4mm Brassmasters Rebuilt Royal Scot, 46109

[Dave Holt]

Other than some fettling and cleaning up, the bogie is now finished and trial fitted.
Bogie ready to fit:




And fitted to the chassis. Boy, are those rear wheels close to the brake hangers. I can see some judicious paring away of the front edge of the hangers taking place.


Dave.

 

[Dave Holt]

Work has progressed on the cylinders. Except for the drain cocks - the castings in the kit are disappointing and nowhere near as good as those in the Black 5 kit, so will have to be replaced - the cylinders are now complete and the piston rods have been added to the cross-heads. A bit more work is required to get a completely smooth action, but this is probably best left till the slide bars are attached to the motion bracket.
An awful lot of work was required before the wrappers could be fitted as the bottom of the laminated slide bars, inside the cylinders, protruded by quite an amount below the bottom of the cylinder formers.
Beginning to look the part, I think.




And with the footplate loosely fitted.






Valve gear support frame next.
Dave.

 

[Dave Holt]

A start has been made on the outside valve gear. I need to make up the expansion levers to determine the correct position for the inner supports which I earlier removed from the valve gear support frame. Experience with another of these models showed that the inner frame members, as etched, are too far inboard and clashed with the front boss of the coupling rods near TDC. On the real locos, these inner frames should be roughly above the connecting rod centre lines. Before re-fixing, I want to make sure the expansion levers will fit in the resulting gap between inner and outers of the frame.

So, the radius rods have to be made before the expansion levers as they become trapped within the curved guides. Hence starting the valve gear.
Progress so far:

Assembly of the LH radius rod was more difficult than it might have been when the short outer lamination (between the die block pin and the reversing slot) pinged off somewhere, never to be seen again, requiring a scratch replacement made from some spare bit of the same etch sheet.
I've modified the valve rod cross-heads by removing the cast rods and replacing with 0.6 mm N/S wire - straighter, smoother and a more scale diameter.

Dave.

 

[Dave Holt]

Not too much modelling right now, mainly due to domestic Christmas preparation duties, but a little progress has been achieved.
The detached inner valve gear support members have been fixed in their new positions, much closer to the outer ones. The openings in the front of the support frame have had to be widened outwards to allow the front of the radius rods to align with the top of the combination levers and a temporary trial fit of the LH parts made, as shown.

Better check the RH side before going any further.
Merry Christmas and Happy New Year to all. Let's hope 2021 is a much more normal year.
Dave.

 

[john lewsey]

Great modelling

 

[Dave Holt]

Thanks, John.
Dave.

 

[Dave Holt]

Hope everybody had as good a Christmas as possible under current restrictions. I certainly did.
Today has been very much a case of a step forward, a step back and another step forward again, so a bit of progress overall.
The mountings for the reverser shaft have been fitted to the valve gear support frame and then used to locate the inner portion of the shaft, which is fixed to the main frames and has the bottom section of the inside gear reversing lever and the central spring balance arrangement mounted to it, although the latter is not yet represented.
The chassis had to be stripped to its bare structure for this work to take place. I always hate taking it all apart as it seems so negative. Anyway, onward.
View, from underneath, of the valve gear frame fitted to the chassis. Originally, the inner frames were designed to be folded down from the inner edges of the frame, so the amount they have been moved inboard can be seen. The inside eccentric rod and drop link/anchor link have been wired up out of the way to avoid possible damage during handling.


The lower section of the inside gear reversing arm can just be glimpsed through the cut out in the main frame.


A general view from above.

Dave.

 

[adrian]

Thanks for posting - the detailing on this is superb. I still have to keep reminding myself of the scale.

 

[Dave Holt]

Happy New Year to all.
The front portion of the outside valve gear is now complete and fitted to the cylinders and support frame. The two latter have been joined into a single removable unit.

And, just to prove I have done both sides:

Dave.

 

[LarryG]

Scot looking good and I can't wait to see it taking a left turn at Delph Junction ha ha.

Happy New Year Dave.
Larry

 

[Dave Holt]

Thanks, Larry.

Houston, we have a problem! Well, several problems, actually.
As shown in the photo, now everything is in place, there is interference between the combination lever and the rear cylinder relief valve, preventing the wheels turning to front dead centre. Obviously, something is wrong.

As it turns out, several things are wrong, with the cumulative effect just mentioned.
First thing to note is the front boss of the radius rod is about in the centre of the valve spindle guide even though the radius rod is set well back from its central position, which suggests something amiss. My first suspicion was that the valve guide casting is too long but, no, it's about the right length. Then I checked the radius rod length - 24 mm - again, correct. However, the radius rod pivot point is about 1 mm nearer the cylinders than it should be at approximately 23 mm. to the centre of the valve spindle guide. This all results in the combination lever being 1 mm to far forward.
This error is then exacerbated by the union link being also too long - about 6 mm centre instead of the scale 5.25 mm.
Finally, the cylinder relief valve casting is also too long - about 4 mm from the rear face of the cylinder against a scale length of 3.26 mm.
All these errors add up to cause the problem.
Fortunately, some spare union links from my recent Black 5 loco are exactly the correct length so replacements can be fitted at the cost of having to remove the existing items without doing any collateral damage. The relief valves can be removed and shortened, again at the risk of some other parts becoming un-soldered and moving.
Hopefully, those mods will solve the problem, because altering the valve gear support frame doesn't appear practical.
Oh hum.
Dave.

 

[David Boorman]

Dave, you can't imagine how welcome your observations are! I thought it was all my fault when I was building the Scot chassis. I have 2 unbuilt Scot kits buried at the bottom of my 'cupboard' - maybe I should think about fetching them out - or maybe I shouldn't!
I also have two Princess kits at the bottom of my 'cupboard'. Is a Princess on your radar for building, if it is, I'll just have to wait until you have undertaken another magnum opus!

 

[Dave Holt]

Hi David.
I think it might have been your re-built Scot chassis that David C asked me to get running? It was beautifully built and the main issues were a clash between the coupling rods and and the valve gear support frame and lack of clearance between the wheel rims and the splashers. I partially solved these by lots of filing and replacing the Ultrascale drivers with the slightly narrower Gibson version. I used that experience to avoid the same problems on my chassis with complete success. However, I didn't appreciate the combination lever/relief valve problem, so perhaps you'd already addressed that or perhaps the relief valves weren't fitted?
Sorry to disappoint, but unrebuilt Scots and Princess Royals are not on my "to do" list.
Dave.

 

[LarryG]

That motion problem really is a bummer when you have persevered so far.

I remember you once telling me that if you had adopted OO gauge your layout would have been completed ages ago. But I cannot imagine you settling for OO. Even I won't any longer although it took a while to get free of it. O gauge is worth considering as we get on in years, and if tolerances are found to be a wee bit tight, brute force & cognitive dissonance usually sorts things....

 

[David Boorman]

That motion problem really is a bummer when you have persevered so far.

I remember you once telling me that if you had adopted OO gauge your layout would have been completed ages ago. But I cannot imagine you settling for OO. Even I won't any longer although it took a while to get free of it. O gauge is worth considering as we get on in years, and if tolerances are found to be a wee bit tight, brute force & cognitive dissonance usually sorts things....

Larry,
"brute force and cognitive dissonance" are two concepts that are difficult to imagine when put together. I don't recall my psychology teachers making any reference to brute force in the same sentence , or paragraph , or chapter. BUT, I'm delighted that you have introduced me to the concept and henceforth I will threaten any naughty kit with a dose of BFCD!

 

[David Boorman]

Hi David.
I think it might have been your re-built Scot chassis that David C asked me to get running? It was beautifully built and the main issues were a clash between the coupling rods and and the valve gear support frame and lack of clearance between the wheel rims and the splashers. I partially solved these by lots of filing and replacing the Ultrascale drivers with the slightly narrower Gibson version. I used that experience to avoid the same problems on my chassis with complete success. However, I didn't appreciate the combination lever/relief valve problem, so perhaps you'd already addressed that or perhaps the relief valves weren't fitted?
Sorry to disappoint, but unrebuilt Scots and Princess Royals are not on my "to do" list.
Dave.

Yes, I suspected it was my build for DC that you had referred to earlier in your thread! When I built that I hadn't discovered that , despite the name, Ultrascale wheels were oversize in terms of 'width' - silly me - just shows that marketing is more important than fact! I also hadn't realised that there were dimensional errors in the rebuilt scot kit - again silly me!

 

[Dave Holt]

I'm now back to somewhere near to state before I noticed the problems. Thankfully, the parts that had to come off did not put up too much resistance and no collateral damage was inflicted - precision, laser guided removal techniques were applied.
Here are the old, over length union links, somewhat wrecked in getting them off, the over length relief valves and the replacement, ex-Black 5 union links, laminated and ready to fit. The opening of the forked jaws was adjusted to fit the combination lever and drop link during fitting.


The replacement union links after fitting. To be honest, they're a better job than the originals, as well as being the correct length.


And with the valve gear unit fitted to the frames. The wheels now freely rotate and the front dead centre position will allow the final length of the relief valves to be determined, but this won't be done till after the valve gear is fully completed with the eccentric rods and return cranks fitted. Just to be sure.

It's not visible in the photo, but the connecting rod retaining bushes have been shortened to eliminate excess end float at the big ends. The return cranks will be soldered to the outer flanges to allow the valve gear to be screwed on and off, as is my normal practice.
Dave.

 

[Dave Holt]

The remainder of the valve gear has been assembled and fitted. No clashes detected so that's a good outcome. That said, without the driving axle springs in position, the coupling rods do hit the rear cross member of the valve gear support frame near top dead centre, but since it's not required to run without springs, I can live with that.




No excuse not to sort out and refit the rear cylinder relief valves now.
Dave.

 

[Dave Holt]

Not much modelling over the weekend, but the cylinder relief valves are back on and clear the combination levers. I've also added a representation of the exhaust passage ways inboard of the front valve chests so that the vacuum relief or snifting valves can be fitted. Strangely, two rather nice N/s castings are provided in the kit but as far as I can see, no mention of fitting them appears in the instructions. Of course, there should be a third one for the inside cylinder. Luckily, I've found a suitable white metal version left over from a previous Brassmasters kit. Not too sure how to fit it as the correct location falls right on the joint between the chassis and the footplate.
Close up of the LH cylinder with white plastic card exhaust passage and cast snifting valve.


And a more general view.

Dave.

 

[Dave Holt]

Error corrected. I realised that I had fitted the outside cylinder snifting valves upside down. This has now been corrected - thank goodness I hadn't fixed them very well in the first place!
The inside valve has also now been attached, probably a fraction low as the mounting hole had to fully in the main frame.
All three valves visible in this shot.

Dave.