Nick Dunhill's Workbench - GNR Stirling Single

[john lewsey]

Blimey that's nice

 

[Nick Dunhill]

It was chassis week. I decided that I would make the loco suspension work with rocking beams in the 4 mm/Martin Finney way. As you can see I marked out an approximate idea on the chassis with a Sharpie. My plan was to move the pivot point of the rocking beam much closer to the driving wheel. In this way more of the mass of the loco would be transferred to the driving wheel, and the loco will hopefully pull a train (unlike the real thing!) A fellow modeller had sent me an article from a Model Engineering magazine explaining how a 7'' gauge SS had been made to perform better by mucking about with the axle loadings. I don't have that much adjustment, but moving the pivot point of the rocking beam is in effect the same thing.



I then thought it would be a better idea to let the thought develope while I made a front bogie.

Adrian Rowland, who did the artwork for my etchings, didn't really know where I would put the frame stays for the loco chassis and front bogie. In truth neither did I! He thought that an etched strip that was the width of the stays would be a good aid. He was right, and the strip had half etched lines allowing me to snap lengths off as required. These could then be modified as needed.



The front bogie stays were placed as in the GA of the real thing, and the unit has some simple compensation.



The wiggly splashers were fitted to the bogie built from the thinner pair of splasher tops.



In this way there is less of the splashers to clatter into the cylinders, slidebars and chassis. It is all a bit tight though.





I moved back to the chassis and cut out the axle area for hornguides. I cut out stays for the rear of the chassis to represent the drag box, and stays at the front to represent the valve chest rear. All the stays in the chassis are 1 mm narrower than those in the bogie. This allows the rear of the bogie to move from side to side by +/- 0.5 mm. The front section of the chassis (from the rear of the valve chest forward) is tapered by 1 mm on each side, and a long stay was shaped to locate everything. This stay will have the bogie pivot in it. In this way the front of the bogie will move +/- 1.0 mm from side to side. You'll have to wait until next week to find if it is enough to go round a 6' rad curve.

Here's some pics of what I did.









I spent today fabricating the bottom of the firebox and ashpan, all from scratch. The stay that is in front of the firebox can't be included as it comes into conflict with the gearbox. Therefore the ashpan becomes the stay. I hope to get a rolling chassis tomorrow....

 

[OzzyO]

Hello Nick,

A nice looking build so far, I seem to remember that someone did a single and added the bars at the rear like you have and compensation bars at the front. Running from a pivot point on the bogie to a pivot just in front of the driven axle running up to the top of the axle box. So the driven axle got as much force on it as possible. When I get chance I'll do you a rough drawing.

ATB

OzzyO.

 

[Yorkshire Dave]

For the fear of being banished, ostracized and exiled from this forum while the purists raise their hands in horror this loco would have been a good candidate for a tender drive .

Two outer axles driven in the tender while the rest of the body could have been packed with motor and weight. This would allow the daylight to remain in the right places in the loco under the boiler and through the frames without the gearbox blocking the view. And would allow full working internal motion.

Perish the thought - we can't have any 'foreign' thinking interfering with tradition... .....Hut, Mantel, Reisepaß, Einzelfahrkarte........gehen

 

[Tim Watson]

But singles must be seen to slip!

Tim

 

[simond]

Do both, DCC, controlled magic.…. You could even engineer the loco to have near zero load on the drivers, so you could do the Casey Jones “throw ‘er in reverse” stop.

it’s all theatre anyway

 

[Nick Dunhill]

I have been working on a couple of broad gauge locos, and today the owner turned up in Sheffield to collect them. He travelled all the way from Melbourne........bearing gifts!



I put the coffee on and made some severe inroads into the Lamingtons, then got back to the Stirling Single.

I began the work this week by making a selection of loco brake hardware.



I pondered the drawing, and the parts, to decide how to attach them. The brake cross beam is between the cab steps. The cross beam bracket drops down from the chassis, and looks to be intigrated into the step backing plates. I thought it might be a better strategy to make the footplate and steps first. The etches contain basic parts to make the footplate in two halves. There is also a rather useful form jig for the footplate.



Each half of the footplate was carefully bent round bars of varying diameters to form the correct profile and then the valence was soldered to it.



These were connected together using the rear drag beam and fitted up to the chassis. Then I realised that the front of the footplate is attached to the smokebox/cylinder block. I made that too! It took a while to form the wrapper but was very satisfying to make!



A well deserved break next week in the windy North Isles, but back on with it the week after. If you would like to see a live presentation of me installing axleboxes, and wheels, into a chassis and making it run (hopefully) why not tune into the GOG Virtual Show 2023 tomorrow. See you there.

 

[Nick Dunhill]

Oh, and this is roughly how I made the smokebox thingy.

 

[Matt.S.]

Beautiful work as usual Nick, however the crucial question in the expat group remains...

Penguin or tim tam?

 

[paulc]

This week began by adding the beading that goes up the front of the tender, along the top of the flare all the way round, and down the front at the other side. Luckily the rear corners are slash cut, and not rounded, which makes the job a lot easier. The etch had some coal rails thereon that were added next. They were fixed in place using 1.4 mm rod, laid on the top of the flare, as a spacer. Half round brass was planted on the coal rail etch to match the bead round the flare.

I modified a pair of Slater's buffers to be self contained, and added bolt details. They were attached to the rear buffer beam with some guard irons cut from scrap nickel silver sheet.

A great big bag of castings and 3D prints turned up JIT. I revisited the tender chassis to finish the brake rigging and add some vac and water pipework details.

View attachment 197924

The hand brake and water valve handles were added to the tender front and the buffers on the front drag beam. Some of the lamp irons were fitted. These were the ones with lining over the cloverleaf base. The outer and upper lamp irons lie over the lining on the rear of the tender and were left off. I had a discussion with the painter first to find the best way forward to paint the rear of the tender and therefore what to make detachable to facilitate this. You can see in this picture where I have lightly scored the position of the lining and drilled holes to locate the lamp iron castings.

View attachment 197925

I fixed the tender top and division plate in place. The brief is to fill the tender with coal after paint, so I didn't bother making the coal space and then plating it over! Mick Davies 3D printed me a nice water filler to finish the tender top. He'll be making a tool box soon too!

The last job was to assemble and fit the axleboxes and springs. I had alternative brass or 3D printed parts and elected to use the cast brass springs and hangers as they were much more sturdy than the 3D printed ones. I used 3D printed axleboxes though as they needed a slight modification to the rear. It's much easier to file away resin.

View attachment 197926

Apart from the aforementioned water fillers and brake blocks all the castings came from Mike Hopkins at Scale-Factors. They are of the highest quality in brass and resin form. Mike has been developing a range of GNR parts for a while, and I lucked-out finding him at a show before I began the project. He had castings ready to go.

So here's the finished tender waiting for me to build the loco. The vacuum pipe staunchion finishes short to avoid conflict with a Kadee coupler pocket to be added post paint.

View attachment 197927

View attachment 197928

View attachment 197929

View attachment 197930

Hi Nick , i love the way you say ' and added some bolt detail ' to the self contained buffers . Did you use bits of wire in drilled holes or 3D printed heads or ????? Please explain .
I also noticed that you've let the sanding mandrel out on it's own , is this wise as mine has a habit of wandering off especially when you need it .

 

[paulc]

Beautiful work as usual Nick, however the crucial question in the expat group remains...

Penguin or tim tam?

Tim Tam , why did you bother asking .

 

[simond]

Many years ago, when about 3, my lad would go next door to watch something on Cartoon Channel, which we did not have. I went to collect him and found an entirely chocolate-covered infant. Happily next door’s sofa wasn’t so afflicted. As we walked back, I asked him what he had eaten to get in such a mess. He described a chocolate biscuit with silver paper. I said “oh it must have been a Penguin”

”don’t be silly, Daddy, it was a chocolate biscuit”

 

[Nick Dunhill]

Hi Paul.
I buy fake fastners from here:

Imitations

Imitations: hex Imitation bolt - imitation hex model screw bare brass

ghw-modellbau.de

Or you can get the old Scale Hardware range from Model Motorcars Ltd in Florida.

I just drill holes in the corners of the bufferbeams and solder them in.

Easy.

I have to say that I'm not really a fan of either Penguins or Tim Tams, but I do like Lamingtons.

 

[paulc]

Hi Paul.
I buy fake fastners from here:

Imitations

Imitations: hex Imitation bolt - imitation hex model screw bare brass

ghw-modellbau.de

Or you can get the old Scale Hardware range from Model Motorcars Ltd in Florida.

I just drill holes in the corners of the bufferbeams and solder them in.

Easy.

I have to say that I'm not really a fan of either Penguins or Tim Tams, but I do like Lamingtons.

Ahhh , that's whats on the plate Nick . I have to say that it's really an excuse for a Lamington . It should be twice as thick for a start .
Thanks for the link to 'Imitations' , i shall pass that info on to a friend over here that models scale 7 as he supplied me the last fake bolts that i needed .

 

[Chas Levin]

There was a 4mm etch kit years ago

Hello John, do you happen to remember who did the 4mm kit please?

 

[oldravendale]

Certainly Rosebud Kitmaster did a kit which, for the time wasn't at all bad. I have one with a new chassis and has been motorised, with details like wire handrails etc.

Brian

 

[michael mott]

I remember when the kit master kit came out I had to have one. I was 12 by the time I was able to buy one. It was my pride and joy at the time.

Michael

 

[john lewsey]

Hello John, do you happen to remember who did the 4mm kit please?

Hi Chas , I understand that it was by Steflox models.

 

[Chas Levin]

Hi Chas , I understand that it was by Steflox models.

Thanks John - I've never heard of them, but I'll do some research...

 

[Mick LNER]

Stelfox at a guess.