61xx / 81xx books with good diagrams and/or GA / frame diagram numbers?

[Guest WM183]

Hi folks.

 

Does anyone know of a book with good (better than the typical weight diagrams) drawings of 61xx or 81xx class Prairies? I want to build one - an 81xx in particular - and the drawings in Russell vol 2, while good, aren't so good I want to scale from them too much? A frame diagram would likely suffice, as reading GAs is... trying in smaller reproduction formats.

Any articles in the GW Journal that may help? I searched the index but not much came up.

All the best,

Amanda

[K14]

GW Journal No. 5 (Winter 1993) has a full-spread GA for the 5101 class. It's comprised of several sub-drawings:

 

98682 - Frame Plan - Lot 284 - 5101 class - Feb 1934

Unnumbered - Arrangement of Boiler Mountings (Cab controls) S/2 Boiler 5101 & 6100 class

87341 - Cross Sections - Lots 257 & 259 - 5101 class - Feb 1934.

Edited May 14, 2021 by K14
extra info

[K14]

Isn't an 81xx effectively a 5101 with a bigger boiler?

 

according to the index, GWRJ 68 has a frame plan for the 42xx class fitted with Std 2 kettle.

 

 

[Miss Prism]

24 minutes ago, K14 said:

Isn't an 81xx effectively a 5101 with a bigger boiler?

 

The 8100s had a No 2, as per the 5101, but the 8100 No 2s were pressed to 225psi. That pressure, together with the slightly smaller (5'6") drivers, bumped up the nominal TE.

 

[The Johnster]

An 81xx is a 61xx with smaller (5'6") driving wheels, and a 61xx is a 5101 with a higher boiler pressure.  A 3150 is a 5101 (which was originally a 31xx) with a bigger (no.4 as opposed to no.2) boiler, and a second class 31xx (introduced 1938) was a 3150 with smaller (5'3") driving wheels. 

 

In chronological order of introduction:-

 

31xx, 5'8" driving wheels, no. 2 boiler

3150, ditto but with no.4 boiler

5101, Collett modernised 31xx conversion, ran into 41xx series

61xx, ditto but with higher pressure boiler (180psi to 220psi) for accelerated London area commuter work

81xx, ditto 61xx but with 5'6" driving wheels for Birmingham area commuter work (steeper gradients)

31xx, Collet 1938 design developed from 3150, with 5'3" driving wheels and no,4 boiler

 

All GWR locos are the same, except when they are different.

[Guest WM183]

Thanks guys!

 

I didn't realize that the 61xx and 81xx were essentially the same as the 5101s. I wish to build a western region parcels train in 7mm, and ive seen some pics of them with 61 and 81 class prairies as power. I love the sleek look of the large prairies.

 

Gonna get those issues of the gw journal. 

 

Amanda 

[The Johnster]

There is no visual difference between the 5101 and 61xx; it is simply a matter of boiler pressure.  There are, of course, minor detail differences to individual locos in both classes, but a 61xx can be modelled by renumbering a 5101, or vice versa. 
 

The 81xx is slightly different, because the driving wheels are 2 inches smaller in diameter.  That’s not far off the normal tyre wear range, but this means that everything else sits an inch lower, and the cab roof is noticeably different, with a higher, more domed, profile.  The differences are small and subtle, and you may find a 5101 masquerading as an 81xx acceptable as a layout model, but I reckon the differences will be obvious if the loco is sitting next to a 5101, especially in 7mm. 
 

Preaching to the converted when it comes to the look of the large prairies, Amanda; I remember them in in service and found them handsome beasts with an air of power and a sort of confidence about them.  If you found a clean one in late BR lined green, with the copper chimney cap and brass safety valve bonnet polished up, they were very good looking locomotives!

[Guest WM183]

Hi Johnster,

 

I plan to use the frame and GA drawing to build the boiler, frames, and so on, and I'll use the profiles from the drawings in Russell for the look of the cab roof, etc. The smaller drivers I did know about, it makes the 81xx just look a bit squatter - and thus leaner - than the larger wheeled versions. I see lots of GWR branch line layouts but very few in more urban or suburban locales, so I may do a smallish parcels depot as a layout. I love parcels stock more than any, the wondrous variety of brake coaches, CCTs, special milk and fruit vans, plain old vacuum fitted covered vans, and so on makes for really interesting looking trains!

Amanda

[kada33]

I don't think anyone has mentioned above 'The Prairie Papers'by Ian Sixsmith. Printed by Irwell Press.

No.1 covers 3150-3190, 4100-4179 & 5100-5199.

No.2 covers 3100-3104, 6100-6169 & 8100-8109.

There are lots of photos and details about the classes, although no GA drawings, as K14 has said that is available from GWJ no.5. I do have a copy of this issue but you would be hard pushed to read any of the dimensions.

Dave

[Guest WM183]

Hi Kada,

I have ordered issue 5 and issue 68 of the GWJ, and even if I cannot read the dimensions, I can scale from a known dimension. I will have to get the Prairie Papers books; I have the Pannier papers series, and the 42xx/52xx/72xx books, and like them a lot! Hopefully these drawings and books, plus the books I have now, can get me there. We shall see!

It also looks like I've got a 42xx drawing on the way too, eh? =)

[Siberian Snooper]

Have a look for  Great Western Moguls and Praries, by David Maidment, published by Pen and Sword,  ISBN 978 1 47382 744 8 the book covers all the classes that have run on the western including the absorbed and BR engines and has weight diagrams with the principal dimensions. This and his other books in the series are well worth the investment.

 

 

[Guest WM183]

Hi Snooper,

I hope to build a 43xx (And a Grange, but I digress) at some point too, so this book will help a lot it seems!

Amanda

[Miss Prism]

12 hours ago, The Johnster said:

and the cab roof is noticeably different, with a higher, more domed, profile.

 

The boiler pitch on the 61xx was 7'11 3/4" and the cab roof was 12'7 5/8" high. The 81xx boiler pitch and cab roof height were each 1" less than the 61xx dimensions.

 

I'm not convinced the respective roofs had different profiles, but maybe I haven't looked closely enough.

 

[Scorpio7uk]

On 15/05/2021 at 01:20, The Johnster said:

In chronological order of introduction:-

 

31xx, 5'8" driving wheels, no. 2 boiler

3150, ditto but with no.4 boiler

5101, Collett modernised 31xx conversion, ran into 41xx series

61xx, ditto but with higher pressure boiler (180psi to 220psi) for accelerated London area commuter work

81xx, ditto 61xx but with 5'6" driving wheels for Birmingham area commuter work (steeper gradients)

31xx, Collet 1938 design developed from 3150, with 5'3" driving wheels and no,4 boiler

 

All GWR locos are the same, except when they are different.

 

One thing that hasn't been mentioned above which I feel is important is that the 81xx and 31xx were rebuilds of the original 31xx and 3150 classes - it was intended to rebuild them all I think but the war got in the way....

 

Knowing the 81xxs were rebuilds explains the differences between them and the Collett tanks - there's quite a few!

 

The cab profile with its separate roof was kept from the original 31xx - which was quite different to Collett's modern 'wrap around' cab/roof.

 

The vertical depth of the 'stick out' portion of the bunker was also much shallower on the 81xx than the 5101/61xx (I think the drawing in Russells book shows this wrongly but it is quite clear on the photograph).

 

The portion of the motion plate above the footplate (immediately in front of the tanks) was also carried over from the original 31xx and is quite different to the 'modern' style.

 

The curve 'drop' portion of the footplate starts closer to the front of the cylinders than on the 5101/61xx so the cover for the pony spring on the footplate is a different shape as it is further forward on the 'curve'.

 

There's also variation on the boiler fittings as most of these were carried over from the 31xx - tall safety valves and cast iron chimneys were carried as an example.

 

I think that's about it - I'm not at home at the moment, so I can't check.

 

It won't surprise you to learn that I have looked into making one of these from one of our own 61xx kits in 7mm which is why the differences are floating around in my head ready to spill onto the page!

 

Thanks

Jeff Ennis

Scorpio Models

 

 

 

[Scorpio7uk]

There seems to be variation in bunker depth, this:- https://www.geograph.org.uk/photo/4977976 shows the shallow depth I mentioned above, but this:- https://www.warwickshirerailways.com/gwr/gwrls235.htm  shows the deeper bunker normally used on the 61xx.

 

Jeff

[The Johnster]

Information useful.  It does look as if Collett thought there was more in the large prairies than he was getting at first, and that this was the rationale behind the rebuilding or new constructions that were firstly the 61xx, secondly the 81xx, and finally the 1938 31xx.  This latter had a radically different cab to the 3150s, a high domed roof affair more like that on a 56xx, 42xx, 5205, or 72xx.  The war intervened, and Hawksworth, in the aftermath and probably under pressure to quickly produce new 41xx series 5101s, apparently had no interest in improving the design any further.  Higher boiler pressure brought about it's own costs and there was arguably no need for a prairie as powerful as a Collett 31xx, a bit of a one trick pony which was red route restricted.  These war and post-war 5101s were built until 1950, many going to South Wales sheds to replace the likes of Taff As and Rhymney Ps.  The larger driving wheels gave them more 'range' on full water tanks than the default 56xx, which was appreciated on some of the longer through runs.  They could also show a clean pair of heels to the 56xx in the few places where line speeds allowed!

 

I have an interest in the 31xx as 3100 was allox Tondu for the specific purpose of hauling the daily Porthcawl-Cardiff 'Residential', for which TDU had previously been given a series of Bulldogs, not the first thing that comes to mind when you thing of Valleys sheds.  It worked turn and about with Ebbw Jc's 3104 on alternate days, allocated for it's ability to get away smartly from the main line stops and keep out of the way of the faster traffic, until a buffer stop contretemps at Porthcawl in 1958 ended the game.  Google images have a 1950 photo of it at Abergwnfi, showing that it did venture into the mountain fastnesses on occasion, so eventually I ought to have a crack at it.  It'll be a kitbash cut'n'shut layout loco, not a dead scale masterpiece, and I will be happy if it reasonably well captures the squat thuggishness of the prototype. Probably based on a Hornby 42xx body with the running plate jacked up a little and an old Airfix 61xx chassis block which will have to be butchered to provide the right ride height.  Or possibly a Bachmann 2251 chassis; the driving wheel diameter is close enough for a 4mm layout model and the axle spacing is correct TTBOMK.  Hornby cylinders and motion should complete it, in BR 1950s plain black with unicycling lion, but there's loads of other stuff to do first.

 

AFAIK it will be the only 00 gauge 1938 31xx in existence!

[Steamport Southport]

Apart from the forthcoming kits from PDK you mean.... 

 

 

New Kits in Progress:

SECR/SR/BR D1 & E1 4-4-0 (Due around August 2021).

GWR/BR 41/51/61/81xx (First test etchings have been assembled).

 

New kits Planned:

14xx and 31xx,

 

PDK 68    GWR/BR '51/61/81xx' 2-6-2 TANK

PDK 69    GWR/BR '31xx' 2-6-2 TANK

 

 

http://www.pdkmodels.co.uk/

 

Been keeping an eye on them for some time. The 56XX has just came out. if I didn't have enough of them already then I would get one.

 

 

Jason

[Miss Prism]

19 hours ago, Scorpio7uk said:

There seems to be variation in bunker depth,

 

Agreed. It seems 8100 was the odd one out, having a deeper bunker inherited from 5100 (ex-3100, ex-99), whereas the remainder of the 81xx had the shallower bunkers.

 

[JimC]

On 16/05/2021 at 18:16, Scorpio7uk said:

There seems to be variation in bunker depth, 

Yes, I had a fair bit of agonising over bunkers when I did my series of drawings. I'm not sure that there weren't three depths over all the large prairies, but I don't seem to have recorded my thinking. 

Maybe it was a last vestige of the bunker free for all earlier in the century? 

 

And later - I'm also seeing variations in the rear tank as witnessed from the rivet line. If you have Russell handy compare fig 512, 515, 518, 523 and 546. Note also that the rivet line on the photos of 8102 and 8103 is quite different from the tank profile sketched in fig 549. 

Edited May 19, 2021 by JimC

[JimC]

I've sketched out the principal variations I can see in Russell on this blog entry.

 

[Scorpio7uk]

I think you're almost there with the depths and rivet lines......

 

No 99 (the prototype), which was later 3100 / 5100 then later rebuilt as 8100 was always different as far as I can see - look at https://www.railadvent.co.uk/2019/12/gwr-tank-classes-steam-locomotives-lost-class.html  this shows the same slope as you've seen on 5100 (with a shallow bunker), when it was rebuilt as 8100 - it seems to have got a 5101/61xx style deep bunker.

 

The 3111/5111 (excluding 5100) seem to all have the shallow bunker with a straight rivet line across - and these seem to have been kept when rebuilt as the 81xx (apart from 8100).

 

The 3150 always had the deeper bunker with the sloping/straight line - and these were kept when rebuilding as the Collett 31xx as you've shown.

 

The 5101 & 61xx bunker seems to have been based on the 3150 design (but slightly different rivet line).

 

I've said shallow & deep, but as you say, I think there seems to be a couple of depths of each!

 

I think the 3150 / Collett 31xx was always slightly deeper than the 5101/61xx due to the top of the bunker of the former being slightly higher than the tank top, whereas on all the other classes, this was inline.

 

There does also seem to be slight depth variations in the shallow design - for instance between figures 546 & 547 in Russell, the depth appears to be different but counting the vertical pairs of rivets going up from the horizontal line - it would seem to be within pair 6 & 7 in both cases - maybe an optical illusion?  I'm not sure.

 

I would ignore the A13 weight diagram - I've found pictures of all the Collett 31xx apart from 3104 and they all show the pattern you've identified from photos (which also matches up with the 3150).

 

Jeff

 

[JimC]

Thanks for that. The vertical section at the back of the 3150 tank seems originally to have been associated with water pickup gear, and only given the slope at the top when the water pickup gear was removed. I've found a photo of a later 3150 that wasn't built with water pickup gear which still has the vertical section, but I haven't het found a clear photo of one between 3150 and 3165 as built.

Its interesting to look at the County Tank photos in Russell, they had at least three styles of tank!

[Miss Prism]

I don't understand how the vertical rivet line on the bunker was associated with the water pickup gear (which was located I believe between the centre and rear driving axles).

 

[JimC]

3 hours ago, Miss Prism said:

I don't understand how the vertical rivet line on the bunker was associated with the water pickup gear 

 

Photo extract of a page from Russell - think this distorted image counts as fair use - showing the frankly horrendous routing of pipework for the water collection on the 3150s. The pipes have to exit above the water level in the tanks otherwise they double as drains! So the upward extension of the back tank gets the water level up to match the side tanks. 

Looks desperate to maintain to me, not the drawing office' finest moment and although I'm not saying I could do any better it's easy to understand how in practice they found it not worth the bother and ripped it out. 

[Miss Prism]

Ah yes, thanks, I had forgotten about that, as you say an horrendous amount of ducting. I had been thinking of the Atlantic Birdcage tanks version.

 

I don't think I've got any pics of 3150-3165 as built.

Edited May 21, 2021 by Miss Prism