Lower quadrant semaphores
The train order signals I'm using have two semaphore blades
and illuminated red, yellow, and green aspects. These are lower
quadrant semaphores. That means that when a blade is fully
down (the vertical position) it is displaying the green aspect.
When the blade is fully raised (the horizontal position) it is dis-
playing a red aspect. When the blade is at a 45
o
angle pointing
down it is displaying a yellow aspect.
A red train order signal tells a train crew that Form 31 train
order(s) are waiting and they must stop and sign for receipt of
the new orders before they proceeding. A yellow aspect tells
a train crew that Form 19 train order(s) are waiting and they
should expect to find the operator out on the station platform,
ready to "hoop up" the orders to them as they pass. Needless
to say, crews preferred Form 19 orders so they could grab 'em
without stopping.
Up the Creek Column - 6
red aspect
green aspect
yellow aspect
arms (13), then installing the control arms back on the servos
(14). Once both semaphore control wires are connected it's
time to install the servo driver electronics.
Servo driver electronics
I chose to use
Dual 3-Way servo drivers to
operate my semaphores. Each of these boards controls two
servos, ideal for my double-blade train order semaphores.
I needed to run my DC accessory power bus into Oakhill to
reach the servos. I mounted the Dual 3-Way controller on the
insulating standoffs that came with it and connected power
wiring and the servo control wiring harnesses to it.
14
13
13: Threading the servo control arm onto the bent sema-
phore control wire.
14: The threaded servo control arm on the servo, ready
to be secured with its mounting screw.
MRH-Oct 2013
