gunrunnerjohn posted:It's quite possible to use that flywheel as is for a PS/2 upgrade, just did one recently with a small flywheel. You just have to devise your own tach sensor bracket. I do them with styrene strips. I curve the first one and glue it to the motor, then cantilever them down to get the proper spacing for the tach sensor.
Here's a link to Custom Tach Tape Images that you can print any tach tape spacing you need to make the speeds work out with your flywheel.
I would agree with this. Why change the flywheel diameter just to use a given tape? I have used custom tapes on smaller flywheels in G scale.
I didn't do this exact engine upgrade. I did do a first edition MTH Allegheny. I don't remember the flywheel being that much smaller?
Some of the old stuff had different gears and you must make a custom tape to get it right anyways. I did a Williams Challenger and although the speed matches my other MTH engines ( I think?), it screams at high speeds from what I think is low gears? Sounds like it's doing 150MPH! So I set the max speed at 50 MPH and try to keep it slower. I just don't like how it sounds. I wanted it to be at the correct speed to match the read out. I am surprised that the board doesn't shut down from the gearing difference. The custom tape must make the board happy? …. or I just didn't get that one right! 
