Re: Mini K-27 link support assembly

It was common on the prototype to have extra lateral motion in he front driver. The builders had a special lateral motion driving box that added nearly and inch to the front driver's lateral motion. It utilized the front driver spring to not only push down in the driving box, but to push it inward to keep the lateral tight on tangents. On curves, the driving box was forced to the side, putting extra tension on the spring, but allowing the driving box to move laterally. Once out of the curve, the downward force on the spring pushed the box back to the inside tightening up the lateral and keeping the locomotive pointed straight ahead.

The 3 large classes of narrow gauge 2-8-2's on the Grande have lateral motion devices on the #1 drivers. K-27's do not. Either it was figured the the rigid wheelbase was shorter and they didn't need them, or perhaps they simply hadn't been invented yet. Another issue with K-27's is the front frame extension extends over the top of the main frame over the #1 driver. There probably isn't enough room between the frame and the boiler for the lateral motion device.

On the standard gauge, the Rio Grande managed to bend 2-10-2's around 16 degree curves on La Veta Pass by putting lateral motion boxes on both the #1 and #5 axles.