Here is where we get to the decoder.  A standard 6 pin decoder doesn’t fit, but the very small version. It will be the Doehler & Haass PD05A-4, or Zimo has the MX615.

In November 2022, the first of the Bachmann Quarry Hunslet was finally released, after being first announced in 2018. After a 10 minute test run, I took the model apart to see what’s in there. Let’s have a look.

Length: 47.6 mm

Width: 23.4 mm

Weight: 33 grams

Wheelbase: 13 mm

Wheel diameter: 6.5 mm

Released: November 2022

It’s a very pretty model, which runs just as beautifully. At least analog, I haven’t tested it in DCC.

It comes with some nice additional parts, including, surprisingly, lamps. These slide over the pins at the front and back.

Take apart

During the process, I keep the housing on a piece of foam, to protect it from damage.

Remove the 4 screws indicated.

Image right: Removing these three screws don’t do anything. The front comes loose, but the back can’t be removed. At least, I couldn’t discover how. It seems all stuck.

I’m digging a little deeper in the model out of curiosity. Removing the one screw that holds the board in place, reveals more of the motor. The motor is a 0716D motor, which means a replacement is available from the Tramfabriek. The gears are M0.3.

If you got that far to take the board out, you will have problems refitting it. But not if you start at the worm end, so the wires are on the outside of the black plastic below. Then you can pivot it to close.

Screws holding the motor in place:

4 x M1.2 L3

When refitting the housing, please make sure the pin of the valve gear slides back into the foot plate, indicated with a red arrow. On both sides of the model!

Sound installation

Next I’ll be doing the sound installation. I warn you ahead of this: the running performance without stayalive is pretty poor, so I would advise you only to go ahead of this if you are prepared to install a stayalive.

Used parts:

Zimo MS500 (Easier: MS490)

Available here


Available here

The four wires (wheel contact and motor) are being desoldered from the PCB. We will not need the PCB anymore. The motor will have to be removed, ideally, for the next step.

Tramfabriek 8 x 15 speaker

Available here

Black Ultra Thin Wire

Available here

While we are drilling, we have to take care of the most challenging part. Drilling a hole through the boiler. I’m not an experienced machinist and the metal was really hard, so my solution was to use an 1.0 mm milling bit and after that 1.5 mm to make the hole large enough for the wires. The regulator got drilled out, but it would have to be removed anyway to fit the parts. 

The location of the hole is high up, about 2 mm from the top. You can’t do it close to the footplate, as that is where the gears go. The wires would be able to pass.

Back to the chassis. After the motor has been mounted again, I put masking tape on the motor and the metal edges. This is of course to protect the decoder from shorts.

Desolder all the wires from the Zimo MS500 decoder, except for the stayalive and sound ones. 

You can see I decided to guide the motor and wheel contact wires under the decoder and fit them at the other end of the decoder. I did this while still finding my way around, so I had some extra wire to move the decoder. But you can also cut the wires short and fit them at the front end of the train to the decoder.

Now the 4 wires, 2x stayalive and 2x speaker, are pushed through the hole in the boiler. I’ve replaced the default purple speaker wires with Tramfabriek black Ultra Thin Wire, so they don’t attract attention on the footplate.

I super glue a piece of 0.25 mm black styreen on the 8x15 mm speaker (I tried the 8x12 mm speaker, as seen on the image, but it isn’t powerful enough in the open space. Those are better in enclosed spaces). In my experience, it doesn’t matter at this scale if you put a small resonator box or a thin, flat piece of styrene on a speaker. The sound quality and loudness is the same. When placed in a model, the model itself will give it a louder sound. Also with this model. I did a comparison. 

My (disputed) opinion: Resonator boxes only make a difference when they are remarkably larger, but most of our 009 models are too small to have that space.

I was planning on doing my own sound, and possibly I will, later, but Digitrains has a really nice sound file for it. This is also where you can get the decoders. They don’t offer the STACO1 nor STACO3A with it, at the moment of writing, but Tantalum capacitors. The Tantalum capacitors will only give you a fraction of a second and I’ve seen the Digitrains converted sound model with these stall regularly during the first public display of the model at Warley 2022. So go for the STACO. 

The speaker and supercaps can be hidden with two figures. I still have to sort that out.

Again, you might be tempted to install a sound decoder without power backup, but believe me: don’t. It will be a very frustrating experience.

It is advised to use the Zimo MS490 as you don’t have to do any milling. It is smaller and will fit between the sides of the frame. When using a Zimo MS500 sound decoder, it needs some milling. The decoder is exactly as wide as the top part of the frame and would sit too high for the model to be closed. So 3-4 mm has to be taken off the top. I’ve done 3 mm, but I noticed it could do with another 0.5 mm.

Here I’ve used a Sharpie to mark the top edge. This is the part that I want to take off, on both sides. I did not take a picture of the milling, but I put the milling bit in a bench drill, then pressed the well packed chassis against it. It goes very easily and quickly, so don’t press too hard.

I’ve used blue tac to protect the gears from small pieces of metal. It will go everywhere!

The result after milling.

You can see the rectangular piece is the 0.25 mm styrene on the speaker. I’ve painted the two supercaps black. Later I decided to wrap them in black insulating tape, so they stay close together. In that case you only need to paint the ends. For correct connection of the stayalive and supercaps, check the manual that comes with it.

The Zimo STACO1 stayalive is glued on the speaker with 0.25 mm double sided tape. I don’t know how long the link stays active, but this is the brilliant stuff I use for many things: It is available from different sellers.