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Clinic - Building An Economic Turntable
Step 1. Size Matters
Measure your longest locomotive or determine the length of the longest locomotive you intend to operate in the future. ( I know this is a somewhat difficult process for some)
 
Step 2. Site Selection
Determine the location for your turntable. Be sure there are no obstructions (girders etc) under the area you have selected. If you have obstructions, now is the time to relocate them.
 
Step 3. Tool Selection
Refer to the Tools list to determine some tools which I found to be handy.
 
 Step 4. Prepare the site
Using a carpenter’s square draw a SQUARE box at least 4 inches longer than the planned length of the turntable bridge on the Homasote or plywood surface. Note: 1/2 inch Homasote plus 1/2” or 3/4” plywood makes a visually attractive depth for the turntable pit floor. Draw corner to corner lines which will cross at the EXACT center of the square (see figure 1.)
Using a compass, draw a circle, centered at the X above (Figure 1.) Drill a small hole (1/16 inch or smaller) through the roadbed and plywood at each corner and the center of the square as indicated by the arrows. See figure 2. These will serve as guides to help you locate the position of the turntable when you are under the bench work.
 
Step 5. Excavation and Construction
Before you break out the saw, cut a square of 1/4” plywood to become the pit floor. It should be the same size as the square in Figure 1. While under the bench work and using the 4 guide holes (Figure 2) drill 4 mounting holes to mount the pit floor under the future site of the opening. Attach the floor to the plywood sub-roadbed. Label one corner of the pit floor and the sub-roadbed with an X. See figure 3.
This will help you when it is time to center the turntable in the opening. Remove the pit floor. I know, you just installed it but the reason will become clear very soon.

After the pit floor has been removed, use a saber saw to cut out the square, NOT the circle. This will allow you to do the work at your workbench instead of under the layout.

While you may be able to cut a clean vertical circle, it may be worth the expense to have a cabinet shop cut the circle for you so you will be sure to have a clean vertical pit wall. Sometimes a jig saw blade will flex producing a pit wall that slants and is not at a 90 degree angle to the sub-roadbed which will cause you problems later.

After the hole is cut, temporarily re-attach the pit floor and draw around the opening where the pit wall meets the floor. Measure the diameter of the end of the Plastic (CPVC) plumbing pipe then drill a hole (using the center hole in Figure 3) the to allow the CPVC pipe to pass through the pit floor. The Atlas turntable has a screw in the exact center of it’s floor. Center your compass on this screw and draw a circle on the floor the same size as the end of the CPVC collar. Cut a small notch approximately 1/8” square in the wall of the CPVC collar at one end. Measure and cut 2 pieces of #20 wire 6” long. These wires will pass through the notch and extend up through the collar and CPVC pipe and through the Bridge floor.

Leave the wires at the 6 inch length for now as it will make assembly MUCH easier. Solder 1 wire to each rail in the Atlas Turntable floor, place the wire through the notch and glue the collar to the floor of the Atlas Turntable making sure it sits centered in the small circle you drew with the compass. Pass the wires through a 3” length of CPVC pipe which will be used to connect the Atlas Turntable to the new Turntable Bridge. Select the bridge of your choice for the new turntable. If a 9” table will meet your needs, an Atlas Through Girder bridge turned upside may work well for you. If you are making a table larger than 9” build the bridge from plastic, wood etc. If you are using an Atlas Through Girder bridge, glue another PCV collar to the center of what would normally be the top of the bridge floor (where Atlas puts the rails and guard rails.) The real bottom of the bridge has a casting mark at the center of the bridge. Drill a VERY small hole through this mark to help you center the CPVC collar.

When the glue has dried, re-attach the pit floor, test fit the CPVC into the collar on the Atlas turntable, pass the CPVC through the hole in the pit floor and test fit the bridge onto the CPVC pipe. At this point your bridge will be too high and that’s OK. Measure the distance from the bridge floor to the surface of the sub-roadbed. Record this measurement and make 4 spacers of the same dimension from scrap wood. Turn the entire assembly upside down on the workbench and glue the spacers between the turntable and the plywood sub-roadbed so you may attach the turntable to the spacers using the mounting holes provided in the turntable.

Attach the turntable motor to the turntable then attach the turntable to the spacers using wood screws. Hint: the longer the CPVC pipe, the more room you have to work on the motor for belt replacement etc after the turntable has been installed. You may wish to make the pipe 4” instead of 3”. Before you glue the CPVC pipe to the bridge and turntable floor’s CPVC collar, remove the bridge and apply the surface of your choice to the pit wall. I like H&R’s styrene sheet called “Pebblestone” I cut pieces tall enough the cover the wall and try to make sure the joints are placed where they are the most hidden from view. I paint it all over with raw umber acrylic paint then paint some of the “stones” with Burnt Sienna. This will produce a strong color contrast that will be toned down by applying a wash of acrylic gray which is gently wiped with a piece of paper towel. The gray will simulate mortar and tone down the color contrast. You may wish to install a ring of rail at the base of the wall to simulate the rail that supports the end of the bridge. I used 2 lengths of square styrene again hiding the joint from view and glued them to the pit floor at the base of the wall. You may put short pieces of railroad tie on the styrene to mount the rail ( I used a length of small styrene painted a rusty color to “simulate” the rail. From any distance beyond a few inches your brain tells you it is a rail as that is what you expect to see. You may need to make some minor adjustments to the ends of the bridge to clear the new pit-rail ring. Test fit the entire assembly one last time and connect a power pack to the turntable motor. Make sure the bridge turns freely within the pit. Paint the pit floor gray and stain it with washes of black to simulate grease or apply white glue to the floor and sprinkle some dirt ( I used some from Colorado) to simulate a dirt floor..

Check again to make sure the new surface on the pit floor does not inhibit the movement of the bridge. If everything is working correctly remove the bridge and glue the CPVC into the collars after passing the wires through 2 small holes drilled beside the rails on your bridge

This is why I suggested 6” wires. It makes the bridge placement MUCH easier.

When the glue has dried, Track Alignment - It is virtually impossible to be 100% sure the track is straight, so here is an alignment tip. Spin the table until the bridge is in line with the approach track, glue ONE end of the track to the bridge floor. Spin the table 1/2 turn and align the track to the approach track. Now you can install the tracks to the engine house and they will be in alignment with the rails on the bridge floor. Trim the wires and solder to the outside of the rails. Apply the railings of your choice to the deck of the bridge (you don’t want your crew falling off the bridge into the pit.)

Connect your power supply to the track power terminals on the Atlas Turntable and test to be sure the polarity matches the track approaching the turntable. If it does not match, simply reverse the wires at the turntable connection screws. I purposely left out the part about painting and applying decals (if desired) to the turntable bridge. You may finish the bridge in any manner of your choice. I applied a scribed siding floor and painted the sides of my bridge with Floquil Old Silver, then stained it with a wash of India Ink mixed in rubbing alcohol. To suggest age I applied some subtle rust streaks using chalk pastels.

Your new turntable will have automatic indexing and polarity switching supplied by the Atlas turntable which has been hidden by your cosmetic enhancements. When someone asks you “What kind of turntable is that?’ Get ready for a look of shock when you reply “Atlas.”

Now, take your favorite Engines out for a “Spin”.

 
Tools -  Jig saw or scroll saw, carpenter’s square, electric drill, soldering iron, white glue, super glue, screws, screw drivers, pencils, inexpensive artist’s compass, Styrene strips, H&R styrene sheet, Atlas Turntable and motor, Atlas Bridge (if desired) 2 CPVC connection collars, 3 to 4 inches of CPVC pipe.

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