How do you move 28 turnouts on a 10 square-foot layout? Hardcore modelers would match the method on the layout with the era and location of the prototype, of course, at least on HO scale. Track scale, the density of the turnouts, track distance and the available space between locomotives and freight cars on the CNJ Bronx Terminal would make hand-thrown turnouts very troublesome, however. Plus, my hand-laid turnouts don’t have springs that hold them in place, either open or close. I was briefly considering BullFrog assemblies from Fasttracks. I rejected the idea for the lack of real estate under the layout and for the control rods and panel knobs on the fascia, though. Powering them electrically and managing their state with DCC accessory decoders was therefore an no-brainer.
As always, I had some constraints to observe. First, available space for the motors under the layout is scarce. In some cases, two motors have to power a three-way turnout where the two throw-bars are just 3/4″ away from each other, and the depth of my frame is 1.5″. Plus, I want a solution that keeps my costs down. I get that with SG90 servo motors (plus extension cable), self-made brackets, and SC82 Service Controllers from Team Digital (one for 8 turnouts) for the cost of about $12 per turnout.
Servo Bracket Design
For the brackets a tried several designs. Mounting the servos with motor shaft horizontal relative to the layout board turned out to be the easiest and most robust way. In some cases I had to place the servo with the shaft vertically. To get a long enough lever, the brackets are based on a 1/4″ thick ground plate made of basswood. All other pieces of the brackets are also made of basswood strips or styrene. To drive the throw-bar of the turnouts I use piano-wire attached to the servo horn. The actuator extents through the layout board and through a 1 mm hole in the center of the throw-bar. The model of SG90 servos I use have enough torque to move the turnouts, even the ones with relative short and hinge-less points.
DCC Control
I’m happy with the Team Digital SC82 product. The controller is easy to program, it supports an ops mode that allows programming during operation from the main track, and so far they proved to be reliable and robust. Although I have a separate accessory controller bus, that bus is normally connected to the track power bus. This way, the SC82 controllers and servos get power from my DCC booster/controller. I’m not using the SC82’s route configuration capability as my DCC controller (ESU Command Station) supports routes. The only drawback of the SC82 is its inability to read the (initial) state of a port and its servo. For this reason, I meticulously maintain a spreadsheet with servo positions and speeds for all turnouts.
Juicing the Turnout Frogs
As mentioned before in the blog, I’m also using a Tam Valley Depot dual frog juicer for two turnouts and a second dual frog juicer configured as auto-reverser for the Wye between tracks 10 and 11. The connection between track 10 and 11 and track 10 beginning with the turnout to track 11 make up a small separate power district. Otherwise the entire rest of the CNJ Bronx Terminal layout is one single power district.