Lemke/Hobbytrain Plasser & Theurer Duomatic DCC Pt. 1: Disassembly

The Duomatic itself.

Stop. (Collaborate and listen.) You just bought one of these fancy Lemke ballast tampers, and you are considering converting it to DCC. You can read a little German, maybe, or at least you can work from photos; or you found another guide on the web. It doesn’t look so hard. Don’t believe everything you read.

I had thought so too, but I soon found I had a dead decoder on my hands. The reason became readily apparent: I have identified no less than four locations where the motor can and does short to the rails, which the included directions fail to mention. Before you dive into your install, even if you don’t use my guide, please look carefully at the forthcoming instructions, where I show you how to fully isolate the motor, and avoid many future headaches.

Update: After consulting with TCS, I no longer recommend the TCS Z2 decoder for this installation. Sadly, the TCS M1 is too large for this installation, and so I have selected a Lenz Silver Mini to replace the Z2.

General Notes on the Model

This is not the best-designed model ever. It comes with some detail parts installed, and others not. I’m not sure what the logic is for this. Some of the detail parts, however, are installed because they are structural elements. The buffers and coupler hooks, for example, hold the shell to the internal metal frame.

Even more bizarrely, all elements are friction fit. No clever catches or clasps here. Removal of any particular part requires only to gently pull it straight out. This means, of course, over time that these parts will come loose. A little PVA glue will hold a piece in nicely, while allowing for future removal if necessary.

Finally, the mechanism is not the best ever. The motor uses a spring drive to engage the running gear in each truck, which is noisy and can lead to binding on sharp curves. I’ve found that if the model stalls or stops on a 280mm (11″) radius curve, the motor often can’t generate enough torque to start up again. To add insult to injury, the wipers and associated circuitry are flaky as well, leading to frequent stalls. Do not expect installing a decoder to improve running performance, because it will not.

That said, here’s how I installed a TCS Z2 Lenz Silver Mini into one of these models. I owe a tip of the hat to Blain Bachman, whose translation and instructions provided the basis for my own explorations. My installation process differs from his in a few key places (and a couple of minor places), and I believe that mine is an improvement, in that it is more cautious about ensuring against shorting the motor.

Disassembly

We will be installing the Z2 Silver Mini into the short cab. The decoder will just fit inside the cab. To get to the cab, we must remove the metal frame holding the motor, which sits just behind the short cab. I take the short cab to be the “front”, and the long the “back” for the purposes of these instructions.

Remove both the fake and the real coupling parts

Begin by removing the decorative coupler elements (hook, buffers); remove the Rapido coupler. These pieces serve to hold the front part of the shell in place. Set them aside in a small dish that you are not likely to spill, and has plenty of room to hold more parts (I used the plastic lid to the model case).

Separating the drive shafts requires a little maneuvering with the tweezers

The front-most, main drive-shaft connects to the rear drive-shaft via a rubber sheath. Pull the rubber sheath towards the motor to free the rear drive-shaft. This frees the motor, which is embedded in the frame.

Gently pull the detail pieces away from the shell.

Remove the side detail pieces, which hold the middle part of the shell to the rear of the frame. These parts are quite delicate, so pull them straight away from the shell, without twisting or bending them, to avoid breakage.

Notice the placement of the black wire (top) and brass wire (bottom).

Remove the screws to the plastic retaining plate on bottom, and remove the retaining plate. Note the placement of the thin black wire (top of photo) and brass wire (bottom of photo), because both need to go back just as they are now, and the black wire in particular can be tricky to get back in place.

Go away, pesky ladder.

Remove the ladder to the short cab. This just gets in the way.

The truck likes to explode, but the technique for dismantling it is easy to learn.

Remove the bottom of the truck by gently squeezing the sides and pulling straight up. The truck may explode, but the chances of breaking anything are fairly slim. Notice the delicate wipers in the top half of the truck, still attached to the frame. Removing the bottom of the truck will help in the next few steps. In particular, it makes getting at the four screws that hold the circuit board above the truck in place. Remove those four screws.

The truck removed, and the circuit board replaced. You don't have to replace the circuit board.

Lift the truck and circuit board gently upwards, and carefully slide the truck off. Having removed the bottom half already, you can observe the wipers as you remove the truck. Avoid allowing the wipers to get hung up on anything. They are permanently attached to the truck, and don’t look easy to glue back in place should they come off. Watch the little black wire soldered to the circuit board. Incidentally, there is no need to desolder either end of the black wire.

The motor simply lifts straight out of the frame.

Remove the motor by lifting it straight out. We need to remove the motor to get at the inside of the frame later on in the install. You can clearly see the spring-drive in this photo.

Illustration of the “toothpick technique”.

Remove metal frame from shell. A toothpick will help ease the frame out: Wedge the toothpick into one of the large holes at the front of the frame, and use it to gently rock the frame side-to-side, while levering it upwards.

Duomatic in parts

And there it is, your tamper disassembled just enough for the decoder installation to move forward.

(Continued in Pt. 2)