Kato Big Boy decoder install (peteski's version)

[peteski]

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.JPG

Here 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.JPG

This 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.JPG

Each 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.jpg

This 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.jpg

Side 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.jpg

The 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.JPG

I 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.JPG

I 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.

[peteski]

Place holder for additional install info.

[MK]

Wow!  Those crazy Kato engineers and designers!   

I'll see if I can find one(s) at Kato's Hobby Center in Toyko to compliment them when I visit!

[woodone]

Peteski, thanks for all these photos. Even though I have my Big Boy under an upgrade to DCC W/sound and torn apart I think these photos will help others under take the challenge of converting one.
Mine is still in pieces has I had some installs to do and have not got them off the work bench yet.

[Tjack757]

Awesome!
Standing by for more info.........

[Dwight in Toronto]

Peter - as always, top notch analysis/prognosis, easy-to-understand written descriptions, and the best closeup pics ever!  Even though I have not yet decided if I want one of these, your ‘autopsy’ makes for interesting study.

Regarding those traction tires on the 3rd driver - looks like Kato put them on the wheel that has the most connecting rods attached to it.  One might think that they could have put them on, say, that 4th driver for easier TT replacement (but I have to surmise that there has to be some sort of sound engineering logic behind their design). 

There have been several comments regarding the difficulty of configuring the headlight for dcc control.  I appreciate why folks would want this, and I accept the fortitude of those who relish the challenge of making it work.  But would it be so bad to just leave it ‘always on’?  I mean, IRL the lamp was probably always on anyways, at least when the loco was in motion, no?  And it’s not as bad as the GS4 factory default, where the upper headlight was perpetually blinking in a rather sorry-looking Mars lamp simulation.  Just say’in!

[peteski]

Peter - as always, top notch analysis/prognosis, easy-to-understand written descriptions, and the best closeup pics ever!  Even though I have not yet decided if I want one of these, your ‘autopsy’ makes for interesting study.

Regarding those traction tires on the 3rd driver - looks like Kato put them on the wheel that has the most connecting rods attached to it.  One might think that they could have put them on, say, that 4th driver for easier TT replacement (but I have to surmise that there has to be some sort of sound engineering logic behind their design). 

There have been several comments regarding the difficulty of configuring the headlight for dcc control.  I appreciate why folks would want this, and I accept the fortitude of those who relish the challenge of making it work.  But would it be so bad to just leave it ‘always on’?  I mean, IRL the lamp was probably always on anyways, at least when the loco was in motion, no?

Thanks Dwight!

I'm planning on posing a full mechanical review of this engine, but all the projects I have on my workbench (off bench), I will likely not do that soon. I wish Kato would slow down their model releases - I can't keep up.  I abandoned the Amtrak Charger DCC install, to work on the Big Boy.

The reason for the traction tire on the third driver is carefully selected by Kato.  That is the only driver driven by a gear (all others are powered by the siderods. That is the optimal design.  Also most of the weight is being carried by that driver (again increasing its adhesion to the rail).  But yes, it will be more difficult to replace than if it was on the 4th driver.  But with this design, it will pulls like a mad team of oxes!

The design of each engine is similar to what was done on GS4.  Most weight is over the 3rd driver, and rest is on the first driver.  Driver 2 and 4 are loosely suspended, with some light pressure exerted on the, by soft springs. You can actually push them up with you finger. That enables them to pick up power from the rails, but they do not carry any significant mass.  So basically the 8-wheel engine in reality acts as it was a 4-wheel engine, with most of its weight over the TT driver.  Very clever.

If you happen to have Kato GS4, you can check the design in person.  First and 3rd drivers do not have any up/down play, while 2nd and 4th driver can easily be pushed up into the frame with your finger.

As for the headlight, if you bother with running all the wires from the motors to have DCC control, and sound, having constantly lit headlight seems sort of anticlimactic. 

[Tjack757]

I 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.JPG

I wonder if that would be a good spot add a PC board with a IDC header, so you could use connectors.

[peteski]

I wonder if that would be a good spot add a PC board with a IDC header, so you could use connectors.

My caption under that photo states "I test-fit a small cardboard rectangle, and it makes sense that those slots are there for a reason.  I'll etch 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."

So yes, I'm contemplating on using a 3-pin connector ( that is how many wires will be running through the drawbar.  Not planning on using IDC-type, just simple male/female machined-pins header/socket with 0.05" spacing and wires soldered to the male part.

[cgw]

hey Peter    have you done any more work on this with respect to hooking up the light board to the decoder?

[peteski]

hey Peter    have you done any more work on this with respect to hooking up the light board to the decoder?

Well, the light board is done and photos are taken, but I still need to write it up, and I have been sidetracked by other things.  I'll come back to this in a bit.

[Dwight in Toronto]

Peter - curious to hear if you’ve made any further progress with this interesting project?

[peteski]

Peter - curious to hear if you’ve made any further progress with this interesting project?

Actually, in my typical OCD fashion, I currently focused my attention on few other projects.  I have to admit that I'm bad, but I will get back to the Big Boy as soon as I can.

I just took a photo of my workbench. Yes, you can still find part of the Kato Big Boy boiler in that pile of stuff.  I'm also working on couple of decal artworks on my computer.  You can say that I'm never bored. I have too many projects. 

[HarryC]

In June I received my DC Kato Big Boy with the project in mind to convert it to DCC.
Your pictures and descriptions in your posting really will help in my conversion which I have not started yet.
Separating the tender from the engine -as you said- was not a problem but I stopped when I found it difficult to remove the boiler front part.
Hope to see your further progress as most probably I will start my project next week.
Thanks and regards,

[Tjack757]

In June I received my DC Kato Big Boy with the project in mind to convert it to DCC.
Your pictures and descriptions in your posting really will help in my conversion which I have not started yet.
Separating the tender from the engine -as you said- was not a problem but I stopped when I found it difficult to remove the boiler front part.
Hope to see your further progress as most probably I will start my project next week.
Thanks and regards,

I also purchased a DC Kato Big Boy back in June and was looking for a decoder install walk through.
I joined this forum in late June after finding Peteski's initial post on the Bigboy.
So far I did a decoder install the UP 4015 SD70M, installed the lighting kits in the UP water tenders and Union Pacific Excursion Train 7-Car Set.
The Bigboy is still awaiting a decoder selection and install.