Some of the commentary below may have been superseded by what is written elsewhere; however, mostly what is here is correct and useful.
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Modules comprise an aluminium and wood frame; a plywood platform, with sides, that carries the railway tracks; standardized aluminium interfaces at each end, which plug into those of adjacent modules; with the whole assembly being glued together with epoxy. The image shows a single track prototype module, upside down, showing the sockets which accept the plug-in telescoping aluminium legs. What is shown weighs a little less than eleven pounds; a similar double track module weighs less than eighteen pounds.
The interface plates show the pin-and-socket inter-module locating system, and three holes in the other face which are for the over-centre latch parts to be installed. The three holes in the pin-and-socket face are a machining misteak. The leg sockets are lined with aluminium tube and have steel washers at the bottom for durability. The multi-part sides were made up because there was no material available long enough for single piece sides on this prototype.
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Interface plates can be of any width, accomodating any number of tracks. As specified currently (which is at the end of the production of three prototype modules), each track has its own complete two-pin-and-socket interface. This single track interface is referred to as a [track-] locator. A multi-locator interface permits splitting of the tracks of a multi-track module into other arrangements of separate railways of fewer-track modules, such as sidings and steam-up bays. By convention there is always a primary track; this corresponds to the requirements of the vector-based railway design software that developed the convention. Currently, only single and double track modules exist except as a possibility supported by the design concepts: a four-track railway has been produced in software, for example. Thus there is just one secondary locator in hardware at the time of writing. And, of course, the single-track modules only have a primary locator.
The reason that the above is important is that practical problems arise very quickly when more than one locator appears in an interface. Problems already have arisen in manufacturing double-track interfaces, where there are two locators, hence four pin-and-socket connections. The difficulty is maintaining adequate dimensional precision.
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Modules can be supported in any way desirable. Sockets are provided in the bottom of the module structure that accept 1-1/8 inch diameter plugs. The standard way to support a module is to use telescoping legs that are 1-1/8 inch diameter at their top end.
A normal module has six leg sockets. These are arranged in pairs in ribs that, in addition to hosting the sockets, are key parts of the module structure. Each rib is a 1-1/2 x 1-1/2 wood board; oak has been used; pine appears to be adequate for strength and dimensional correctness, and is less than half the cost of oak. The length of a rib is either 6-1/2 or 16-1/2 inches, for single or double track modules respectively. It is adequate to cut these ribs to size prior to assembly. Cutting oversize with subsequent fitting has been shown to be unnecessary since there is a little flexibility in the aluminium module sides.
Ribs are cut to size and then the socket holes are cut before installation in the module; this makes manufacture simple. The hole centres are 1 inch from the ends of the ribs, i.e., on 4-1/2 or 14-1/2 centres. The position of these holes is not critical, the legs plug individually into the sockets. The holes are drilled with a 1-1/4 inch Forstner bit on a drill press. This has proved to be more difficult than it sounds because of serious heating of the bit. Drilling the oak, even with multiple tool withdrawals and cooling intervals, caused blueing and dulling of the bit. For either wood, a carbide-tipped bit is just about essential for extended use.
The holes in the ribs are lined with 1-1/4 dia x 0.058 wall aluminium tubing, and a steel fender washer 1-1/4 dia in the bottom of the hole. These linings are glued in place with epoxy; however, to date, everything has fitted so well the glue is barely necessary. The cylindrical liners are 1-1/4 long, the holes 1-5/16 deep, the washers stock size, and the resultant assembly keeps the liners from protruding above the rib. None of these dimensions is critical, except perhaps squareness of the holes to the rib, in general a neat job is quite adequate for the purpose of the socket. A 30 degree included angle (15 degree lathe cut) is put on the entry side of the cylindrical liner.
Practice on the prototypes has been to drill the socket holes prior to assembly of the ribs into the module structure; but insert the lining components after that assembly. This is changed for production, so that ribs can be completed, including inserting the socket liners, prior to new module assembly.
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last-modification-date: 11 Aug 2015