[R-390] Plastic Gears

David Wise [email protected]
Mon, 2 Feb 2004 13:53:07 -0800


I repaired one of the bevel gears in mine.  The
plastic they used shrinks over time, and eventually
gets so tight on the metal core that it bursts.

I ground out the hole until when the break was squeezed
shut it was a sliding fit on the core.  Then I roughened
the core and glued them together with JB Weld.  A
plastic wire tie held the break shut while the epoxy
hardened.  Not satisfied with this, I also reinforced
the gear with a washer JB-Welded to its flat backside.
(As with the main bond, I roughened the surfaces.)
Being a bevel gear, the slight decrease in diameter was
inconsequential.  It's been trouble-free for a couple of
years now.

This technique may also work on the spur gears.

One other thing.  I found the detents to be ridiculously
stiff on the Range and Deviation switches, and took
out a couple of leaf springs from each.  They're much
lighter now (without being sloppy), which is very important
for my unit as it doesn't have the original Range and
Deviation knobs.  No doubt the originals got their
flanges broken off from the stiff detents!

Love my 8640B,
Dave Wise

> -----Original Message-----
> From: Sam Doughty [mailto:[email protected]]
> Sent: Friday, January 04, 1980 7:18 AM
> To: [email protected]
> Subject: [R-390] Plastic Gears
>=20
>=20
> Help!, my 8640B just busted a gear in the Range selector assembly.
> Would anybody know where I could find one or does anyone of you
> have a spare or a junker for sale? Was in the middle of an alignment
> and can't go any father.  =20
>=20
> Thanks,   Sam
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>=20