5. Cutting the Hub and Putting the LEGO Wheel on a Motor

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There are just a few steps remaining before the aluminum replacement hub is ready to be put on the motor. However, before cutting the hub off the rod, try putting the rubber tire onto it to make sure you don’t need to perform any more machining or fine-tuning.

Cutting the replacement hub from the rod stock workpiece using a hacksaw with a bimetal blade.

Cutting the replacement hub from the rod stock workpiece using a hacksaw with a bimetal blade.

Use a hacksaw or cut-off / chop saw to remove the hub from the workpiece. Since this is a rough cut operation, be sure to leave a little extra length.

The hub is being cut off from the rod stock fairly late in the process. Remember that this is because the small size of the hub would have been awkward to work on by itself. The longer workpiece provided an excellent way to secure the hub while it was being machined.

Using the LEGO tire, a black Sharpie felt-tip permanent marker marks the extra height to cut off from the aluminum hub.

Using the LEGO tire, a black Sharpie felt-tip permanent marker marks the extra height to cut off from the aluminum hub.

Place the aluminum hub into the LEGO tire. Mark the excess material on the rough-cut end of the hub using a black Sharpie felt-tip permanent marker. Then, remove the rubber tire and mill off the rough end until no more of the black mark remains.

Completed LEGO-replacement metal hub attaches an off-the-shelf miniature DC motor to a rubber LEGO tire.

Completed LEGO-replacement metal hub attaches an off-the-shelf miniature DC motor to a rubber LEGO tire.

Insert a setscrew into the hub, but don’t screw it all the way down until after the hub is slid into position on the motor shaft. After tightening the setscrew, the top of the screw should be flush or below the outer diameter of the hub, or else the tire won’t fit on.

One of the issues with using a setscrew in an original LEGO piece is that the plastic is likely to crack. In comparison, the home made aluminum hub won’t have that problem and will hold up much better over the long run.

The LEGO replacement hub is finished. It can be used on variety of mechanisms and robots. Not bad for using the wrong tool for the job (milling machine vs. a lathe)!