If you go shopping for replacement wheels for your lawn mower, lawn
cart, whatever, you'll generally find two types: an all-plastic
wheel with no bearings at all, just a hole through the middle that
spins around the mounting bolt, or a metal wheel with the lousiest
stamped steel ball bearings they could manage to concoct.
Sometimes you can even find a hybrid: a plastic wheel with lousy
stamped steel ball bearings pressed into it. Whatever, all of
these types of wheel are absolute junk. The plastic wheels
quickly wallow out the openings so the wheels wobble, and they easily
get plugged up with grime and get difficult to turn. The ball
bearing wheels rust and get loose and sloppy very quickly, and fall
apart shortly thereafter. Both of these things will be squeaking
all the time, no matter how often you oil them, since they're exposed
to the weather and have no seals to keep rain and grit out.
It would be possible, of course, to make a wheel that uses good
quality ball bearings, with seals to keep contaminants out. It'd
last forever. But it's definitely a case of overkill; you'll be
installing bearings capable of thousands of RPM and hundreds of pounds
of load to support one corner of your crummy little lawn mower.
You'll be lucky if the set of four wheels doesn't end up costing more
than the mower.
This is not an application that calls for high-dollar, well-made
equipment. It calls for low-priced parts -- but there's no reason
that low-priced parts can't be well-designed for the application.
Here's the idea: design plastic wheels with oversize plastic ball
bearings. No metal parts at all. The wheel itself would
have the outer races formed into it. The inner race would be a
sleeve that fits around the standard axle bolt on a lawn mower.
There are two rows of plastic balls about 1/2" in diameter. And
there's a ball cage on each side, also made of plastic, that simply
snaps into place around the balls. The ball cage can easily be
designed to nearly fill the opening between the inner and outer race,
keeping most of the dirt and grit out. With balls this large, the
grit small enough to get past the ball cages wouldn't significantly
hinder the rolling action. Being plastic, the bearings would not
require any lubrication.
The end result would be a wheel that only costs marginally more than
the wheels presently on the market, would weigh about the same as the
existing plastic wheels (less than the existing metal wheels), and
would roll easier and last longer.
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