This is a fixture for painting the wheel sets of Athearn locomotives, e.g. PN 40019. Though not skilled, I am better with spray paint than with a brush and had a relatively large number of wheels to paint.

The fixture masks the driving surface of each wheel and the central hub. Masking the central hub is not necessary for more modern Athearn locomotives, but I was curious to see if it could be done.

The fixture can be used to paint both single wheels and full wheel sets. When painting single wheels, only a single fixture side piece is necessary. The wheels can be set in the side piece and secured with tape, which also masks the inside of the wheels from over spray (see pictures) and can be used to hold the wheels as the paint dries.

When painting full wheel sets, two side pieces and a center piece are necessary. Screws (2-56) are used to secure the side pieces to the center piece, clamping the wheel sets. Nuts are pressed into hexagonal recesses in the center piece. As can be seen from the pictures, three additional screws had to be added due to the flexibility of the 3D-printed parts. The holes for these additional screws were drilled after printing. Closing out the fixture with painter's tape prevents overspray of the bearings and gears.

The lengths of the screws are:
4 count: 1/4 inch
2 count: 5/16 inch
1 count: 1 inch

Potential enahncements include:

• Properly incorporating additional clamping fasteners into the as-printed design. Increasing the stiffness of the side pieces may also be beneficial.
• Adding a tang to the rounded side of the center piece to facilitate holding the fixture during painting.