Brassmasters Rebuilt Royal Scot, 46109

Dave Holt
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Dave Holt » Sat Sep 19, 2020 2:05 pm

The reverser linkage and shaft for the inside valve gear has been fitted, as have the bogie mounting spacer and ash pan sides. The bogie mount has had to be altered to give clearance for the inside cross head and drop link. The ash pan sides are replacement for the kit items because 46109 had a rocking grate and hopper ash pan in the period being modelled, whereas the kit items represent the earlier type of pan.
Inside reverser arrangements:
Scot_037.JPG

Scot_038.JPG

Hopper ash pan:
Scot_039.JPG

Might be coupling rods next.
Dave.

Dave Holt
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Dave Holt » Mon Sep 21, 2020 8:30 pm

Well, it turned out not to be the coupling rods next. I decided to assemble the MJT gearbox conversion instead. The replacement sides were tried in place using the brass rod originally used to align the inside cylinder as it was the right size for the frames and the gearbox sides, prior to fitting the axle bushes. The trial fit showed that a small notch was required on the lower sloping edge of the sides in order to clear a keeper plate cross-beam with axle in its lowest position on the suspension.
Here is the new gearbox set up with the original Escap RG4 side for comparison and also end on with the gears in place.
Scot_040.JPG

Scot_041.JPG

And here with the gearbox/motor in roughly the right position in the frames. A torque reaction link will engage in the new, hollow gearbox spacer at the top, front of the box. This latter feature is a replacement as I misplaced one of the original solid pillars. I was cursing initially and then realised the benefits of a hollow replacement.
Scot_042.JPG

Perhaps it really will be the coupling rods next?
I've been taking measurements of the width over wheel bosses, cylinder centres, etc., to determine thicknesses of rod bosses and spacer washers and am happy with my scheme. Previous experience with a part built (by someone else) Scot chassis showed there could be significant clearance issues, so I had the driving wheel bosses machined to the scale standout and the axles shortened accordingly. Seems to be paying dividends.
Dave.

Dave Holt
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Dave Holt » Mon Sep 28, 2020 11:32 am

Well, I have finally got round to making up the coupling rods - and the connecting rods, too. I've also been working on the crankshaft and eccentric. The former is in final assembly stage whilst the latter is ready to fit once the crank is finished.
Here are the rods and eccentric. The eccentric is seen from the side which fits against the RH crank webb. The connecting rods are not from the Scot kit because I don't like the shape - to wide at the boss and too narrow at the small end, in my view. These are modified from some spare Black 5 etches.
Scot_043.JPG

Axle boxes and horn guides next.
Dave.

Dave Holt
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Dave Holt » Thu Oct 01, 2020 7:55 pm

Axleboxes and hornguides have been assembled, matched and suitably marked so they can be kept together when fitted to the chassis. Also, the crankshaft has been built up and the previously shown eccentric attached to the RH web.
Scot_044.JPG

The crank is not the one whose photo started this thread. Sadly, that version met its end in a futile attempt to silver solder the assembly. The replacement has been assembled using a high strength grade of Loctite for the crank pin and slow setting Araldite for the axle. All the joints are pinned after drilling through the webs into the shafts. The eccentric is also pinned to the web. The axle will not be cut between the webs till after the wheels have been pressed on and quartered (or should that be "thirded"?)
Dave.

Dave Holt
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Dave Holt » Fri Oct 02, 2020 3:36 pm

Hornguides now fixed into the frames.
Here we see the chassis set up in my Avonside Works jig, with both sets of rods in the extension pins, just for good measure.
Scot_045.JPG

Scot_046.JPG

And making extra sure using my extended axles.
Scot_047.JPG

And with the crank axle in position.
Scot_048.JPG

Just noticed I've got one on the centre axleboxes in back-to-front.
Dave.

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barrowroad
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby barrowroad » Fri Oct 02, 2020 4:42 pm

Hi Dave,

Coming on well even with the minor issue of annoying hornblock:-)

Robin

Dave Holt
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Dave Holt » Fri Oct 02, 2020 10:22 pm

Thanks, Robin.
I've now turned round the recalcitrant axlebox and re-tried the extended axle jigs and rods and all is OK, so no harm done. Phew!
Dave.

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Horsetan
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Horsetan » Sat Oct 03, 2020 12:08 pm

Dave Holt wrote:....crank is not the one whose photo started this thread. Sadly, that version met its end in a futile attempt to silver solder the assembly. The replacement has been assembled using a high strength grade of Loctite for the crank pin and slow setting Araldite for the axle. All the joints are pinned after drilling through the webs into the shafts....


Dave, is it possible to get a close-up of the pinning of the inside crank to the axle, please?
That would be an ecumenical matter.

Dave Holt
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Dave Holt » Sat Oct 03, 2020 2:31 pm

Ivan,
There's not much to see, unfortunately - as the attached (slightly out of focus) photo shows.
Scot_049.JPG

I drilled four holes, 0.6 mm diameter, in the edge of the webs, passing through the axle and crank pin. These were opened out to about 0.62 mm with a number drill, to suit the nominally 0.6 mm brass wire I used as pins. The wire had a slight flat filled along its length to allow air to escape from the blind holes. The wires were inserted with a good coating of Loctite bearing/sleeve retainer and cut and filed flush with the edge of the webs. Hence just a hint of brass colour against the steel webs, in four places.
Hope that helps.
Dave.

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Horsetan
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Horsetan » Sat Oct 03, 2020 3:23 pm

:thumb

That's sufficient for me, thanks.
That would be an ecumenical matter.

Dave Holt
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Dave Holt » Mon Oct 05, 2020 11:32 am

Front and rear driving wheel sets have been prepared and temporarily fitted into the chassis.
Some minor trimming of the crank axle balance weights and the adjacent frame spacer/keeper plate cut-outs is required to ensure nothing catches at the extremes of the axle box travel. Probably, with the loco riding on the springs, these extreme positions would never occur, but best to be safe.
Scot_050.JPG

Scot_051.JPG

Scot_052.JPG

A bit more work is required before the centre axle can be assembled. One job is to lock the crank pin screws by adding wire stapes along the slot in the head and into the wheel centre, either side.
The other issue has been caused by a problem with the modified gear box. On inserting the axle and final drive gear, the whole box was found to have a very notchy and gritty action when rotated. I've tried to eliminate this by driving the box with a drill and using very fine grinding paste on the offending gear teeth. This, together with careful use of my engineer's scraper on the teeth has made a vast improvement in running. However, the jaws of the drill chuck have damaged one end of the axle. I've dressed the blemishes out but am wondering whether to replace the axle with a new one, taken from a spare pack, although this will need shortening to suit the thinned wheel bosses. A friend machined the existing axle, but the replacement would have to be done by hand. So, a bit of a dilemma.
Dave.

Dave Holt
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Dave Holt » Mon Oct 05, 2020 2:19 pm

And then there were six.
Scot_053.JPG

Went with the original axle as the two spares I found were too short!
Dave.

Dave Holt
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Dave Holt » Tue Oct 06, 2020 9:43 pm

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.
Scot_054.JPG

Scot_055.JPG

Dave.

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Jol Wilkinson
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Jol Wilkinson » Wed Oct 07, 2020 8:10 am

Dave,

three cylinder locos had the coupling rod crankpins set at 120 degrees to equalise the push/pull from the three pistons. For model locos, 90 degrees gives the optimum transmission of forces between the crankpins, from the gear driven axle.

While too late in your build process, I suggest that a 90 degree setting should always be used for models.

Jol

davebradwell
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby davebradwell » Wed Oct 07, 2020 8:46 am

Odd wheels is a new one, Dave although I've had 2 different tyre diameters in a set - have you checked this? There's certainly something funny going on as the spokes are in a different position in the leading wheelset but this may just be a different angular position of the crankpin. As for 3 cylinder crank setting, I now opt for a whole number of spokes that will give me an angle greater than 90 but less than 120. Even 108 feels happier than 120 deg. Never had a crank, though!

DaveB

Dave Holt
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Dave Holt » Wed Oct 07, 2020 10:13 am

I take your point, Jol. My thinking was to try to even out the three sets of connecting rods and valve gear, which will create a certain amount of resistance to rotation. My earlier model of Rebuilt West Country class, Taw Valley, has 120 cranks and runs very smoothly indeed.
Dave, the odd wheels on the model is quite deliberate. It appears that wheel sets on Jubilees, Scots and Patriots were interchangeable and after rebuilding, various Scots ran with one or more sets of Stanier wheels. The spoke alignment issue is because the original wheels had the pin in line with a spoke, whereas the Stanier wheels had the pin between spokes.
Dave.

IANATEXTON
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby IANATEXTON » Wed Oct 07, 2020 4:09 pm

The joys of striving for prototype accuracy!

If there is any difference in the crankpin throw between the Stanier wheel set and the others, then when the coupling rods are horizontal the distance between the crankpins would be different from the distance between axle centres.

As the coupling rods are the same length as the distance between axle centres, any difference in crankpin throw would show up as a tightness in the rods. That might be the cause of the problem.

Ian

davebradwell
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby davebradwell » Wed Oct 07, 2020 8:12 pm

I did wonder if I was jumping into a trap with the wheels, Dave but couldn't really see any difference in the crank position. B1s could have odd sets of wheels but at least it's the same moulding, just different balance weights. I'm sure you'll sort it out but slight differences in throw are a distinct possibility - it can even happen with all wheels nominally the same and Sharmans were prone to this. Interesting idea about having a constant drag, too. There should certainly be no trouble with 120 deg cranks but I do wonder how running will be affected by wear - if a 2 cyl engine is built accurately then it continues to run smoothly even with remarkable amounts of wear. Perhaps I just worry too much!

Your Scot's already a fine thing and a classic prototype, too.

DaveB

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Horsetan
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Horsetan » Wed Oct 07, 2020 9:56 pm

Dave Holt wrote:...., the odd wheels on the model is quite deliberate. It appears that wheel sets on Jubilees, Scots and Patriots were interchangeable and after rebuilding, various Scots ran with one or more sets of Stanier wheels. The spoke alignment issue is because the original wheels had the pin in line with a spoke, whereas the Stanier wheels had the pin between spokes..


Slightly OT, but there are a few preserved engines that sit on mixed driving wheels today:

58850 (ex NLR)

4003 (GWR)

5043 (GWR)
That would be an ecumenical matter.

Dave Holt
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Dave Holt » Thu Oct 15, 2020 7:46 pm

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.
Scot_056.JPG

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
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Dave Holt » Fri Oct 16, 2020 10:19 pm

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.
Scot_057.JPG

and the RH side.
Scot_058.JPG

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.

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Horsetan
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Horsetan » Fri Oct 16, 2020 10:34 pm

Dave Holt wrote:...When it's all done, no doubt someone will point out I've got it wrong.


Image
That would be an ecumenical matter.

Dave Holt
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Dave Holt » Sat Oct 17, 2020 3:39 pm

Here is the trailing wheel-set with the rather different profile balance weights on the two sides, as mentioned previously.
LH side.
Scot_059.JPG

RH side.
Scot_060.JPG

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

Dave Holt
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby Dave Holt » Mon Oct 19, 2020 9:48 am

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. But how?
Does anyone have any information about these mods or access to the drawing?
Dave.

triumph3
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Re: Brassmasters Rebuilt Royal Scot, 46109

Postby triumph3 » Tue Oct 20, 2020 1:45 pm

Dave, I will check on my photos to see if all rebuilt Scots had hopper doors.

David


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