7mm Steph's Southern workbench - Another from Mr Adams

[PhilippakristianaGrimsley]

I know it would be useful for say the Drummond loco's not withstanding the steam valves being under the cylinders, as I believe they were between the cylinders, but the arrangements for the eccentrics and connecting rods would be the same, I believe Laurie Griffin now produces a full set for Drummond loco's, this I read in the O Gauge Gazette, I wonder if say a Great eastern inside motion set will suffice as that was where W. Adams was before joining the LSWR?

 

[Steph Dale]

To be honest, I'm not convinced it's right for a Southern (or ascendants) loco at all and may only be representational.

Laurie does do the Drummond set; I supplied the research, @SimonT of this parish did the 3D CAD work and @Nick Dunhill did the test build on the couple of T9s he's recently built, the build up of the first sets starts with this post: Nick Dunhill's 7mm workbench. | Page 16 | Western Thunder. It differs in more than just details from the example posted. In the same way that (for example) you wouldn't expect motion from an LMS Duchess to fit a GWR Castle, yet both have Walschaerts/Heusinger valvegear operating to similar principles.

Eccentrics and eccentric rods vary enormously between locos with inside Stevenson motion, depending upon whether the loco has straight, or rocker-shaft driven valves, whether the inside or outside rods are forward or backwards, whether the expansion link moves up or down for forwards gear, what valve type is driven by the 'gear, whether there's an axle in the way, personal preferences of the designer or workshop, left-hand vs right-hand lead, etc, etc. So, if you're going to model the inside motion it's always worth trying to find a suitable Arrangement drawing - assuming one exists. Then all you need to do is pitch off the dimensions and build it according to the drawing and it'll be something like correct.

If you want to get into the theory and practise of valvegears then the Reidinger and Lake book I referenced a post or so ago is a good starting point and I think has been recently re--issued by Camden Steam Services (it is, see here: Valves & Valve Gears for Steam Locomotives · 1940 · | Camden Miniature Steam Services). For a less detailed look that's perhaps better for us modellers I recall the HMRS did some papers that explained the differences in layout of various valvegears.

Steph

 

[PhilippakristianaGrimsley]

Thank you very much, I'll look into buying a copy, though your talk of either left/right hand lead has got me scratching my head, I thought left hand drive had left hand lead and vice versa, I can see the idea behind the left hand drive over right hand drive, the simple reasoning is that most of the signalling is to the left side of the track, the exceptions being reverse shunting signals, even signal gantries had the signals to the left or directly over the road the signal controlled, I speak from personal experience, I used to drive for EWS until medically retired.

 

[OzzyO]

Left hand lead, is that the L/H wheel has it's crank-pin set at approx. 90 Degs. in front of the R/H wheel. Nothing to do where the driver is sitting. Then you get into the inside or outside admission valve gear question.

OzzyO.

 

[PhilippakristianaGrimsley]

I have a copy of the loco drivers pocket handbook that goes into inside valve gear and tells how you can work out where things are between the frames, yes it does include looking at the outside rods, wherever the outside cranks are the big ends are 180 degrees behind, yes one side will be 90 degrees in front of the other. But what has to be taken into consideration are the eccentric sheaves that the eccentric rods rotate on, it is their angles I do not have on the tip of my tongue at the moment.

 

[Steph Dale]

...wherever the outside cranks are the big ends are 180 degrees behind...

Not always, see 'Stroudley balancing' where the inside and outside cranks are in the same position. Interestingly, not just used by the LBSCR either; some GWR locos had the same. For example, if you look at a 2251 there are two positions of balance weights on the centre drivers; some have conventional and some have Stroudley. GWR isn't my 'thing' but wonder whether some of the locos had wheelsets from withdrawn locos.

Any idea @OzzyO? You picked up on the balancing of my 2251 in my valvegear thread: Inside valvegear in 7mm. Techniques and components | Western Thunder

Steph

 

[PhilippakristianaGrimsley]

I believe my book says something about that

 

[OzzyO]

I have a copy of the loco drivers pocket handbook that goes into inside valve gear and tells how you can work out where things are between the frames, yes it does include looking at the outside rods, wherever the outside cranks are the big ends are 180 degrees behind, yes one side will be 90 degrees in front of the other. But what has to be taken into consideration are the eccentric sheaves that the eccentric rods rotate on, it is their angles I do not have on the tip of my tongue at the moment.

I was not talking about inside valve gear. I mentioned about inside or outside admission (valves) of the steam into the cylinders. If you have the book that I'm thinking of it should tell you about it, the best part to look at is the part on Ex. S.R. Merchant Navy or Battle of Britain class locos.
The angles of the eccentric sheaves are set at about (IIRC) 15 deg fore and about 15 deg aft of TDC on both sides.

Not always, see 'Stroudley balancing' where the inside and outside cranks are in the same position. Interestingly, not just used by the LBSCR either; some GWR locos had the same. For example, if you look at a 2251 there are two positions of balance weights on the centre drivers; some have conventional and some have Stroudley. GWR isn't my 'thing' but wonder whether some of the locos had wheelsets from withdrawn locos.

Any idea @OzzyO? You picked up on the balancing of my 2251 in my valvegear thread: Inside valvegear in 7mm. Techniques and components | Western Thunder

Steph

That's going back a bit Steph, the wheels may have been reused from possible the old Dean goods built around the time of Stroudley? Most C.M.Es. knew each other and would all try some new ideas from each other to see if it worked better on their railway. IIRC I have seen photos of some large driving wheels (6'6"+ maybe off an outside framed 4-4-0) in Swindon using the Stroudley balancing. So maybe it was just a thing of its time with no gain or loss, apart from all of the extra weight on the wheels? I honestly don't know.

OzzyO.

 

[PhilippakristianaGrimsley]

Thank you OzzyO, I will check my book

 

[PhilippakristianaGrimsley]

I received my latest copy of the O Gauge Gazette today, I have finally picked up my bottom jaw from seeing the class T9 model, OH MY GOD, it is the real thing in miniature, plus I saw the inside motion for the Drummond D15, talk about weird and wonderful but it faithfully reproduces the original in 7mm to the foot scale.