Kit: Zimo MX648 with SugarCube9
Hattons first lone venture into loco manufacture has resulted in this pretty little SECR Wainwright P Class, in a wide variety
of liveries. Looks like a fabulous effort, but let's find out how easy it is to add DCC Sound...
4 screws to remove chassis from body... drops out nice and simply, revealing a neat mechanism with a 6pin DCC socket. OK for
standard DCC, but not enough length behind the socket for a direct plug-in MX649N sound decoder - other options needed...
The instruction leaflet supplied with the model suggests removing a side weight to make space for a 'SugarCube', and to file up
some space in the cab to put a sound decoder, and helpfully suggests that you shouldn't attempt this unless you know what
you're doing! Fair comment, and not surprising given the tiny dimensions. It reminds me of Hornby's Terrier in terms of size,
but the design internally is far better, and there are options.
A quick measuring up of the removable weight tells me that it would require a custom enclousre for a SugarCube speaker, or
going for something much smaller like a Minnow. I'm not keen on that and it is clear that with minimal chassis modifications we
can get an MX648 sound decoder into that space, and opt for a full size SugarCube9 speaker on the cab floor. This approach
certainly works for the "Bluebell" model, because the cab doors are closed and the speaker will be hidden from view - some of
the other variants of the 'P' have open/no doors, so isn't quite such a neat approach, but I think I'd still go for it.
To get access to the cab space, we remove 4 more screws and carefully pull the body top off the frame, being especially careful
to keep the hand rails vertical and lined up for later reassembly.
With the motor popped out and mechanism covered with masking tape (not shown), we take a grinding disc and carefully Dremmel
the side with the removable weight down flat. This creates more than enough space for the MX648.
Next we prepare the decode, removing the protective sleeve so we can get rid of the surplus wires (we aren't adding any lights
to this model, so remove blue, white, yellow, green, and brown. Then re-cover with Kapton tape.
The model's PCB is removed and we solder the decoder's grey and orange motor wires directly to the motor terminals, and join
the red and black decoder wires to the pickup wires. Secure the decoder onto the side of the motor with some thin double-sided
tape, and use tiny blobs of Black Tack to keep the wires tucked in place.
Time to test the motor control, and that it goes in the right direction - if wrong, then reverse the grey and orange wires.
Remember to insulate the speaker wires while you do this test - you don't want to be shorting those anywhere or with each
Ok, so next we will position the full-sized SugarCube9 speaker in the cab and route the speaker wires. We file a little of the
bulk-head to make a channel for the speaker wires. I did this in the dead centre on this model, but in retrospect it would have
been better to make the groove to one side, as it would better avoid the motor worm when reassembling. Even so, the wires can
be placed away from the worm as they will sit lower once re-inserted.
A spot of SuperGlue on the cab floor. Paint all visible parts of the speaker black, and reattach the body onto the frame, with
the speaker wires located in the groove we just created. The trickiest bit of this whole install is getting the hand rails to
go back in their respective eyelets, so take your time getting this right!
Connect up the speaker wires to the purple wires of the decoder.
Tuck everything carefully and secure wires in place with small blobs of Black Tack, then re-assemble and test.
In conclusion, the Hattons SECR P Class is not nearly so hard to install sound into, with a decent speaker, as I expected.
Running qualities are OK, although this is a very small model and does seem to stall a bit. The method we've used to fit the
speaker and decoder means that there is ample room for the kit, so no risk of crushing anything, and I believe it should be
possible to add a stay-alive kit using the Zimo SPEIKOMP components and perhaps 2 or 3 Tantalums. That's an upgrade for another
day though - for now, we have a working DCC Sound 'P' Class, and how pretty is that!?!