Scratch-built Turntable - Diamond Scale Motor Kit
02/15/2006
This page covers the assembly of the Diamond Scale Products "Turntable Motor Kit" (part number MK-111). This kit, when assembled, provides the means by which a turntable is rotated. Power is supplied to the motor, and the universal joint, which eventually connects to the metal rod installed under the bridge of the turntable, rotates at a slower rate than the motor.

The first photo shows the various bags of parts removed from the box. As was the case with their turntable bridge instructions, the instructions for assembling this motor kit were complicated and unclear. It uses such terminology as "oil-filled bearings", "pinion gear", and "bull gear". Unless you are a mechanical engineer, these terms mean nothing. The two drawings and the two photos included were only of little use (actually, they confused me more than helped). I hope that these photos will be of help to others who have ordered this kit and need a little extra help. Or, if you are considering purchasing one of these kits, to be aware of what you are getting yourself into.
Scratch-built Turntable
The first step is to remove the two case halves from their sprue. I used a knife to carefully cut them loose, and then filed down the remaining bit of plastic.
Scratch-built Turntable
There are four gears included in the small parts bag. There is one large one, one small one, and two medium-sized ones. There are also three round metal rods (bearings) included. Two medium-sized ones and one long one. The two medium-sized ones need to be inserted in the hole of the two medium-sized gears. Eventually these two bearings will "ride" in two of the holes in the plastic case. To get the gears to sit in the correct spot on the metal bearings, use the case as a guide to install the gears. I placed the metal bearing in one of the matching holes in the case, and placed the case on my workbench. Then I pressed the medium-sized gear onto the metal bearing until the gear hit the case. This is an extremely tight fit (which is what is required), so some amount of force is necessary. At this point it doesn't matter which case half you use. This is shown in the next photo.
Scratch-built Turntable
Do something similar with the other medium-sized gear and matching metal bearing. This second gear doesn't need to go down the metal bearing as much, because it needs to mesh with the small gear molded onto the first medium-sized gear that was just installed. Leave just a small clearing between the two medium-sized gears so that they do not rub against each other. Note that the case is used to determine the relative position of the gears on their bearing rods. Final installation of the gears will be done after the motor has been mounted.
Scratch-built Turntable
The large plastic gear slides onto the long metal bearing. One end of the bearing needs to stick out about 1/8. This is shown in the next photo.
Scratch-built Turntable
The motor is mounted to the outside of one of the case halves. One of the case halves has two small holes in it. There are matching holes in the "output" end of the motor. Two small machine screws are supplied to install the motor to the case (machine screws have a tight thread cast on them). The other screws in the kit are used to connect the case halves.
Scratch-built Turntable
The machine screws are installed from the inside of the case half. You will need a small Philips or flat head screwdriver to install these.
Scratch-built Turntable
The smallest of the four plastic gears needs to be mounted onto the shaft of the motor. Note that one end of the plastic gear has a flat bottom molded into it. This end of the gear needs to be on the motor's shaft closest to the motor. The open ended side of the gear needs to be up. This is shown in the next photo. Be sure not to press the gear down so far that it rubs on the plastic case. Leave a little space.
Scratch-built Turntable
Using the case half that has the motor installed, start inserting the gears. First install the medium-sized gear that sits closest to the case (the first one we put together above). This gear will mesh with the small gear mounted to the motor shaft.
Scratch-built Turntable
Then install the second medium-sized gear.
Scratch-built Turntable
Before inserting the large gear into the case, we first need to insert one of the brass rings into the appropriate hole in the case.
Scratch-built Turntable
Insert the large gear into the metal ring, with the long end of the shaft sticking out of the case on the motor's side. The photo below shows the gear being inserted. Push it all the way down until it reaches the other gears.
Scratch-built Turntable
The two case halves can now be squeezed together. Move the long shaft by hand to see if the gears are movable. If not, see where the binding occurs and fix it. Mine seemed to work right away.
Scratch-built Turntable
The universal joint is being attached to the long metal bearing in the next photo. The supplied Allen wrench is used to secure the universal joint. One end of the universal joint has a small hole and the other has a larger hole. The end with the small hole is installed onto the metal bearing. The other end will eventually be installed onto the metal rod that is mounted to the turntable (sorry about the picture).
Scratch-built Turntable
The final assembly step is to install four screws to attach the case halves to each other. Two of the screws also need to incorporate the two plastic hinges. These hinges will be used to attach the motor assembly to the framework of the layout in the future. The plastic hinge on the left didn't seem to fit well. I will trim a piece of the corner off so that it fits around the motor. Also, the holes in the hinges are too small for the screws, so I had to force the screws through them. Final alignment of the hinges will depend on how the motor assembly will be attached to the bottom of the turntable.
Scratch-built Turntable
The last step was to actually supply power to the motor and see if the universal joint moves. I attached some test leads to a power pack and connected them to the leads on the motor. Polarity doesn't matter, but what is important is to make sure the voltage sent to the motor does not exceed 10 volts. Having built the kit once, it now seems fairly straight-forward to assemble it. However, when you first read the instructions it seems like a very daunting and confusing project. I hope this page and the photos will help you assemble your kit. It took me about an hour to assemble it, and I found it to be an enjoyable project. The motor and gearing is somewhat noisy, but the instructions say that things will get better the more the unit is used. I also found that with a small amount of voltage the unit turned rather quickly. The instruction sheet states to insert a potentiometer (a variable resistor) to help slow down the motor. That is all final tweaking that can be done when the whole turntable is installed.
Scratch-built Turntable