In between fighting a nasty cold and catching up on Alkem Scale Models orders, I did a little development work on my O Scale truck design. My objective is to make the overall width of the standard O gauge trucks as narrow as possible. This will allow the car bodies to hang over the trucks more prototypically. Standard O gauge wheel sets are already about 0.0729 inches too wide due to the wider track gauge. Adding another 0.14 inches between the outside face of the wheels and the inside of the side frames to fit the Intermountain axles was making the trucks too wide. I decided to reduce this distance. To do this I had to file about half of the needle point off the end of the axles on my Intermountain wheel sets. I am using IM Wheel stes because they are less expensive than the alternatives. I looked at NWSL wheels but they are more than double the cost.
The photos show the results. The revised standard gauge narrower trucks sit between the original wide standard gauge trucks designed to accommodate the full width of the Intermountain axle length and a P48 truck. As you can see the narrow design is not quite as narrow as a P48 truck, but about 0.090 inches narrower than the earlier standard gauge truck. Note the narrow truck doesn't have brakes but the other two do. The working brakes will still work with the narrower design without modification.
All three cars roll freely. Because of the axles rests on the taper the wheel sets can move laterally a bit in the trucks, but that doesn't seem to increase rolling resistance.
Looks like these might be ready for production.