The title pretty well describes the following except to note that you are not confined to just HOn3. This conversion can be used for any gauge between HOn3 (10.5 mm) and standard gauge HO. The gear box and the tabs that hold its cover on are probably too wide to do HOn30 (9mm or HOe gauge).
Another thing this illustrates is that getting into narrowgauge doesn't have to be expensive. This conversion can be accomplished for a little over $100 and yields a smooth running Kato-powered loco that can pull the wallpaper off the wall. While it won't scratch the steam itch, it is equipped with a steam generator to enable it to pull passenger trains.
First a side by side comparison between one of my NW2M locos and a yet-to-be-modified standard gauge Kato NW2.
Notable is the loss of the tapered hood section, replaced by a full width hood all the way to the cab. This provides space to model the steam generator and dynamic brakes (conceptually) while providing extra space to locate the decoder (physically) without the need to hack at the chassis weight.
Getting the shell off the chassis is a bit tricky. Here is a link to Kato's instructions:
Body Shell Removal for HO Scale NW2
The small retaining nubs cast into the chassis halves should be filed down to make things much easier the next time.
This pic illustrates what you'll find once the halves of the chassis are split apart. It's a lot like many N scale locos with each half of the chassis isolated from each other by some plastic bushings.
From the factory, the motor and LEDs are electrically suspended between the two opposing polarities of the chassis halves which are connected to the opposing rails under DC power.
For DCC, we must isolate the motor so that it is powered only through the dcecoder, while providing power to the decoder from the rails. Pulling the motor shows where to connect to do this, as the motor has two brass strips that feed it power.
Each touches one half the chassis. On the chassis, use a bit of Kapton tape to ensure the strip contact can't contact the chassis halve in the future. Solder the gray lead from your decoder to one of the contact strips and solder the orange decoder wire to the opposite contact strip.
To allow the newly connected wires to be routed into the reassembled chassis halves, a small amount of mods must be done. The first path is via opening a small path via file or Dremel cut-off wheel.
The second is via another small indent that is just to the left of the first.
Make sure to round off any sharp edges that might present and later cut your wires and short them out where they pass through the isolated halves. BTW, this is essentially how you DCC a Kato NW2 even if you don't go narrowgauge.
To get the two motor leads back to the cab area where the decoder will be located, use a Dremel wheel to cut grooves along the top inside edge of each chassis half to privide clearance for the wire underneath the shell. This pic show them with the decoder hanging out BEFORE the wires are secured in the grooves with a piece of Kapton tape over them.
You'll also see that the red and black leads from the decoder to track power proviuded by the springy wipers underneath have been soldered securely. This is a good time to caregully (without contacting the decoder or lighting wires to the track except via the wipers) test run the loco on DCC so check if this part has gone well.
Next we turn to the trucks.This shows how each axle is composed of a plastic center gear with metal half axles pressed in to gauge.
Sorry about the focus. The half axle on the left is unmodified. The one on the right has been modified by cutting the inside axle that goes into the gear, otherwise it risks touching the opposite half when the wheel is reassembled at the new narrower gauge! After deburring, reassemble them to gauge, then use the continuity function on your miltimeter to check there is no continuity between the sides.
Here's a comparison of the narrowed axle set in the lower position in the truck frame and the unmodified wheelset in the upper position.
As you can see, any gauge between these two is easy to accomodate, so you're not limited to HOn3.
Contact between the wheels and the wiper strips is provided by a side contact with bishings the fit over the end of each axle. This is an unmodified one, propped against a wheelset. The axle end, however, goes at the ends of the side contact. The middle of the side contact points up and is the contact against the wiper. You'll bend it out a little to better contact the wiper strip.
Here is a trcuk with the modfied side contacts in place. You can see how each of their ends now jogs in, then is bent straight so that full conact with the axle ends can be maintained despite the narrowed wheelsets.
Once the trucks are ready, turn the assembled chassis on its side, loosen the screws holding it tiogether just enough so the top of the truck can be rocked into place, first one the the other, capturing both trucks and giving a RTR chassis. Again, watching to guard carefully any dangling contacts or decoders against touching the rail, test run your powerful little loco on the narrowgaue after checking the gauge of all the wheels if it doesn't seem there's an issue otherwise will sometimes reveal one knocked out of gauge.
Next up, modding the shell.
Mike Lehman
Urbana, IL
With a tested, running narrowgauge chassis you're ready to make it look good. If you are a modeler of one of the road names that Kato decorated this model from, you may even have little need for painting, but YMMV. Since I'm doing a version of the Rio Grande, I've been able to obtain complete shells with the details, etc and needed to do little painting. You'll need a complete shell plus enough of another one to cut the center section out to extend the straight hood all the way to the cab.
Here's a shell with another sliced up in front of it, with one of my earlier NW2M (as I call these) locos in the background. I've started the first cut on what will be the main shell once it's modded.
Here the first cut is finished.
In this pic, the donor shell (with a white Southern stripe at its bottom) has been cut to just the length needed to fill in and keep the cab flush with the back of the main chassis. The cab still needs to be chopped in this pic.
This pic illustrates how far to cut the cab down. I should've used the Rio Grande one instead and I could've saved a bunch of conspicuity stripes, but this one will be a little different.
This is the modded shell awaiting paint and final application of details.
I managed to salvge the light packages and reconnect front and rear easily with just the wirer supplied with the decoder. Got a few more pics to take to show how the cab, plows, and couplers attach.
That's a really nice looking loco Mike and great tutorial. Looking forward to part 3!
Simon
WOW! That is one fine tutorial Mike! Well Done!!
Don; Prez, CEO or whatever of the Wishram, Oregon and Western RR
Mike, thanks for sharing all this. Great work on the model.
Even though this is something I will never do, I love to see the amazing work others are doing.
-Kevin
Living the dream.
Very impressive, Mike. I always enjoy seeing your layout and your models.
Nice work, Mike. I do have a question...is it possible to press the axle shaft in the wheel? This way the shaft could stay the same length and might fit the pick up strip better.
I'm planning on an Sn3 version.
Chuck - Modeling in HO scale and anything narrow gauge
Thanks to everyone for your kind comments!
trwrouteI do have a question...is it possible to press the axle shaft in the wheel? This way the shaft could stay the same length and might fit the pick up strip better. I'm planning on an Sn3 version.
It might be. You'd still need to trim the projections that hold the shaft that are cast as part of the gear. I didn't evaluate closely, but with standard gauge the inner ends of the half axles are probably pretty lose to touching. I've never worried too much about being precise when I shorten the gear projections to accomodate HOn3, although doing so could be helpful with retaining minimum gauge.
This mechanism would work quite well with Sn3. The cab might need to be reworked for S scale. For instance, you probably don't want to cut it shorter like I do for HOn3.
Tidying up some loose ends here.
First, the cab retainers. Looks spooky, but I used 1/4"square plastic to the cab that fit into "battery box" enclosures I added next to the cab on the walkways.
Kato makes the walkways as a separate part. I glue the modded hood assemebly to this piece. You also will need to open up the included walkway where it narrows where the hood previously narrowed. Slice it open enough to better fit the widened hood there.
With the retaining dimples filed down, you need another way of retaining the shell. I added snowplows at each end. The couplers connect via a snap in retainer that was with the loco. I added a thick piece of plastic that snaps into the bottom part that the Kadee 714s I used have a suitable mount for their screw to be retained. With the chassis in place inside the shell, the coupler/rertainer assemblies snap in and protrude past the snowplows to keep things from falling apart when it's picked up.
I used Details West PL-207 snowplows. The footboards are cut-off and the plow is applied in position so that it clears the track, but is low enough to allow the coupler to protrude at the right height. You'll need to take a file to the center top of the plow to open up a slot for the coupler to set right.
The "dynamic brake" detail is a Details West WH-163, which is actually a EMD F unit winterization hatch. This is supplemented by vent screens on each side, which are FS-1303 Cannon and Company Inertial Filter Screens. A small bit of tubing and a steam generator vent faked up with a spare kit part complete this work on the widened part of the shell.
Awesome, Mike. The cab retainer idea is for sure something I'm going to use. I like the way that you take other parts, such as the winterization hatch, and use it for a completely different purpose. This build is very creative and you have done an excellent job!