So the latest of my wild-arse ideas: a dual gauge turntable.
Long story short, my latest layout idea is an end of the (standard gauge) line town where a narrow gauge railroad starts and heads into the hills. The narrow gauge would have it’s engine facilities in that town. As this is late steam era, it would seem appropriate to have a way to turn the standard gauge locos as well. So logically, the two would share a turntable. (This is all HO and either HOn3 or HOn30 BTW)
At first thought, you’d simply put ‘regular’ dual gauge three track on the turntable, but when you turn it 180 degrees, the third rail doesn’t line-up… right?
So what’s the solution?
I was thinking one could make the dual gauge track on the turntable bridge FOUR tracks: One set of Narrow gauge tracks sitting inside a set of standard guage tracks. Then you could have a special set of track on the approach that moves the dual gauge trains from the three rail to the four rail configuration… maybe a special one-pointed turnout that moves the wheels from the ‘shared rail’ to the new fourth rail while moving the third rail over?
Just add the additional rail when the table is turned 180 degrees. Will sort of look like a bridge with guard rails. Set the rail w/ a guage and set w/ CA. You could predrill and spike it for added security. Indexing of the table for narrow guage would be the only issue when the table is turned. may need a momentary sw control to bump it to the alignment.
that is a good question. i have not seen this in the prototype, but anything is possible.
your idea of having 4 rails on the table would require 4 rails on every track going into the round house and a transition point (4 rails to 3 rails) for every other piece of track.
is it possible to have a transfer from one side of the track to the other side ON the turntable? this way you can enter the table (3 rails), the engine would crossover to the other side of the track, and then depart the table on 3 rails? this would result in always having the track lineup correctly and reduce the # of special track work.
or just leave the 3 rails the way they are and pay speical attention when lining up to depart the table. (worst option)
Use 4 rails on the turntable. There is no need for every track approaching the turntable to be 4-rail. If you have two leads to the turntable, one can be narrow gauge and the other standard. If you have a single lead, you’ll need a single-point switch on 3-rail dual-gauge to convert it to 4-rail track. For the stub tracks, they can be any combination of narrow-gauge, standard gauge, and 4-rail dual gauge at your whim.
The 4-rail solution works fine. It’s simply a different indexing point for standard and narrow gauge. You can use the normal dual-gauge track configuration for leads and stalls, with 1 shared rail and 1 opposite rail each for standard and narrow gauge. Or, you can dedicate some stalls to standard gauge, and some to narrow gauge.
There will be a small kink in the alignment, because the centerlines of the standard and narrow gauge tracks aren’t the same. However, this should be small enough to ignore.
With 4-rail dual gauge, both the narrow and standard gauge tracks use the same centerline. I wouldn’t make do with 3-rail and put up with a kink. There is already enough opportunity for mishap happening at turntables. Besides, a shift to 4-rail is a nice mechanical/scenic effect.
If you are good with your PC, you can manipulate the screen for max view and use Print Screen key to copy the view to your PC. Then use a photo manipulation application to process the photo to suit you. I do that a lot for one or two pages of interest.
The reason dual gauge turntables have four rails is to keep the center of gravity of the locomotive over the center of the center bearing. Having the weight to one side would be just as bad as having it offset toward one end of the table.
I saw some very small dual gauge turntables in Taiwan 40 or so years ago - 762 and 600mm gauge, IIRC, on sugar cane lines. The gauge might be smaller, but the same principles apply.
I’d certainly agree with both of those points. I have very little knowledge of dual-gauge trackwork. Would a transition from 3-rail to 4-rail involve a moving-point system like a turnout, or could it be accomplished simply, with something as uncomplicated as a frog?
Thanks to the OP for a thought-provoking topic, by the way. I love this outside the box stuff.
There is a drawing in the article referenced in my above post showing the arrangement using a single regular switch point or a single-rail stub switch. There is no frog as no rails cross another…
And let’s not confuse dual gauge with 4-rail gauntlet track. Gauntlet track is where double track is partly merged where one rail of one track crosses over into the other track and remains there for a distance. This unusual arrangement occurred where the double track crossed a single-track-width bridge or tunnel. Gauntlet track has no points but does have two frogs. One frog entering the gauntlet, and one frog leaving.
How soon I eat my words. Page 41 of April’s MR shows gauntlet track for a railroad car scale. It has four rails so one set goes on the scale and the other set avoids the scale. Here the gauntlet track emerges from a single track. This is done with two points but no frog.
The Colorado Railroad Museum here in Golden, Colorado has a dual guage armstrong turntable in use. There are four rails on the turntable and the single approach track uses the second configuration that Rich posted. Our club also has a dual guage gallows turntable that is also dual guage. Some stalls of the round house are standard and some are narrow. there is one that is dual guage and uses 4 rails. hope this helps
Or as a totally wild idea you could make a cross-shaped turntable, where the narrow guage and the standard guage cross at the center of the turntable at a rightangle
This is really a unique piece that will solve problems and simplify the construction of a a narrow guage turnout.
As for the turntable operation, Narrow guage use w/ 4 rails on the beam, just use the turntable as if the standard rail doesn’t exist. The indexing would be my only concern. That’s why I mentioned a momentary sw control to bump the table motor to alignment. Using Renegade’s suggestion from the CO RR museum, you have the options with the stalls as well.
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