How to make a model railroad turntable drive mechanism.
This takes you through the process of building the drive mechanism .
This image shows the assembled drive unit.
This mechanism uses a geared down high torque 12 v DC motor. Control indexing of that motor as you wish. We, however use an indexing control circuit that you review at DIY Turntable
Turntable Drive Mechanism Materials Required
- Motor
- Gears – Worm Gear And Drive Gear
- Worm Gear Axle
- Ply for top and bottom mounting plates
- Threaded rods with nuts.
- Slip ring
- Tube as a “drive rod”
- Bearing
- Shrink Tube
Get most of these parts in a package here. KKKKK
Procedure
Prepare your top and bottom mounting plates. Cut two pieces of ply 10 by 16 cm.
Drill a hole in one plate 22 cm in diameter. The bearing is designed for a press fit and that is not the best for the ply. So carefully sand the diameter a minuscule larger. I use a Dremel cylindrical sanding tip. A rat-tail fie will work fine. Add some glue to fill the gaps and hold it in place.
In the other plate drill a 22 mm hole.
Insert your slip ring in the bottom plate. Then drill holes to fasten the slip ring to the bottom plate.
The drive rod sits on top of the rotating protrusion on the slip ring. Shrink tube covering the joint makes a simple but strong bond.
Before you make the joint, cut the tube so that you have sufficient room to connect to the wire leads.
It is time to cut the threaded rod to length.
Holes for the rod must be drilled in the top and bottom plates. And they have to be drilled so that the drive rod is perpendicular to the bottom plate when drive rod is inserted into the bearing.
I do this by clamping the plates together and checking alignment with a square as I rotate the rod. The plates are moved until the rod stays vertical.
Drill the holes and put the rod in place.
If after drilling, things are not perfect, enlarge the holes in the top plate and move it until things are perfect.
Adding The Drive Gear
We need a gear with a center hole equal in diameter to the diameter of the drive rod.
Instead of buying an expensive custom made gear, use a step drill to open the hole in a cheap plastic gear. The image to the left shows before and after.
Now we undo all the shaft alignment. Remove the top plate and slide the gear over the drive rod.
Replace the top plated and go through the alignment procedure again.
Adding The Motor
First we add the worm gear to the worm gear axle.
The axle will be connected to the motor shaft with shrink tube. The shrink tube acts somewhat like a universal.
The motor will be placed at a distance from the drive rod. So the axle will have to be supported by a bearing of some sort.
I bend some thin acrylic sheet to make the bearings. How to do that is here. MMMMM
Put the drive train in place.
Some motors vibrate like all heck. So I mount them in sponge.
You are ready to go.
Indexing The Turntable
Now it is a matter of controlling the motor so that it stops at the correct track.
Here is the indexing system that we use. Read about it here.
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