Getting Your Bearings Right

Morning project: Replace the bearings underneath this bad boy, so it stops binding when it rolls back and forth.

Step 1: Detach the gantry from the trolley plate underneath it. The bearing trucks are bolted to the bottom face of the trolley plate.

Step 2: Hoist the gantry up a fraction, just enough to clear the trolley plate . . .

. . . just enough so you can see daylight between the gantry framework (on top) and the trolley plate (which it normally rests on).

Step 3: Start advancing the trolley plate out from under the raised (and braced) gantry, in order to open up access to the bolts that attach the bearing trucks to the bottom of the trolley. Keep advancing . . .

. . . and advancing, until the trolley plate is clear out from under the braced gantry.

Now you have access to all the bolts that go through the trolley plate to hold the bearing trucks onto the bottom of it.

Step 4: With the top face of the trolley plate exposed, undo the bolts that attach the bearing trucks to the bottom of the trolley. (The bearing truck is the C-shaped hunk of metal directly underneath the plate from where he’s loosening a bolt.)

Step 5: Slide old bearing trucks down guide rail to remove.

Step 6: Amuse self by gasping at how trashed the old bearings got.

This is a bearing truck turned belly-up. Normally this side of the bearing is what slides back and forth on the guide rail.

See the row of balls, a little bit hidden, toward the top of the picture? There’s supposed to be another entire row right underneath that, and you can see the channel for them—the bearing race—but they’re all missing.

See the deep groove that cuts halfway across the bearing from the right? That’s not supposed to be there at all. That’s the spot where a single ball got stuck under the bearing and was dragged back and forth long enough to erode that groove into the steel of the bearing truck. Nice. What’s amazing is that the gantry was still going back and forth at all.

Step 7: Slide new bearing trucks down guide rail to install under trolley plate.

Step 8: Reposition trolley plate under gantry again. Align and re-attach. Check for extra parts. Cross fingers. Repeat above steps under opposite side of gantry. Put away tools. Go home.