USA NW-2
For the conversion on my NW-2's I had mixed feelings. I wasn't too sure what couplers to use because kadee specs two different coupler kits depending on how your track is laid out. The 787's for large radius curves and the 831's for small radius curves. To figure it out before I made a mistake I sent off some e-mail asking Kadee what they consider wide radius curves compared to small radius curves. What they told me was kind of surprising but a welcome answer non the less:
Hello Mr. Foster, thanks for your e-mail inquiry.
We use 4 foot radius as the dividing point of small and large. Anything smaller than 4
foot is tight or small radius and 4 foot and above is larger radius. We "try" to
test our conversions to see how small a radius of curves the car or loco will negotiate
when coupled to various lengths of cars, both coupled and with the couplers in the
"delayed" position.
Sam Clarke
Kadee Quality Products
Now that I had a good answer to work by, I decided to use the 787's because I have a cow and calf set that I want to run together and having them close coupled really looks cool and very prototypical. In fact, the difference between the two configurations is about an inch. With the 787's I have 3/4 of an inch between the step boards on the ends of the engines. On my tightest curve I still have close to 3/16 of an inch clearance between the units so everything is great. All of my switches are Aristo-Craft wide radius and the engines run fine through them too. They can even work through two switches back to back which makes a pretty tight "S" curve.
After
removing the stock USA coupler and coupler mounting arm you should be left with the
mounting posts still attached to the engine. The instructions that come with the 787 kit
are pretty strait forward but some minor modifications are required to make the new
couplers work correctly. Pictured here are a modified gear box on the left and a stock
gear box on the right. Make note of the 1/8" hole drilled in the modified box. It
will be used to mount the new coupler to the USA mounting post. The instructions detail
this step but they missed the next one...
In order
for the assembled coupler and gear box to mount correctly onto the mounting post it was
necessary to make a small cut in the gear box lid. Look closely at the picture to see the
modification on the left lid compared to the original lid on the right. I failed to get a
picture of the mounting post but when you look at yours, you will notice that there is a
raised circle on the end to help the coupler mounting arm rotate smoothly. Along with the
raised area there are two more raised sections, one pointing towards the front of the
engine and one towards the rear. The small notch in the gear box lid allows for the
assembly to fit snugly onto the mounting post and if you make the notch just right, it
will also aid in centering the new gear box on the coupler mount. This Kadee conversion is
intended to give you a solid body mounted coupler that is very close so it's important to
make everything fit just right and the notch is the ticket.
You can now assemble the new coupler like any other Kadee (following the
directions of course). Once that is done mounting the assembly is very simple. All you
need to do is attach it to the engine with the new #4 X 3/8" screws provided with the
Kadee kit. In this picture you should also notice the small white .010" shim that I
installed to raise the coupler to the correct height. Sometimes it doesn't seem like it
but a small shim can make a noticeable difference in the finished height of your couplers.
I know this
picture isn't that great but it should give you some idea of how nice these engines look
when they are close coupled. I should have also taken a before picture to show how
terrible they looked with the stock USA knuckle couplers installed. If you decide this
conversion is too close for your layouts functionality, the 831 conversion should work
just fine. It will not get the engines as close as the 787 couplers but you should still
be very happy with the new look as well as the improved performance and dependability.