Ore Cars Part 18 – Poorly designed Kato trucks

The members at the club advised me that the Kato Barber S-2 70 ton truck is the preferred option my ore car project.  These particular trucks feature roller bearing faces that actually rotate with the wheels.  A few of the members pooled their resources and bought the 16 pairs of trucks I needed for this project, so I set about readying them for the cars that they would eventually be mounted beneath.

IMG_1887

These are supremely smooth rolling trucks, and the detail is outstanding.  As I went through them to install the roller bearing caps and prep them for paint and weathering, I discovered that they didn’t conform to NMRA standards.  The gauge on all of the wheel sets was uniformly too tight.

IMG_1889

A simple opposing twist of the wheels slides the wheels  outward from each other, but then things got a bit complicated.

IMG_1891

These trucks are not designed with needle ends that fit into conical impressions in the back of the truck frame, like standard old-school plastic trucks.  In order to get the animated affect of the roller bearings, Kato designed the axles with a finely machined race just inboard from the ends of each axle.  The race snaps into the plastic truck sideframe from underneath and the roller bearing caps fit onto the ends of the axles.  Kato gets extremely smooth performance out of this approach.

However, when the wheel sets are pulled into gauge, too much friction is created between the inner edge of the race and the side frame.  The trucks roll very poorly when set to the NMRA standard, and some sets would not roll at all.  This would be great for modelling cars with the hand brakes applied, but otherwise it looked like we might have to return them and find another solution.

Before I completely threw in the towel on these, I found that if I set the wheels to be at the very minimum to meet the NMRA standard, the trucks still roll well. The adjustment had to be very precise, because if I set them even the tiniest bit too wide, they wouldn’t spin when they were mounted.  In the photo above, you might notice that this wheelset is set as tight as it can be and still conform to the standard.  For those of you keeping score, that’s 16 cars or 32 trucks, or 64 wheelsets.

They don’t roll as nicely as they did when they came out of the box, but they still roll well.  Anyone using flextrack and commercial switches on any kind of “normal” layout would probably never have a problem with using these trucks straight out of the box.  But our layout is anything but normal.  The magnitude of what what we’re undertaking pushes everything to the extreme.  We wear out and rebuild model locomotives that would serve the typical hobbyist a lifetime without any kind of failure, so we’re quite disciplined at adhering to standards.

In the end, we decided that we could use the Kato trucks as long as each wheel set was very precisely tuned to be in gauge and still roll reasonably well.  You can see that they are very nice models of the Barber S-2, so I’m pleased that it worked out.

IMG_1892

IMG_1893