7-1/4 and 7-1/2 Dual Gauge

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Mike Venezia wrote on Chaski.org:

My track in Jackson, NJ, The Iron Acres Railroad, was a dual gauge railroad. Many visitors came with both gauges (7-1/4 and 7-1/2 inch gauge). It took a bit of experimenting to get it to work but it did. My gauge in the curves was set to a strict 7.562 inch and the straights were about 7.530. We would machine a larger (1/2" wide I think) slot in the switch frog and widen the gap at the points. We then set the Back to Back at exactly 6.875 keeping a very minimal space between the guard rail and the stock rail. I would put about a 2.5 to 3" lead on each end of the guard rail to bring the train over smoothly and keep them from wandering. I had a few problems with a couple visiting engines that had wheels that were less than 0.750 inch wide but for the most part once I got it figured out we had lots of fun.
Dual gauge railroads require a lot of close tolerances and a bit more maintenance the a railroad set up to run one gauge. If I do build a railroad at my place in PA it will be 7.5" only to cut down on having to be so finicky.

Nick Edwards wrote a detailed description of his * Wimberley Blanco & Southern Railroad Dual Gauge Track.

The Washington County Railroad supports dual gauge operation. From their website:

Our track gauge is precisely 7.5 inches. The switches have guarded frogs making it possible for 7.25 inch gauge equipment to operate. The guarded frogs make it necessary to require that the wheels on all railroad equipment be at least 3/4 of an inch in width. The wheels on 7 1/2 inch gauge equipment must be no wider than 13/16ths of an inch while the wheels on 7 1/4 inch gauge equipment can be up to 7/8ths of inch in width. The flange profile should conform to the IBLS Wheel Standard established in 1974.