Nick Dunhill's Workbench - GNR Stirling Single

[nickd]

New project week, and this time it's a GNR Stirling single.  I have commissioned some etchings to save time/money on the cutting out, and have made a start on the tender chassis.  All well so far.......

 

 

 

 

It'll make the above.

[Pebbles]

This is interesting as Malcolm Stefox did a kit for this model towards the end of the 1980s. I believe it was reviewed in a "Great Northern News" of the time.

Edited September 29, 2023 by Pebbles
missing script

[Coal Tank]

Hi Nick,will these etches be available

John 

[nickd]

Hi John.

I hadn't really thought about that, the etches were only done to save me lots of cutting out and therefore save my customer loads of money.  They're not really designed to be a kit, there's no tabs or slots etc, but if anyone wants a set I can't see that being a problem.  Let me build it first so we can see if the etches require any revisions.

 

Nick

[chris p bacon]

 I note it's 0.45mm brass, Is this 4mm or 7mm ?

[nickd]

Hi Chris, I only build in 7 mm.  Nick

[chris p bacon]

2 hours ago, nickd said:

Hi Chris, I only build in 7 mm.  Nick

Thanks Nick, I've only done one set of etches in 7mm and opted for .55 Nickel Silver, it worked well.

[nickd]

Hi Chris, I always seem to default to 0.45 mm (18thou?) as it is thick enough for most parts of 7 mm models.  I always cut things that require lots of shaping from 0.3 mm NS though as they are much easier to form accurately.  Perhaps my rolling bars are too feeble!

[nickd]

It's sometimes easy to look upon a tender as being an afterthought, and I seem to have only built one other loco with a tender recently.  I think I fell down that rabbit hole.  The tender is going to take a bit more time than I would have liked, but at least the etches are very good for this build, no mistakes so far except for ones of my own making.  This brings me on to the castings for this project, most of which have been produced by Mike Hopkins at Scale-Factor and look very good.

 

 

I noticed that the real tenders have an inner chassis rail running from end to end just behind the wheels, with the well of the water tank sitting just inside.  Adrian Rowland at Northstar design, who produced the CAD for the etches, extended the inner chassis etch down a little to incorporate the sides of the water tank that are visible through the lightening holes in the tender chassis frames.  I thought building a little extra detail between the frames, such as the water tank, would be a good way of disguising the 'O gauge' tender inner chassis and showcasing Mike's castings at the same time.

 

First Mike pointed out that the drag beam I had made was wrong, and should be much shorter with a wooden plank between two plates.  I built this, using a plastikard beam (at the request of the painter,) and shortened the inner chassis to suit.  I also made a more detailled drag box using a left over 3D printed tender spring from a previous job that just happened to fit.

 

 

I closed the water tank and made the vacuum reservoir/tank that is attached to the bottom of the water tank well.  There were no etchings for the brake hangers, but there are parts for the pull rods.  I made the hangers and got Mick Davies to print brake blocks.

 

 

I'll complete the chassis and tender underframe when Mike's castings arrive. 

 

I moved on to build the tender body and the tender front.

 

 

Not all of the tenders have the tool cabinet on the tender front so there are no etches for it.  It is, however, quite an easy thing to scratchbuild.  The flares are always quite tricky to form.  There were thin, half etched, strips for the flares provided in the panel of etches.  They were curved by laying them on a strip of old conveyor belting, placing a rod of the appropriate diameter on top and jumping on it.  Attaching them to the tender in the correct orientation and height is tricky.  I made a little jig so I could position the strips accurately on the tender sides.  The last job was to make a tender top.  I didn't bother making the coal space the correct shape, as the brief is to fill the tender with coal.

 

 

 

More next week when the castings arrive from Mike.  I seem to have Paul O'Grady and Lucy Mangan watching my every move.

[Camperdown]

Nice to know the spring for the loco-tender drawgear is there, even if it can never be seen trackside.  But are you sure it's the right way round?  I would expect it to be the other way, although I expect you have an official drawing to back you up.

[nickd]

Well spotted.  You are right!

Edited October 6, 2023 by nickd

[Camperdown]

41 minutes ago, nickd said:

Well spotted.  You are right!

Makes much more sense.

[nickd]

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.  

 

 

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.

 

 

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.

 

 

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.

 

 

 

 

[30368]

15 hours ago, nickd said:

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.

Truly lovely work at the highest level.

 

Good to see that you (may) read a jolly good newspaper!

 

Kind regards,

 

30368

[roythebus1]

Having just read the article further up the page about the Triang L1, mention is made of the "boxing in" underneath the boiler to hide the X04 motor. I see the prototype of the Stirling Single has the boiler boxed in behind the driving wheel. Is this to cover the X04 motor in the cab? :)

[nickd]

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....

 

[roythebus1]

Nice to see proper loco building is still alive and well in these days of "everything out of the box" locos.

[nickd]

thanks.  I do my best....

[nickd]

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.

[nickd]

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

 

[bluestag]

Heavens!   Nice work!   " 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!)"    Barry Luck described the same concept in MRJ 20 many moons ago.   I still refer to it when my ambition for a LNWR Problem Class single comes along.   Now, that one has a few rivets on it....

 

The Problem Class is a smaller loco, and I need to find room for a speaker, as my locos are digital with sound.   About the only place for one is the firebox.   My practice is to solder a shelf of tinplate in the firebox and use the magnetism of the speaker to stick it to the shelf.   A bit of insulating tape is required in my set up to protect the decoder from a short.

The compensation beams look good.    The driver will only move up and down a little, but the rear carrying wheel will move in relation to the body quite a bit.   At least that is how I see it theoretically.   I have been running slightly undersized carrying wheels of late to prevent a touch to the footplate.    I'd suggest you test it on some less than stellar track while proving against shorts.   Possibly arrange some deliberate humps in the track; solder a bit of brass to the top of a rail.    Or both rails.

Edited November 5, 2023 by bluestag

[nickd]

Oh, I overlooked that.  Although I did build a couple of GWR Queen class locos a while ago using this principle and they seemed to work OK.  I'll test it out.

 

Although as a loco builder, perhaps it isn't my problem if my customer has less than stellar track?

[bluestag]

9 hours ago, nickd said:

Oh, I overlooked that.  Although I did build a couple of GWR Queen class locos a while ago using this principle and they seemed to work OK.  I'll test it out.

 

Although as a loco builder, perhaps it isn't my problem if my customer has less than stellar track?

No, you have to build the bally thing to run, or it is a shelf model.   I build my own locos, and have to make them run on my layout.    They have no purpose for me if they do not run.   As it happens, you COULD swap the rear wheel for a slightly smaller wheel, without needing to do much more than shim the interface between the bearings and the beams.    That would not be any trouble.   If you do have a touch and a short, you can resolve it in minutes.

[bluestag]

Oh, I see now.    Those are screws standing the beams from the bearings.    Very good, too.   You can get the ride height dialed in exactly.    I like that.    If you do end up with a smaller wheel, you can make it up with the screws.   V nice.

[nickd]

I had a little detour last week finishing this Broad Gauge loco.

 

 

This week I'm back on the Stirling Single, and will be now until it's completed.  

 

I began by fitting up a Slater's SG29 motor, and testing the chassis under it's own power.  Happily it went round a 6' radius curve with a little to spare.  With the motor in place it seemed like a good time to install the eccentrics for the valve gear.

 

 

There's just enough room to squeeze a pair of eccentrics and a locating pin between the sides of the SG29 gearbox and the horn blocks.  I had some steel eccentrics machined a year or two ago and cleaned 4 of them up.  Soldering them directly to the axle, obviously, wasn't an option.  I opened up the axle holes in the eccentrics and soldered them onto a short length of brass tube with the same ID as a Slater's axle.  I drilled a 0.6 mm hole through the brass tube, up against the outer eccentric, to accept a 0.6 mm driving pin.  The assemblies were held in the correct position and the axle drilled, through the holes in the brass tube, to also accept the driving pin.

 

The Stephenson Link motion was assembled from Laurie Griffin castings, and will be fitted up once some cast valve rod supports arrive.

 

 

The next job was the brake gear.  I had already made lots of the components, but could not assemble them until I had made the footplate, but specifically the cab steps.  I had already made the footplate, see above.

 

It appears that the Stirling Single brake shaft trunnions are part of the cab step backing plate.  Who'd have thought!  I made the cab steps and then an inner assembly, attached to the chassis, to support the brake parts.  This is how it is arranged

 

 

 

 

More brakes and a footplate to come soon.