Jim Champ's "Introduction to Great Western Locomotive Development"

3516, a Stella condenser (built apparently to work the Severn Tunnel). I tend to think of these locos as large outside-framed Metro tanks.

 

The first thing that intrigued me was the 1345 rebuilds. Why rebuild 0-6-0ST as 0-4-4s? Looking at RCTS they are noted as having been unsteady at speed, rather like the 3521s. The first of them were built by Avonside for the Monmouthshire, a line that seemed to have had a very odd collection of locomotives. That got me looking at what else came from Monmouth, and I noted three similar Avonside 0-4-4Ts with back tanks, rebuilt by Swindon with saddle tanks 1897/9. That in turn made me look for Avonside, and I turned up this page: 
https://www.gnrsociety.com/locomotive-class/sturrock-0-4-2-suburban-tanks/
Doesn't the 241 series carry a bit of a look of the 3521s? Sturrock had been principal assistant to Gooch on the GWR, and the 241s were put together to work the Metropolitan lines when the GWR had a disagreement with the Metropolitan. It seems very unlikely that Dean would have been directly influenced by an 1865 design in 1887 though.
I shall try and figure out a style for basic sketches of some of these types. I just don't have the information to do my normal style of sketch without them appearing to be more accurate than they really are.

No 1 in post-1882 2-4-0T form. I'm not sure why it was classed as 'experimental', because the Metro tank design had been established by then. As larger versions of the small Metro, I'm surprised these didn't make it into a production run - I don't know what their weights were, but they would have been very useful on the heavier suburban work.

 

I'm trying to work up a sketch format that I can do reasonably quickly and which doesn't imply a level of accuracy that doesn't exist, yet is sufficient to be usable for comparison purposes. How does this seem?

 

 

This is the 1865 Sturrock built by Avonside for the GNR.

 

The first of Deans experimental types No 1 started life with a very unconventional front bogie, which was a unique and rather complicated suspension type. Later it was converted into a conventional 2-4-0T as per @Miss Prismpost above.

 

 

This is a representation of the notorious yet elusive 4-2-4T No 9 which is reputed to have never left the factory. Only the sketchiest of information survives on this locomotive, and even that is debatable. LA Summers and Mike Flemming make a convincing argument that the recorded bogie dimensions are transposed front to rear, and I have followed their lead. The tanks are reported to have stretched beyond the smokebox, but all else is guesswork. 

 

No 13 in its original form as a 2-4-2 with a back tank and a well tank.

 

 

 

And this is (roughly from a photo) one of the first few 3521s. 

 

 

This is 34/35 as built, with a saddle tank.

 

 

Here's 34/35 in their 0-4-4 days with a back tank.

 

 

And this is the 1345 class, the ex Monmouthshire 0-6-0ST modified to 0-4-4.

Edited April 30, 2022 by JimC

On 07/05/2021 at 08:50, Miss Prism said:

3516, a Stella condenser (built apparently to work the Severn Tunnel). I tend to think of these locos as large outside-framed Metro tanks.

 

They were part of a whole group of tender and tank engines that are very similar, with 17*26 cylinders.  Looking at the build date they were surely designed as a group. As a reasonably conventional class they're not so much what I was thinking of. 

 

3201 2-4-0, Lot 65. 3201 was built before the others, in Dec 1884, and immediately sold to the Pembroke and Tenby Railway, returned1896.

3501-10 2-4-0T Broad Gauge, Lot 64 built 3/1885 - 5/1885. Converted to Std gauge and 2-4-0 1892

3511-20 2-4-0T, Lot 64, built 5/1885- 9/1885.  Altered to 2-4-0 1894/5

3202-3205 2-4-0, Lot 65 built 6/1885 - 8/1885

2361-2380 0-6-0. Lot 67, built 9/1885 - 5/1886

1661-1680 0-6-0ST, Lot 69, built 6/1886-11/1886

1661 1680-1700,0-6-0ST, Lot 71, built 11/1886 - 6/1887

 

I think it will be reasonable to distinguish the long wheelbase 0-42T and 0-4-4T from the others.  3521, 3541, 1345 and 34/35 all seem to be long overall wheelbase/short driving wheelbase locomotives. I'll speculate that flexibility to handle curved track may well have been part of the design aim. The drawback seems to have been that at least some of the designs were terrible riders, with a track record of derailments.

No 9, although in many ways more related to tender locomotive development - see @MikeOxonblog for an interesting side by side of a No 9 model and a Dean single, seems to take the flexibility and also the poor riding a stage further. The original form of No 1 also seems to be about flexibility.

The Stellas and the rebuilt No 1 seem of a type chassis wise, and, in spite of quite different frame design, perhaps with much in common with the Joseph Armstrong 2-4-0T.

 

I need to think further about the others. Got to beware though, its perilously easy to construct great card houses of speculation about designs, only for them to fall when further facts become available.

 

 

Edited May 10, 2021 by JimC

As an exercise I've just been attempting to draw relationships of wheels with track with different wheel arrangements.  It speedily became apparent to me that this is a far more complicated subject than I had ever realised, and that a reasonable study would involve some very serious mathematics, well beyond my competence, and large tables of data to present the results, which would be rather indigestible in any format other than textbook or technical paper.

However my little study served to educate me in the very beginnings of the subject, so I thought I would pass the results on. The attached sketch should blow up large enough to be able to make some sense of it. Here are some notes, most of which will probably be more than obvious to any professional railwayman, or for that matter trained engineer, and most likely most chassis building modellers too.

For simplicities sake I have limited this to three arrangements. Green is a fixed wheelbase 0-4-2 (or 2-4-0 or 0-6-0). Red is an 0-4-2 with a radial trailing axle, and the wheels spaced evenly. Blue is an 0-4-2 with the driving wheels closely spaced in the manner of the 3521s and others above, and still a radial axle. The 4th sketch is all three superimposed. You'll need to enlarge the thumbnail and use a big display to get much from this I fear.

My first realisation was just how bad the 0-6-0 arrangement is for spreading the track and wearing rails and flanges. In any given fixed wheelbase an odd number of wheels is the worst case. I now understand better than before flangeless centre driving wheels on ten coupled locomotives. On the other hand its the best for lateral stability and minimising throwover on curves.

My second surprise was that shortening the wheelbase on the driving wheels has a considerable effect, more than I would have thought. I think Dean must have been seeking to reduce flange and track wear on the 3521s and their cousins. But the price that must come with it is lateral instability and increased throwover on curves.  I also started thinking about how side control to return the radial axle to the centre must have a significant effect on the wear on track and wheels, especially leading wheels. My understanding is that sideways control, and how best to achieve it, was an engineering challenge well into the 20th century, so its unsurprising that Deans design team struggled with what must have been a new topic. Perhaps the 3521s needed a deGlehn style bogie?

 

Another interesting thought is how uneven wheel spacing may have advantages. My little thought experiment started with an 0-6-0 design with all 3'6in wheels evenly spaced on a 16 foot wheelbase - 8ft + 8ft, and 12 tons weight on each wheel. I then moved the leading pair of wheels from eight feet apart to four feet apart, shortening the overall wheelbase to 14 feet, so the wheel base is 4ft +10ft. There should still be 12 tons weight on each driving wheel, but not only is the locomotive kinder on the track because the wheelbase is shorter, there's also less of a spreading effect on the track as the centre drivers are not on the apex of the curve.  The complications and tradeoffs of different arrangements seem almost endless.

 

Edited April 30, 2022 by JimC

 

I was idly scanning locomotive drawings (as you do) and I was struck by how much this locomotive matched the general style of the Dean 0-4-4s, with short wheelbase and a long gap to a short wheelbase bogie, although it is rather larger. They were built in 1885 by Beyer Peacock for the Mersey Railway, and three ended up with the Great Western via the Alexandra Docks Company.

 

 

Edited April 30, 2022 by JimC

While sorting out the graphics in this post, I looked again at the images, and what occurred to me about the ADR 0-6-4T especially is that what we have here is basically the Stephenson's long boiler type, but with a trailing bogie for more coal and water. The preserved Kitson ex Consett Iron No 5 is a slightly unlikely survivor of this type. I couldn't readily find an unrestricted photo to upload here, but there are plenty of images on this page. 

https://preservedbritishsteamlocomotives.com/kitson-works-no-2509-consett-iron-co-class-a-no-5-0-6-0pt/

Edited April 30, 2022 by JimC