Corbs' Cobbling - Is it electric?

[Compound2632]

Photo of drawing below:

 

610D7B72-4A21-4787-9BDE-24388AC65D30.jpeg

 

Plus photo of corresponding dimensions/technical info:

 

DAB131C9-EABE-4F75-B5C2-DA7EAD88F917.jpeg

 

The detail is all in this book:

 

7A1A082D-54B7-4872-87A1-B158F085BE7E.jpeg

 

Which is a must have if you are, like me, a big fan of the M&GN! It does mention in the book that the locos might have been better if built with 5’6” wheels, rather than the 6’ as drawn.

 

Does look remarkably similar to your mock up, just with a parallel boiler as opposed to the tapered one fitted to the N class.

 

That is, proposed by the Derby drawing office - absolutely nothing to do with the LNER. The Derby drawing office sketched out a good many attempts at a large passenger tank engine, starting with a 4-4-4T right at the end of Johnson's period in office. A few years later, they had nearly all the elements of the "Fowler" 4P 2-6-4T - excepting superheating - but plumped for the 0-6-4T "Flatiron". This is all discussed in an article by David Hunt in Midland Record No. 9.

[Corbs]

Hey Corbs,

 

Do a rendering of the suggested Smell / Rigg type loco from a spliced together Gronk-Peak contraption instead of all these admittedly nice blue kettles. If you do. indulge me with East African Railways red like the EECo. class 90's.

 

http://www.mccrow.org.uk/EastAfrica/EastAfricanRailways/NairobiMPD.htm

 

The class 85 diesel is a contraption also.

 

You can do it !

 

Gibbo.

 

Helloooo, I had a quick go at it, a bit low res but it was the best I could find at the time!

http://www.rmweb.co.uk/community/index.php?/topic/14790-imaginary-locomotives/page-137&do=findComment&comment=3218349

[RedGemAlchemist]

Hmm. What about Boco then? Is a MetroVick Type 2 not fitting for your incarnation of Sodor?

[uax6]

Hi Corbs,

 

In backdating Daisy the DMU, try the LMS Paxman contraptions seen on this page,

 

http://www.davidheyscollection.com/page20.htm

 

Also to be found on page 9 of BR Fleet survey 9

 

It was created from motorising LMS open brake thirds, I have no idea what colour it was but its got speed whiskers! Brian Haresnape's Fleet survey books are great for all kinds of forerunner type project pictures of various main line locos, shunters and multiple units both diesel and electric.

 

 

 

It was painted in BR MU green...

 

Andy G

[Gibbo675]

It was painted in BR MU green...

 

Andy G

Hi Andy,

 

Thanks for that, a model of one of those is on the long term to do list but I've only ever found black and white photos of it.

 

Gibbo.

[uax6]

You need a couple of the Period 1 LMS all steel brake 3rds to make it, they were integral bodied vehicles, so didn't have any underfloor trussing, which made them perfect to hang the Paxmans on. I think Comet do them... 

 

Andy G

[Gibbo675]

You need a couple of the Period 1 LMS all steel brake 3rds to make it, they were integral bodied vehicles, so didn't have any underfloor trussing, which made them perfect to hang the Paxmans on. I think Comet do them... 

 

Andy G

Thanks again,

 

I shall likely convert them from Airfix/Dapol bodies and roofs with scratch built sides, I have a diagram drawing and photos to work from so it should be reasonably accurate. I do like a good cut and shut !

 

Gibbo.

[Corbs]

Hmm. What about Boco then? Is a MetroVick Type 2 not fitting for your incarnation of Sodor?

Oh by all means! I read that BR considered doing the same with the Class 28 as with the Class 30 - replacing the unreliable power units with new engines. The Irish locos with Crossley motors received EMD 645E engines, what if the NWR had bought some Type 2s and had them re-engined too?

[RedGemAlchemist]

I would love to see your take on BoCo, probably one of my favourite characters!

 

I have been wanting to do a model of him ever since Heljan first did the 28s. I have been umm-ing & ahh-ing about it for ages but having now seen someone else do it on Twitter, It convinced me I NEED one!

 

- Alex

Agreed. Boco is awesome. I love the Class 28 (one of the few diesels I truly have affection for) and would happily have one running on KLR rails. If the Heljan ones weren't so damn expensive.

 

Oh by all means! I read that BR considered doing the same with the Class 28 as with the Class 30 - replacing the unreliable power units with new engines. The Irish locos with Crossley motors received EMD 645E engines, what if the NWR had bought some Type 2s and had them re-engined too?

Sounds like a plan. Would you be keeping his original number (D5702) or going for a new one?

Edited July 4, 2018 by RedGemAlchemist

[timbowilts]

What about trying to find a Hornby Dublo Metro-Vick Co-Bo?

 

Tim T

[Compound2632]

Courtesy of Wikipedia, I learn that the Metro-Vic Co-Bos were all transferred to the Barrow-in-Furness area towards the end of their short lives, which would seem to explain how they came to be working through onto Sodor.

[Gibbo675]

Agreed. Boco is awesome. I love the Class 28 (one of the few diesels I truly have affection for) and would happily have one running on KLR rails. If the Heljan ones weren't so damn expensive.

 

Sounds like a plan. Would you be keeping his original number (D5702) or going for a new one?

Hi There,

 

Silver fox do a resin kit but they are pretty hard to come by, there is a built up one on eBay at the moment.

 

Gibbo.

[Corbs]

I've been wondering about how to number the NWR diesel and internal combustion locos. Perhaps D prefixing type, then number within type, e.g. D201 for the first loco of type 2 in the fleet?

 

Back amongst the land of the kettles, the two donors arrived today so I set to work. The GBL loco was easy to unclip all the bits I didn't need. The Hornby Fowler is made from that lovely plastic that's so nice to work with and saws seem to go through like butter.

 

 

Boiler begone.

 

 

Now, with the N Class' running plate having been notched, we can see that the top part of the tank shouldn't rest on the running plate. A large part of the wheel ends up inside the tank and the cab is far too low.

 

 

Now with more of the inner tanks cut away to account for the taper boiler, and the frames removed from under the tank extension, the Fowler portion seems more in proportion!

The side tank extensions will be shortened back to the second boiler band to give less overhang. 

No.301 appears as a comparison for size but also to show the general tank arrangement I am going for. As with the photoshop, the bunker will be shortened and lowered. I guess that these locos will spend half their time running in reverse so perhaps more visibility will be appreciated. I'll need to make some spectacle plates as it didn't come with any.

 

Edited July 5, 2018 by Corbs

[34theletterbetweenB&D]

...Back amongst the land of the kettles, the two donors arrived today so I set to work...

 

Now with more of the inner tanks cut away to account for the taper boiler, and the frames removed from under the tank extension, the Fowler portion seems more in proportion!

The side tank extensions will be shortened back to the second boiler band to give less overhang. 

No.301 appears as a comparison for size but also to show the general tank arrangement I am going for...

 I would suggest not shortening the side tank extensions, unless the work it is intended for is very short range and/or there's a serious route restriction requiring low axle load. That's a class 4+ loco based on the boiler and engine unit, and 2,000 gallons tank capacity is appropriate

 

It certainly looks to have a bit more oomph to it than the rather weedily under-boilered looking Fowler and Stanier 2-6-2Ts!

 With even less grate area, and the Derby B design boiler I safely deduce yet inferior performance to the poor old bread vans. It will start flagging if speed has to be maintained above 30mph with a 2P load. The B boiler was designed for puff along on slow freight for a few miles  - and rest - puff along on slow freight for a few miles  - and rest - and repeat.

[Corbs]

Haha! I must have been sawing at the same time you were writing that, no matter.

 

 

The distance Norramby-Barrow is roughly 20 miles, part of my reasoning was reducing weight for increased acceleration on the commuter trains. Perhaps I should retain some water capacity in the bunker and not cut it down to a 2-6-2T but leave it as a 2-6-4T as with the Metropolitan K Class (also derived from the N)? I would probably still lower the bunker height.

[34theletterbetweenB&D]

Twenty miles is reasonable, so if that's the maximum working turn non-stop then you are good. The Metropolitan K's were indeed a real world kit bash from Woolwich mogul parts to produce a 2-6-4T. Yours is much prettier, mainly thanks to the downward quadrant feature in the side tank sheeting.

[NeilHB]

Looking good so far Corbs! 

 

I think definitely better as a 2-6-2T, but that's personal preference - at the moment it looks very rear heavy! I'd still lower the bunker height - or would it be easier to add an extra mm or two to the cab height? You mentioned the need to build a new rear spectacle plate anyway. 

 

I also then wonder if the chimney would benefit looks wise by adding an mm or two in height to that as well? 

 

Looks ideal for Norramby-Barrow services though  

Edited July 6, 2018 by NeilHB

[RedGemAlchemist]

I also then wonder if the chimney would benefit looks wise by adding an mm or two in height to that as well? 

I agree. Looking great so far, but I'd say the chimney could be a teeny bit taller.

[Compound2632]

Remember the heritage of the Derby 2-6-4T (and similar machines) - a 0-6-4T with vastly improved front end, itself derived from a 0-4-4T layout; side tanks and rear bunker being S.W. Johnson's invention for this wheel arrangement, when he was still at Stratford.

 

EDIT: I was forgetting the main difference between a 0-4-4T and a 0-6-4T or 2-6-4T - the four-coupled engine has both coupled axles ahead of the firebox (so it's the tank engine equivalent of a 0-4-2) whereas the six-coupled engine has the third coupled axle astern of the firebox (like a conventional 0-6-0). So the six-coupled equivalent of a 0-4-4T is a 0-6-2T, as is patently obvious if you compare pictures of Wilson Worsdell's Class O (LNER G5) and Class N (LNER N9).

 

So 2-6-4T or 2-6-2T - it could go either way!

Edited July 6, 2018 by Compound2632

[Gibbo675]

 I would suggest not shortening the side tank extensions, unless the work it is intended for is very short range and/or there's a serious route restriction requiring low axle load. That's a class 4+ loco based on the boiler and engine unit, and 2,000 gallons tank capacity is appropriate

 

 With even less grate area, and the Derby B design boiler I safely deduce yet inferior performance to the poor old bread vans. It will start flagging if speed has to be maintained above 30mph with a 2P load. The B boiler was designed for puff along on slow freight for a few miles  - and rest - puff along on slow freight for a few miles  - and rest - and repeat.

Hi There,

 

Don't worry abut the boilers capacity to steam !!!!

 

• The boiler could very easily have a a differing arrangement to its tube nest that allowed for a greater degree of super-heat.
• Another improvement to the boiler's capacity to steam could be that the valve gear could have been altered from short to long lap with port and head modification in conjunction with its lead/lap functions altered to allow a free exhaust at speed
• The smoke box draught arrangement may have been enhanced with altered blast cap and choke area ratios although I doubt this last modification would be as good as it could be for I note that Corbs has not opted for external steam pipes which would indeed be more complex upon an external admission engine as opposed to the internal admission of the Fowler tanks original scheme. The cylinders could have been replaced but the return crank would need to be put into the opposing quadrant.
• If increased super-heat and new cylinders are fitted then the steam circuit could also have been enlarged to reduce boundary layer friction and increased manifold effect within the steam circuit.
• The locomotive looks to have a good barrel to fire box ratio which means plenty of crown sheet area which is where most of the steam is generated within the boiler and therefore likely sufficient grate area in any case.
• Another problem that is quite obvious that would reduce the steaming rate of the boiler is that the top feed clacks are mounted on the sides of the dome which will cool the steam flow through the regulator into the steam circuit when the feed is on, these could be re-sited as top feeds on the front ring of the boiler.
• Is the locomotive fitted with an exhaust stem injector?
• Grate area is therefore not the be all and end all of seam production for if Corbs incorporates all of the modifications as listed then the boiler will run quite happily with a greater flow of top air burning off the free carbons over the brick arch rather than relying on the fixed ones upon the grate, this of course depends greatly upon the type of fuel use upon the grate.
• Should Corbs make all of the above modifications he will have to remember to run a fully atomised lubrication system with I would suggest Morris oils Plutus 1000 grade oil to avoid excessive ring and liner wear making sure that adequate drift instructions are followed by loco crews.

Best of all most of the modifications are mostly internal so you can't see them in 4mm scale which makes life easy !

 

Gibbo.

[James Harrison]

I'm liking this.  It's another of those bashes that just looks 'right'. 

[Corbs]

Thanks chaps and for the interesting discussion. I find that the more I learn about these, the happier I am with the bashes and photoshops I make, because following real life practice has a satisfaction all of its own.

 

As far as the workings of the loco go, I'm going to show my ignorance here and admit I do not know what the 'Derby B' design boiler was used on, was the one Maunsell used on the N Class a derivative of this boiler? As with this 2-6-2T and the Metropolitan K Class 2-6-4Ts, the workings are lifted directly and without modification from the N Class, so rather than seeing this as a modification of the Fowler loco, this is an SECR N Class 2-6-0 with side tanks and a bunker riveted on.

That being said, other than what I've read online I don't know much about the N Class' ability to steam other than they were perhaps criticised for being a bit under-boilered due to Maunsell's standardisation policy.

 

SECR N Class:

 

Metropolitan Railway K Class (built from N Class 'Kits'):

Edited July 7, 2018 by Corbs

[34theletterbetweenB&D]

The B type boiler was a little old MR round top from C19th. Apart from the generic Stephenson layout common to the large majority of locomotive boilers, little in common with what was used on the N which was a far more modern design. The top feed 'dome' wasn't a steam dome at all but a housing for a series of trays designed to prevent relatively cold feed water reaching the boiler shell and setting up thermal stress, something that was very much the go at the time in boiler design circles. The regulator valve was in the top of the firebox casing. It really matters little where the feedwater enters so long as there is no chance of any liquid water directly entering the regulator valve.

 

The limit on the boiler is set by the maximum steam rate that can be maintained against the replenishment water rate, which is principally determined by the heat supply, which is directly proportional to grate area all other factors being equivalent. There are a lot of such factors, but the science was pretty well understood by the 1930s and that's what it came down to. Grate area is fundamental. In boilers of equivalent design quality operated properly, bigger grate means more steam supply.

[Compound2632]

I think what was meant was that the Belpaire version of the Midland's B boiler was used on the Fowler 2-6-2Ts - the saturated version used on many Midland 2-4-0s and 0-6-0s from the post-Great War period onwards was classified G6, the 2-6-2Ts had a superheated version, G6S. The boiler on a N is much larger, but these engines have many Derby features, thanks to James Clayton.

[Northmoor]

Oh by all means! I read that BR considered doing the same with the Class 28 as with the Class 30 - replacing the unreliable power units with new engines. The Irish locos with Crossley motors received EMD 645E engines, what if the NWR had bought some Type 2s and had them re-engined too?

In my imagination of Sodor, they bought the whole fleet of surplus Class 29s straight from BR.  The Paxman engines had solved most of the issues with the NBLs, they were only scrapped as a non-standard class of just ten.  This wouldn't have been an issue on the small Sodor network.  

 

I also assumed they bought 94xx tanks (because many were withdrawn before they even reached their first boiler overhaul, or had only just had one) and only withdrew them in the mid-70s when they could buy 10-15 year old diesel shunters like the 04s, straight from BR at scrap value.

Edited July 7, 2018 by Northmoor