Building Train Mountain Switch Points

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Glenn Brooks
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Joined: Mon Nov 10, 2014 1:39 pm
Location: Woodinville, Washington

Building Train Mountain Switch Points

Post by Glenn Brooks »

Note: Jeff Mills, President of Train Mountain sent along the article below and asked if we would post to our discussion board. Jeff describes how TM currently builds steel switch frogs, to improve longevity and safety on the TM right of way.


Train Mountain Development of the Steel Switch Frog

By Jeff Mills


All of the original switches at Train Mountain used cast aluminum switch frogs. These were used in conjunction with the aluminum West Cost Rail on Port Orford Cedar ties. After decades of use of the cast frogs it became apparent that a more robust and wear resistant frog was needed, thus complementing our upgrade to steel rail on plastic ties. Our search led us to Maricopa Live Steamers who manufactures a steel frog for their own use and also sells them.
Upon analyzation of the Maricopa Design it was determined that their fabrication process had too much machining. Also a significant amount of router work needed to be done on the ties. Russ Wood and Richard Cox started to modify the Maricopa design. Their design goals were to use as much Off the Shelf Materials as possible with the lowest amount of machining time.
The most important part of the switch frog is the heel (the isosceles triangle shape) in the middle of the frog. This has to be a precise part which keeps the wheels tracking in the desired direction, preventing a derailment. The sharpness of the point is what makes the frog work. This is where the cast aluminum frog falls down in performance. As this point gets worn and then breaks off. When this occurs the wheels passing through the switch will take random tracks causing what is known as a split switch. A result of this is either a derailment or the trucks on a car end up on two diverging tracks, both of these are undesirable.
On the Train Mountain designed frog the heel in the middle of the frog is cut from ½” thick steel plate. This is precisely accomplished with a CNC water jet cutter. Being that TMRR does not have a CNC water jet machine this is the only part outsourced. We are fortunate that a company in Klamath Falls has produced these parts for us at a reasonable cost.
The rest of the parts are cut from ¼” x 2” strap steel, ½” x ½” square steel bar stock and ¼” x 1- ½” strap steel. This stock is cut to size on a band saw, deburred made ready for welding. Laying out of the parts for welding is accomplished by using some ¼” spacers and a careful placement of the frog heel and securely clamping into place (see accompanying photo). Once welding is completed the frog is ready for installation.
Train Mountain primarily uses two radii switches 75’ and 100’ these require a #9 and a #11 frog respectively. The number designation of the frog is determined by the distance from the point going toward the base where the base is one inch wide. Hence#11 is 11” from point to where the base is 1” wide. There are numerous reference materials that explain this and other factors of design.
Train Mountain is currently making the switch frogs in batches of 25. These fabricated switch frogs have significantly reduced both the time and expense of building a switch. For additional information on this subject please refer to Discover Live Steam June 2007 article titled, “Switch Building at Maricopa Live steamers”. We have prepared a document with how to instructions, drawings and photos. I can forward this document to you by e-mail, contact me at jhmills51@ Hotmail put into the subject; “Switch Frog”. We are making an effort to have this fabrication document on our web-site in the future.
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Steggy
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Re: Building Train Mountain Switch Points

Post by Steggy »

Glenn Brooks wrote: Sun Dec 16, 2018 12:36 pmNote: Jeff Mills, President of Train Mountain sent along the article below and asked if we would post to our discussion board. Jeff describes how TM currently builds steel switch frogs, to improve longevity and safety on the TM right of way...When [the point of the heel wears down/breaks off] the wheels passing through the switch will take random tracks causing what is known as a split switch.
Not to nitpick, but what was described is a "picked frog," not a "split switch." The latter occurs when a wheelset manages to open the gap between one of the points and the mating stock rail.

Properly positioned guard rails will reduce the likelihood of frog picking, but won't compensate for damaged or excessively worn frogs. Some railroads have used self-guarding frogs in low-speed turnouts, as illustrated below. No guard rail is used with such a frog.

self_guarding_frog.jpg
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rkcarguy
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Location: Wa State

Re: Building Train Mountain Switch Points

Post by rkcarguy »

I like the design pictured better. However, the flanges and gaps between the rails in the frog and guardrails are far larger in scale than in real life. I think this makes it easy for a wheel to try to pick the frog and there is nothing to keep the wheel set from doing so. With a guardrail, it's practically foolproof, I still mounted guardrails on my first turnout.
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