Removing Athearn Genesis GP7u Truck Side Frames
Coincidentally, my Atlas Y&MV SD35 552 did not have the wheels painted so I performed that task along with the 200 and 201. The Atlas trucks are a bit easier to deconstruct than the Athearn Genesis trucks. Though they are fundamentally the same style, the tabs on the Athearn Genesis units are a bit more difficult to access. Also the brass contact strips in the Athearn Genesis truck side frames are locked in place as the plastic tabs are melted, essentially riveting them in place. This means that even when the truck side frames are separated from the truck assembly, there is still a wire keeping the side frames attached to the model.
Upon first inspection, it was not evident exactly how the truck side frames were attached. I researched the exploded parts diagram provided by Athearn Genesis to determine that the trucks were essentially connected like on Atlas units. This means that the underside of the gearbox is a removable "drip pan" attached with four tabs. These tabs are between the back side of the wheels and the outside of the gearbox so there is little room to maneuver.
Athearn Genesis did provide holes in the metal locomotive frame that allow a small flathead screwdriver to pass through and access the top of the outer tabs. When the trucks are turned as far as then can freely rotate, this hole aligns on a tangent pathway leading to the tabs inside the wheels.
From here it is simply a careful process of prying tabs on the drip pan over the nubs on the gearbox to free the bottom pan. Once the first two are free, the remainder of the tabs come off easier.
Care must be made to handle the model cautiously as there are many detail pieces that can be easily damaged during this process. Once the drip pan has been removed, the model must remain upside-down to prevent the wheel assemblies and gears from falling out. With the drip pan removed and the model upside down, the truck side frames can be pulled out of the gearbox. As soon as the side frames are removed, the bottom drip pan needs to be snapped back in place to keep the contents in place and keep dirt and foreign objects out.
I considered cutting the wires to paint the truck sideframes and then soldering them back, but I think it will be easier to mask the model with the truck sideframes exposed for spray painting. With the truck sideframes now removed from the truck assemblies, the wheels are exposed and ready for painting. I still have a bottle of Floquil Rust which I simply brush on, being careful not to paint the axle ends which are needed to conduct electricity to the brass strips in the truck sideframes. I also am careful not to paint the flanges or the treads of the wheels, however, paint here can be cleaned up easily with the locomotive under power on rails covered with an alcohol or paint thinner coated paper towel.
Look for truck painting and re-assembly in the next update!