Sunday, February 19, 2017


My SP Cascade Line features a number of turnouts located quite near the layout edge.  Most of these use manual pushrod throws with BluePoint switch machines.  A significant issue for me has been that my normal pushrod mounting through the layout fascia is significantly below the distance between the top of the BluePoint machine and its throw bar.  The close-to-the-edge turnout locations needed some way to eliminate the under-layout height difference when the switch machines were mounted directly to the subroadbed underside.  The throw rods for these machines typically are only two inches long, which creates too much vertical component to the movement if connected directly to the machine throwbar.

Eugene Classification Yard with three turnouts mounted near the layout edge.

My initial design solution for the height difference led to my creation of an offset throwrod attachment bracket mounted to the switch machine throwbar.  While this bracket brought the throwbar attachment down to a level where the throwrod could be mounted on a level.  While this seemed to satisfy the geometry needs, the actual service history has not been good.  There was a bit of flex in my brackets.  Quite a bit of force needed to be applied to overcome the slight over-center force needed for the BluePoint machine.  Often, my operating crews tagged these switches as un-throwable.

Original offset throwrod attachment bracket on BluePoint machine on the left.  The machine on the right, mounted further away from the fascia, could accept the slight vertical angle of the throwrod.

When I mounted the BluePoint switch machines for a couple of the aisle-side turnouts in the Eugene Arrival-Departure Yard, I finally tried a simpler idea.  I added a spacer block between the subroadbed and the switch machine.  Duh!  That much simpler idea is the right solution.  I should have listened to the advice offered up in Mechanical Engineering 101—the simplest solution usually is the best solution.

After the last operating session, wherein at least one of these aisle-side mountings had to be thrown—with difficulty!—from underneath, I realized I needed to systematically remount all of those switch machines.  As with all such projects, once the initial installation has been done, the rest go much swifter.  I re-mounted nine manual throw machines.  They needed spacer blocks 3/8 to ½ inch thick to compensate for the mounting height differences.  I got quite good at removing the old mount, installing a spacer block, and remounting the machines with longer music wire activation rods inserted in the switch throwbars.

Remounted manual switch machine on the left.  The spacer block between the subroadbed underside and the BluePoint switch machine solves the height difference issue for the throwrod mounted in the layout fascia.

The new mountings provide a solid, easy switch throw, perhaps easier than any of the other manual switch throws on the layout.  This should solve this operating problem.

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