Friday, May 3, 2013


The challenge of successfully laying out a yard on a ninety degree curve requires careful attention to geometry, innovation, and a few compromises.  The photo at RR-East Oakridge illustrates the split into the four major track groups at Oakridge.  Left to right are the depot tracks (house, siding, mainline), four yard body tracks, the engine facility (eventually splitting into four tracks) and the turning wye and its miscellaneous spurs. 

RR-East Oakridge.  Incomplete “siding” in the foreground is for the sand house.

As noted in the previous post on Oakridge (, I began by laying out the depot tracks.  These three tracks form the inside radii of the ninety degree curve.  These tracks include the mainline with its higher track standards (42” minimum radius and #8 turnouts), which established a broad curve as the inner base for the remaining track splits.  My original full-size track planning used #6 turnouts for the yard tracks.  I found I needed to use a couple of #8 turnouts (with their extra length and shallower divergence angle) to match the inner curve formed by the mainline.  This used more length before the curve, which impacted subsequent track splits for the engine facility and wye.  It appeared I was running out of space for these latter track splits. 

The solution was to slightly curve several #6 turnouts for the engine facility and add a modest curve before the first turnout off the wye.  The choice to curve the #6 turnouts was not taken lightly as it effectively tightens the curves for those tracks.  I was careful to keep the resulting curves broader than the 36 inch minimum for secondary trackage. 

I still needed a solution to the space issue (tracks pushing further toward the wye tail).  I could not get all three tracks into the engine shed plus the run-around track in the available space.  The compromise solution, compatible with the curved #6 turnouts, was to drop down to 32 inch radius for the outer pair of engine shed tracks.  This compromise of my design standards is acceptable for me because I know all of my SP steam, including a 4-10-2, will work around 30 inch radii.  This was proven in my former operations at the Cal Central Model Railroad Club which had a 30 inch minimum radius.  Ironically, the engine facility run-around and the first engine shed run through tracks (the inner pair of the facility) have broader curves, so any long wheel-base visiting equipment can still use the facility.

Oakridge Engine Facility.  Engine shed features two run-through tracks and one stub.  The oil track will be outside the shed and machine shop although it appears to overlay the paper template for the shed in this photo.

Oakridge Engine Facility.  Engine shed and machine shop outline has been trimmed for this photo.  Boiler house (foreground) has been dry (tape) assembled to check for fit within the wye.

Oakridge Wye

Oakridge.  Engine facility lead will be extended to RR-West switch ladder behind the camera.

RR-West Oakridge

RR West Oakridge.  Depot is an American Model Builders SP Depot Type 22 kit.  This is a stand-in for the actual Oakridge depot, which was a modified version of the SP Type 22 (hipped roofs and open air extension).

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