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.


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.


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


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.



11 thoughts on “Ore Cars Part 18 – Poorly designed Kato trucks

  1. We discovered that the gauge problem existed with all HO Kato freight car trucks. There is an ACF ride-control truck available from them, too, and we had to adjust the gauge on those as well. They are a friction bearing design which we used under a lot of cars. Since they had a solid axle, they didn’t create the same binding issue the Barber trucks had, but they still needed to be fixed since they would not make it through our turnouts without adjustment.

    The reason we have an issue and most would not is that we use the minimum NMRA clearance spec for our handlaid turnouts, which means anything with tight gauge binds against the guard and wing rails in our frogs. Minimum clearance results in finer looking flangeways, and better looking turnouts, and if everything conforms to standards, smoother operation. I suspect that the tight gauge on the Kato trucks occasionally runs afoul of commercial track, and causes mystery derailments. It’s amazing the entire production manages to all be below NMRA specifications.

    • We use minimum gauge in our flangeways. These Kato trucks have to be at the absolute minimum gauge or else they bind too much to roll. I regret our decision to go with Kato over Kadee.

    • Various members bought 16 pairs of these trucks at different stores over the course of a few months. I suppose a bad batch would be distributed far and wide, so it’s possible. But I can’t imagine that anything can change in their injection mould that would cause variation from batch to batch.

      I’m inclined to subscribe to Jurgen’s theory: they’re designed to be narrow be in order to be more forgiving on mass-produced switches that are not built to our strict standards. These trucks are super slick out of the box and seem to have nearly no friction to keep them from rolling on forever. Putting them in gauge puts the brakes on them to the extent that they won’t roll more than a few inches. I needed to tune each wheel set as tight as possible while still meeting the NMRA standard in order to get them roll a few feet under their own weight.

      Are your Kato trucks the ones that have the animated roller bearing faces? I think yours might be the ones with static faces. The wheels slide along a solid axle, spreading the wheels apart does nothing to chance the friction at the bearing surfaces. This would account for a difference in design and performance, rather than a variation from one batch to the next.

  2. And I thought Athearn Genesis Trucks were the only ones to feature a rotating end cap. I can’t easily use the Genesis trucks with Proto:87 wheels because of axle diameter, maybe the Kato trucks would work for me.

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