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Building a Bulleid - 'Down Under' - Part 2

Update and photos by Roger Lainson, May 2021.

Progress is being made – the cylinders, smokebox, boiler and brakes are all finished, and the casing nearly so.

Cylinders and Smokebox

                                
The outside cylinders were also machined from solid flow-cast iron like the inside cylinder.  The valves are ringless – I spent some time practicing the use of inside and outside laps on a dummy cylinder/valve – and I think they will be ok.  When finally connected up, the loco ran on compressed air with no trouble.  A bit stiff at first, but as one of our club members remarked, there's no point in building a worn-out loco !  It has eased up with a little running on air now and then.  I like the 3-cylinder papapa-papapa rhythm!

The smokebox is fairly similar to the prototype, except made of brass.  The top (with the chimney silver soldered into it) is completely removable to help with connecting up steam pipes and superheater.  The bottom plate, with 5-hole blastpipe, bolts to the top of the inside cylinder.  The cowl took a bit of bashing to get right, and is copper (but will be painted of course).


Boiler

The boiler is a bit different to the one drawn by Keith Wilson.  Firstly, everyone I consulted advised me to forget the combustion chamber – unnecessary and very hard to repair if a leak develops, they said.  So I duly forgot it.

Secondly, the barrel is untapered, made from a single length of 6" x 3 mm copper tube.  The only real advantage of the tapered barrel is that because it increases the relative volume of water at the back of the boiler it might reduce the water gauge drop when going over the top of a hill (and our club track does have a hill).  However after extensive calculations I decided the effect was negligible.

                                    
I predict that going from 1-in-40 up to 1-in-40 down should cause the gauge to drop by about 0.66" (which sounds reasonable).  Without the taper, the drop is predicted to be only 0.003" more!  If you want to see my calculation results, have a look at http://www.hme.org.au/misc/waterlevel.php.

Hence the taper is not worth the trouble.  As it happened I had a suitable length of tube which I acquired a long time ago (and old enough to be 1/8" not 3 mm), so that settled it.  A few other boiler changes arose from the Australian Boiler Code (or more accurately, from advice about the code from our friendly Club boiler inspector).

Girder stays on the firebox crown are not permitted in the Australian Code, so rod stays were used instead.  I wasn't too happy about Keith's throatplate design, so rather than a sort of split plate with an unsupported butt joint, mine is a full flanged throatplate of conventional design. 

                                    
Finally, the longitudinal stays were omitted, and instead the smokebox tubeplate and the backhead were each made of 4 mm copper with an interior 4 mm doubling plate fitted to the upper part of each.  This extra thickness legitimately allows the stay spacing in that area to be increased to the point where no longitudinal stays are required.  Of course the tubes support the lower part of the smokebox tubeplate and there are rod stays for the lower part of the backhead.

Actually making the boiler was easier than I thought, although quite a lot of work.  It's also pretty heavy and needed a large garbage can of pickling acid.  My back was grateful when it was finished! On the way it was inspected twice, and then tested to 200 psi for 20 minutes as the Australian Code requires.  It will need a steam test (to prove the safety valves are adequate) before being put into service.

Brakes

                                    
The brakes were straightforward, given Ian Tiplady's invaluable comments and diagrams about the little bits that Keith Wilson didn't quite get right (see this site under 'MN Rebuilds – Ian').  Most of the components were laser cut from mild steel – with some spare copies, because the brake gear is obviously very vulnerable to derailments.  On a ground-level track (as is usual in Australia), derailments are not common but can certainly be expected to happen occasionally.

I decided against steam cylinders to operate the brakes.  Yes, this is (another) serious departure from a true model, but my reasoning is as follows.  When driving on a ground-level track in Australia, passenger cars are always braked adequately (usually vacuum operated) and it's far better to have the train stop the loco than the other way around, which risks wheel locking and wheel flats.  For light engine running, the tender brakes can be used. 

On the other hand, the one time when one really needs a locomotive brake is when unloading or loading the loco from a car or trailer – a runaway can be a heart-rending disaster.  So I have fitted a pull rod where the steam brake cylinders would have been, and brought it back (via one transfer lever) along the outside of the firebox to a screw operating tower in the cab.  This will be invaluable when parking the loco on our Club unloader/hoist, or even on the track in the car while securing it.


Cab and Casing

                                
In another Bulleish decision (function over form), I made the casing from quite heavy brass sheet.  The cab, middle section and smokebox section are all one sheet each, with the brass coerced into a suitable U-shape.  This turned out to be quite difficult to get just right. 

I had some formers laser-cut from 20mm board, both inside and outside ones, and basically rolled the sheets and then forced them to fit between the inside and outside formers.  The difficulty was the U-shape for the middle section came out a bit twisted, and was very difficult to straighten.  If you try the same method, I would advise being very careful about the symmetry of the initial bends.

The centre and front sections of the casing will be attached with a few strategically placed screws, but the cab is attached with locating tabs at the front and just two thumbscrews at the back.  This will allow the cab to be very easily removed – so that the grate can be then removed in one piece from the left (port) side of the loco.  I have learnt from club members with vaguely similar locos (e.g. the Australian 38 class), that grates which have to be removed through the firebox can be a right pain.  The grate will be of the "rosebud" type (lots of drilled holes, to about 30% air) which suits our local fuel, and in one piece of 10 mm steel.

                                
Where next?

Finish the casing and cab, finish the cab controls and gauges.  Then paint and detail.  Oh and make the tender body, of course.  Not too far to go !

Click here to return to  Part 1 of Roger's article.