Traverser

Too complicated.

Unless you need to enter and exit at both ends, a sector plate is much simpler. It only needs a single pivot point and can be aliged simply enough by hand.

Use a bathroom door bolt to lock it into position and power one rail through that, Power the other rail with piece of attached lamp flex.

Not only possible, someone has already done it. Take a look at this thread on RMWeb

Of course, if you have the money to throw at it (and assuming that this is going to be part of the modelled area and not just the 'fiddle yard'... :~)

Not really. OK, motorising it and getting it to stop in the right place is probably non-trivial, but for a hand-powered one a properly constructed traverser is a delight to use.

There is a lot to be said for sector plates, but it seems that for ones over a certain number a lot of thought and possibly maths needs to go into getting the curves right.

I've seen quite a few fiddle yards that do that, even ones that have traversers instead of sector plates, and it does seem to be a very reliable system.

Not really. Just a pencil on the end of a long piece of string with a panel pin on the other end. Just lay the tracks so they line up with the incoming track and curve them so they finish up parallel.

If you do that you don't need an indexing system which you do if it's mechanised.

Many years ago Mike Sharman had an exhibition layout called Bogsworth Junction, that was railway archaeology, with standard and broad gauge locomotives from the 1840s and 1840s,

When he operated the turntable he used the train controller. lining it up by eye. But this isn't an option with the drive from a scanner.

Trivialish with a stepper motor. Electronic controllers tend to have Run and Jog modes to get them SBO.

Rubbish! Gordon Hopkins of MERG did exactly that on one of his layouts. He used to have a website for his RPC kits but I can't find it now.

MBQ

I took the scanner apart today, and set up a wood & metal framework for the 'table' to move along. I think I'll need to buy an IC to convert low- power signals from a microcontroller to high-power signals for the stepper motor. I found a guide here:

My first post was unclear; I want the traverser to act as part of a small fiddle yard. It will probably have two or three tracks, long enough for a locomotive and a few wagons or a two-car DMU. And I'm trying to keep costs down, to leave money for the locomotives.

If you are using a baseboard width of 12 inches or more I would also think in terms of the selector plate suggested by Chris, far simpler and if there is clearance (diameter of the selector table) allows whole trains to be turned.