Might I suggest using the FP280-KN dual shaft can motor made by SMC and available on EBay for $3.25 each. Railroad Mel found this one when we were looking for a replacement for the very similar but discontinued Mabuchi FK280 can motor. I have used the SMC units to remotor several Blue Box EMD F7 locos and they run fabulously! I used Plastruct 1/8" diameter styrene tubing to adapt the 2mm shafts of the SMC motors to the standard Athearn flywheels. This way, you only have to change the motor -- the rest of the Athearn drive line remains in place. These motors draw little current and provide plenty of power. They run quietly, too.
One note about the SMC motors is that they were intended to be used to power side view mirrors in autos. As these motors could be located rather close to stereo speakers mounted in the car doors, they have an anti-interference shield attached to the outside of the motor. However, it is fairly easy to remove these shields resulting in a motor that is basically an exact clone of the discontinued Mabuchi motor.
The basic dimensions (with the anti-interference shield removed) are:
Shaft end to shaft end -- 50 mm
Bearing to bearing length -- 35 mm
Can length (without bearings) -- 31.5 mm
Can width (rounded sides) -- 24 mm
Can thickness (flat sides) -- 18 mm
Shaft diameter -- 2 mm
Shaft length (terminal end) -- 8 mm
Shaft length (plain end) -- 7 mm
The only limiting factor to get this motor to fit in your NW2 (SW7) project would be whether there is more than 18 mm of clearance between the sides of the shell hood. Good luck!
Hornblower
There's a lot of threads on this topic, there's a few suggestions here: https://cs.trains.com/mrr/f/88/t/282280.aspx
NWSL did some blue box repower kits, but there aren't any listed on their website currently.
In one of my loco builds, I used a Kato HM-5 motor alongside trucks that used Athearn components. Athearn Genesis motors should also use the same stock mount found in newer Blue Box models I think. Both of those options might be a bit overkill, but they come with flywheels that are easy to use hex drive shafts with.
-Peter. Mantua collector, 3D printing enthusiast, Korail modeler.
So a while back, I got a strange little NW2 painted in Great Northern black. Initially, I thought it was Revell, but after close examination. It's clear that it's a well-done kitbash of a bluebox SW7. It had been given a little snowplow and had its grille modified. The switcher appeared to be a simple undecorated shell with decals on it to represent GN Black.
The mechanism is old. While it does have a flywheel, the motor is still gray and the side frames are metal. The Locomotive was probably built in the 60s or 70s.
I have already gotten some parts for a potential rebuild, I found an Athearn SW1000 to salvage trucks from, and a C&C Cab to replace the stock Athearn Cab on the NW2. Not sure what to use for the motor because the old one was not very healthy and didn't run well.
I'm not really sure what motor to give the little switcher. Any suggestions for what I should do with the little locomotive?