The Odometer Car
Norm StenzelDescription
Norm Stenzel knows that the track on his Brandywine and Benedictine model railroad is exactly 324.5 feet. How does he have such a specific number? He made an odometer car. Norm took a digital counter from RadioShack and mounted it in a 50 foot boxcar – something with double doors so the screen can be seen would also work.
Wiring it to one of the trucks was easy, the hard part was finding a wheel set that rotated a full 10th of an inch. This he just happened to be able to find in his junk pile. One revolution of the wheel needed to read one 10th of an inch. The odometer car is able to read off the exact number of inches when it is ran along the track. Simply by running the car around his railroad from point A and back to point A, Norm discovered that his track was exactly 324.5 feet. What a clever and easy way to determine track footage.
You said your track is 324.5 feet. Now, how do you know it's point five? How did you get down to that decimal point? Well, one of my gadgets here is a, I built this. I call it an odometer car. I took a digital counter from Radio shack, mounted it in a 50 foot box car. Well, it doesn't have to be a 50 foot box, I just need something with double doors so I could see the readout. Wired it to one of the trucks. The hard part was finding a wheel set that went a 10th of an inch every time it went around. I finally did find a set. I can't tell you who made it. I just got it out of my junk box. When it turns it-- One revolution registers a 10th of an inch. I just literally run this thing around the railroad and go from point A back to point A and it's 324.5 feet.
Something seems wrong with the math. If a wheel set traveled one tenth of an INCH per revolution it would be 0.1 inch / pi = 0.032 inches diameter which is under a scale 3 inches in diameter. That's a pretty tiny wheel. I suspect the travel is one tenth of a FOOT per revolution. That is a wheel diameter of (0.1 foot / pi) * 12 = 0.38 inch diameter or a scale 33.23 inches diameter.
That is spectacular,how did he wire it to the truck wheel,amazing that he said that was the easy part. May be hard to find a wheel though.