John Merefield
Photos by the author

IN ITS EXHIBITION FORM, Charman’s Dairy standard gauge model railway is ten feet of scenic layout on two five foot by 18 inch boards. It is flanked by two five-foot fiddle yards enabling through trains to run on its BR Southern line with a rail-served dairy. A Western Region branch line joins by way of a junction. This makes a total of some 20 feet of operational layout.

The Dairy end of the layout, which needs an extension to enable passenger services to access the halt properly when in home running mode. A heavy Z Class SR shunter has brought in empty stock ex Bournemouth West and awaits its return.

I’m as keen as anyone to get the layout onto the exhibition circuit. but whilst we await the chance for model railway shows to get under way again post Covid-19, the layout does not leave home and can’t be set up in its entirety. My small garage will only house the 10-foot scenic section. This is adequate for testing new developments and running in of additional stock but is otherwise severely limiting. For example, it’s not possible to practise movements designed for entertaining the public, or simply play trains. My partner in crime David Allen suggested that we should construct extensions to overcome this. So, I’ve set about the task to produce a couple of monocoque cassettes that will cantilever from the dairy end of the layout. A third serves at the far countryside (Whitchurch Halt) end. The construction of one of these cassettes is described here. They are simple in design, fairly lightweight but strong, and although they don’t contain any especially original features, they might prove a useful concept to other Guild Members facing similar restrictions.

The kit of parts 1 and 2

Apart from being a valuable way of lengthening the new layout during home running, it seemed sensible to consider the possibility of using these planned extensions at future exhibitions as well. In this way, three-coach trains might be marshalled instead of the two-coach limit on our Bodmin North layout (Gazette Vol 21 No 3, May 2020). Cantilevering them off the ends of the fiddle yards would give some 24 feet of total running potential. In the first instance and simply for home running, as the tracks reach the very end of each scenic board, the new extensions could be connected directly with G clamps.

In my case, when operating at home I wanted to be able to extend the two scenic boards by use of these cassettes without using the two fiddle yards, as I'm short of room. The two main layout boards have tracks that come up flush with the ends of the boards. This is so the two fiddle yards with their rails can be aligned tightly. Any cassette attached there to replace the full fiddle yard needed to come flush with those rails. But the furthest ends of the fiddle yard lines have been stopped short, to allow them to be manoeuvred. So, for operating at a show where the fiddle yards are in use, and then to extend further with the cassette, one end of each new assembly needed an overlap. Thus the extension had to be reversible according to whichever mode (home/cramped or show/expansive) was in progress. Working at home means that such cassettes can be simply G-clamped to the end of the scenic boards where space is limited. And running can commence speedily. At a show, the extra two feet in addition to the fiddle yard would enable 3-coach trains to be run, if that floats your boat.

The base for the tracking is 12mm depth by 96mm width MDF cut to 610mm (or two feet). The tracking is produced from two strips of 2mm depth by 20mm wide non-anodised aluminium, also cut to 2 ft. I prefer the flat strip as the angle version can get in the way of coupling and uncoupling. The end supports for the MDF base are 17mm depth by 70mm wide softwood cut to 96mm length. Shorter softwood strips at 17mm by 70mm by 32mm make up the two central supports. Electrical stranded wire eventually trapped under the aluminium strip will use the connector block contacts to link with the main layout across board, which eliminates soldering.

Scoring the aluminium strip prior to drilling the fixing screws

The sides of the monocoque are fabricated from 5mm plywood and shaped as shown. Extra width was cut so that these plywood sides extended to give a protective sidewall of about 43mm height; not too low so that stock can tumble off, but not too high to prevent coupling and uncoupling. Rather than a simpler box shape, the ends are triangular. Architects assure me that triangular structures are the most robust and additionally they allow the G clamp to be inserted at either end to fasten it to the main layout board (i.e. one end capable of being attached to the main scenic board at home and the other end for attaching to the fiddle yard at shows). I’m no chippy but cutting out the shape is readily achieved using a fret saw and a rasp to smooth out the mistakes. The sides were simply screwed in place and not glued, in case any modifications were needed after trials.

The first aluminium strip sets the spacing The supporting blocks are secured to the MDF With the first aluminium strip in place, the second can be accurately distanced Spacing using the 32mm width plastic card strip The completed monocoque cassette

The end supports need to be screwed and glued for added strength to the underside of the MDF base. The central shorter sections come next. The support blocks are secured to the MDF base (shown on previous page) countersinking the screws to leave the upper surface of the MDF even and available for securing the aluminium tracking later.

Drill bits have a habit of wandering over the aluminium strip so it pays to score it beforehand with a punch before drilling. In this case a 2mm drill bit was followed by a 3mm one before a countersink was used to lower the profile of the securing screws. The aim here was to keep a low profile lest the plethora of detailing parts found on rolling stock these days were fouled and lost forever.

Once the first aluminium ‘rail’ was fixed in place, about 12mm from the ply edging a strip of plastic card cut to 32mm width was used to space the second aluminium tracking. Yes, brass would be better but I’m no smithy and spacing using this method has worked well so far.

With the second aluminium tracking added, the end screws can be slackened off to thread in the electrical feeds and trap them. Grooves can be cut in the side supports at this stage and a plastic card strip inserted to stop any runaways. The completed cassette is shown below.

With the cassette lined up and secured with a G clamp, it is ready for testing. You really have to be confident of its strength as something rather heavy and valuable will be suspended on it in space, which is why these versions have been limited to 2 ft in length. An engineer (and no, I’m not one of those either) would have to advise on what would be the maximum length possible of such an assembly, given the geometrics involved.

On a sunny June day, the fiddle yard has been added to the scenic section of the layout on the garage ramp and the cassette attached to it. An S15 has successfully passed through Charman’s Dairy on the stopping service towards Bournemouth West, via the fiddle yard. The leading coach is a Bulleid Second which has strengthened the two-car Maunsell set coupled behind.

Show trials begin