4mm Dave's SR Loco Workbench - Adams A12 Jubilee

[dltaylor]

One of my main areas of interest is the Southern in the West Country, and in recent years I've built quite a few SR locos in 4mm scale.
My current project is a Maunsell U-Class, based around the old DJH kit, but with the addition of the more recent chassis kit from S.E.Finecast, and a Hornby tender.
As this loco is destined to run on Beaminster Road, we needed a West Country based loco. 31610 filled the bill, it having been photographed at Exmouth Junction with a 3500gallon tender.

I'll give a quick precis of the work to date, and more detailed description from then on.

Firstly, the DJH body kit, and some pretty good castings considering its age. Lowered the boiler slightly as it was too high in relation to the footplate.



Some of the DJH etchings



The SEF Chassis kit



Putting it all together showed some of the compromises in the DJH castings; the cab floor is too high, (should match the tender) the main drop sections of the footplate should be deeper, as everything is 3 inches higher than on the N-Class, leading me to think that the same footplate castings are used in the two kits.



The solution was to saw through the drop sections of the footplate, insert a spacer and solder it all together again.









Result, a deeper drop and matching footplate levels. The difference can be seen by the gap below the cab sides, these needing to have the front section filed down to seat on the new footplate.




More to follow,
Cheers, Dave.

 

[dltaylor]

Turning to the SEF chassis, this too needed a bit of surgery to make it fit the new footplate. Again it appears to be designed to fit all variations of the mogul (U, U1, N, N1, W) but in terms of detail and fidelity its well ahead of the DJH offering
Motor chosen was a Mashima 1424 Flat Can, and HighLevel 54:1 SlimlinerPlus gearbox



Adding a set of Romford/Markits 24mm wheels leaves it looking loke this



My pickup preferences are ultra-conventional, a strip of PCB mounted on the underside of the chassis, with nickel-silver wire wipers on the backs of the wheel flanges.

 

[dltaylor]

Detailing around the front end included a new smokebox wrapper; the cast version had no riviting and was slightly flared, being wider at the front than the rear. It was however nice and round in section.
Front bufferbeam was built from the DJH etchings with a a bit more riviting added. Footsteps are pure DJH.







More soon,
Dave.

 

[dltaylor]

Turning to the cylinders, SEF supply a fold-up etch with all the holes correctly located, and cast cylinders that push on to the ends.
Crossheads and slidebars are beautifully (and solidly) cast in nickel-silver.



A trial assembly revealed a hitch, the cylnders stick out much to far, almost a scale foot outside the footplate!
As hollowing out the whitemetal was a non-starter, I filed back the etching. The left hand cylinder is about right, the right hand as supplied



Rather than a plain hole, I soldered a piece of tube in place for the piston rod to run in; the square hole above it takes the slidebar.



Putting it all together: (but nothing fixed yet)



Bye for now,
Dave.

 

[dltaylor]

When it came to testing the all the bits together, a problem appeared. Testing the crosshead in the slidebars revealed a maximum back and forth movement of 8mm. However the crankpin throw of the supplied wheels gave a movement of nearly 9.5mm; Problem! Had I got the right wheels? A check of the loco data said cylinder stroke 28 inches, scaling to 9.333mm, so yes.
So increasing the crosshead movement it had to be. I managed to lenghten the slidebar slots VERY carefully, using an old blunt junior hacksaw blade. Still not enough, so I shortened the crosshead slipper (the flat bit that actually slides in the slidebar slot). Success! slightly under 10mm ov movement.

Slidebars were soldered to the cylinder assemblies with their fore-aft position quite critical. Indeed it took three or four goes to get it right. Anyway its all there now and the photos SHOULD show the mods, if you can see them!





Cheers, Dave.

 

[dltaylor]

Following the crossheads and slidebars, comes the motion bracket. The SEF part is a lovely brass casting, but even that needed a bit of fettling up and bending straight; and brass doesn't bend as easily as whitemetal!
In addition, the etched yokes that support the expansion link need bending to a "U" shape (appropriately) and soldering on. To mount and pivot the expension link I drilled right through the holes in the yokes and through the brass casting in order to solder a 14ba nut on the inside.

This end shows the yokes drilled through


This end shows the screw and expansion link in place.


The whole casting from the front, nuts are not yet soldered.


The slot in the frames to accomodated the bracket is a bit on the large side, but no matter. Thge bracket needs to be positioned to match the rest of the valvegear and mate with the slidebars; so I will have to build the rest before I can fix anything in place!
Dave.

 

[dltaylor]

One issue with this chassis kit is the fore & aft positioning of the cast brass motion bracket, relative to the rest of the valve gear. When I built this chassis for the W some time ago, I realised that the eccentric rod was too long, so this time, when assembling the valvegear, I started at the cylinder end and worked backwards. This gave me the correct position for the motion bracket, which did not correspond to the slot for it in the frames. I lengthened the slot and used a strip of pcb to fix the spacing. Its Araldited to the motion bracket at one end and drilled for the main chassis/cylinder/body fixing screw at the other. This ensures that the motion bracket remains in the correct position.
I HOPE the photos make this clear!
Cheers, Dave.

 

[Rob Pulham]

Welcome Dave good to see you posting on here , you have been busy

 

[Jon Gwinnett]

I started liking each individual post, but all I can say is what a superb thread. As your 7mm layout was one of my and my late Father's great inspirations, I'm really enjoying seeing you turn your hand to the smaller scale.

(My personal favourite was the tiny extension featured in an old RM. Oozed quality, careful observation and delicate touch. Just lovely )

 

[Dog Star]

Now our own Dikitriki knows all about work necessary to get some kits together... and after reading this topic I do think that maybe we are occasionally a tad tough on JLTRT.

regards, Graham

 

[dltaylor]

Its Alive, Its Alive! All valvegear is now assembled and running smoothly, just needs a bit of tidying up.
I'll get some photos up later.
Cheers, Dave.

 

[AJC]

Very impressive work that (and good to hear that it works). Are you going to leave that horrid cheesehead bolt on the motion bracket on display David? Something of a pet hate of mine I'm afraid, understandable though it can be.

Adam

 

[dltaylor]

Heres a photos showing the completed valvegear, but as reported earlier it still needs a bit of finishing off. Runs a treat though.
Had to file thetop of the expansion links down as they fouled the footplate. On the real hing the top end dissappears behind the valance, but that doesnt work with solid whitemetal.

Very impressive work that (and good to hear that it works). Are you going to leave that horrid cheesehead bolt on the motion bracket on display David? Something of a pet hate of mine I'm afraid, understandable though it can be. Adam

Thanks Adam,
Yes the bolt is staying, as its holding everything together! Its 14ba so its a lot less conspicuous on the model than in the photos. Once its all chemically blackened it will be even less visible.

Cheers,
Dave.

 

[dltaylor]

I started liking each individual post, but all I can say is what a superb thread. As your 7mm layout was one of my and my late Father's great inspirations, I'm really enjoying seeing you turn your hand to the smaller scale.

(My personal favourite was the tiny extension featured in an old RM. Oozed quality, careful observation and delicate touch. Just lovely )

Thanks very much John, I'm touched to hear that. I must add that the 7mm narrow gauge is still very much alive and kicking. Charmouth has been out again recently, and may have some more invitations in the pipeline. Bridport Town is my regular exhibition layout at the moment.
To be honest, loco building in 4mm standard gauge and 7mm narrow gauge are very similar the way I do it, using similar standards and components. Often room for bigger motors in the narrow gauge stuff though, specially a big tank loco.

All the best,
Dave.

 

[AJC]

A pity, it does spoil the model to my eye, especially since the equivalent fixing on the real thing is rather subtle. That said, I'm not sure how I'd do it - probably by blackening the linkage and taking a deep breath while soldering the thing up and snipping back afterwards. That or tapping the casting and screwing it in from behind? It's a personal hang up (and looks a lot worse in 7mm standard gauge where frankly it's inexcusable).

Having said all that, I'm currently (very, very slowly) building a Standard 4 4-6-0 out of Mainline and Comet bits and have every intention of cheating by using spares from the Hornby model for the motion and cylinders! If I'm doing that why not buy and Hornby/Bachmann one and re-wheel to EM? Well, before either were even thought of I was given all the bits inclusive of a set of Sharmans and had already re-worked the tender...

It's still an impressive bit of work though, cheesehead or not.

Adam

 

[dltaylor]

Hi Adam,
I tend to take the pragmatic route of being able to take dismantle the assembly of moving parts if neccessary, I much prefer that to slodering everything up solid. You can always fill in the slot in the screw head (as long as you can get it out again) with a bit of blu-tac and some black paint.
Cheers, Dave.

 

[AJC]

Hi Adam,
I tend to take the pragmatic route of being able to take dismantle the assembly of moving parts if neccessary, I much prefer that to slodering everything up solid. You can always fill in the slot in the screw head (as long as you can get it out again) with a bit of blu-tac and some black paint.
Cheers, Dave.

Perfectly fair enough. I accept this is my hang-up!

Adam

 

[Oliver Bulleid]

I pushed David into publishing his work so that I could fill in the prototype bits and explain why this particular prototype was chosen, the loco will be a regular performer on Beaminster Road.

31610 was an Exmouth Junction loco and regularly ran up to Yeovil, my favourite image was taken in '55 and the loco is fitted with the 3500 gallon tender though by the end of the decade it acquired the larger 4000 version.

​

31610 was to be built as a K class tank engine, but the 1927 Sevenoaks crash disaster involving a previously built example of the class meant that production was shifted to tender engine examples at the last minute.

​

​

31622 at Eastleigh courtesy of Charles Verrall​

​

Tim

 

[dltaylor]

I'm still suffering from unfortunate distractions, but modelling IS taking place! Brakegear is underway, a job I often find more fiddly than the valvegear. I'll put some photos up when theres something to show!
Cheers, Dave.

 

[Wizard of the Moor]

Dave,

I've just enjoyed reading this thread and I'll add my appreciation to that above. Lovely work!

How did you go about making the spacer for the drop sections of the footplate, as shown in the first post? I'm pretty sure that I wouldn't find a piece of scrap whitemetal just the right shape lying in my scrapbox.

Cheers,

James