From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: I Hate Mechanic Work - Bearing question
Date: Tue, 03 May 2005 15:03:05 -0400
Message-ID: <9ahf71d9tfigfl6q467n8t1a334bqm11ms@4ax.com>

On Tue, 03 May 2005 18:17:43 GMT, "Gary" <me@do-not-email-me.com>
wrote:

>
>"Chris Bryant" <bounces@bryantrv.com> wrote in message
>news:pan.2005.05.03.18.03.35.16237@bryantrv.com...
>> On Tue, 03 May 2005 17:41:37 +0000, Gary wrote:
>>
>>> And so my question: Is it safe to continue to run the bearing after
>>> scrambling the order in which each bearing was placed?
>>
>> I would strongly suggest replacing it.. very, very strongly. Bearings are
>> cheap, sitting by the side of the road waiting for a wrecker is priceless.
>>
>Where does one find bearings?  Are they generally available at your local
>automotive parts store such as Napa, Autozone, or Advance?

Yep.

>
>Will the parts store have a catalog listing for bearings for a '96 24M Terry
>travel trailer?

No.  But you buy bearings by the bearing number.  A (usually) 4 digit
number etched on the race.  In the case of tapered bearings like your
wheel bearing, you'll need the bearing number and the shell (outer
race) number.  Good idea to take the old parts when you go.

>
>Do bearings come in a standard size or do they have to be custom fitted,
>such as piston rings?

Standard sizes.

>
>Finally, same questions above for the grease seal?

The grease seal has a number on it too.

Now some advice for re-assembly.  The outer race is an interference
fit with the hub.  Some folks call it a "press fit" but that's not
completely accurate since the race is not pressed in.

The race's OD is slightly larger than the ID of the hub.  The proper
way to install the race is to put it in the deep freeze and get it as
cold as possible.  This shrinks its diameter.

Right before the installation, heat the area of the hub with a torch
until it is "spittin' hot".  That is, if you lick your finger and tap
it against the metal, the steam will cause a little spit.  About 400
deg, to be technical.

To install the race, have the hub hot and the race cold.  Place the
race over your thumb and forefinger, expanding them to hold the race
by its inner diameter. Quickly position the race over the hub and drop
it in place.  If it doesn't drop all the way down, QUICKLY tap it down
with a brass drift, hammer handle, etc. to seat it.  If you don't do
this very quickly (1 second at most), the race will absorb heat,
expand and lock itself in place wherever it came to rest.

To remove the race,

Heat the hub to spittin' hot.  Position it upside down on some sort of
support, say, a milk crate.  Using a can of canned air or R134a held
upside down so the liquid will discharge, very quickly chill the
inside of the race, trying not to get any refrigerant on the hub.
Simultaneously tap the race from the opposite (hub) side with a brass
drift or anything else soft you have handy.  Only a very gentle tap
will be necessary.  In most cases the race just falls out when
chilled.

The old fashioned way is to rub the race with an ice cube.  The
refrigerant method is faster plus you don't burn your fingers so often
:-)

Before installing the bearing, pack it thoroughly with grease.  You
can buy a little grease packing tool but I find it just as fast and
effective to do it by hand.  I put on a pair of surgical gloves and
then just rub the grease into the rollers with my fingers.

Drop the bearing into the race in the hub and then install the seal.
To install the seal, grease both the outer and inner surfaces, then
position it on the hub.  Find a socket that is the same diameter as
the seal or a tiny bit smaller.  Position this over the seal and drive
it home using a soft face hammer.  Drive the seal all the way down
against the stop.

I like to pack in some grease behind each bearing before I stick the
hub back on the axle.  Once the hub is back on the axle, the nut must
be properly tensioned.  Unless your manual says differently, use this
procedure.

Screw down the nut fairly tightly, say, 30 ft-lbs.  The bearings will
drag at this torque.  Slap the face of the hub in several places with
a soft hammer.  This will help take up any space that may remain in
the bearing train.  The nut will likely be (nearly) loose.  Back the
nut off a turn, spin the hub and repeat once more.  The nut should not
loosen any this time.  If it does, repeat again.

With the nut loose, tighten it until there is about a 20 pound drag on
the hub as measured at the lug bolt.  My Dexter axle instruction
illustrates this with a string attached to the lug and tugged with a
fish scale.  Slowly loosen the nut until the hub rotates freely.  Add
another approx 1/8th turn of looseness, align the cotter pin hole and
insert the pin.  Fill the grease cap with grease, tap it in place and
you're done.

John

From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: I Hate Mechanic Work - Bearing question
Date: Wed, 04 May 2005 12:14:03 -0400
Message-ID: <0esh715on25f0v2gie8belcs4uaoh8b7jr@4ax.com>

On Tue, 03 May 2005 13:37:18 -0700, Alan Balmer <albalmer@att.net>
wrote:

>On Tue, 03 May 2005 15:03:05 -0400, Neon John
><johngdDONTYOUDARE@bellsouth.net> wrote:
>
>>The race's OD is slightly larger than the ID of the hub.  The proper
>>way to install the race is to put it in the deep freeze and get it as
>>cold as possible.  This shrinks its diameter.
>>
>>Right before the installation, heat the area of the hub with a torch
>>until it is "spittin' hot".  That is, if you lick your finger and tap
>>it against the metal, the steam will cause a little spit.  About 400
>>deg, to be technical.
>
>I've installed new bearings in more than one trailer, and never had to
>fry or freeze anything.

No doubt.  There are always more than one way to do things, some good
and some bad.  The difference between shadetree mechanics and the rest
of us is that we know the difference.  the ones who remain shadetrees
are those who won't or can't learn from others.

this is an example.  Sure you can beat the race in and out.  I've done
it on occasion.  Beating the race in, in particular, can do a number
of things.  Chip the race.  Break it.  Divot out metal from the hub.
result in a cocked race.  With thin metal, even break the hub.

Similarly, I've installed many a race without cooling it.  Just heat
the hub enough that the race fits in.  Cooling simply gives me more
margin to work with.  Saves me having to remove the race and do it
over if I'm not fast enough.

FWIW, the heating and cooling method isn't "my" method.  IT is the
method taught by the major bearing mfrs, most electric motor mfr and
most industrial powertrain component mfrs.  I've attended a number of
schools from various mfrs.

The electric motor shop where I moonlight has a variety of induction
heaters for this purpose.  One heats the inner race for when bearings
interference fit onto a shaft.  Another heats the hub or endbell.
Faster and more uniform than a torch but the result is the same.

When the job involves a $40k motor and a bearing that costs several
hundred dollars, doing it right the first time takes on a whole new
meaning.