MANUAL TURNTABLE

IMG_2400

The locomotive staging level has a manual turntable to allow inbound engines to be turned so that they are oriented in the right direction for operations on the layout.  The turntable track is powered and has a reversing feature for the track polarity.  It is rotated by hand and aligned with a brass key.  Building such a turntable is relatively easy, especially for wiring.

The turntable on my staging elevator is built up from polystyrene sheets and boxed shapes.  This offers the advantage in building it to a customized height.  This method of construction is time consuming though. Alternatively, I made up a second manual turntable for a Free-mo staging module that was made from wood.  Unfortunately, I do not have that module any more so I don’t have pictures to show.  It was much easier to build from wood, but I discovered that it is better to build it from a hardwood, minimum poplar.

At the heart of the design is a 2.5mm DC jack and receptacle shown below. This provides power to the rails at all times during rotation.  This can be found at an electrical supply store.

IMG_2604

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 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.

No matter which construction method is used, the only accurate hole needed anywhere is in the centre of the turnable where the DC plug mounts.

I soldered the plug to a brass plate that was then screwed onto squares of styrene as shown below.  The turntable with built-up squares was carefully drilled to the centre of the turntable before the pug sub-assembly was installed.

IMG_2606

A better way to do this which avoids the soldering that may melt the insides of the plug (I know this happens) is to file a couple of flats on the flange on the plug (near the thread).  The flats keep the plug from rotating when the turnable is rotating, avoiding twisted wires.  Then build styrene strips around the flats that glue onto styrene squares.  Lastly another square can be glued onto the top of the stack to trap the plug in place.  I did this on the wood turntable not making the stack as high as shown above.  This allows the end of the plug to enter the accurate centre hole drilled in the wood.  It is then screwed in place like shown above.

The receptacle is mounted in a .031″ brass sheet (below), but .060″ styrene should work also.  One thing to keep in mind when working the assembly is to ensure that the plug is engaged correctly in height.  The brass plate is held by four screws with washers and double nuts.  The holes where these screws go into are quite a bit bigger so that the receptacle assembly can be centred at final assembly.  This is handy in case this sub-assembly needs to be dismantled and assembled in the future.

IMG_2591

To centre the assembly (below), I have four screw driver holes that match the receptacle assembly mounting screws so that the turntable can be adjusted to the tracks and the receptacle tightened in place.

IMG_2587

Also seen above are the wires leading to the rails for track power.

I did not glue the track in place.  To hold the tack in place, I used styrene strips to the tie height and held the track down with a square of .015″ styrene sheet.  There are four of these retainers.  .080″ x .080″ strips, as guides, align the track on the turntable.  This way, the track can be removed without damage.

IMG_2590

When initially aligning the track, I aligned one end of the turntable to the staging track, leaving the other end free.  Using a Ribbon Rail straight gauge I aligned the turntable track to the centre staging track which was spiked in place on the staging level.  The other staging tracks were not spiked at this time.  Then I glued the guides and retainers to this end of the turntable.  Next, the table was spun around so that the other end was aligned and glued.  Lastly, the other staging tracks were spiked relative to the turntable rotation required, also using the Ribbon Rail gauge.

IMG_2588

A key (above), was made from 1/8″ diameter brass wire with close fitting brass tubing CA’d to provide a stop when installed.  The upper tubing isn’t needed and I don’t know why I added it!

IMG_2603

A Dual Frog Juicer controls the track power polarity.

Advertisements