Roller Bearings and What Kills Them
Grit kills a bearing long before load does, and on the coast the grit arrives with salt already in it. The wheel specification used at Mount Pleasant Sliding Gates Narcoculture is sealed for that reason, since sliding hardware on a Mount Pleasant driveway runs in an atmosphere that finds any opening in a race and stays there.
Sealed and Unsealed
An unsealed bearing has an open race protected only by a shield, and it depends on periodic lubrication that almost never happens. A sealed bearing is packed at the factory and closed with a rubber seal on both faces. It cannot be relubricated and it does not need to be, and it will outlast an unsealed wheel several times over here.
Why Grease Makes It Worse
Owners often grease the outside of a wheel that is running rough. On an exposed roller that grease becomes a collector, holding sand and shell dust against the seal until the seal is abraded through and the abrasive is inside the race. A dry film lubricant on the wheel stem is fine. Grease on the wheel itself shortens its life.
The Three Sounds
A dry rumble that rises with speed is a race that has lost its lubricant. A regular click once per wheel revolution is a flat spot or a cracked ball, and the wheel is finished. A grinding hiss that varies along the run is usually not the bearing at all but debris on the track, and cleaning the track will settle it.
Testing Without Tools
Disengage the operator, move the gate to mid travel, and lift each wheel clear where the design allows. Spin it by hand. It should turn several revolutions freely, run silently, and stay square to its stem. Any rocking on the stem is a worn stem or a worn housing rather than a bearing, and replacing only the wheel will not cure it.
Replacement Timing
Wheels are inexpensive and the labour is most of the cost, so they are replaced as a set rather than one at a time. A seized wheel that gets dragged flattens on one side, and a flat wheel then hammers the track and the frame on every cycle, which turns a cheap part into an alignment job.