4mm Brassmasters Rebuilt Royal Scot, 46109

[Dave Holt]

Even the original axle has proved too short but Ill have to live with it. With hind sight, it might have been better to swap the middle and rear axles, but it's too late now as I'm not inclined to take wheels off once fitted.
The crank pin bushes have been made up and they, together with the coupling rods have been fitted. The wheels go round, after a fashion, but some further work will be required to get smooth rotation. I think 120 degree cranks are intrinsically more difficult to set up than 90 degree. Also, there is some suggestion of a rod centre discrepancy on the front left despite the careful use of the axle setting jigs.
This loco has a different type of wheel set on the front axle - Stanier pattern bevel rim. with pin between spokes and built up balance weights, compared with the middle and rear sets, which are original plain rim with cast balance weights. Naturally, the Gibson wheels must be from different moulds, so although they are nominally the same diameter and crank throw, there might be some very slight variance between the two types.
Hopefully, the slight jerkiness can be eliminated by judicious opening of the coupling rod holes, but I don't want it too sloppy to start with.




Dave.

 

[Dave Holt]

Not much progress in the last week, partly due to going away for the weekend (Ffestiniog Railway) and partly due to ongoing problems mentioned below.
Anyway, I now have a proper crank axle, i.e. one without a continuous axle through the middle. The centre section was cut out with care using a piercing saw and the inner web faces filed flush.
Here it is, seen from the underside, with the inside connecting rod tried in place. All looking very encouraging.

I needed some encouragement as a persistent issue with getting smooth rotation with the rods on was beginning to sap my enthusiasm. A slight tweak of the centre axle thirding and judicious opening of the front crank pin holes seems to have almost got it sorted, creating the will to carry on with the next stages.
Dave.

 

[Dave Holt]

I think I'm entering a minefield! Driving wheel balance weights on Scots appears to be absolutely fraught, with lots of opportunities to get it wrong. The history of the various changes to the appearance of the balance weights is explained, in some detail, in the Wild Swan profile book but even so, it's quite difficult to get ones head round. There were changes to try to solve rough riding with the original locos and then further changes on the rebuilds to suit different coupling rod designs. The Brassmasters kit provides a selection of different balance weight shapes but doesn't quite cover those fitted to 46109 during the period modelled.
The front (Stanier pattern) axles is reasonably straight forward, being the same as a Jubilee or rebuilt Patriot. This style is not covered by the kit, so some etched weights by Comet have been used. I filed most of the up-stand of the etched rivets off as 46109 appeared to have almost flush rivetted weights.
The intermediate axle had modified original weights and my initial assumption was that opposite sides would have similar shaped weights, but no, the two sides are subtly different profiles.
These arrangements are illustrated below.
First the LH side.

and the RH side.

The rear axle is even more confusing. The LMS wheel balance drawing clearly shows a basic crescent shaped weight with single spoke gap additions, different on the two sides. However, a very good side on photo of the loco clearly shows that the arrangement specified for the LH wheel is actually on the right. I can only surmise that at some stage the rear wheel set was fitted back to front. The, what I now assume to be the LH weight is included in the kit, but the RH will have to be made from a spare centre wheel weight much reduced in size.
When it's all done, no doubt someone will point out I've got it wrong.
Dave.

 

[Dave Holt]

Here is the trailing wheel-set with the rather different profile balance weights on the two sides, as mentioned previously.
LH side.

And the RH side.

The crank pin screws have been reduced to length since the photos were taken. The nuts are 16BA opened out to 14BA.
Dave.

 

[Steph Dale]

Who makes the crankpins Dave? They're rather neat.

Steph

 

[Dave Holt]

Steph,
The crank pin bushes are modified Ultrascale items. When used with their wheels, the bush inserts into a recess in the wheel boss such that its location does not depend on the 14 BA screw. For use on Gibson wheels, I solder the rear washer to the bush and file flush at the back, to make a top hat bearing. The front bushes are simply shortened to screw up against the back washer.
All 4 mm scale, of course.
Dave.

 

[Steph Dale]

Dave,
Aah yes, that makes sense - is there any reason you've used the Ultrascale ones rather than those produced by Gibson?
Steph

 

[Dave Holt]

Yes, Steph.
Many years ago, I was advised by a superb modeller (the late John Hayes) that the Ultrascale bushes were a better fit on the 14 BA screws that I use, than Gibson bushes and found it to be so. Ultrascale have the additional benefit of supplying the screwed recessed type which I use extensively, not only for front wheels behind valve gear but also as a flanged mounting for return cranks, speedometer cranks, etc.
Dave.

 

[Dave Holt]

Help and advice needed.
The Wild Swan profile book includes the Pipe & Rod drawing for the rebuilt locos having the original style ash pan. That drawing carries a note that separate drawing shows modifications required for locos fitted with hopper ash pans. As a minimum, I can see that the large diameter exhaust steam pipe to the injector must have been re-routed to avoid being under the ash pan hopper doors.
Does anyone have any information about these mods or access to the drawing?
Dave.

 

[Steph Dale]

Dave,

That, too, makes perfect sense, although it's not something I've noticed. I've just ordered a couple of packs of new Gibson ones this evening to replenish stocks so I'll have a look when they arrive and see what I find.

Many thanks,

Steph

 

[Dave Holt]

I think I may have solved my pipe routing problem.
My concern was that the original routing of the exhaust steam supply pipe would interfere with the hopper ash pan doors. However, I've looked at the Pipe & Rod drawings for the Caprotti fitted Black 5's, which also had hopper ash pans, and have established that where the pipe runs alongside the hopper, it is 1'-11/2" from the loco centre line - exactly the same as the standard Scot pipe. So, the normal pipe would presumably be still OK with the hopper ash pan.
Looking from the side, the pipe bobs up and down like a big dipper to clear the sloping bottom of the ash pan. By chance, this results in the lowest point coinciding with the position of the hopper operating shaft and bracket, so it looks like the exhaust steam pipe would pass under the operating linkage bracket.
It might not be right, but it would appear that the standard pipe run would still suit a hopper fitted loco. In the absence of better information, I think I'll settle for that.
Dave.

 

[Dave Holt]

Slow but steady progress since the previous entry.
The brake gear has been made up and a start made on he exhaust steam injector assembly. Although this latter is rightly considered to be cosmetic detail, and might be expected to be added later in the build, because the exhaust steam delivery pipe is a chunky, immovable lump that will affect pick-up location and routing, it seems sensible to fit it at this stage. The injector is fixed to the rear of the chassis but the pipe will be removable.
The photos show the chassis with the brakes fitted (these are also removable), the injector and its mounting brackets fixed and the start of the exhaust steam pipe (front section, oil separator and front mounting bracket) resting in the foreground.





A start has been made on the hopper ash pan door operating mechanism as. The exhaust steam pipe has to wiggle its way under the mechanism and over the nearby brake stretcher as it makes its way rearwards.
Dave.

 

[Dave Holt]

The pipe has been extended rearwards, complete with wiggles and mounting brackets.

One last piece to do to join it to the injector.
Dave.

 

[Dave Holt]

The pipe is now complete, with the final section added this morning. Although located in the end of the cast tail of the injector, it is not fixed there and is held in position by two mounting brackets. The final detail was the addition of the drain valve at the lowest point (or highest, when viewed from underneath!).










There's a further section of this pipe at the front end, where it connects to the inside cylinder block. As this part passes through a hole in the inside motion plate, it can't be fitted till after the motion plate is fixed - and that can't be done till after the footplate and outside motion bracket are made.
Dave.

 

[Dave Holt]

Some of the pipes and hoses around the back end of the loco have started to appear. A couple more - vacuum brake and steam brake to tender, still to do.








Dave.

 

[Dave Holt]

The remaining rear end pipes and hoses have now been made and fitted. Just the ash pan damper door levers to fit to complete the back end of the chassis.
After battling the vacuum pipe into place and fixing, I realised that I'd forgotten to add the triangular flanges where the pipe joins the connection from the driver's brake valve and where the drain valve is located. Since the photos were taken, I've added a representation of the outermost (and most visible) flange by opening the centre hole into a slot, to pass over the pipe run. It will have to do.






Dave.

 

[Dave Holt]

The basic cylinder structure and slide bars have been made up and temporarily fitted to the re-assembled chassis. Getting the cylinder frame to fit to the chassis has been a bit of a struggle. With the cylinder unit folded and soldered up, it definitely didn't want to fit into the slots in the frames, the spacing being quite a bit out. Some fairly serious hacking at the inner edges of the slots and a bit of distortion of the cylinder cross members has resulted in an acceptable fit.
A cross head has been inserted into the LH slide bars for the purposes of the photo. At this stage, the slide bars are loose in the cylinder frame but are now captive.

Dave.

 

[Dave Holt]

A start has been made on the footplate unit.It's necessary to have the basic unit made up in order to form the outside valvegear bracket folded to the correct width - it has to just fit inside the footplate valance.
The photos show the chassis fitted to the chassis. The kit is a bit lacking in regard to fixing the two together, with no mention or obvious provision for a rear end fixing. I've modified the parts to use two 14 BA screws at each end. I had to re-position the RH rear screw as I found I couldn't hold the screw and guide it into its hole due to the exhaust injector pipework. These kind of issues arise when you add more detail than the kit designer envisaged, I suppose.






Some time ago, I tried to get a friends Scot running and found the clearance inside the splashers too tight to allow reliable running. To try to avoid this problem on my loco, I had the wheel rims machined to scale width (scale 5.5 inches) and the front and rear wheel sets do have adequate clearance. I'm shortly going to have to decide whether to try and move the centre splashers outwards slightly to allow for some side play in that axle.
Next, though, is the rear end footplate overlay, under the cab.
Dave.

 

[Mike Garwood]

Starting to look like a Scot now Dave. Lovely work. I don't envy you sorting the middle driver splasher spacing out. The way you've described the problems it's like it's never been built in P4 before or these problems would have been designed out. Having to thin the wheels to scale is something most kitchen top modellers would not be able to do. Good on you for getting to grips with the problems.

Mike

 

[Dave Holt]

Mike,
There certainly have been some P4 examples built previously. In fact, there was a write-up in MRJ by Alan Sibley in which he did move the splashers out, if I remember correctly. The clearance needed inside the splashers depends not only on the width over the wheels (the chassis I struggled with had Ultrascale, which are a bit wide) but also on the minimum radius curve to be negotiated and axle side-play allowed. There's been some discussion about this latter on the Scalefour web site, in relation to frame spacing.
Before hacking the model, I will try it through the cross-overs on Delph and test for shorting on the middle axle.
Dave.