Copenhagen Fields & TFW’s workshop

[Tim Watson]

The Raven NER 4-6-2 class now has an ‘engine’ with the connecting rods roughed out and the cross heads and pistons in place. The connecting rods will require fluting, amongst other things.

Tim

[Mersey508138]

That is a high quality level of skill I can only dream of achieving, well done.

[Tim Watson]

Perhaps a bit crazy. 
With such large big end bearings, it would have been churlish not to include separate brasses.
Tim

[Tim Watson]

Holding your work whilst working on it is one of the biggest challenges in 2mm scale (and others). The simplest way is to glue the component to a bigger piece of metal to hold in the vice.  The holding area can be flooded with a puddle of fast setting cyanoacrylate and then the rod dropped into place: the glue is then ‘set’ with some accelerator liquid. The photo below shows how I set up the con rods for re-drilling the big end holes in the brasses. The measured position from the little end was marked with a fine marker pen and then the table shifted on the axis using the dial from the little end reference point: the drill more or less landed on the spot (I erred on making it a touch shorter). Removal and clean up with a scalpel blade is straightforward.

Once it all felt pretty free, the temporary plastic insulation collar was replaced with a steel version. The top of the cross head was coated with a black indelible marker pen, to act as an anti-flux. The steel collar was cut from a 0.4mm bore syringe needle.

A minuscule amount of this German flux was applied to the tip. This flux is excellent for steel, it is a bit ‘oily’ and very corrosive. 

The iron is brought into contact with the pin and flux with just a small amount 145 degree solder on the tip. It boils up the flux and the solder immediately flashes into the joint, at which point the iron is removed, of course.  I have never got on with cigarette paper washers when assembling valve gear as they make the joints too sloppy. 

The con rods are a very close fit to the slide bars at top and bottom of the crank throw, but they just kiss past, I don’t think the bars will need any adjustment. The big end will probably have a turned collar made for it. 

The alignment on the frames, wheels and valve gear is quite satisfactory, without any nasty bends anywhere: an advantage of working to a true scale / gauge. 

The front steps will need to be robust and well fixed as they must not touch the connecting rod (at least on one side).

Tim

[Tim Watson]

Two of the things that puzzle me with the Skittle Alley are whether the reversing gear balance weight (seen above the frames) was visible when the engine was in forward gear.

Also, at some point, it seems that the wheels had some extra square-shaped weights added to the crescent shape as-cast. My engine will be in near original condition so I suspect it would not have the additions. Anyone any ideas?

Tim

[Tim Watson]

Measuring spot heights on locos / rolling stock can be achieved using surface plates and gauges / markers for model construction. My take on this is to use a piece of Tufnol with some PCB  ‘rails’ set tight to gauge to locate a chassis very precisely (i.e. no side movement on the wheels). This block also has a coupling height gauge incorporated. 

The way it is used is that a digital vernier is zeroed on the thickness of the block and ‘rails’. The block material needs to be of consistent thickness, but also quite hard and shiny to allow a vernier jaw to slide easily. The loco is positioned on the block, being held with one hand, and then the callipers used to make measurements or perhaps scribe a line for e.g. handrail stanchions.

The photo shows that the Skittle Alley boiler height is a fraction under, but should be about right when it gets a coat of paint…

Tim

[Tim Watson]

The Raven 4-6-2 class is now mechanically complete. It slightly ‘stuck its elbows out’ on the slide bars when running and so a restraining wire was soldered across the back of the crocodile, using 145 deg solder. 

https://youtu.be/EoCENm7k2bI

The driving wheels are lined out at the hub but the rims are not yet black. 

Tim

[Tim Watson]

Darlington works has been a bit quiet of late with a slight diversion into 4mm scale scenic modelling for the MRC’s OO layout. However, I did make the cab sides for the NER 4-6-2 class at the Missenden modelling weekend. 

Subsequently, the spectacle plate was made from quite thick brass as well as the running plate top. This is 5thou steel shim, being stronger than brass or N/S and able to take a good chemical blacking.  The cab sides were obviously made as a pair, sweated together for cutting and filing. 


I decided not to put on the external cab window beading as it is very fine (in reality) and generally gets in the way of the black and white lining. The cab window frames are required, however, but only one is visible as the engines always ran with the rear window slid forward. Representing the rear slides was worthwhile and will also gave a greater surface area for soldering on the roof at eaves level.  The window layer was aligned using a couple of stainless steel pins through the handrail knob holes whilst soldering. 

Next stage was to get the cab erected and the footplate extension boxes in front of the spectacle plate. 

The rear cab roof support was made from thick brass and the whole assembly held in place with two bolts - the engine is being designed with ease of painting in mind, breaking down into useful sub-assemblies. 

The next job will be to make the styrene pattern for the back head, which substantially fills the cab, seats and cab floor. A good job for demonstrating at Ally Pally next weekend. The loco now looks that little bit more complete. 


Tim

[Mersey508138]

Although nearing completion I have to say what an absolute masterpiece of engineering

[Tim Watson]

Still a long way to go… thank you for the comment.

Tim