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Barney - design and etching


antyeates1983

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It's about time that I introduced my next locomotive project, which has actually been going on since before I started the Scrap Tank. It's a Barney 0-6-0. It started with the Worsley Works etch, but has morphed into a project using my own etches for the chassis and body, as well as for a 6-wheel tender (the Worsley etch provides the 8-wheel type). The main reason for not sticking with the Worsley etch was the fact that I wanted to do my own tender including axleboxes. I reasoned that I might as well make etches for the loco as well, to make construction easier and facilitate a built-in gearbox as well as including additional details.

 

 

As with the Scrap Tank, I started with an AutoCAD drawing based on that in Peter Tatlow's book on Highland locomotives. The drive will be conventional with a motor in the tender and universal coupling to a simple gear train driving the rear axle of the loco. This arrangement allows the gears to be hidden in the firebox, whose location makes driving the middle axle more awkward. The plan is for the tender body to be pivoted on an additional axle muff at the rear, so that it transmits its weight to the rear of the loco via the drawbar.

 

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To give them a bit of rigidity and (hopefully) avoid the need for extra bearings, I opted to etch the loco and tender frames from 0.4mm phosphor-bronze rather than nickel-silver. A little bit thicker would be ideal, but 0.4mm is available from PPD. With this thickness I am using the 6.4mm PCB spacers from the Association shop to give me a width over frames of 7.2mm. 

 

As well as the chassis etch I've produced more conventional 0.25mm nickel silver etches for the loco and tender. Again, I drew the artwork in AutoCAD but followed my usual procedure of doing the "hatching" afterwards in Adobe Illustrator, which works much better for this. The images below from the etch artwork give you an impression of the format of the etches. The numbers are a new innovation (for me!) of creating an "instruction sheet" at the time of drawing the artwork, so that I know what they all are when I come to build the thing later!

 

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The tender etch is actually the larger one because much of the bulk of the loco comes from the boiler/firebox, which I'm making from brass tube rather than etching. Cyan and red things on the drawings relate to half-etched areas on the rear or front. Below is a photo of the real loco etch in nickel silver.  The quality of etching from PPD is fantastic. Something else I now do is to always make at least two copies of any etch, even a "test etch" like this. The second one is much cheaper and provides spares of everything so as to allow for unanticipated learning experiences that often occur during construction. Otherwise I end up wasting time trying to fabricate replacements for some of the parts. (Of course, that may be necessary anyway if the ones on the etch aren't the right size!)

 

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The artwork for the phosphor-bronze chassis etch is generally simpler. The next photo shows the tender frames. I included temporary "extensions" with cross pieces to hold the frames. These are a loose fit. The modus operandi is to first hold the frames together using the Association frame spacing jigs, as in the following photo. The p/b cross pieces are then soldered in place. This then allows me to remove the Association spacing jigs as necessary to solder the PCB spacers where required, knowing that things are still positioned accurately. The various small holes in the frames are for Simpson springs and to hold the brakes in place. (Yes - this time I plan to include brakes...)

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Finally, here are the loco frames. The design is similar except that I tried to match the shape of the real frames and springs, and included an integral gearbox to hold the worm. I've soldered it up already here. This design doesn't allow for easy adjustment of the worm mesh (except by enlarging the wormshaft holes and fitting bearings), but in theory it should be correct to begin with. I'll find out later!

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Now this is exciting. 

 

Two things I have learnt about worm mesh during the rebuild of a pannier tank (still not finished though it was started some time ago when you were at the beginning of the scrap tank build) is that it could be helpful to paint the inside of that fold up worm 'box' a very light colour so that the mesh is quite visible when looking into what might otherwise be darkness behind and the mesh can be adjusted a tiny amount by bending the upright between the main part of the frame and the 'box'. 

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Thanks - these are good suggestions. I should be able to try out the worm mesh soon as I think I have the correct gearset in stock.

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