Imaginary Locomotives

[melmerby]

GWR got effectively that when they reboilered the two  EX-MSWJR 4-4-4 locos in 1924, http://roxeymouldings.co.uk/product/294/4l5-mswjr-4-4-4t-gwr-rebuild/

They were never very good as they had too much weight on the bogies not enough on the driving wheels..

The idea of the earlier 4-4-4T was to relieve the weight over the drivers when using a standard No.4 boiler but it was never proceeded with and a 4-4-2T with the smaller number 2 was later built

The No.4 was tried on 2230 but was not satisfactory and a No.2 was refitted (RCTS).

 

Keith

[PhilJ W]

The LNER denoted wheel arrangements using a letter.  0-6-0 locos (tank or tender) were J type, 2-6-2s were V type.  4-6-2 was A type and 2-8-2 was P type.  I don't know if they even hypothetically assigned a letter to the 4-8-2 arrangement.

The LNER used the entire alphabet for classification except for the letter 'I' because it might be confused with the number 1. The letter 'Z' was originally allocated to 'odd' wheel arrangements but in the end only covered 0-4-2 types. Classes U, V and W did not exist on the LNER at grouping but were added when such types came into use. The V class (2-6-2) included four types of locomotives but class U (Beyer-Garrett) and W (4-6-4) were one offs. The only class to have two different wheel arrangements was the 'X' class which was for single drivers which had both 4-2-2 and 2-2-4T types. At the grouping the Letters U, V and W were vacant but were eventually used.

[Satan's Goldfish]

GWR 4-6-0 'King' (Top), becomes 4-6-2 'Emperor' (middle (evolution of The Great Bear maybe?)), which becomes 2-8-2 'Crack-pot Dictator' (bottom) for those tricky South Devon banks. TGB inspired tender because I like them, smoke deflectors added because seem to suit them!

[WD0-6-0]

Which becomes 2-8-2 'Crack-pot Dictator' (bottom) for those tricky South Devon banks.

 

Strange to see a western loco with cylinders so far forward but I think they all look quite smart

Edited April 18, 2018 by WD0-6-0

[Satan's Goldfish]

Just noticed I didn't do a very good job of lining up the rods and wheels on the Crack-pot Dictator. Duly amended as it was going to bug me:

[CHAZ D]

GWR 4-6-0 'King' (Top), becomes 4-6-2 'Emperor' (middle (evolution of The Great Bear maybe?)), which becomes 2-8-2 'Crack-pot Dictator' (bottom) for those tricky South Devon banks. TGB inspired tender because I like them, smoke deflectors added because seem to suit them!

Emperor Ming would seem appropriate for a GWR Loco

[melmerby]

The bogie tender just doesn't look right to me.

 

How about outside bearings as on later SR bogie tenders, or even a stretched version of the eight wheeled GWR one?

 

Keith

[34theletterbetweenB&D]

Just noticed I didn't do a very good job of lining up the rods and wheels on the Crack-pot Dictator. Duly amended as it was going to bug me:

 Let me bug you some more. Work out where the inside cylinder's slide bars, crossheads and connecting rods are in relation the to front coupled axle.

[jcm@gwr]

 Let me bug you some more. Work out where the inside cylinder's slide bars, crossheads and connecting rods are in relation the to front coupled axle.

 

Plus, unless the front wheels have a flat top to them,

they might have a problem without any splashers!

[Satan's Goldfish]

######, I can remember thinking 'must add splashers' as well.

 

Ref inside cylinders; they're bits I can't see on the King, where are they supposed to be on that?

[34theletterbetweenB&D]

Part of the cylinders and valves are in the cuboid chest protruding forward from under the smokebox to just behind the bell on the front platform. If you imagine the full outside cylinder and valvechest overlaid in that forward position you will see the conflict between the leading coupled axle and the slide bars and rods, to make the connection to the crank axle.

[runs as required]

All 4 cyls are in line - as Stanier took off to the LMS

Could you not do a 4 cyl 2-8-2 as Gresley did his P2 but with outside Walschearts gear rockers just working the corresponding inside cyl ?

dh

[Satan's Goldfish]

Part of the cylinders and valves are in the cuboid chest protruding forward from under the smokebox to just behind the bell on the front platform. If you imagine the full outside cylinder and valvechest overlaid in that forward position you will see the conflict between the leading coupled axle and the slide bars and rods, to make the connection to the crank axle.

  

 

Noted, will see what can be done...

 

All 4 cyls are in line - as Stanier took off to the LMS

Could you not do a 4 cyl 2-8-2 as Gresley did his P2 but with outside Walschearts gear rockers just working the corresponding inside cyl ?

dh

Rods to inside pistons would still clash with the axle on the front driver. They can clear it if inclined slightly (diagrams of that are several pages back in the 'GWR Mallet' section). That may be a simpler solution the problem, but less commonality of parts.

 

 

My other mess up I've just spotted is the shadow from the cab onto the firebox; should be less shadow towards the bottom to show the box gets wider.

 

Much more work required

[melmerby]

Could you not do a 4 cyl 2-8-2 as Gresley did his P2 but with outside Walschearts gear rockers just working the corresponding inside cyl ?

dh

You mean as Stanier did on the Duchess?

The problem with 4 cylinders on the UK loading gauge is fitting everything in if they are all side by side.

On Gresley's large 3 cylinder locos there is little space to play with and fitting in a 4th cylinder and valve would be very dificult, hence the divided drive with the inside cylinders well forward.

For practical reasons 4 large cylinders means a bogie up front. If inclined any amount they would likely interfere with the smokebox & draughting

 

Keith

[Satan's Goldfish]

You mean as Stanier did on the Duchess?

The problem with 4 cylinders on the UK loading gauge is fitting everything in if they are all side by side.

On Gresley's large 3 cylinder locos there is little space to play with and fitting in a 4th cylinder and valve would be very dificult, hence the divided drive with the inside cylinders well forward.

For practical reasons 4 large cylinders means a bogie up front. If inclined any amount they would likely interfere with the smokebox & draughting

 

Keith

 

Hmmmmmm, crack-pot dictator class needs to be 4-8-2 then really. May need to shrink the drivers down a bit same as with the LNER P3 on the last page.

[The Johnster]

GWR 4 cylinder 4-6-0s copied the cylinder layout of the de Glehn compound atlantics, with the outside pair driving the middle axle, which is why they are set back a little and any outside steampipes are bent into an S shape to feed them.  The inside cylinders drive the leading axle, and are set forward to protrude between the frames in front of the smokebox.  In order for the width of these to be accommodated, the rear of the inside block just clears the front of the outside cylinders, and there is an outwards joggle in the frames at this point.  The layout was repeated on The Great Bear and Stanier's 'Princess Royal' pacifics.

 

The Gresley/Peppercorn/Thompson 3 cylinder engines also had the inside cylinder driving the leading axle, but in this case the cylinders took less room as there were only 3 of them, and no joggle in the frames was needed, a structurally better solution.

Edited April 18, 2018 by The Johnster

[melmerby]

Hmmmmmm, crack-pot dictator class needs to be 4-8-2 then really. May need to shrink the drivers down a bit same as with the LNER P3 on the last page.

You are now coming up against the limitations of the British loading gauge. (We wouldn't have had this problem if the GWR had stuck to broad gauge! )

For "super power" locomotives the Duchess is getting near the limit and IMHO is why many of these fanciful designs would be impractical to realise, if rather appealing in their nature.

 

Cheers

 

Keith

Edited April 19, 2018 by melmerby

[melmerby]

 

 

The Gresley/Peppercorn/Thompson 3 cylinder engines also had the inside cylinder driving the leading axle, but in this case the cylinders took less room as there were only 3 of them, and no joggle in the frames was needed, a structurally better solution.

It's a pity Gresley refused to acknowledge that the conjugated valve gear he used on his later creations was actually a Swindon product patented by Holcroft in 1909!

The GWR stuck with 4 cylinders but if they ever had decided to use 3 presumably that's the layout they would have used.

 

Keith

[Compound2632]

Part of the cylinders and valves are in the cuboid chest protruding forward from under the smokebox to just behind the bell on the front platform. If you imagine the full outside cylinder and valvechest overlaid in that forward position you will see the conflict between the leading coupled axle and the slide bars and rods, to make the connection to the crank axle.

 

The ends of the valve chests can be clearly seen on a front three-quarters view. Likewise on the Princess Royal and Coronation classes.

[JimC]

there is an outwards joggle in the frames at this point. 

Note that the joggle disappeared from 1926, when they were able to bend a dish into the frame to clear the bogie wheels instead. 

 

It's a pity Gresley refused to acknowledge that the conjugated valve gear he used on his later creations was actually a Swindon product patented by Holcroft in 1909!

The GWR stuck with 4 cylinders but if they ever had decided to use 3 presumably that's the layout they would have used.

 

Holcroft got a reasonable amount of credit in the early days. AIUI Gresley came up with an implementation independently but Holcroft gave him some ideas for significant improvements. I think its debatable whether Swindon would have used Holcroft's gear on a 4-6-0, it did give rise to slightly irregular valve timing, as did the scissors gear I believe, and Churchward's valve gear man Pearce put a lot of effort into very carefully shaped rockers to minimise this. The GWR wee much fussier about valve timing than some neighbouring lines.

[Satan's Goldfish]

Right, I've cheated. I used a Grange for smaller drivers on the Crack-pot Dictator and noticed it had different cylinders (I'm assuming it's a 2 Cylinder machine rather than 4?), as well as its drivers, I chopped the front pony in half and used that instead of the cylinders from the King. Also corrected the shadowing at the back of the fire box and remembered splashers this time! Tender is still TGB inspired (hence inside frames rather than outside).

[The Johnster]

i would not have thought of putting de Witte deflectors on a GW loco; surprising how good they look.  The smaller diameter smokebox and the chimney design of GW locos made such provision superfluous in practice, but the use of the double chimney on a 2 cylinder mikado may well have changed matters for all I know...

Edited April 19, 2018 by The Johnster

[melmerby]

Here is a link to the cylinder pattern for a new build P2:

 

https://www.p2steam.com/wp-content/uploads/2015/04/09131601-Cylinder-block-Lentz-Franklin-B-valves-view-2-11-9-16.jpg

 

You can see that 3 cylinders inline is just about the limit. If you want 4 there ain't much room unless you mount them far forwards as Churchward, Collett & Stanier did.

 

 

Right, I've cheated. I used a Grange for smaller drivers on the Crack-pot Dictator and noticed it had different cylinders (I'm assuming it's a 2 Cylinder machine rather than 4?),

 

A Grange is a two cylinder loco with inside Stephenson's gear and rockers to the outside valves as were (virtually) all GWR 2 outside cylinder locos except the one mentioned below.

 

Now how about rotary gear on the GWR 2 cylinder loco?

 

https://upload.wikimedia.org/wikipedia/commons/thumb/a/a6/Swindon_railway_station_geograph-2428215-by-Ben-Brooksbank.jpg/1920px-Swindon_railway_station_geograph-2428215-by-Ben-Brooksbank.jpg

 

Keith

Edited April 19, 2018 by melmerby

[tomparryharry]

I'm thinking about an up-rated 47xx. Collet cab, and oil fired.

 

Even possibly a 4-8-0. All of the lineage from the earlier 47xx. Numbered in the 4750 class.

 

Cheers,

 

Ian

[Corbs]

Not quite the same thing but a 4 cylinder 4-8-0 from a few pages ago...