After lots of exciting announcements, the DC version of this model was finally delivered. It's nothing like I have ever seen. While the tender is of conventional design (almost identical to the FEF3 tender - they even share some parts), the loco's design is unique. The Big Boy loco is also a fairly complex puzzle to disassemble. But no glue joints to worry about - everything snaps or screws together.
Kato is known to sometimes over-engineer their models, but this one has taken the over-engineering to the next level, as if the Kato designers were trying to outdo themselves. This type of design unfortunately makes it not very DCC-friendly. But then again, because there are two separate articulating self-contained engines, with a headlight mounted on the front engine, there really was no good way to make this loco more DCC-friendly Some interesting hard-wiring will be required inside of the loco.
KatoBigBoyChassis01.JPGHere is the "naked" mechanism. I should also mention that the this models the multi-part plastic shell is also used as structural components. And with precise Kato tolerances, everything fits perfectly - basically no unused empty spaces anywhere. It seemed that it would be difficult to neatly route the wires.
KatoBigBoyBoilerChassis01.JPGThis is that unusual (what I'll call) boiler frame. It's a split frame which electrically connects both engines. The electrically-live tender drawbar connects to the back of the rear engine's split frame, and since the boiler frame connects both engines electrically, 3 drivers per engine (snce one each has a traction tire) will supply power to the tender.
KatoBigBoyRearEngine02.JPGEach engine is a fully self-contained power unit, and also utilizes a blackened split-frame. All the drivers (except for the 3rd which has a traction tire) pick up power, and the coreless motor is electrically connected to the engine's frame. Visible is the wire from the back of the motor with a metal contact which is inserted in the frame. You can place each engine on the track and run it as if it was a powered locomotive. The pivot post for the engine is the gray plastic post with the phosphor bronze rods on the sides. Those rods contact springy metal pickup wipers installed in the boiler frame (those wipers were removed in the photos so far). That's how both split frame engines electrically connects to the boiler frame. Also, both engines swivel at the pivot post. This design makes the DCC conversion a bit challenging.
I should also mention that unlike in the past were split-frame designs utilized either plastic spacers, screws, or some other type of plastic clips to hold the halves together (so the frames could be easily taken apart and reassembled), in this model Kato uses press-fit plastic spacers. I suspect that disassembling those split frames would loosen those spacers, which would not be a good thing. I did not attempt to disassemble them (there shouldn't be any reason to do that anyway).
Next, upon further examination, I believe that Kato did make allowances for DCC conversion. This was not obvious at first. Still, adding the wiring will be a bit tricky. Since the boiler's plastic shell fits tightly against the boiler metal frame, it appears that Kato molded wire-routing channels into the top of the frame.
KatoBigBoyChassisChannelsTop.jpgThis photo shows the channels in the frame (the bottom copy of the photo shows them highlighted in green). They appear to be purposfully made (not just some design artifacts). The narrow diagonal channel appears to be for routing the headlight wire (more info in the next photo).
KatoBigBoyChassisChannelsSide.jpgSide view of the chassis. The channel here is again highlighted in green on the bottom photo. The narrow diagonal channel on the boiler frame aligns with a channel molded into the front engine's frame. That channel seems to be designed to hold the wire coming from the headlight mounted at the very front of the frame. Will cover this in more details later.
KatoBigBoyWireClips02.jpgThe motor mounts on each engine also appear to have some features (channels and clips) molded in for routing motor wires out of the way when converting to DCC. Clips are molded in each motor mount (different for each engine, since each has a different pivot point) allowing routing the wires up through the top of the boiler chassis, into those wire channels on the top.
KatoBigBoyBoilerChassisSlots01.JPGI also noticed another interesting feature in the boiler frame. At the rear there are two slots, as if Kato intended them to be for holding a small PC board.
KatoBigBoyBoilerChassisSlots02.JPGI test-fit a small cardboard rectangle, and it makes sense that those slots are there for a reason. I'm planning on etching my own PC board to be a junction for the loco's internal motor and headlight wires, and the wires in the drawbar connecting to the tender. If I have room, I will also mount a connector on that board to allow for the tender to be easily disconnected if needed.
It would be interesting to see how Kato handles their factory installs of Tsunami decoders, but I'm not about to buy one of those. Hopefully someone out there will have the balls to take one of those apart to see how Kato did it.
That's it for now. I will continue appending info to this post as I progress with the DCC install. Next up will be the DCC conversion for the headlight.
