G-Scale Graphics odometer

This tool gives you an easy way to calculate track length
Bill Zuback
Track odometer

G-Scale Graphics
5860 Crooked Stick Drive
Windsor, CO 80550
Price: $59

Odometer PC board and display mounted to base, measures 2" x 4.25" x 1"
9-volt battery clip (battery not included)
Reed switch
4 small magnets
connecting cable
Magnet attached to wheel
Kevin Strong
Kevin Strong
Kevin Strong
Garden railroaders often talk about their railroads in terms of how many feet of track they have. But how do you figure out how much track you have? If you want a true answer, you need to measure it. That’s where an odometer can help.

The G-Scale Graphics Track Odometer is a small circuit which measures distance and displays a readout on an LCD display screen. The distance is measured via a magnetic reed switch and magnets, which are mounted to a wheel on a car. The diameter of the wheel does not matter, as it’s the number of times a magnet passes by the reed switch that determines how far the car has traveled.

First, attach the magnets onto the back of the car’s wheels. If you have steel wheels, the magnets will stick by themselves. If you do not, a small drop of cyanoacrylate adhesive (CA) will hold them in place. The odometer comes with four magnets. The number of magnets used determines how often the distance is updated on the display. For example, if your wheel is 1" diameter, that means the wheel will travel 3.14" for every rotation. If you use one magnet on the wheel, the counter will update every 3.14". If you use two magnets, it will update every 1.57" traveled. If you use four magnets, it will update every 0.78" traveled. Most modelers will likely find two magnets to be sufficient. That’s what I used.

Once the magnets are on the wheel, you need to attach the magnetic reed switch onto the car so it will be able to sense the magnets as it passes. I hot-glued the reed switch onto the truck bolster.

The odometer comes wired with a plug to connect the magnetic reed switch to the board so you can remove the odometer from the car. The PC board has screw terminals, so you can also wire the reed switch directly to the PC board if it’s a permanent installation. For my purposes, I ran the wires from the truck up around the side of the flatcar to the board. If you use all the wire provided, you have about 18" from magnetic sensor to base unit.

The LCD screen is about 1" wide, and is easily seen in daylight. It’s worth noting that the screen is removable if you wish to display it in the window of a caboose or similar. You will need to unscrew it from the board and build a 4-wire jumper cable. The necessary connectors can be purchased from electronics supply houses.
Once the odometer is mounted on the car, you need to calibrate it. Measure a distance of 10' on your railroad’s track. Put the car at one end, press and hold the calibration button until you get the calibration screen, then roll the car along the 10' distance. Press and release the calibration button again after you’ve reached the full 10' distance. Press the reset button and the counter resets to zero.

The board measures in both imperial (feet) and metric (meters), though you must do separate calibrations for each. It will not translate one to the other.

Now all you need to do is couple the car to your locomotive and run it around the railroad. (My mainline is 261.7' for a round trip.)

I soon got to thinking of fun things you could do, like put it in a train that’s running for an open house to see how far your train ran over the course of the day. I’m sure you could find other creative uses.


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