Reworking a San Cheng / Tower GWR 1361 0-6-0ST

[Guest Isambarduk]

Some may have seen this topic elsewhere (I posted it on the G0G Forum where it elicited no real comment) but I thought that it might appeal to people here - if not, I'm sure you'll let me know! 

 

I have been reworking a 'Tower Brass' GWR 1361 class 0-6-0ST that I bought as a non-runner from Randolph Chang when he closed down his factory.

 

The Tower Brass model of GWR 1361 Class as received​

Actually, like so many of the models from this stable, particularly the earlier ones, the upper works are well engineered and are quite well detailed compared to the lower works, which rather let the models down, but they do all run very well. On this model, I have undertaken my usual reworkings of the motion, draw gear, vacuum and steam heat pipes and so on but the frames required quite drastic surgery to set them at more nearly the correct distance apart and to spring the driven centre axle, which was rigid in the frames. All this is a bit 'run of the mill' but I thought there might be some interested in how I made a new smokebox door.

Unfortunately, the smokebox door on the Tower Brass 1361 Class model is quite wrong but, being part of the ‘face’ of the locomotive, it really does need to be rather better so I decided to make a new one.

 

The smokebox door on the model (left) and on the prototype (right)​

I dare say that I could have found a casting, and I did make a few tentative enquiries at the G0G show at Kettering (and 'thank you' to Warren Shephard for a most helpful discussion), but I decided to make a pressing. I have done this before, but not for a door with a dished reverse curve such as this one, so it seemed like an interesting challenge. The principle is to make a punch and die with a means of restraining within it a disc of brass which is to be formed into the required shape.

 

The wooden die (left) and the restrainer (centre) assembled (right)​

I machined a hole in a piece of hardwood to form the die and I turned an aluminium ring as the restrainer, which is held to the wooden die with six roundhead screws.

 

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Punch and die lined up in the pillar drill

I turned the head of the punch from a piece of dowel and mounted it on a steel shaft. The roughly sawn out brass disc (the blank) is firmly trapped between the restrainer and the die and the punch is pressed through the restrainer to form the blank into a dished door. Properly, the punch and die should be mounted in a press but I used my larger pillar drill.

 

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The first attempt at a pressing

For my first attempt (above), I used a brass blank of 15 thou (0.38mm) thickness and it was a reasonable success, but for the coggles in two places around the edge. My second attempt with a blank of 10 thou (0.25mm) thickness was as near perfect as things get in this less-than-perfect world, so I was well pleased.

 

Machining the surrounding ring​

The second task was to make the thin surrounding ring. The challenge in many machining operations is getting a good hold of the job.  In this case, the simplest way that I knew of was to use a ‘solder chuck’: simply put, you solder the job to something that you can get a good hold of, machine the job and then unsolder it again. I soldered a ring, which I had roughly sawn out of 15 thou thick brass, to a piece of waste etch of the same thickness and screwed this to a piece of hardwood (the back of the piece that I had used earlier as the die) that I could easily hold in a four-jaw chuck. In the image (above), the inside diameter of the ring has been bored and the outside diameter is now being turned to size.

 

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The finished door

There is a sizable hole in the front of the smokebox into which the dished part of the finished door (above) nicely fits so that the ring sits down flush on the front, centred on the surrounding rivets.

 

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To complete the job, I reattached the hinges and made up a new set of dart handles. I modified the hinges slightly to look more like the prototype but, in the end, I decided against trying to move the lower hinge pin, which should be below the lower hinge, as there was really insufficient room for it in the correct place. This is one of the limitations of working with RTR models and kits, even very good ones; there are some design errors that require so much work to correct that it’s just not worth the effort, otherwise I would be better placed working from scratch.

So, to recap, here is the replacement door in comparison to the original:

 

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Original door (left) and its replacement (right)

And here is what the finished front end now looks like in comparison to how it looked before:

 

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Before (left) and after (right)

Now, you may agree with one of my friends who commented that I was nuts when I told him what I'd been up to, but it all depends what you find fun. I have enjoyed this part of the journey and I am a little closer to my final destination on this one, although there is a long way to go.

If there is interest in this kind of fun, I will be more than happy to write illustrated posts about other modifications (on this loco or on others that I have reworked, eg 8F, Black Five, Hall ...) just let me know.

David

[LaScala]

Superb David.  Always enjoy your upgrades and your engineering approach is fascinating.

[Talltim]

Very nice work, always good to see a technique in action, as it were. I wonder how they got the door shape so wrong, poor research or cost of forming the more complicated shape?

[John R Smith]

Nice job, David.

 

Many years ago, I used to come down to Cornwall to visit 1363 when she was at Bodmin General MPD with the Great Western Soc. She was (and still is, I hope) a smashing little loco.

 

I think your work on the smokebox door was well worth while.

 

John

[81A Oldoak]

Well worth the effort David.

[peter220950]

David,

 

Excellent as ever, and an inspiration to us all.

 

Only one question, and definitely not a criticism, would it have been easier, or even possible, to have turned it up on a lathe as a 'one-off'? - I'm a great fan of doing stuff for the sake of it, sometimes it's more satisfying to get a result and learning new things along the way, rather than following convention. - Just interested that's all.

 

Keep up the good work, and keep us enlightened!

 

Peter

[brianusa]

Great work and a particularly nice model. In all honesty, I wouldn't have noticed.

 

Brian.

[Guest Isambarduk]

Thank you all for your kind words ... I'll take them as a cue to carry on then!

 

"Only one question, and definitely not a criticism, would it have been easier, or even possible, to have turned it up on a lathe as a 'one-off'?"

 

Indeed it would, Peter.  That was my first thought and I have tried it before but I found it quite difficult to produce the smooth curves, so I made a pressing which I was more confident would produce the desired result. (I had thought of turning it out of plastic, which would have been easier and, after all, once it is painted, there would be no difference in appearance.)
 

"I'm a great fan of doing stuff for the sake of it, sometimes it's more satisfying to get a result and learning new things along the way, rather than following convention."

 

I understand because I suffer from this affliction as well.  It can slow you down a lot but you do learn lots along the way.  Seriously, I did it to see if I could and now I know that I can; I might never need to do it again but it was a 'journey' that I might never have taken otherwise.  I just like making things.

 

David

[Guest Isambarduk]

"I wonder how they got the door shape so wrong, poor research or cost of forming the more complicated shape?"

 

I wonder about that too, Tim.  From my experience of these models by San Cheng Crafts, I would say that it is a genuine error that crept in between design and production.  Inevitably, there are compromises in detail on commercial models that are pitched at this level in the market, particularly below the running plate, but there are relatively few 'pure errors' such as this.

 

David

[Jintyman]

Excellent piece of work, I love your website David, some wonderful pieces of engineering there, including that wonderful working inside valve gear.

 

Jinty

[Guest Isambarduk]

Thank you, David. 

 

Ah, yes, that mesmerising Walschaerts and Joy valve gear [see http://youtu.be/7TP5_pATslE and http://youtu.be/W1whemhJJD4 , respectively]. In comparison the internal Stephenson's [ http://youtu.be/ffHfy9MZrG4 ] is quite tame!  There is a bit more info about the models that they are from at: www.davidlosmith.co.uk/Valve-Gears.htm

 

David

[Guest Isambarduk]

Thank you for all the interest shown here in this project. Perhaps another bit of rather more straight forward reworking, making some balance weights, might also be of interest.

On the model as supplied, the balance weights are the correct shape but their front faces were barely flush with the rim of the wheel whereas they should stand slightly proud of the tyre.

 

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The first job was to mill away the front of the old balance weights (above) to make a good base onto which I could epoxy glue some new styrene balance weights. I have made balance weights before, both from brass and from styrene, by turning discs and then marking out to cut the inner arc, but I have never found the latter that easy.

 

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This time, I turned out two blank discs and, although I started the marking out, I decided to machine the inner arcs on each of the sectors.

 

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I machined a shallow hole in piece of softwood that was of the same diameter as the blank discs and I then screwed a little bridge across it to hold the embryo balance weight whilst I machined the inner arc.

 

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Clearly, the inner arc is of a greater diameter than the blank disc so it was necessary to offset the piece of soft wood in the chuck by the requisite amount.  I mounted the chuck on a rotary table, which I then moved to the appropriate position so that the finished balance weight was the correct width.

 

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Milling the styrene was easy and was a matter of rotating the rotary table a few times until the waste material fell away.
 
 

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The raw balance weights were over length but I used epoxy to glue them in position and then I trimmed them to length in line with a spoke.

 

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Finally, I machined some new crankpins and bushes to suit the modified rods.

David

[Guest Isambarduk]

Amongst smaller alterations and improvements to the RTR GWR 1361 class, I reworked the cylinders.  The cylinders on the model appeared rather weedy in comparison to those on the drawing and in photographs, which are rather beefy for such a small loco.
 

 
Cylinder before (left) and after reworking (right)

 

I machined a spool-like core with cylinder covers at each end, around which I was able to wrap the original cladding.  I was also able to reuse the stuffing box and the slidebars from the original arrangements.  Although I had increased the width of the frames (and swapped them left for right, but perhaps more of that later), I had to make up a thin spacer to push out the cylinders to their correct overall spacing.
 
David

[2ManySpams]

Those new cylinders are a big improvement IMO. Food for thought.

[Guest Isambarduk]

I have finished reworking this 1361 class loco now, it just needs painting and reassembling, and I shall finish the write-up when my new camera arrives so I may take some decent images to illustrate it.  My 'old faithful' Canon PowerShot A480 seems to have taken a dislike to taking close-ups with a reasonable depth of field, so it will be put on outside duties only, at which it seems quite content!   David

Edited November 6, 2016 by Isambarduk

[Guest Isambarduk]

I can now finish the write-up as my new camera arrived (the first one failed to) and I have taken some reasonable images to illustrate it.

The original motion brackets were a quite unlike the massive brackets of the prototype so I drew up a dimensioned sketch and made a trial pattern in plastic before making the two parts in brass. As may be seen in the image below, I modified the design to include an additional fixing lug at the top of the bracket.

Motion bracket: dimensioned sketch (left), original, trial pattern, replacement

The right hand motion bracket is in place (below) and, just in board of it, may be seen the bracket to support the leading brake hanger. The vacuum ejector pump, which is mounted on the motion bracket and driven from the right hand crosshead, was not in line with the piston rod as it should have been so I corrected this and added more detail.

The cylinder drain cocks that were originally fitted to the model were of a later pattern (below, left)

so I made up assemblies to represent the earlier pattern (that have been reinstated on preserved No. 1363) using some castings from Warren Shephard as a basis (right).

Cylinder drain cock assemblies

The motor and gearbox were originally rigidly attached to the frames so that, although the leading and trailing axles were sprung (with Tufnol hornblocks in guides with springs and keeper plates from above), the centre axle was fixed.

I machined up an additional pair of Tufnol hornblocks for the centre axle and arranged to spring them and to retain them with keeper plates in a similar fashion. I discarded the motor mounting plate so the motor and gearbox are now free to float with the centre axle.

I always enclose the gearboxes on my locomotives; this was important when they normally ran on a friend’s extensive garden railway but it seems to be good practice to me anyway. I covered the unguarded gears (above, left) with a simple cover plate that is screwed to two of the gearbox stretchers and sits between the cheeks (right). The upper screw also retains a bracket to hold a pin that engages on a stretcher in the frames to provide the resisting torque for the motor (ie it prevents the motor from rocking backwards and forwards within the body but it does not impeded its rise and fall with the axle).

 

More to follow.

 

David

 

[Guest Isambarduk]

I reduced the depth of the frames, as they were far too deep, and I exchanged them left for right, which allowed me to push the frames out so that they were 27.5mm overall and to fit wider stretches (frame spacers). The flanges at the top of the frames, which originally turned outwards, now turned inwards and I removed all the portions that were not required to leave lugs to hold the horn block keepers and springs; not only did this improve the appearance, it allowed the motor and gearbox to fit easily between the frames.
 

Although I needed to allow for this extra width in reattaching the cylinders, sand boxes and so on, it was not difficult and resulted in a pleasingly small gap between the back of the wheel and the frames.

Surprisingly perhaps, the GWR 1361 class has no brakes on it leading wheels so I needed only machine four plastic brake blocks and four pairs of brake hangers, and to fabricate the associated rod and plate work.
 

This assembly neatly clips over the four brackets on the frames to butt up against the remainder of the brake rods and the cross-shaft.
 

Also visible in this image are the representations that I made of the firebox washout plugs that are visible between the frames, in front of the trailing brake shoe.

With more authentic shallower frames, I was able to make up decent looking brackets for the cross-shaft and to make suitable cranks for the hand and steam brake operating gear.
 

More to follow ...

David

[Guest Isambarduk]

On the body, other than the smokebox door, I reckoned that there was relatively little work to do. There was nothing very wrong with the original cast whistles but I knew that I could easily make better looking turnings.
 

 

Whereas the covers to the steam pipes had flanges at the smokebox, there were none at the running plate so, using a coping saw, I cut out some horseshoe-shaped flanges and soldered them on.
 

 

As usual with these RTR models manufactured by San Cheng Crafts, I reworked the drawgear, vacuum and steam heat pipes/hoses. Although I have described this before (see: www.davidlosmith.co.uk/LMS_8F.htm and www.davidlosmith.co.uk/LMS_Black_Five_Jubilee.htm, for example), here is the result for this loco. To provide a good key and to help hide any chips, I have chemically blackened the drawgear prior to painting.
 

 

The representation of the reach rod and crank was a rather caricature of an affair but I improved it with a yoke at the outer end; the inner end (to the left) disappears inside the cab, so it needed no alteration.
 

 

I believe that I have now covered the most interesting bits of reworking that I undertook but I would be happy to answer any questions or to clarify any points. I will post more images when I have painted and reassembled the loco.

David

[Guest Isambarduk]

As you may see above, my final words, on 31st December, 2016, were "I will post more images when I have painted and reassembled the loco.".

I painted this loco during the summer, at the same time as I painted my Hudswell Clarke 0-6-0DM and my Victory class with a Lambton cab (I'm still working on the more demanding lining on the tanks and bunker on this one) and here it is.

 

David

[Brinkly]

Lovely work David, it is nice to see 'proper' modelling and improvements on such a lovely prototype. Your work has realy lifted the model.

Kind regards,

Nick.

 

Edit-typo

Edited August 30, 2018 by Brinkly