Jim, I requested an HO bridge from Diamond with S scale ties, I think an HO 75' Small Girder model. The bridge is about a foot in diameter in real life, just over 50 scale feet.
This is intentional to keep larger power away from Leadville, should some wander onto the layout at some point. It will easily accommodate all the C&S locos on my roster. The real bridge was a 50 footer.
This has been an interesting project. I am of the mind that it is really 2-3 models, not just one. There is the bridge, the pit and all the approach tracks. Plus, it has to operate and transmit power. Not a project for a beginner, though Diamond and NYRS make it about as easy as can be.
I thought of modifying a Walthers model--and came very close to doing so. However the right bridge length was not available, and Patrick Tillary--who modified an HO Walthers model to a 65-footish S-scale bridge--advised me that the indexing memory was volatile. He had to re-index the tracks if he unplugged the power for the table. Jack at NYRS assures me this is not the case with his indexing system.
To think that I turned a Diesel on a Sellers once in the late 70's but didn't know what it was, I just assumed it was an NZR design. We built Locomotives and rolling stock, why not Turntables. If only I had known then I would have got a picture of it. Grrrr.
Okay, I found my Tiffany plans in a Narrow Gauge Annual.
Pondering this project over the past couple days, I think this is another opportunity for some forced perspective. On the layout, the turntable will be on the east side of the mainline, towards Poverty Flat and adjacent to the backdrop (it fills the corner opposite of Hemlock Street). The Pit is somewhat close to the backdrop, but far enough away that I need something to distract the eyes from the intersection.
Studying the photos that Chris posted, I noted that the Tool House appears to be at a slight angle to the Refer (in fact they were probably set in line and may have shifted over time, or it could just be the photograph). Anyhow, the plan is to slightly angle the Tool House forward, and place the Tiffany refer to the rear. Then it occurred to me that by building the Refer at a smaller scale would enhance the distance--Rick's rendering of the Valuation Map indicates these structures were over 40' from the edge of the pit, whereas on the model they will be half that distance.
So, I will build the Refer HO scale for a bit of atmosphere here. A HO figure will seal the deal.
The Valuation Map also indicates a fence at this location, and that will also help hide the edge where the backdrop meets the layout.
On the leads I also mirrored these with the outbound track nearest the backdrop. Here, I will use the Sand House (which still stands) and the Coal Bins to hid the backdrop-layout edge.
Ken, I really did consider building the Sellers bridge. I found a diagram--I think provided by Rick Steele and out there on the web--of the size and configuration of the holes. It would not be a hard project using styrene and Archer rivets. But the Diamond Scale Model bridge is built on a wood superstructure, so the holes would have had to been drilled through the wood sides, giving away the thickness of the sides.
I can't believe I spent all those years in HOn3 either, small as it is.
Are you going to model the service track, from turntable to Tiffany shed, as in the photo? Forced perspective of the track from Sn3 at turntables edge to HOn3 at the shed? There is probably an app that will calculate gradually shorter ties!