Dual Gauge Frog
Modeltec, May 1984
It's as Simple as that?
Somewhere in the dark, distant past, a glitch got mixed into the Live Steam Hobby and, as a result, some of us building in inch-and-a-half scale ended up using 7-1/4" gauge while others used 7-1/2 inch gauge. Many impromptu conferences have been held year after year, resulting in activity ranging from finger wagging to finger pointing and the profound utterance over and over again of "Tsk, Tsk!"
See 7-1/4 vs 7-1/2 Gauge.
Somewhere in that same dark, distant past, the idea surfaced that some of the greatest inventions were made by people who didn't know that "it couldn't be done."
Lacking documented proof of reason to accept the situation as insurmountable, the Lake Meauwataka & Wildwood Railroad was designed and built with one of its prime concerns that of operating both 7-1/4 and 7-1/2 inch gauge equipment on its rails.
The accompanying article tells of its success and one quick glance at the photo above is usually enough reason for the viewer to exclaim, 'It's as simple as that!?!?"
Three factors have made possible the operation of equipment built to either gauge:
- 1. Minimum radius of 100 feet for curves so no widening of gauge is necessary to accommodate large locomotives.
- 2. Installation of self-guarding frogs at all turnouts using 1/8 by 1-1/4 by 6 inch steel strap two six-inch lengths of 1/4-20 threaded rod with four springs held in place with washers and nuts.
- 3. Switch points positioned to clear back-to-back dimensions for 7-1/4 inch gauge equipment.
The 1/8 by 1-1/4 by 6 inch steel strap has two 17/64 inch holes drilled 5/8 inch in from each end and 1/4 inch from the bottom of the strap. The two top corners are ground to 1/4 inch radius and then bent out to permit entry of any wheels with a wider-than-usual tread. The strap is bent in the center to match the contour of the frog casting (in this instance, No. 9 frogs from Railroad Supply Corporation. Cannonball Enterprises Ltd has available the spring-loaded, self-guarding frogs designed by Karlson Model Products which mate with Culp rail). Matching 17/64 inch holes are drilled through the frog and the guards bolted in position with the 1/4-20 threaded rod as shown.
It's as simple as that!
See also 7-1/4 and 7-1/2 Dual Gauge.
