If you use a stereo plug …

… or more, you’ll have more on table power for different effects without feed wires twisting.

• a light
• a table house with an attendant smoking a fiber optic cigarette
• a welder making a repair, etc.
• could be switched with a decoder of course you only need track power to run a mobile decoder. 

Will follow with interest.

CADRail

Like all my other track planning, I started with CADRail.  The prototype is manually operated.  Men drop down into the pit and literally push the locomotive around.  Because this is the turntable on my logging branch, I wanted a similar, rustic, down-n-dirty sort of turntable.  Bob's version was a scale 44' long, but I made mine 56' to accommodate my logging Shay, Heisler and the 2-6-0 that will run the local freight.  That also makes it long enough for a 1st Gen Diesel, should the railroad buy any of those.  

As you can see below, this is smaller than my original plan. But it will be a more realistic size for a manually operated operation.

Smoking Attendant

Mike, I like your idea!!  What a cool addition that would be.

Raw Materials and Track Mounting

The prototype for Bob's bridge started life as a timber turntable and was rebuilt several times as locomotives increased in weight.  In the final version, reclaimed bridge girders were used on the sides to provide the strength needed for the newest locomotives.

I had an old bridge that I scratch built many years ago using Atlas bridge girders.  This was in the days when the girders had detail on both sides, unlike the through girder bridges sold today.  The base of the bridge was thick styrene.

I disassembled that bridge and had the basic components for my new turntable.

The old bridge was painted black.  I used this to my advantage, and scribed crosshairs in the bridge to mark the exact center.  Then I used that, along with calipers, to mount some MicroEngineering bridge track as close to exact center as I could manage.

Bridge Girders

I cut the girders down to size and glued them back together in a butt joint.  Then I used a jig to glue the girders to the sides of the bridge. (click the images to zoom in)

My bridge opening turned out to be slightly narrower than the NMRA gauge minimum width.  I didn't think to use the gauge ahead of time, DUH!  But I like the looks of it, and I tested all my locomotives for fit, so I'm good! 

I weighted this assembly and let it dry.  Then I added some leftover Micro Engineering bridge parts along the tops of the girders to add detail and hide the butt joint.

Michael where did you

Michael where did you purchase the stereo plug? It would make a good simple, bearing wiring set up for a hand powered turntable. BTW, most of them which I came across as a locomotive engineer just had a wood or steel post/pole which was pushed by hand not in the pit but by walking around the edge of the pit.

Thanks, for sharing.

Barry 

There's more to using a stereo plug............

Mike Hughes has a great idea but............a stereo plug has 3 contacts.  A mono plug has only two which is all you need to power the rails on the bridge.  If you want an additional lighting feature then you come up one contact short using a stereo plug.  But wait..........there is a solution.  For the one extra contact point simply install a short piece of brass tubing to the top of the arch that is located at the pivot point in the center of the bridge.  Just like in real life place a power pole near the edge of the TT.  It's real easy if you make this out of brass tubing also.  Solder a small solid core wire to the top of the pole and drape it across to the brass piece of tubing at the top of the arch.  Place a "blob" of solder on the end of the wire and push it down inside the tube.  As the TT rotates the blob will just rattle around in the tube and still make contact.  The overall scene will look prototypic and now you have two contact points for that spotlight on the control shack.

An alternative to the "blob" is to use a second brass tube that will slide inside the first tube attached to the arch.  Sand on this tube a little to insure a loose fit between the tubes.  Solder the draped wire to this very short piece of inner tubing.

U can purchase a stereo plug at.............

any electronics supply house.  Check Radio Shack Online , Mouser Electronics or my favorite Digikey.  Don't forget to get the jack that goes with it. 

The center line through the jack MUST be perfectly straight up and down from every angle or the TT will dig into the dirt at some point in it's rotation.  A good idea would be to mount the jack on a piece of aluminum of substantial thickness.  Then using 4 screws placed 90* apart,  screw this to the underside of your plywood base.  This way you can use shims between the aluminum plate and the plywood  to level the TT so it rotates without dragging.

2, 3 and 4 pin audio plugs

Hi,

3.5mm (1/8th ") plugs are available in 2, 3 and 4 poles. For a recent project I found it easier to buy a piece of extension cable with molded-on plug and socket. I cut that in half and attached the wires to where they're needed. Voila, pre-wired plug and socket

Especially with the 4-pin versions I'd consider how to replace the socket and plug if they should wear out (without having to rebuild the whole turntable). I'm using a 3D-printed sleeve for my pre-wired socket rather than gluing it in directly - which can be replaced should I need to exchange it for one that has slightly different dimensions.

Have fun and stay healthy

Gallows Style

I want to build a small turntable for my logging scene as well. I'm a bit more interested in making it look very 'remote country side'. I posted some pics here
https://forum.mrhmag.com/post/logging-locos-logging-track-plan-logging-mill-mainline-pickup-12213119

...and in other portions of that subject thread.

Note the manner that the turntable is rotated,..

This is where my logging turntable will be located,..
 

Going to have to read this

BTW. I now recall that this suggestion of using On30 track in the logging are is superior,..
https://forum.mrhmag.com/post/logging-locos-logging-track-plan-logging-mill-mainline-pickup-12213119

Center Hole

I think I recall you had a problem getting your center hole EXACT. I had that problem as well,...documented here,..

https://forum.mrhmag.com/post/building-your-own-turntable-12215516

Progress

Thanks for the interesting comments everyone.  Keep 'em coming!

Here are some more pics of my progress.  I'll skip the gory details and show this pic where the wiring on the turntable is done and I've applied some support girders and wooden cross members.  I used my CAD printout to curve the end timbers to match the pit diameter.

Adding the Phono Plug

Now things started getting serious.  I clipped and bent back the leads on the phono plug (which I got on Amazon).  There was a nub in the bottom center which I couldn't file off because it holds on one of the electrical leads, so I drilled a recess in the center of the table, and left myself some wiggle room to position the plug exactly when I glued it in place.

Phono Plug Continued . . .

I spot glued the plug in place with a dab of 5-minute epoxy.  I had to find a way to hold the plug vertical, and also to center it left and right and front to back.  This was . . . difficult.  I finally struck on a curious solution.  My son gave me some rollers from Lexmark printers (he works on them) to use as flatcar loads.  One of them fit perfectly over the phono plug, so I fit it on, then used four angles to hold the plug vertical.  At the same time, I used a ruler and my caliper to measure the location of the plug from the ends and sides of the table.  WHEW!

Ingenious Solution

to mounting the plug.

Espee over Donner

Phono Plug Continued . . .

When the epoxy set, I built an octagon around the plug with some stripwood.  This is mostly for appearance, and to provide a pool to fill with epoxy.  I found that the plug had tilted slightly during my work, so I used some clamps and my angles to support the plug at 90 degrees, then filled the hex with 5-minute epoxy and let it set overnight.

Result: a firmly affixed pivot for my turntable that carries power for the rails as well.

Phono Jack Base

With the plug done I turned to the phono jack base.  Bob mounted his base in a piece of heavy plastic, so I decided to do the same.  I drew an octagon in CAD, traced it to a scrap from my old bridge, and cut it out with the score-and-snap method.  Then I used a succession of drills to make a hole in the center to mount the jack.  

I plan to paint this concrete color, or cover it with stripwood, during the final detailing.  My plan was to glue this directly to the foam base of the turntable pit so the jack would be at 90 degrees to the base.

Lift Out

And I thought the lift out bridge on my layout was a lot of work to construct.  That was NOTHING compared to your turntable.

Great job, and ingenious solutions devised to overcome construction difficulties!

Keep up the good work!

This is along the lines that

I suggested in an earlier post.  I would not glue this down until I first plugged in the TT and rotated it completely around.  It will be very amazing if your plug turned out to be exactly 90* to the bridge even though by your pictures you put a lot of thought into it.  If you find the TT does not rotate level all the way around you will be forced to shim up a corner of the plastic jack plate before attaching it permanently.  All the best.  Constructing one of these is not as easy as one would expect.

Centering the jack

Hi,

this is a very nice solution to centering the jack and I guess it works nicely now

There is a "standard solution" to the problem of centering the jack in the turntable, however I think it will not apply in your case, as you have a very shallow underside of the turntable (personally I found the "standard solution" very un-intuitive and it took me a while to actually understand it).

The trick is to create a rectilinear hollow in the underside of the turntable. The plug gets attached to a block that fits the hollow (across the turntable) but is shorter than the hollow lengthwise. When the turntable rotates, the block can "wiggle" and compensate for a little bit of misalignment but will rotate with the turntable. (that needs enough space in the underside of the turntable to actually fit the block).

Maybe you can use a similar trick for the socket - have it on a plate or block that has a bit of wiggle, but doesn't rotate, if you need to.

Keep us posted

Have fun and stay healthy

Connecting Drive Shaft to Turntable Bridge

Not as important on small diameter turntables, but still a consideration,...description plus photos,....

In case anyone is needing a 4 conductor jack and plug

Circled back to this thread today.  If you're ever looking for weird stuff, there isn't an electronics problem that an aviation type hasn't solved!

• 4-pole plug and if you need it, a  jack  (I know this stuff is pricey, but ... so is everything else attached to airplanes!)

Now, of course, for all the ideas I mentioned early in the thread, a decoder only needs track power and many of them now have up to 8FX outputs!  So I guess a 2 pole plug will work just fine.

Good Comments

Thanks for the kind comments and also the insightful advice.  Especially the part about the floating block.  I hadn't thought of that, which is amazing because that's exactly how my CMR 135' turntable is built.  It works flawlessly.  Too late for that now; plowing ahead!

Anyway, I'll show in the upcoming posts how I addressed the centering problem.  It didn't work perfectly, but I'm much farther along and I think in the end everything will work as planned.  

Stay tuned!