back up parts must have been a major advantatge for this.  The Barry is an example of a complete railway bought off the shelf, the result of the business ambitions of David Davies of Ocean Collieriers, who decided he wanted a railway and a port to export his coal from bypassing Cardiff Docks.  So he formed the company, and it bought in locomotives, rolling stock, signalling equipment, everything you needed for a full sized train set, from outside manufacturers, and built a workshop on Barry Docks to keep it all running.

 

Even companies that built some of their own locomotives, like the Taff Vale, or designed their own and had them built like the Rhymney, bought in rolling stock and signalling equipment; only the very biggest concerns, the likes of the GW, LNW, Midland, were able to do it all in-house, and even these bought in when it was convenient for them to do so.  They were prevented by law from building locomotives or stock to sell on, though of course their products did find their way to other railways via the secondhand trade.

[DenysW]

So our mineral Garratt of a couple of pages back gets a Coronation Class boiler which pushes the loaded weight up closer to 200 tons (i.e. 50 tons more than the loaded LMS units), and ends up as 2-8-0+0-8-2 or 2-8-2+2-8-2 depending on axle loadings. 

 

I suggest the Coronation as the source of the standard boiler because I believe it's about the most powerful consistent with UK loading gauge and manual stoking.

[Compound2632]

6 minutes ago, DenysW said:

So our mineral Garratt of a couple of pages back gets a Coronation Class boiler which pushes the loaded weight up closer to 200 tons (i.e. 50 tons more than the loaded LMS units), and ends up as 2-8-0+0-8-2 or 2-8-2+2-8-2 depending on axle loadings. 

 

I suggest the Coronation as the source of the standard boiler because I believe it's about the most powerful consistent with UK loading gauge and manual stoking.

 

But the Coronation boiler goes against the Garratt principle of making the boiler relatively short. It's compromised by having to sit over the coupled wheels of the Pacific. 

[Flying Pig]

I'd leave the boiler to Beyer Peacock.  

 

[PenrithBeacon]

44 minutes ago, Compound2632 said:

 

But the Coronation boiler goes against the Garratt principle of making the boiler relatively short. It's compromised by having to sit over the coupled wheels of the Pacific. 

And also by being tapered, so it's lighter at one end. A shorter, parallel version would probably work

Edited December 1, 2021 by PenrithBeacon

[Compound2632]

23 minutes ago, PenrithBeacon said:

And also by being tapered, so it's lighter at one end. A shorter, parallel version would probably work

 

Agreed. As @Flying Pig says,

 

49 minutes ago, Flying Pig said:

I'd leave the boiler to Beyer Peacock.  

 

[PenrithBeacon]

45 minutes ago, Compound2632 said:

 

Agreed. As @Flying Pig says,

 

 

Not sure I would. Beyer were very conservative in their design practice. Such a locomotive would need a bit of innovative thinking. 

[Zomboid]

You'd want to use a specific Garrett boiler though, rather than import the compromises inherent in a fixed chassis locomotive boiler (as well as all the compromises that a Garrett locomotive brings with it, worst of both worlds...).

[DenysW]

All of the above comments are technically sound and I agree with them.

 

But if the only way to get a fairly specialised new class past Head Office is to say the major cost involved is in a standard component that's already in service, thus very low design costs and optimisation costs, what would you do? It would also push you into using 2-8-0 engines from an existing design as well. Better a chimaera than no new locomotive?

[Compound2632]

10 minutes ago, DenysW said:

But if the only way to get a fairly specialised new class past Head Office is to say the major cost involved is in a standard component that's already in service, thus very low design costs and optimisation costs, what would you do? It would also push you into using 2-8-0 engines from an existing design as well. Better a chimaera than no new locomotive?

 

The standard component(s) it would make more sense to re-use in a Garratt design are the cylinders and motion, along with other common components such as wheelsets and axleboxes.

Edited December 1, 2021 by Compound2632

[The Johnster]

I am not sure what the position was regarding B-G's patent and building B-G type locomotives in house at Swindon.  I agree that the best B-G type locomotive for the Western Valley iron ore traffic would have been one designed and built by B-G, but as this is 'imaginary locomotives', let's assume that Swindon decided to build a locomotive laid out as something like a B-G out of Churchwardian standard components.

 

4 cylinders of the same size as those on a 42xx (and 5202, 72xx, Saint, Star, Churchward County, 28xx, original 47xx, Grange, and large prairie) need to be supplied with steam by a boiler big enough for the job and able to raise steam at a rate consistent with keeping the boiler to pressure while working hard for fairly long continuous periods at low speed.  We want to up the load from 26 wagons assisted from Aberbeeg (42xx/5202) to as many as possible ideally worked throughout unassisted.  Lets say 40 wagons.  The taper boiler is lighter at one end than the other but this can be offset by repositoning the leading bogie pivot.  I'd say that the no.4 of the 42xx/5202 would struggle with 4 cylinders of that size with that steamraising requirement.

 

A no.1 boiler managed to supply enough steam for a 4-cylinder Star, often working hard out to Savernake with heavy expresses, so might do the job.  But it is a bit too close for comfort, and the Castle boiler is probably a better idea, a proven steamraiser also capable of feeding 4 hungry cylinders with manual firing.  There are bigger boilers of course, those from the 47xx and King, but there are weight and possibly loading gauge overhang issues now.  There's also The Great Bear, yeah, right...

 

The motion and valve gear would be the standard Swindon affair with inside Walchaerts, and as we are not bound by B-G's patents, I would prefer to see the engines at the inner ends of the power bogies where they are closer to  the boiler, and less heat is lost in the steam pipes.  I would also prefer to see chimneys and exhaust arrangements for each bogie carried on the bogie, though a chimney and conventional smokebox is needed for the boiler.  The boiler can be mounted quite low in the frames of the central section which will make the fireman's job easier. 

 

I doubt if my 40-wagon unassisted train can be done with this boiler, but it might manage 31 unassisted (the assisted 9F load) or 40 assisted from Aberbeeg.  It would be a long beast, though, and might fall foul of headshunt length at the steelworks end; I don't know enough about this to be certain, but flag it up as something to be aware of.  Assistance from Aberbeeg was less the deal breaker it might first appear, as practice was to leave the train loco and the banker coupled while the hoppers were emptied at the steelworks, and use the banker as the train locomotive on the run back down the bank to Aberbeeg. where the banker cut off for it's next job and the van and original train loco were run around, the original train loco having acted as a steam powered brake van on the descent.  This saved time at the steelworks and gave a good rear brake down to Aberbeeg, not a place you wanted to be running away through...

 

I'd suggest another possibility, allowable as this is 'imaginary locomotives'; a new Swindon boiler based on the no.4 but increased in diameter to the limit of the loading gauge, a short fat boiler, more in line with B-G practice and perhaps employing a wider firebox than Swindon was used to as it doesn't have to fit between the frames.  This format was very successful in the Canadian Pacifc F class 4-4-4.  The Swindon no.4 could 'steam on a candle' (Harold Gasson discussing City of Truro' career at Didcot in the late 50s), and a fattened version seems to be a viable propostion for the Western Valley.Garratt.

[JimC]

47 minutes ago, DenysW said:

Better a chimaera than no new locomotive?

Better a good existing class than a lousy new one though eh?

 

---

We do have the Beyer Garratt proposals for a 2-8-0+0-8-2 and a 4-6-0 + 0-6-4 for the GWR.
https://www.beyergarrattlocos.co.uk/bgpix/gwr280-082.jpg

Unfortunately I can't read all the dimensions on the on line drawings, but its clear that its a relatively short boiler and without much taper, and a pretty wide firebox. If I read the drawing correctly though the heating surface numbers are something like 25% larger than a King boiler, and I reckon the diameter scales to the region of 6'8, 8 inches larger than a King boiler. The numbers I can read seem to make it twice the size of a standard 4 and rather bigger than the LMS Garratt boiler. I suppose its logical - a standard 4 was enough for a 2 cylinder front end at low speed (eg 42) but not for the same at higher speed (Cook records how the 43s would run short of steam on heavy and fast vacuum freight), so equivalent to two standard 4 boilers ought to be right for two front ends at freight speed.

[whart57]

21 hours ago, The Johnster said:

Boilers, for obvious reasons, are very strongly built and likely to last for a very long time if they are looked after.  What wears out is the joints between the end plates and the tubes, and any pipe union joints, rather than the cylindrical pressure vessel part. because of the stresses caused by expansion and contraction and by repeatedly depressurising and repressurising. 

 

 

There was one other factor in the nineteenth century regarding boiler changes and that was the change from coke to coal firing. Most Parliamentary Bills approving railways made the specification that locomotives should "consume their own smoke". What MPs thought a locomotive builder could do about that was a mystery then and still is now. However the amount of smoke was reduced by burning coke instead of coal and that's what most engines of the 1840s and 50s did. However during the 1850s engineers experimented with ways of burning off the tars and gases in coal smoke and thus reducing overall emissions. Long fireboxes were tried along with double fireboxes but the simplest and most effective solution was the brick arch where the red hot bricks did the burning off.

 

However changing the firebox meant changing the boiler and a lot of mid-nineteenth century boiler replacements were actually firebox replacements.

[Compound2632]

1 minute ago, whart57 said:

However changing the firebox meant changing the boiler and a lot of mid-nineteenth century boiler replacements were actually firebox replacements.

 

I would like to see some evidence to support this statement.

 

As far as I'm aware, on the Midland (where the brick arch was invented) the supports for the arch were added to existing fireboxes - so a modification to the existing boiler (or firebox if you prefer). It wouldn't have been the stunningly simple solution it was if it had required large expenditure on new boilers.

 

4 minutes ago, whart57 said:

the brick arch where the red hot bricks did the burning off.

 

Again, that's a new one on me. I understood that it was simply the increase in path length for the incoming air over the firebed providing a better distribution of oxygen and hence more complete combustion. 

[whart57]

13 minutes ago, Compound2632 said:

 

As far as I'm aware, on the Midland (where the brick arch was invented) the supports for the arch were added to existing fireboxes - so a modification to the existing boiler (or firebox if you prefer). It wouldn't have been the stunningly simple solution it was if it had required large expenditure on new boilers.

 

 

That's why the Midland solution was adopted so widely so quickly after being invented. Other fireboxes though were more complicated and couldn't just be altered like that.

[Miss Prism]

48 minutes ago, JimC said:

We do have the Beyer Garratt proposals for a 2-8-0+0-8-2 and a 4-6-0 + 0-6-4 for the GWR.
https://www.beyergarrattlocos.co.uk/bgpix/gwr280-082.jpg

 

The drivers seem to be 4'8" with a 15" throw.

[JimC]

Doing a bit more scaling from the drawing, the boiler appears to have a roughly 14ft barrel and the firebox about 9ft externally. No combustion chamber unlike the most successful pacific boilers, but a 9ft firebox casing is quite a bit longer than the Bear, so maybe the proposal was for something partway between conventional wide and narrow boxes.

[MikeOxon]

2 hours ago, whart57 said:

Most Parliamentary Bills approving railways made the specification that locomotives should "consume their own smoke"

I suppose the modern equivalent is to "consume their own CO2"

[PenrithBeacon]

2 hours ago, whart57 said:

 

There was one other factor in the nineteenth century regarding boiler changes and that was the change from coke to coal firing. Most Parliamentary Bills approving railways made the specification that locomotives should "consume their own smoke". What MPs thought a locomotive builder could do about that was a mystery then and still is now. However the amount of smoke was reduced by burning coke instead of coal and that's what most engines of the 1840s and 50s did. However during the 1850s engineers experimented with ways of burning off the tars and gases in coal smoke and thus reducing overall emissions. Long fireboxes were tried along with double fireboxes but the simplest and most effective solution was the brick arch where the red hot bricks did the burning off.

 

However changing the firebox meant changing the boiler and a lot of mid-nineteenth century boiler replacements were actually firebox replacements.

Please offer evidence for these remarks. 

[Corbs]

7 hours ago, Zomboid said:

You'd want to use a specific Garrett boiler though, rather than import the compromises inherent in a fixed chassis locomotive boiler (as well as all the compromises that a Garrett locomotive brings with it, worst of both worlds...).

I think a Garrett boiler would be way too small and underpowered for a railway locomotive, unless it was just shunting a couple of wagons around a yard.

 

 

 

[John Besley]

10 minutes ago, Corbs said:

I think a Garrett boiler would be way too small and underpowered for a railway locomotive, unless it was just shunting a couple of wagons around a yard.

 

 

 

Do you mean Richard Garrett's of Leiston....

[Corbs]

2 minutes ago, John Besley said:

Do you mean Richard Garrett's of Leiston....

 

Come now, ask yourself; would I be so pedantic?

[MikeOxon]

21 hours ago, PenrithBeacon said:

Please offer evidence for these remarks. 

There's a lot of information about the modifications made to allow coal burning, without generating excessive smoke, in Chapter X, p.131, of E.L.Ahrons 'The British Steam Railway Locomotive 1825-1925'

[PenrithBeacon]

1 hour ago, MikeOxon said:

There's a lot of information about the modifications made to allow coal burning, without generating excessive smoke, in Chapter X, p.131, of E.L.Ahrons 'The British Steam Railway Locomotive 1825-1925'

Yes, I know what's in Ahrons, but 'warts57' went way beyond what Ahrons and others have written about this matter. It is that part of his quote that needs further clarification