Hornby's 2020 Large Prairie model is a very welcome addition, and there are numerous options when converting to DCC sound,
ranging from very simple, to as involved as you like! We have 3 different approaches here so you can pick one according to
your skill level and inclination...
Kit: MX648R; IceCube18X13X07-1W
The Ice18X13X07 speaker sits underneath the bunker without any modification. The only thing you'll need to do is lengthen the
speaker wires a little.
Just to prevent any wires accidentally fouling the motor, we put a thin Plasticard platform above it - probably not needed, but
better safe than sorry. The MX648R slots easily into the metal 'wings' provided under the chimney, with the 8pin plug being
All done and ready to put the body back on - simples!
Kit: MX648R; Rail Exclusive Baby Boomer 26X20X08-1W; LifeLink+6800uF SuperCap for stay-alive
The basic installation is simple with the decoder mounted in the slot at the front of the chassis and the speaker in the coal
bunker. This requires running wires over the motor all the way back to the coal bunker, but there is no room for a large stay
alive super capacitor.
I decided that I could place all the components into the coal bunker but the inside had to be removed and the coal moulding
replaced about 2mm lower to allow real coal to be used.
The grey GROUND wire needed to be soldered directly to the decoder (a new wire). The blue wire (POSITIVE) was then connected to
the capacitor to the point on the 8pin plug where the blue wire sits (alternatively we could have simply de-soldered the blue
wire from the 8pin plug as there is no lighting in this model). The super capacitor is wired up via a YouChoos LifeLink, which
is insulated, then mounted on the side of the capacitor and taped up.
The wires from the decoder are shortened and the unused wires wrapped up and held out of the way with insulation tape.
The wires from the 8 pin plug is fed down through a channel in the chassis and taped into place.
First the super capacitor is inserted with the LifeLink on top.
Next the speaker is inserted, followed by the decoder and the wires are tucked in while the chassis is inserted into the body.
I found that these CV changes worked well with this model:
- CV5 - 160 - top speed
- CV6 - 1 - Linier control
- 33 - fedback
- CV266 - 85 - sound volume
- CV267 - 32 - 4 chuffs per revolution of the driving wheels
Example 2 images and words courtesy of Roger Keen, Keen Systems
Kit: MX645R (hard wired); Lurve9 2W speaker; LifeLink+17000uF SuperCap; Firebox Glow
Of course, in true YouChoos style, we wanted to push the limits of kit in this model, and this is what we came up with...
Remove the metal decoder-holder weight so we can modify it, and remove all the electric gubbins, so a decoder can be hard-wired
directly to pickups and motor.
The 'wings' of the metal weight are ground down, which creates a large long space under the chimney where we will put an even
Here is the chassis all modified and stripped down ready for our kit...
The screw mounts where the 8pin DCC socket was are chopped shorter, but not flush, as we need a bit of a noggin near the
flywheel to ensure that our kit doesn't rest on the flywheel. A quick check with our MX645 to make sure there is some
clearance (the MX645 has had its' sleeve removed and re-covered with Kapton tape to make it thinner overall).
The 17000uF SuperCap is covered in Kapton tape (as the case of the cap is the GROUND). This sits squarely on the bunker
While we are at it, we add a firebox glow SMD LED. We've gone with a Nano one, which sits flush into a drilled hole - the nano
is just as bright as the standard SMD LED, so it works really well in the cab.
A thin Plasticard platform protects the motor and gives us a neat area to connect the wires, including the protective resistor
for the firebox LED.
With the milled chassis weight protected with Kapton tape, we can simply fix a Lurve9 speaker (2W 4 ohm dual SugarCube
component) under the chimney. Note that this speaker requries the larger MX645 decoder - the smaller MX648 can only drive 8ohm
Kit: MX648R retaining 8pin plug; Rail Exclusives BabyBoomer 26x20x08-1W; LifeLink with 17000uF SuperCap
A variant of some of the above approaches, which is also very simple and neat. Requires opening up the bunker, and extending
the speaker wires, but otherwise quite straight-forward.