Okay, Mark. First, a disclaimer: because I built everything in a whirlwind in a short time, I cannot claim to have followed the instructions to the letter, so I might have left out, or changed, a step in the TT’s construction. IOW, I may have been the source of error.
That said, I found that I had to shim the motor (I am asuming you’ll motorize?) so that it would mesh reasonably well with the large black gear attached to the bridge spindel. I folded over some paper, or light cardboard, and wedged that between the motor and gear housing and the long side of the motor, itself. I didn’t overtighten the little screws, either, in case the whole system was going to reject the shim catastrophically.
Then, I found that the bridge, and therefore its big gear, wobbled excessively, and the shim was not the whole cure. So, I cut plastic, or thin styrene left over from a plastic model, and glued two rectangular pieces between the nether side of the pit and the big metal washer that would otherewise be against the pit, uppermost on the spindle. I placed a piece on either side of the spindle. See pic below.
That cured the wobbles. To this day, it works well.
Another problem (sigh): the pit isn’t round…at least, in my case. So, even with everything motoring as it should, the bridge binds at places. Test yours in place to ensure that you don’t have that problem. Test with a heavy loco. Both directions, complete revolutions. If you’re good, then good for you! If not, get out your Dremel, and a burr wheel, and grind away. Go light, because that pit wall is only a mm thick, or so.
Lastly, I found that the wipers, the brass ones that provide power to the bridge rails, were not dependable from revolution-to-revolution. They shifted, or the metal rings were not aligned so well and forced them to shift over time. Sound locos were hit and miss as the bridge turned.
