I'm amazed! Nobody suggested yet that you build your own. If you want a smooth operating TT mechanism, go down to your local bicycle shop and get a front wheel hub. It has a beautiful ball bearing setup to rotate the axle. Mount it in the center of your pit. Next, take a stick and some plaster. Drill a hole through the stick and use it on the axle to create your pit wall and floor. Make a step for the pit track. I would say that you should make your own bridge, but since you already bought one, use it.
As for indexing, Bowser made a neat set. It used a fiber optic under the approach tracks and a LED or small light shining through a pin hole in a mask on the ends of the bridge to trip the power interupt.
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My apologies to the group. I had trouble getting the web site with the construction description to load. It has some neat ideas. I'm changing my comments, but leaving my construction comment (which in some respects is similar to the web site concept) and I'll add another.
A very simple method of powering a turntable with the bicycle hub as a bearing is to attach a large plywood disk with a groove cut in the edge to the bottom end of the axle. Then have another smaller pulley mounted so that a part of the edge sticks out of the side of the layout benchwork. Run a belt between the two. You can then rotate the turntable by hand.