Roundhouse
I've built several versions of roundhouses over the years and as many
versions of turntables to go with it. Here is a pdf document
which defines a standard for a really big roundhouse done in a modular
fashion. Perhaps others will find inspiration in it.
Every roundhouse needs a turntable. Below are a couple of picutres of a turntable I worked on a while back:
(click image for larger view)
Pictured During a build. The
track is cut at the edge of the turntable. The turntable pit is
about five bricks deep.
A close up of the motor that drives the
turntable. The polarity switch reverses the polarity of power on
the turntable track with every 180 degrees of rotation automatically.
In more recent versions, I've used a circle of 9v track with a dummy 9v
train motor to provide power to the turntable track. This keeps
the power cord from getting too twisted. It also provided a more
reliable support for the ends of the track.