This week’s post is a little bit different in that it’s a guest post.  Fellow N Scale modeller Mike Musick has written an article about improving Con-Cors N Scale U50s, Turbines, and my imminent C-855 by replacing the wheel sets.

So without further ado, I hand you over to Mike.

BETTER WHEEL APPEARANCE FOR CON-COR U50 MODELS
(Also applies to Con-Cor Veranda Turbines)
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The Con-Cor U50’s ungainly aesthetics are not helped by its oversize wheels. In all production runs the wheels measure to a scale 48″, versus the prototype’s 40″. While the 0.025″ increase in model height alone doesn’t alter the proportions perceptibly, the too-large diameter plus the oversized flanges of the 1970s design result in the wheels being visible above the truck frame, giving the model a toy-like appearance.

Oddly, the Con-Cor/Kato model of the PA produced prior to the U50 had nearly-correct wheel diameters. Replacing the U50 driven wheels (eight of the sixteen) with PA wheelsets is a straight-across swap since the gear and axle sizes are the same. However, it does require the sacrifice of an out-of-production PA model, and carries forward the large flanges of the era. It also doesn’t solve the issue of the undriven idler axles on the inner U50 trucks, which have cone-point bearings.

Fortunately, there are wheels and point-axle wheelsets available from Northwest Short Line (nwsl.com) for retrofit. The separate wheels work well and look good, but will require fabrication of half-axles to work with the Con-Cor gearing. We are specifying 42″ wheels as opposed to 40″ to stay out of trouble with truck frame clearance issues on less-than-perfect track.

NWSL Wheels
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Powered axles use NWSL #96000110, “N scale WHEEL ONLY, 42″/64 NS, 3/32″ bore”. You will need eight (8) wheels per locomotive.

Unpowered axles use a custom wheelset, specified as “N 42″/64 wheels on Pointed 1.5mm x .560″ axle (4/pkg)”. A single package of four (4) wheels covers each locomotive. Specify bright NS finish to match the powered wheels.

Installation
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Removing wheelsets is a simple operation. Remove the two screws in the driven trucks, and the outer frame will lift off, with the idler truck probably lifting off at the same time. The driven wheelsets will be easy to remove. On some production runs there is a brass shim on one side of the center frame, be sure to note the orientation before removing the second axle.

With each idler truck separated from the driven truck, unscrew the single frame screw from the weight to access the wheelsets. Snap out the wheelsets and replace with the NWSL point-axle versions. Reassemble frame and set aside for later assembly with the driven trucks.

Carefully remove the half-axles from the gears by firmly pulling. Be careful to not use any bending forces against the plastic gear shaft since it is easily bent, resulting in a wobbly finished axle.

For the new half-axles, use 3/32″ K&S brass tubing in the standard hobby-store wall thickness. Cut eight pieces of this tubing to a moderately precise 0.193″, as this determines wheel gauge. Dress each cut end with a needle file, then insert each piece of tubing into a wheel so the end of the tubing is flush with the outer hub. Don’t rely on measuring the old half-axles to determine axle length. They are 0.200″. The 0.007″ difference corresponds to the narrower tread of the NWSL “/64″ wheel size.

DO NOT try to press the new half-axles onto a gear shaft! At least not yet. The tubing must first be reamed to fit the gear shaft; attempts to press-fit without reaming will likely result in a broken gear shaft. First dress the inner edge of the tubing with a micro needle file or jeweler’s cone reamer, then follow with a #52 (0.0635”) drill bit (Be advised that a 1.65mm bit might be too large and 1.6mm too small. Try the larger bit first with a scrap of tubing for snug fit. Forcing a too-tight, smaller reaming size risks breaking the axle), reaming the entire length of tubing. This will make for a firm but not-too-firm press fit on the Con-Cor gear shaft. With both half-axles on the gear shaft, check gauge and adjust if necessary.

Repeat the process for the other three driven axles, then reassemble. Don’t forget the brass shims in the proper locations if your model had them. Be sure to observe the orientation of the idler truck since it is very easy to install upside down. Check run the loco and you are all done.

Mike also provided a few photos to show the difference in an original and converted U50 model; the original wheelsets are in the loco on the left.

Close up the gap between the truck and rail head is notably different as well as the lack of flange protruding above the truck.

In this shot you can clearly see the difference in flange width.

Below is a close up of the NWSL wheels in place.

And a shot of them before they were attached to the drive axle.

I leave you this week by saying thanks to Mike for his post and to let you know that I will be at Brighton Model World this weekend with all of our N Scale module layout, ‘Solent Summit’.  So if you are in the area and are coming to the show please come and say hello.