How many access tracks should I put in for my turntable/roundhouse? I have two in the plans but wonder if thats is enough?
Brent
I have seen many photos of two access tracks. Some only had one track. Your choise.
Here is a photo of a small yard that use to be near my area in 1910.
Rich
Somewhere in my junk I have a photo of a stand-alone turntable - no roundhouse, no engine storage radials, no servicing facilities (water cranes at the ends of the mainline siding, the yard switcher arrived from a terminal an hour’s run away with a full fuel bunker, and ran back at the end of its shift on the last few lumps…) It stood at the end of a single track spur that was the extension of the A/D track…
My plans call for two turntable approach tracks, which is what the prototype yard I’m (sort of) modeling had. At the other end of the TTT, the turntable has two track access, but actually seems more like a revolving section in the middle of a continuous track.
Chuck (Modeling Central Japan in September, 1964)
I remember many years ago seeing a turntable in Holyoke MA tha that one track. No storage tracks or roundhouse. Were it was located was a few industries and a good size coal company for distributing coal thought the area. Coal was also dropped of at a steam and electrical power plant in the area. It was at the end of the line as i recall and the loco had to be turned. It was stuffed into a corner.
Rich
I would recommend one or two.
Youse call that a small yard!! please oh please describe a big one for us…[%-)]
The local RR museam has a full roundhouse, about 30 stalls, and it has five entrences.
Well since my original question I have been looking at a lot of old photo’s and if I had to draw a conclusion from all the photo’s, it all depends on the size of the roundhouse. It appears that on average there is one access track for every six stalls of the roundhouse. Makes sense, the more business a roundhouse does the more access tracks you will need. I am thinking a six stall roundhouse on my layout, so I will put in two. It never hurts to have a spare.[swg] Thanks for all your input.
Brent
Batman:
Railroad civil engineers, being a cowardly and superstitous lot, like to plan for unexpected problems. With two access tracks, you can still reach the turntable and stored power if a disabled loco blocks one. Two disabled locos, while not contrary to Murphy, are much less likely.
You can find this and nearly everything you want to know about roundhouses in this book:
http://books.google.com/books?id=gIs5AAAAMAAJ
It is an awesome collection of knowledge. Don’t be fooled by the date. By 1893, a great deal of what we think of as modern steam-era facilities had reached nearly their final form…and a lot that were old even then stayed in use until the diesel infection set in. 
For instance, the author recommends that room be left between roundhouse and TT, if room is available, enough to store one engine, and that tracks be slightly graded up into the house, so that equipment can be moved if threatened by fire.