Blog Archive

Wednesday, February 15, 2017

The Case of The Missing Rivet


As Christmas 2016 approached, and Puffing Billy's 6 train running began in order to accommodate the annual summer rush, G42 was taken out of traffic and rolled into the workshops for a 'B' exam. 

Now removing our biggest locomotive from service at the busiest time of year might sound a little counter-intuitive to some, but there is method in the madness!

The 6 train running period sees 4 NA class locomotives and 4 carriage sets in service, and with the limited rolling stock currently available to us, we can only make up 4 NA sized trains. 

Therefore, without the ability to make up a Garratt sized train, there is no point in G42 running, and so the workshops take this time each year to carry out planned maintenance.


The regular B exam sees the workshops carry out such work as a boiler washout, checking and maintaining the spark arrestor, and any small jobs which have been noted by the engine crew in the logbook.

This particular exam also coincided with an internal boiler inspection. This requires all the washout plugs and fittings to be removed from the boiler, so that the internal condition of the boiler may be assessed.

The boiler fittings such as valves, gauge glasses and safety valves must also be taken apart for visual inspection.


It was during the boiler washout that the things suddenly got interesting!

Whilst cleaning out around the firebox, a rivet head was washed out through one of the rear foundation ring sockets.


Now G42 is our only A roster locomotive which still retains a riveted boiler, and a boiler that size contains a lot of rivets, so the question was; where had it come from?

Trying to answer this question involved all sorts of creative thinking, including torches, mirrors, and a borescope.


The location was eventually discovered through advice from those who carried out the initial restoration of the boiler, careful study of the drawings, and the purchase of a Go-Pro video camera on a selfie-stick which could be poked through the inspection covers and viewed on a computer screen balanced on top of the boiler!

The previous series photographs were taken showing the inside of the boiler; looking down into the dome opening, forwards looking at the front tubeplate, and rearwards looking at the firebox and crown stays.


Above, the rivet head which came out in the wash is on the right, whilst the remains of the rivet, after drilling out, is shown on the left.


The rivet was found to be one of a series which retain a thickener plate across the backhead of the boiler, through which the longitudinal stays are attached.

Above, the cladding and insulation has been removed, and below, the remains of the rivet drilled out.



With the hole cleaned out and the threads cleaned (above), a new stud was manufactured to be a tight fit in the existing thread (below).



Above and below, with the new stud tightened into place, the circumference is caulked in order to effect a steam tight seal with the boiler plate.

Caulking is a process carried out on riveted steel structures, whereby a blunt chisel or similar is driven into the metal adjacent to a joint, and has the effect of displacing the metal and creating a tighter seal.


Following a hydraulic test which showed no leaks, the loco was steamed for the boiler inspector who professed himself happy, and G42 returned to traffic in time to bear the brunt of the Chinese (Lunar) New Year traffic.

Tuesday, January 31, 2017

NG/G Update; Rounding out 2016


Quite a range of jobs have been carried out or are now under way, and there is plenty of work to do, as the photographs demonstrate. Above, the NG/G16 boiler cradle, complete with boiler, sits suspended between the 2 engine units for the first time in nearly 20 years.


Brake hanger brackets, shafts, air reservoirs and actuating cylinders have been fitted, complete with Vesconite bearings. The next stage for the brakes is the layout and plumbing of all the pipework required to make the system work.
Riveting of the remaining boiler cradle frame stretcher and footplate brackets has been completed, and the running boards are currently being drilled ready for final fitting.


Above, one of the newly fabricated steam pipes, in this case running from the smokebox to the leading engine unit, showing the connection for the drifting steam.

Below, steam pipe connections below the smokebox being trial fitted.


Above, the newly fabricated steam pipe that resides below the cab floor, supplying the hind engine unit; this also has a connection used to supply drifting steam from the drifting valve.

Below you can see the steam pipe ball joint mounted in position within the hind pivot casting.

All the completed steam and exhaust pipework is being painted, and the lens rings which make the seal between the pipe flanges are being lapped in.



All the new regulator components have been machined ready for assembly, including new castings obtained through the good offices of the Ffestiniog & Welsh Highland Railways, and have been trial fitted to the boiler.


Above, the original expansion links have been measured and assessed, and new bushes will be manufactured as required. The die blocks were found to be past their prime, and new ones will be machined.

New expansion link trunnions have been profile cut and machined, ready for assembly. The trunnions are the pivots about which the expansion links rock, driven by the eccentric rods from the return crank, thereby giving linear motion to the piston valves.


The existing crossheads were condemned at an early stage, so drawings were produced, patterns manufactured, and new ones cast. These have been partially machined to accept the slipper, side liners, piston rod and gudgeon pin.

The crosshead slippers are currently having new whitemetal cast prior to machining.



Brand new intermediate reversing shafts have been machined and assembled, which sit in the pivot center castings at each end of the boiler cradle, and transfer the movement of the reverser to the weighshaft on the engine units.

Below, new return cranks have been manufactured, ready for fitting.


Side rod bush drawings are complete, patterns have been made and a full set of new bushes have been cast (above).

Below, rough machining has started in preparation for casting the white metal bearing faces into the bushes.



Drain cocks have been dismantled, overhauled and reassembled, in readiness for attaching to the cylinders, whilst below, the actuating cylinders for the drain cocks, front sanders and rocking grate are all being overhauled and new linkage drawn and manufactured.





The safety valves are in the process of being overhauled, with some parts (damaged beyond repair) having been borrowed from NG/G16 127, currently in storage at the Menzies Creek museum. The life expired springs are to be replaced with a spare set purchased for G42, as the safety valves on both engines are essentially the same.
Cladding sheets for the boiler have been designed and all the sheets laser cut and rolled prior to delivery. All but 2 fitted perfectly and the incorrect ones have been re-manufactured.


The backhead corner trim from the original boiler will be re-used, having been modified to suit the new Klinger type gauge glasses, and the cladding plates redesigned to allow for a reduced number of boiler washout plugs.

The new boiler only has about one third the number fitted to the original design, and this was deemed suitable bearing in mind the quality of water available at Puffing Billy, and the effectiveness of the water treatment we use.




Following the re-gauging work, the motion brackets were found to be out of line, rectification of which could have been a major task, with the result that the engine units might have had to be sent out for further machining work.

After some investigation, we were able to source a mobile milling machine, which was set up mounted to each engine unit in turn, and all the rear and top faces of the motion brackets were re-machined to bring them back in line. The weigh shaft mounting brackets are currently being machined to suit.


Above, brand new spacers to fit into the pivot centres between the boiler cradle and the engine units, individually machined to size in order to ensure that both ends of the boiler cradle sit at the correct height above rail level.

The valve gear components are currently being assessed, worn holes measured and new bushes and pins drawn up for manufacture.



Above, progress refurbishing the reverser stand by the NG/G16 volunteer team continues. Drawing for a brand new screw and nut have been prepared and an order placed for manufacture.

Below, brand new machined annular ring castings for the 4 piston valves, provided by IXL Foundry of Geelong.



Setting up and fitting of the 4 pairs of slidebars between the rear cylinder covers and the motion bracket is currently underway, involving much machining, bushing of oversized holes and fitting of shims.

Below, the steel wire 'string line', which is set up to run on the cylinder centre line, allows the slide bars to be set up accurately, ensuring the crosshead and piston rod run true to the bore of the cylinder.




This stamp on one of the slidebars showing not only the SAR running number, but also the builders number and the slidebar's location on the locomotive, in this case RHT - Right Hand Trailing.

Final setting up and welding of the water balance pipes from the pivots, alongside the boiler cradle, to the injector water feedwell is almost complete, with just the pipe joints to be finished. The valve (Centre of photo) allows the water supply from the hind tank to be isolated. There is a similar valve controlling the flow of water from the front tank, and with both valves closed, the filter in the feedwell can be checked/cleaned.


Finally, on the 9th August, the boiler cradle, complete with boiler, was married with the engine units for the first time in about 20 years. Making use of both workshop gantry cranes, the boiler and cradle were lifted and the 2 engine units rolled underneath before it was lowered into position.

Whilst there is still a lot of work to do before the engine enters traffic, this gives a good indication of the scale of the project, what has been achieved so far, and what remains still to be done.


Monday, January 16, 2017

Ashpan Part II



The air box has been modified somewhat from the original concept, in order to increase clearances around the rear pony truck. Above and below, the first stage of the redesign, with damper fitted, can be seen.



Each hopper has its own bottom slide fitted, in order to dump ash, and these two photographs show the slides and their operating mechanism being trial assembled.


In order to try and clear all the ash from the hoppers without having to go underneath and manually hose them out, a drench pipe was made and fitted, with the aim of sluicing the ash out using water.

The pipe, with slots along its length, runs across the back of the pan. A little trial and error was required to get the position of the pipe, and the hole sizes, to be just right; the video below shows one of the trials:





Following completion and fitting, 6A went back into traffic for testing, yielding no major issues. The one minor issue so far is that the drench pipe doesn't always clear the pan on its own, and the access doors at the rear (just visible in the photos above and below) have to be opened to allow access for a hose.

The Office of the National Rail Safety Regulator were notified, as a requirement of our accreditation, and they raised no issues either; the new addition to this NA, in it's stage 1 version,  has been in use for some months now, and performs admirably.

Watch this space for the Stage 2 enhancements!