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135 foot Turntable Project

I originally scratch built a 120' turntable using the Bakersfield Turntable as the prototype in 1991.  The  October 1989  issue of Model Railroader Magazine had the plans for building the bridge superstructure.   The article was titled "The Santa Fe's 120 foot through truss turntable".  It served me well but as with all my scratch built mechanical devices it had some minor problems.  

               This is my scratch built 120' Turntable
The bridge frame is made from K&S .25" x .032" brass channel.  I made the rotating shaft from multiple sizes of K&S brass tubing ending up with a 5/16" shaft.  I used gears from a used Federal Signal rotating beacon off a retired Fire Truck and a 24 volt gear-motor from an Air Force surplus servo package that I found in a bin going to the trash in 1963.  I will miss seeing it on my layout but it was time to go.
I had indexing problems from day one from gear slop and had to do the final positioning by five finger hand.


To resolve the problems I purchased a CMR 135' Turntable Kit in August of 2000 and that is the reason for this overhaul.  I started the assembly but I had to set the unfinished turntable on the shelf because of my heavy work load.  I retired in December 2007 and now I'm going to finish my project and install the 135' turntable with my remodeled and detailed Korber roundhouse.


This is a view of my CMR Turntable bridge where the tracks meet from the roundhouse.



This is the CMR 135' Turntable ready to accept my scratch built Through Truss superstructure. The plywood base has been cut to accept the CMR pit. All the track has been cut to mate with the bridge rails. The CMR kit was intended to have a hand rail on each side of the bridge. At this point of construction all the mechanical parts have been checked out for proper operation and alignment.  

I can't say enough about the CMR Turntable, it is by far the finest kit that I have had the pleasure of assembling.  It is a laser cut Acrylic kit and every part is a precision fit.  The .45 RPM Dayton Gearmotor works fantastic (that would have taken care of my gear slop on my old turntable).  The bridge turns very smoothly at a very realistic speed. It stops on a dime when the gearmotor is wired for dynamic breaking.


Attaching the turntable pit to the plywood is next.  After that is complete then I will add some scenery then it will be ready to install on my layout.

It's coming along


The turntable and track are attached to the plywood.  I used a thin mix of Elmer's Glue-All to secure the ballast and gravel.  The next step is to clean up the track and apply some rust weathering.  Bakersfield gets very hot in the summer so I'm going to add some shade trees for the yard workers to have a place to eat lunch and have coffee breaks.


This view shows the brass power pole and the brass wires going to the power tower on the bridge. They deliver the power to the negative rail on the bridge.



This is the completed turntable and pit.


All of the closeup pictures are cropped from the original 4000 x 3000 pixel shots with my new Canon A1100 IS camera.  It really is a good camera.


This is my first attempt at weathering my turntable pit.  I used a very thin mix of Folk Art Rust & Black Acrylic paint and let it run.  The rails are painted with a Brown Rail Floquil paint pen.  That really makes a difference in the looks of the track.  The paint pens are very easy to use but is time consuming and takes two coats to look real.  It takes the toy look out of the track.


There are five 1½ volt lamps on the bridge, one inside the control shack and one above the door on the outside.  There is a lamp pole on each end of the walkway and one hanging under the platform on the power tower above the bridge.


This is the top of the bridge power tower


The connection on the top of the tower works. It has a 1/16" brass tube that the power hub center pin plugs into, a wire soldered to the bottom of the brass tube runs down to the bridge through the 1/4" tower girder. This powers the negative rail on the bridge. The power pole .015" wire from the pole to the bar/hub on top of the tower are brass. The pit rail is connected to the positive rail. The pit rail to ball bearing wheel connection is very intermittent when used by it's self.  To prevent the intermittent power problem I paralleled the pit rail and the center shaft.


Here the men on the power bridge are preforming preventive maintenance to the electrical slip-rings where the power connects to the bridge.


The process is slow but it's a lot of fun adding the scenery and detailing.


The turntable maintenance crew is at work.

This is a drawing of my proposed idea to provide additional power sources to my turntable bridge for lighting and the indexing system.


Building it was much harder and time consuming than my drawing made it look like.  When I drew it up it looked like it would be a very easy project.  Drilling all the holes in the washers took 9 drill bits.  The soft copper washers would grab the small bits and break them.  Soldering them together was another unexpected problem keeping all the holes inline.

After completing the assembly I used a bolt to hold them in my drill press to rotate the copper rings and used a file to give the "MEL" Slip-Rings a good smooth contact for the brushes.

The project turned out perfect and works great. 


Slip-ring assembly


This is a closeup of the four contact slip-ring assembly to provide power to my turntable bridge lights and the photocell for positioning. The bridge track power is through the brass center shaft/pit rail & the power tower.

The brush holder is made from a block of nylon and uses LBG G gauge wheel brushes for power pickup, LGB #63120.  I drilled 4 holes in the nylon block on 1/4" centers with a # 14 drill bit to hold the brushes.  The slip-ring spacing is 1/4" center to center.

The all thread in the foreground is 10-32, the brass center shaft is 1/4" and the slip-ring assembly is 3/4" in diameter.

I found a good source for Acrylic/plastic material at a local plastic fabrication shop, their leftovers are much cheaper than hobby suppliers and they have a lot more to pick from.

This is a front view of my home brew slip-ring assembly.


I built the slip-ring assembly to give more electrical circuits to the bridge.  The long all thread is needed because of the increased length of the shaft from the addition of the slip-rings.  The nylon brush holder is mounted on the all thread so that it is easy to adjust the carbon brushes to match up to the slip-rings.  The longer mounting bolts doesn't effect the motor drive system as there is virtually no drag from the bridge. The gear motor is a Dayton 2L003 12 DC .45 RPM.
This is the rear view of the slip-ring assembly.


Left to right on the connector block are turntable motor power, indexing photocell, lighting power and track power. 


This is a short piece of track used for engine over run when coming from the yard.


As you can see I have a lot of scenery finishing work ahead of me.  I bought a Top Side Creeper to help me get 4 feet closer to the center of my layout, unfortunately it falls 18" short of the center where I need to do a lot of work.  It's climbing time again.


That looks so good!  I've been wanting a good operating turntable for over 40 years.  This one works great too.