Mike, thank you very much for the drawings. I think that I know the answer to this question... where do the legs fit into the baseboard structure?
The legs fit into the outer slots at the board ends and the top horizontal beam takes the weight of the board - the verticals stop short of the top of the board and therefore there is no chance of the top being pushed off of the sides.
How does the baseboard-plus-leg structure gain stability along the long length of the board? (that is, resistance to wobble / flex if a load is applied at the end of the baseboard).
The stability is gained by virtue of the leg being a snug fit into the slot and if two leg units are used on every other board the lateral stability is also 'built-in' as it were.
The presence of alignment dowels indicates that there is more than one board for the layout.... how many of the boards have two sets of legs?
As many as you wish, obviously one board has to have the two sets so that whether with a straight run or an oval
it is the anchor board - first up last down and everything else radiates from it.
Might these boards be for Slattocks?
No, they were for a branchline extension off of the continuous run which could also be exhibited as a branchline end to end with an optional fiddle yard. Unfortunately, events overtook the whole plan - our landlords gave us notice to quit as they needed the site for redevelopment and the rest as they say is history.
However, we (Wirral OGG) have just moved into new premises - just finishe dthe redecoration this week, and will be erecting our test track shortly and there is a proposal for a similar type of extension for consideration, once we have everything up and running again.
Hope this answers your querries, but come back again if you need anything else. By the way, this leg arrangement is also used by the North Wales and West Cheshire OGG on their test track - 35' x 15' and it is very stable and has to be taken down after every running session and stored until the next one.
cheers
Mike