Copenhagen Fields & TFW’s workshop

[Atso]

The 2mm scale etches were kindly made available from Paul Craig’s artwork reduced in scale. Tony Gee had made one in 4mm scale as a test, but the coal space shape was probably not quite correct, requiring further modifications. That is quite academic in 2mm scale as it will be occupied by an 8mm diameter motor. Might be nice to get some 3D printed axle boxes. Does anyone have some decent drawings for them?

Tim

Hi Tim,

Let's have a chat about the axle boxes next time I see you. I have a set of Isinglass drawings for the B2 so I'm sure that something can be knocked up.

[Tim Watson]

After a few days in Lynton in the camper van, with zero internet and phone coverage, I have made the side rods for Valour using the kit etchings. Nick Eason has designed these for a sprung / compensated chassis in 4mm scale, so they have a correctly articulated joint. This feature is not needed in 2mm FS, so I very carefully made the joint solid, taking care to maintain the inter - pin dimensions. This paid off, because as soon as I had assembled the chassis with temporary testing muffs the rods worked with zero binding! This is a first for me, but the chassis had been drilled on a new watch-making co-ordinate drilling machine I am very lucky to have.



Not the most exciting picture.

Tim

[Horsetan]

....Not the most exciting picture.

Someone was clearly still awake at quarter past the one in the morning

[LNER4479]

Not the most exciting picture.

Tim

Well, it might not be the most exciting picture but fascinating for me to see it in 2mm scale.

For what it's worth, I had the same experience with the 4mm version, ie solid rods and it all revolved beautifully first time. I didn't have to tilt the modelling board very far at all before it started moving off on its own. I combination (I think) of accurate design by Nick and - in my case - use of a Poppy's jig.

Look forward to more news as the build progresses.

Graham

[Tim Watson]

Valour’s worm gear housing has been fashioned from a lump of brass using my John Stevens watchmaking mill / drill. It can be seen with the milling head in this picture, with a tooth brush for scale.


The head was then changed for the drilling attachment to drill the 1.5 mm hole for the worm shaft. There is zero backlash in the x-y table, although obviously one doesn’t rely on this when using it. I find Roco RTD excellent drilling and tapping lubricant.


The milling head can be tilted at all sorts of jaunty angles, as can be seen for making a clearance slot for the worm wheel.


The brass block was filed to be a tight fit between the frames and then drilled through the frames for the fixing bolts at tapping size, with the worm positioned on the worm wheel at the correct meshing centre (the worm is over-long). The frame holes were then opened up to clearance size.



This photo includes part of my thumb for scale, with wheels just in place and not anywhere near the correct gauge: they will be hard up against the frames when completed. The block was then milled back by 0.5 mm to avoid shorting out on the other side of the split frames. Finally the sharp corners were removed, as good engineers don’t like sharp edges.


The last photo shows the two 16 BA bolts nestled into the frames. The worm will be shortened and have a thrust washer between it and the bearing block. The universal joint from the tender motor drive will be at the right hand end.


Tim

[Tim Watson]

Quite a good view of Valour’s worm / worm wheel set up with one wheel removed.

The worm has had been trimmed to length and thrust washers fitted. Whilst the 38:1 worm wheel is visible in a broadside view like this, it will not be such an issue when the engine is complete - and will certainly not show on CF!
The chassis was re-assembled with wheels set to Irish broad gauge: final gauging will follow chemical blacking of the frames and wheels. It turned over by hand OK:
https://youtu.be/Is7_Nc_JY8k

It was then put under power.
https://youtu.be/cC3YFkvQgFc


Good enough for government work.

Tim

[manna]

G'Day Gents

Where does one start...........Brilliant work.

manna

[Tim Watson]

The reason for making Valour’s front end removable was to enable the front end to be made independent from the main chassis as it is quite complicated, with an awkward motion support bracket. As the etch has been made in 8 thou nickel silver, the slots or tabs need adjustment; I find a fine slotting file ideal for opening out any slots. Careful cleaning up of the etch cusp is also important to ensure a good fit of components, when dealing with a kit that has been reduced from four to two mm scale.

The slide bars consist of two components that make up a Tee section.


The motion support bracket folds up into the required shape very well and it simply requires the slidebars soldering in place.


Four hours later...

When people look at models they often say, “You must have a lot of patience”. I think it’s actually more a case of perseverance.

The outside cylinders are angled and so need to be lined up carefully with the centre driving wheel. This was achieved with sighting rods which were also used to align the motion support bracket with the cylinders.


The L&R brackets are held in place with the two 16 BA bolts at the front with some PCB on top to stabilise them. These brackets could be permanently soldered to the front frames when the detailing and mechanical bits are complete, if the PCB is too visible under the boiler.


The next job will be to machine the rear cylinder covers and stuffing boxes, the piston guides to fit in the motion support brackets, followed by the crossheads and piston rods.

The final picture is for scale:


Tim

[Atlantic 3279]

Excellent coverage of the construction process.

[Tim Watson]

I really didn’t like the lump of PCB on the motion support bracket: it would have been too visible. It was therefore replaced with another piece of copper clad, slipped in under the nickel silver cross pieces towards the front, where visibility is restricted by the frames. At the same time, I made two dummy bits of valve gear for the inside cylinders which serve to strengthen the joint and show some ‘business’ in the area.



The rear cylinder covers, piston rod guides and a temporary front cylinder alignment jig were turned up and fitted. The rear stuffing boxes will need filing to a lozenge shape for the top and bottom studs.


The alignment of all the assemblies has stayed true, as can be seen by the piece of pivot steel acting as an indicator. The pistons will be made of this very useful material. .


Crossheads will probably be made next.

Tim

[Tim Watson]

Crossheads are always quite fun to make. Silver soldering is a good way of ensuring that at least the piston and inner crocodile are nice and solid. The starting point is a piece of thick metal (0.7mm thick) to fit between the slide bars with a notch at one end to accommodate the 0.5 mm diameter piston. This also benefits from having some flats filed on to it to give a more precise location.


The silver solder was in a paste form and very easy to flash the joint with a little gas flame.


This was then placed in the vice and the socket for the piston filed into the end, rounding off the corners, taking advantage of the safe sided file.


Alignment in the slide bars was then checked: at this point it should be a tight fit.


Followed by a 1mm diameter hole to accommodate the little end of the connecting rod.


This was then opened out rearwards to be able take connecting rod. The outer face of the cross head can also be seen resting against the slide bars.


Making two of anything can be easily achieved by sweating two pieces of metal together and roughing out the shape, just once, then separating them. The little end pivot hole is 0.3mm diameter.


The two components were soldered together using a tapered stainless steel pin to stabilise the outer face by holding it on a charcoal block whilst the inner face was held onto it with downward pressure on the piston. This assembly was joined with electrical, relatively high melting point soft solder, as I didn’t fancy my chances at the whole lot not melting down into a blob if I tried to hard solder it. I normally use steel for valve gear - which would be less likely to melt, but as this is kit is etched nickel silver, that is what I have used here.


A tight but smooth fit is what was aimed for at this stage. Subsequently, the mating surfaces of the cross head slippers were filed using a slotting file to give a running clearance with the groove locating the cross head on the slide bars.



The outer cross head face was filed to represent the prototype and the piston socket dressed to look more convincing. The little end of the connecting rod will have a pin silver soldered to it and the round outer boss of the cross head will be represented by a washer soldered onto this pin to hold it in place.


It never ceases to amaze me what you can do with a phone camera.

Tim

[john coffin]

Whilst you Tim never cease to amaze with what you can do with solder
and files to produce something that is only 2mm scale.

Thanks

Paul

[Atlantic 3279]

Agreed. Wonderful work.

Don't those very clear images of such small parts make the fine file marks look frightening!

[Tim Watson]

I need to improve my finishing...

Tim

[Atso]

Absolutely stunning work Tim, but then, I wouldn't expect anything else from you.