PS...I'm still having trouble finding the correct tach tape, don't fully understand why Dave Hikel's method calls for something more than 48 stripes when MTH uses it as a standard. My steam chuffs, driver revolution, and speed are still a bit off. I timed the engine over my 1/3 mile mainline. It should have taken 20 seconds to go the 1/3 mile at 30smph, but I had to increase it to 35smph to get the 20 seconds.
Seems to me if your Williams goes 30/35=85.7% of commanded speed, then you need to have 85.7% of the 48 stripes or 41.1 stripes. Since stripes must be even, you'd use 42 stripes or 21 black + 21 white and live with an "uncorrectable" 2% speed error.
If your speed numbers are accurate and assuming Williams and MTH scaled the wheels properly (same diameters of the model), then MTH must be using a Gear Ratio of 18 instead of Williams' 21. 18/21=85.7%.
