What is the Speed of Your Layout? – Part 2, Operation by Gravity?

In Part 1 I described the concept and construction of my layout. Now, how to make it work?

My original idea was to have the layout tilted slightly at an angle, as the Earth is tilted on its axis. A train would start out on the low side of the tilt and once it had climbed a certain distance up the “hill” the layout would turn on its own and the train would stay in one place. This proved impossible to execute. The train would climb and, as expected, reach a point where gravity took over. The layout would gather so much momentum that it spun the train around backwards to the down slope of the “hill”. This repeated surging was not pleasing to watch.

I decided that I needed a motor drive to turn the layout at a constant speed. Scrounging through the small motor bin at Princess Auto I found the solution. It was a 12-volt motor mounted into a gearbox (about $15). I rigged up a mechanism to mount the motor on the tripod shaft just beneath the bottom of the hollow centre core. This device doubles as the mounting platform for the electrical contacts described above. I cut the bottom off a metal coffee can and hot glued the resulting tube around the base of the hollow centre core of the layout. This particular coffee can was made with several grooves molded into its circumference which formed perfect pulleys. I then positioned a rubber drive belt around the coffee can “pulley” and the output shaft from the gearbox which, as luck would have it, was knurled and provided good traction. Power for the motor was supplied from the variable DC output of an old model railroad power supply. Here is a close up of the motor and the mechanism to hold the electrical wipers against the turning circuit board disc.

This powered design worked very well – the layout speed could be set to match the speed of the train running in the opposite direction, thus keeping the train in one spot all the time. However, glee quickly turned to disappointment when the two would become unsynchronized in less than a minute. The problem was with subtle variations in the speed of the layout motor as well as that of the train. These variations are not noticeable to the eye, but they exist. To get the desired effect, the speed of the train or of the layout had to be repeatedly adjusted – not much fun doing that all day long at a show! I needed to devise a way to automate the adjustments.

To be continued…