NW-2 Cow & Calf

Overall:

Thankfully, there are no traction tires on the wheels. I will probably remove the sliders and see if they still run well. Have not tried the smoke units yet. I think the locos could stand a bit more weight. I have a cow and a calf so far. Many railroads use a cow and one or more calves. 

Interestingly, the NW2 and the S4 never came with traction tires, and also the typical brass bushing/bearings on the axles are not present, the axles ride in a plastic saddle that is part of the motor block.

Nice level of detail, and the typical tradeoff, nice small details, but easily broken, note: the small plastic loops for the coupler cut bars are easily broken.

In order to change the headlight bulbs in the NW-2 you have to remove the headlight lens which can be difficult to remove.

The railings press into little plastic cups that are glued to the frame with small, fragile pins on the bottom.These are easy to break off.

These locomotives have the same "cracked axle" syndrome as virtually all other USAT locos. Parts are easy to get. Fix the axles as usual, but there's less clearance in the motor block, so if you use thick tubing, you might have to grind some plastic away from the axles.

 Kadee Couplers:

Truck mount: trim off the tang, leaving about 1/16" of the thinner tang projecting from the thicker part. This allows you to use the existing hole that held the hook and loop. You can use the screw from the hook and loop. This is for 831 couplers.

Kadee also recommends cutting 5/8" off the tang, and you also need to cut 7/16" off the gearbox shank, and  trim a slot in the lid 11/32" wide and 5/32" deep to match the sides of the pivot arm. This will allow closer coupling, and should work on curves under 8 foot diameter.

For larger curves, over 8 foot diameter, you can use the 787. I have not tried this yet, to see if it gives close coupling. 

Click here for the Kadee installation sheet

Disassembly:

The fuel tank comes off with 4 screws, and only goes on one way. You do not need to remove it unless you want to.

First there are 8 screws to remove from underneath. As with many USAT diesels, some are best accessed with a slim philips head screwdriver between the sideframe and the motor block, after twisting the block into the best location.

First remove the 2 deep set screws where the 2 red straws are, they are easy to reach.

Now remove the 2 deep set screws at the front of the loco, the leftmost 2 with the yellow straws in this pictures. By turning the truck to align with the screw holes you can reach between the motor block and the sideframes.

Now for the final 4 screws. These are in the approximate location of the middle set of 2 straws. There are actually 2 screws near each other on either side of the loco centerline. Two screws are deepset and they attach to the body, these are the middle 2 yellow straws. There are also 2 smaller, short machine screws. These attach to a metal bracket that holds the front of the cab down. These smaller screws are not deep set, and have machine threads. They are quite short.

The front of the loco has a tab that engages the chassis, so carefully lift up from the cab, not the front end and as you swing it up, the tab in the chassis in the front will disengage.

Wiring variations:

It appears there are 2 variations, an early version and a later version.

The difference seems to be in how the trucks are connected to the circuit boards.

In both cases, there are a total of 6 wires from each truck:

• 2 for the motor
• 4 for track pickups (2 internal to the motor block and 2 picking up from the ends of the axles / journals)

Early Version

The picture below shows the 6 wires coming up from below:

2 - yellow and green are the motor wires, (note they are in a 3 pin JST connector)

2 - red and black from the track pickups in a jst connector at top right

2 - another red and black from track pickups but soldered to the green board at right

Below is another variation, where you can see similar wiring but without the 3 pin header shown on the board above.

Again, the red and black track pickup wires come up and are soldered to the board from below, and the other red and black pickups come up to a jst connectors and eventually go to the same place on the board, thus connecting the track pickups for the end of the axle and the internal power pickup together.

You can also see the green and yellow wires coming up from the motor block, but then the 3 pin jst with the unused center blue wire solders to J6, J7, J8

(picture courtesy Dan Perrott)

So to wire to the loco without cutting wires, separate the 2 pin jst connectors and plug a male and a female into the 2 open connectors, you will now have 4 track pickup wires for that truck, and two reds and 2 blacks.

Then for the motor connector, get a female 3 pin JST and just wire the outer 2 leads for the motor.

Now you wire this up carefully, since I did find that one end of the loco had the 3 pin JST wired in reverse (!!)

Newer versions of the NW-2 are wired like most of the USAT locoslocos, JST connectors for both the motor and track pickups.

In the picture above, all the wires are red and black!

The track pickups are to the connector at the top of the picture, since there are 2 point of pickup in the motor block, there are 2 wires "per rail" so 4 wires total.

The connector at the bottom is the motor wires, since there is only one motor, then only 2 connections.

DCC Install:

There's several ways to do this. The "traditional" DCC install is to basically disconnect everything, ignore the circuit boards, and change all lights to LEDs, and you would also do something about the smoke unit.

Another way is to let the original board handle the power for the lights and smoke unit. I call this the "quick and dirty" installation. This is where you feed the track pickups as usual to the decoder, but then use the decoder motor output to basically feed the entire loco like it was on DC, i.e. the decoder motor outputs to to the main circuit board where it was taking power from the rails.

Quick and dirty installation

As I have mentioned elsewhere, this is very easy and quick to do, since no soldering or cutting of wires is necessary. But this method has the disadvantages that you don't have constant lighting, and cannot control the lights individually. Also, running the smoke unit might overload the decoder output. Finally, some locomotives have voltage regulation circuits for lights that go absolutely nuts when powered by PWM (pulse width modulation), especially Aristo ones. In this case you may have to change to LEDs, or do a normal full decoder install.

To proceed on the quick and dirty:

Look at the wires/connectors from each motor block/truck. Each truck has 2 connectors, but there is a difference. One of the 2 connectors has 4 wires in it, 2 red and 2 black. The other connector has just one red and one black.

The connectors with the 4 wires are the power pickup from the wheels. This is because there is an internal wire touching the axle, as well as a wire on the journal where the axle tip touches.

Buy matching connectors so you can plug into the trucks and the main board. (allelectronics.com)

1. Disconnect only the connectors that have 4 wires (this is one for each truck). Now take two of your new connectors and plug them into the "loose" wire from each truck. Now you have 4 wires that represent the power pickup to each truck.
2. Now is the time to realize that USAT uses two identical trucks, and they are “reversed” from each other. So on one truck the red wire is the right rail, and the red wire is the left rail on the other truck.
3. So, you have 4 free wires/leads from the new connectors you just plugged into the motor blocks. Let's assume your new wires are red and black. Since the pickups are reversed in polarity between the front and rear trucks, you need to take the red wire from the front truck and twist it with the black wire from the rear truck. Do the same for the other 2 wires. Onve you have done this, you now have 2 leads (each made of 2 wires of different colors twisted together), one for the right rail and one for the left rail. (by consolidating the pickup wires between the trucks)
4. Now is the time to get out our ohmmeter. Connect it to one of the twisted pairs you just created, and check all the wheels on the loco. You should find continuity between the wire pair and all the wheels on ONLY one side/rail, tag this set either right or left.
5. Test the other pair. If it does not have continuity for ONLY the other side/rail.  Put a little piece of tape on this pair and mark it also. Now you have the right and left track pickup leads ready to connect to the decoder. Connect them to the proper terminals on your decoder
6. Now it is time to feed the decoder motor output to the main circuit board (notice that we never disconnect the motor lead connectors between the main board and the trucks)
7. add a new connector to EITHER of the two "empty" connectors that go to the main board, either will do.

The two wires from this new connector plugged into the main board go to the “motor” output of the decoder. Don’t worry about the polarity. Connect them and if the loco runs backwards, then you switch these leads.

I need to emphasize again that you ONLY disconnect the 2 connectors that have 4 wires in them.

To recap, what you have done is disconnected the track pickups from the USAT main board, and fed the track pickups to your decoder. Then you have fed the motor output of the decoder to the main board, thus powering the lights, smoke unit and of course the motors.

Note that the lights will work like a DC loco, vary in brightness with speed, and you cannot control them separately.

Speakers:

There are 2 places to put speakers, like many USAT diesels.

Fuel tank:

The traditional location is in the fuel tank, under the loco and is held with 4 screws. It is "keyed" so that it can only go back on one way. The space inside is 1-1/8 inches deep. There is a circular relief inside the bottom that is 2.65" in diameter.

It's easier to select a speaker with no mounting flange, but I have often sanded off the mounting flanges on a speaker to make it round. I use a disk sander to accomplish this.

Visiton speakers are a good fit, good sound for shallow speakers.

I've used the Visaton FRS-7 (grinding off the flanges) with success. It's 31.8 mm deep, exactly 1-1/8". It has good response down to 200 Hz, and useable about down to 150.

Ferenc Joó reports that the Visaton K64WP will fit with no modifications and is almost as loud as the FRS7 even without an enclosure. It's not going to give you the lower frequency response, really don't expect much below 300 Hz.

Top Grill:

Ferenc reports that the Visaton K50 speaker will fit well, and is very thin, but really needs some kind of enclosure behind it.

Since I normally use QSI, I have the prime mover sounds come from the fuel tank, and the higher frequency sounds like bell and horn come from the "top" speaker, so often I do not need an enclosure there, since it acts mostly as a tweeter.

Results:

 Here's a nice video by Ferrenc Joo, who installed a Titan in an NW-2: