Converting an Sn42 Turntable to S Standard Scale

The turntable being used at Wiarton is a Walthers Powered HO 110 foot which turns out to be about 80’ in S Scale.  This is about 5 scale feet too long but considering that steam locomotives are always between 3 to 5 feet longer than their prototypes; this should not be really a problem appearance wise.

Because of the location of the turntable, I will have to leave the backdrop open for access in case of a derailment.

The first order was to take the deck off the bridge.  It was fairly straight forward.  Before doing so, I marked colours on the centre post to remember which wire went to which rail.  The carriage wheel sets have been removed as well.  They will be eventually replaced.

The Bridge Being Dissected

The deck comes off with screws which are a bit hard to get at.  If you are doing this be careful not force anything or break any parts of the mechanism. 

Top of Bridge Minus Deck

What remains is shown below.  The carriage wheelsets are back on again.

Deck Removed Wires Lengthened

The hole where the wires come through is about three quarters of an inch in diameter.  I suppose I could have simply put an S Scale track on top but I was concerned about alignment at the ends and how much extra I would have to build up the track work approaching the turntable.  Also the HO turntable bridge would not have ended up being the correct width.  By making a new deck, I could control the width and add 1/8” to each side.

Next I measured and marked out where the centre of the turntable pit would go and cut out the hole in the Styrofoam.  I found that I needed to add a bit of bracing using styrene sheet.

Once done, I put the bridge back in the pit with some S Scale track on it.  I placed some cork roadbed and track up to the edge of the pit and tried to get a handle on how much I would have to build up the deck in order to have both the track on the turntable and the feeder track vertically level.  It turned out that I needed to shim the deck of the bridge 0.240” and the lip of the pit 0.100”.  To do this, I cut out 3 sheets of 0.080” styrene for the turntable deck which were one quarter of a real inch wider than the HO deck.  I drilled a ¾” hole in the centre for the wires to pass through.  I also had to add some small lengths of wire to the existing wire to make them long enough to reach the track.

Laminations Being Glued On

The gluing of the track to the deck had to be done carefully so it would line up equally on each end.  I measured and marked carefully then put masking tape down each side to make sure that there would be no variation.  I glued the track down using water based contact cement and let everything dry for the recommended 24 hours.

Track Glued Down

The bridge was placed in the pit and a track alignment gauge from Ribbonrail was used to align the track at both ends.  I powered it up and let it rotate to make sure.  One of the neat things about this turntable is that it comes with a control panel and you can press a CW (Clockwise) or CCW (Counter Clockwise) button to nudge it into place if things don’t always line up automatically.

I also cut and laminated pieces of 0.060” and 0.040” styrene to shim the lip of the pit.  I bevelled these pieces and glued them on the lip where the feeder track enters and on the opposite side.

I am quite pleased at the result.  I will eventually finish detailing this with proper sides and railings but for now it does what I want and well.

CNR S-3-a 3702 going for a ride!

This turntable worked out really well.  These come in HO scale lengths of 90’, 110’ and 130’.  They are not cheap but do come with everything including a nice control panel which will allow you to program where the turntable stops.  It is an easy way to do indexing.  I don’t need indexing at Wiarton since they only used the turntable to turn the locos 180 degrees.  Apparently the steel combines were never turned.  I am not certain about the wooden ones that ran before 1955.  I wanted something that was easy to install and easy to use.  This fit the bill quite nicely.  I plan to use the 130’ version for Owen Sound.  Next up, the installation of backdrops.


2 thoughts on “Converting an Sn42 Turntable to S Standard Scale

  1. Interesting work, Andy.

    What made you decide to increase the height of the deck, rather than (say) raising the height of the pit by supporting it with a piece of ¼” ply, carefully cut to provide a suitable hole?


    1. Good question. The reasons I did not increase the height of the pit was because the pit is so shallow on the prototype and I wanted to widen the deck.


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