Keeping it Rolling (Smoothly)

For several years, train builders had been using the standard train wheels in those chunky, unrealistic encasings. Then some people came along and changed things for the better.

3mm tube used on an “arch bar” freight truck. Photo by Cale Leiphart.

Enter the infamous “3mm tube method.” The idea here is to use a 3mm tube and insert it in clips or the equivalent:

The metal axles from Lego which clip into the wheels are inserted into the tube, and then lubricated to reduce resistance as much as possible. This design has been the mainstay for many years. But now train builders have been looking for the next best thing.

The answer? Ball bearings! Tiny ones, at that. Andrew Mollmann has discovered a bearing which is able to be press-fitted into a technic pin hole. It turns out, an MR52zz bearing fits right into a technic brick, albeit snugly. The Lego axle then fits through the center of the bearing.

Bearings have begun to slowly creep their way into train MOCs. Andy Mollmann and Cale Leiphart have been doing some testing on their own. Both have incorporated them into common freight truck designs:

Cale Leiphart’s new bearing equipped trucks.

Testing resistance compared to lubricated 3mm tubes:

And testing pulling power:

It’s always cool to see people think of new ways to do things. With less rolling resistance, cars can now be a little heavier and trains can be longer, but a locomotive doesn’t have to be any more powerful than it was.

Though, I’m sure we’ll come up with a new method for that too, sometime.

5 thoughts on “Keeping it Rolling (Smoothly)”

    1. I set the bearing on a sturdy workbench while I warm up the Technic brick with a hot air gun, not a ton, maybe to about 120-150F, and then I place the Technic brick on top of the bearing. Then I use something sturdy and flat to press the Technic brick on to the bearing. You have to want it, you’re putting a 5mm bearing in to a 4.8mm hole.

  1. I’ve noticed that 3mm brass tubes are not exactly 3mm, depending on where you live: in the US, it’s mostly 1/8″ or 3.18mm. Over here in Europe, 3mm is 3mm, which let’s the tubes float a bit in the clips. You’re better off with using #4081 “Lamp Holders” than open U or C-clips. I haven’t noticed any impact on the rolling behavior though, but I don’t have any 1/8″ to compare to. Maybe Glenn can tell about it as I built his PRR cabin car with 3mm tubes while the rest of his stock is probably 1/8″?

  2. I used Andrew Mollmann’s idea and bearings on a set of trucks for my Ore cars. Once I made a depth gauge and figured out the order of assembly it was pretty easy. Performance is better but no where near the Lego truck. I used technic beam #32316.

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