From: Richard (metal@fullwave.com)
Date: Wed May 05 2004 - 10:36:02 PDT
It's good that the tracks look OK, but if you're
just talking about the grousers (bars that stick out
and dig into the ground), then you have a few other
things to check. Well, if you're talking about a lot
of money anyway. If you're getting 'em cheap, say,
$500, then don't worry about it. A running 4-71 is
worth 500 by itself.
The track "rails" and "pins", which are what the
track-pads are bolted to, are real important. There's
a procedure for checking the slop, to see how badly
the pins are worn. They can be turned down and
bushings installed. Expensive though...
In fact, just so you know, if this is your first crawler...
EVERYTHING about undercarriages is expensive! <grin>
If the pads are loose on the rails, you may be about to
be frustrated.... When run with loose bolts, the boltholes
get "egged out", so that the bolts NEVER stay tight after
that.... Eventually, you'll get a pad lip which slips UNDER
on the side that it's supposed to be OVER, and then you
start bending pads, etc.. About all you can do, short of
replacing the rails, is weld the bolts in and run the thing
until it dies.
Also, the rails themselves wear down, and become more
rounded at the sides. Eventually, they won't track on
the idler properly, and you'll start "throwing tracks", which
is a real pain in the ass.
The idlers themselves wear out. The "ridge" in the center
needs to be tall enough, and "square" enough, to keep the
rails on it. Otherwise, you guessed it, you start throwing
tracks. Did I mention that's a real pain in the... ?? <g>
Finally, check the sprockets. If the tips of the teeth are
sharp, they're badly worn. In many cases, you can run
a cat for a more years that way, but in some cases, you'll
have trouble. They make inserts to weld in the "pockets"
between teeth, but again, they're expensive. Did I mention
"expensive" yet?
Also, the track-rollers are important. You'll notice that
they're made with a profile designed to carry and guide
the rails. If they're all chewed up, it'll cause trouble. Plus,
they usually have rolling bearings inside which need replacement
from time to time. The bearings aren't cheap. But I suppose
I mentioned 'expensive' already, huh? <g>
Basically, if they aren't throwing tracks now, you're probably
good for hundreds, or even thousands, more hours. But if
they DO walk out of the tracks now, then it's almost
guaranteed to be expensive to make them stop doing it.
Oh....first thing to do is check the track tension. There's
usually a zerk fitting used to pump grease into a big
cylinder which tensions the track. It's gotta be right or
the tracks will walk off, even with OK tracks. But if too
tight, you'll eat up all those expensive parts very quickly.
If you buy 'em, get the manuals ! Whatever they cost
ya, it'll pay off in the first weekend working on it.
hope this helps, and have fun. Crawlers are great...
Richard
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