Shortly I will be in the process of setting up a 90’ walthers turntable with a 3 stall roundhouse. My question is how far does the turntable have to be from the roundhouse?
the “circle” of the roundhouse has a center, that should be the center of the turntable
Draw a straight line down the center of each stall until they meet. That is the center of the turntable.
This method should work just using the two long side walls.
Not necessarily. The walls may be parallel to the track in the outer stalls, and not built on a line that passes through the centre of the turntable. It is safest to assume that only the centre line of the tracks pass through the centre of the turntable.
Andrew