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Operating model railroad crossing gates

How to install working crossing gates on a model railroad layout.

Create realistic crossing gate operation using Tortoise™ slow motion switch machines or R/C servos.

The Signal

This example shows how to make operating crossing gates with O scale signals by NJ International driven by Tortoise™ switch machine motors. The motors move the gate arms at realistic speed when operated with an Azatrax MRX3 crossing signal controller.
HO scale and N scale installations are shown below.
The NJI gates come with an actuating wire that extends out the bottom of the base. Unfortunately, this wire is attached right at the gate's pivot point, so it requires a lot of force to move and has very short range of motion.
This wire is soft, so it can be removed with a firm, steady pull with pliers.
Drill a small hole in the crossing arm counterweight as far from the arm's pivot as practical. The goal is to create as much leverage as possible so the motors can provide smooth motion. The hole should be just large enough for your actuator wire. Piano wire, 0.015 or 0.025 in. dia. works well.
Mount the signal by shoving a length of 3/8 in. brass tubing firmly into the base. Run the wires through the tube. Drill a 3/8 in. hole in the layout, then place the signal.

The Mechanism

To provide vertical drive motion, the Tortoise™ switch machine must be mounted horizontally under the layout. Figure 2 shows how to do this.
Fig.2 shows the use of an 'L' bracket to mount the Tortoise switch machine motor.
A transverse wire connects the actuating wire to the motor output. The transverse wire allows the mechanism to have more 'give.' The movable fulcrum allows you to adjust the range of motion and change the mechanical advantage.
Alternatively, Circuitron's Remote Signal Activator kit may be used to mount the Tortoise™ switch machine motor and connect it to a crossing arm.
Your careful efforts installing working crossing gates will reward you and your visitors many times over.
crossing arm actuator wire
Fig.1 - Actuator wire connects to a hole drilled in the crossing arm counterweight.

Switch machine mounting.

Fig.2 - Mounting the motor under the layout.

HO scale working crossing gates

Josta refined the Tortoise™ mounting method and took these photos on his HO scale layout. He is using NJ International signals with crossing gates.

gate motor under table Josta ran the gate arm actuating wire at a 60 degree angle. He then mounted the Tortoise switch machines under the layout base at a 60-degree angle as well. He says,
"I used 0.030-inch music wire for the horizontal lever of the motor, and another 0.030 section of music wire for part of the vertical pushrod. These two wires are connected with tight loops at each end as the photo shows. Then I used a cable clamp (available at auto parts stores) to clamp the 0.015 music wire from the NJ gates to the 0.030 wire from the motor. Just loosen the clamp to move the gates to the desired up and down points.
"I move the fulcrum on the Tortoise motor as needed to give the desired range of motion. If there's too much play due to the flexing of the 0.015 wire, just move the cable clamp up closer to the gate; that's why I use 0.030 wire as it's stiffer."

NJI crossing arm The actuating wire is 0.015-inch music wire, placed on the back side of the signal where it is not so easily seen.
See the smooth action of Josta's excellent installation in his YouTube video:

N scale crossing gate installation with Tortoise™ motor

N scale gate
David Bilek placed this N scale NJI crossing gate and its Tortoise™ motor on a lift-out base to simplify assembly and maintenance. He can also take it with him when his layout moves.
David added LEDs to those N scale crossing gate arms and wired them to an Azatrax crossing signal controller so they flash in prototypical style. Amazing work, David!

N scale crossing gate installation with 9g R/C servo

N scale gate with servo servo with gate N scale gate with servo
Model railroad crossing gates can also be operated with servo motors. Servos are widely used in radio controlled, or 'R/C' airplanes, boats and cars.
The three photos above show an N scale NJI crossing gate with a 9g mini-servo. Examples of this type of servo are HiTec model HS-55 and Futaba S3111.
Before mounting your servo, determine in which direction it will rotate! Not all servos are the same.
We have mounted the servo to the underside of a lift-out section with double-sided foam tape and a metal corner bracket, available in hardware stores. For best adhesion, remove any labels from the servo and clean the mounting surface with alcohol to remove oil and grease.
It is a good idea to build your crossing on a removable platform, particularly if you model in the smaller scales. The platform can be built and adjusted on a workbench, rather than making fine adjustments from underneath the layout.
A length of 0.015-inch (0.4mm) steel music wire replaces the actuating wire that came with the signal. Note the hairpin bend in the wire. Making this bend allows you to make small adjustments to the gate position.
The Azatrax MRX3 crossing signal controller will operate crossing gates with either Tortoise™ motors or servos.

Tortoise™ slow motion switch machine
• Circuitron part no. 800-6000
• Download Tortoise installation instructions here [pdf]
• Use with any scale
• Made in USA

Tortoise™ Motor
$17.50 each
Tortoise™ Remote Signal Activator (RSA)
• Circuitron part no. 800-8100
• Remote mounting mechanism for Tortoise™ switch machine
• Cable actuation for one crossing gate, semaphore or turnout
• Easy precise adjustment of stops
• Download RSA installation instructions here [pdf]
Tortoise™ motor not included (see above)

Circuitron Remote Signal Activator
$12.20 each
Tortoise™ 2nd Cable & Actuator
• Circuitron part no. 800-8101
• Use with Remote Signal Activator kit above to operate a second crossing arm with one Tortoise™ switch machine
• Easy precise adjustment of stops
Requires Tortoise™ motor and Remote Signal Activator above

Circuitron Add-on Cable & Activator
$6.50 each
Terminal blocks to simplify signal and Tortoise™ motor wiring
Euro-style 2-circuit and 12-circuit terminal blocks
• Solder short wires to your Tortoise and signals safely on your workbench
• Place terminal block under the layout near motor or signal location
• Mount Tortoise and signals according to instructions
• Make connections to layout wiring with a screwdriver
terminal block

Terminal Blocks
Number of circuits

Tortoise™ and the turtle logo are trademarks of Circuitron, Inc., Romeoville, IL

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