STAGING TURNTABLE

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I have built this staging turntable before so it isn’t really a concept.  When I was with the Credit Valley Free-mo Group, being a self-serving steam guy, I wanted a means of turning my Erie USRA Heavy 2-10-2 locomotive at the end of a run.  So I built a double-track staging turntable.

This device is handy for any size layout.  It can represent a non-modeled portion of a railroad – an engine terminal, a wye, a balloon loop.  Its relatively small size, dictated by the largest rolling stock to be turned, might be useful to the compact modeller allowing operations that would otherwise not be possible.  It is easily hung on a wall for storage.

The two lead tracks also allow it to be used as a run-around at the end of a branch line (that is, without turning the locomotive, but using the turntable like a turnout).  If single track operation is required, the track block can be deleted, the table shortened that amount, and the turntable brought up to the layout edge.  I would leave .060″ clearance between the turntable tracks and layout tracks.

Since I considered this as staging it was left in natural wood finish with two coats of Varethane for protection.  It is still in use with the Group although I am no longer a Free-mo’r.

At the end of this posting there is a downloadable CAD drawing.  The dimensions are in inches and can be adjusted to more specific needs.  Screw positions are included.

This is a manual turntable meaning it is rotated and aligned to a track by hand.  I found that there is enough friction between the turntable and table top so that a track alignment and locking feature is not needed.  However, this feature can easily be made by drilling holes from the turntable into the table top and using a pin as a lock.

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The tracks are powered and a Dual Frog Juicer (setup as an auto-reverser) corrects the track polarity for DCC operation.  This keeps things very simple to build.  The turntable is wide (4-1/2”) for stability and the sample I made has a 15-1/2” length.  As opposed to the manual turntable on the first level of the Fillmore engine terminal staging elevator, this turntable is made of wood – I found poplar to be a better choice than pine for flatness and drilling the important center plug hole (holes drilled in pine “swell” making their size difficult to attain).  The rest of the construction can be made in pine, as I did.  Table top is 11mm birch plywood or similar.

In the following, I will describe the design and give hints how to build it…

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There is a .060″ gap between the turntable track and the lead tracks.  This clearance is also between the turntable block and the track block.  The ends of the tracks are flush with the end of the blocks.  It is highly recommended that tracks be soldered to brass screw heads placed directly underneath the rail, lest they get caught on a shirtsleeve and get ripped up by accident.

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I used a 2.5mm DC Jack Plug and Receptacle found at the local electronics supply store as the means to provide the pivoting and track power.  This is what would be found on a typical power pack.  They come in a few lengths.  One important thing is to set-up the correct engagement depth of the plug to the receptacle.  If track power is lost or intermittent while rotating the turntable, the plug is not set at the right depth.  The depth can be adjusted by shimming the receptacle plate (using washers at the screw locations) or a styrene shim under the jack plug assembly.

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The plug goes on the turntable and the receptacle is on the layout.  There are two prongs on the plug where I soldered two 22 gauge solid wires that lead to the rails.  The receptacle has three prongs.  Only two are needed.  I found out which ones by having the plug mounted and wired on the the turntable, the receptacle pushed on, and a coin held across the rails.  Using a voltmeter measuring resistance, I tried the prong combinations until I found continuity.

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I use two nuts on each receptacle plate screw to lock them in position.

When laying the (flex) track, I aligned one end of the turntable to a lead track, using a Ribbon Rail straight gauge, leaving the other end free.  The lead track was then spiked on the track block.  The other staging track was not spiked at this time.  Then I spiked the end of the rail on the turntable.  Next, the table was spun around so that the other end was aligned to the lead track using the gauge and and then spiked.  Lastly, the other staging track was aligned and spiked relative to the turntable rotation required, also using the Ribbon Rail gauge.

Here is a picture of the Dual Frog Juicer installation – very easy, just follow the included instructions to configure it as an auto-reverser.

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Click here for the downloadable CAD drawing (StagingTurntable).  Please note this is configured for Free-mo – the 4-1/2″ board on the left of the drawing is replaced with 1×2 in the preceding pictures.

That’s all there is to it!

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