Sunday, September 8, 2019

Turntable mechanism

A while ago I posted a series of photos showing the construction of a turntable for Thomaston. I installed the pit on the layout but ran into “analysis paralysis” when I couldn’t decide whether to motorize the turntable or rig up a manual control mechanism. I finally decided on manual, since my preference is to use manual controls wherever that would have been the case in real life (turnouts, uncoupling, etc.). The breakthrough came when I found a set of gears and a rotating turntable brick in an old box of legos:


The lego turntable brick has a 1/8” bore, so I epoxied some eighth-inch brass tubing into the bottom of the turntable, making sure that it was perfectly perpendicular:


The gears have a 3/16” bore, so I bent some 3/16” steel rod to make a crank. The white gear is attached to a 4x4 lego brick bored at 11/64” to give a press fit on the shaft in case I need to adjust it. In the photo below you can also see the pin that runs through the vertical turntable shaft and engages the nubs (the official lego term is “studs”) on the blue gear. The baseplate is still taped in place because I’m still adjusting everything to be centered and level – a surprisingly finicky process.


The mechanism turns smoothly with very little slop, but can be disassembled in seconds if I need to remove the turntable in the future. And the total cost was $3!

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