Bearing replacement

Bearing replacement

Post by John Deeri » Sun, 21 Oct 2001 11:18:47



Hello,

A friend of mine replaced the front bearing on his Supertigre S61
by force(used a bearing puller), I subsequently discovered
that the proper way was to heat the case in an oven and it would easily drop out.

What are the implications now ? The engine has not been started and appears
to turn ar normal.

Thanks,

J

 
 
 

Bearing replacement

Post by Bob » Sun, 21 Oct 2001 12:41:16


The proper way to remove a bearing is with a bearing puller. And the proper
way to insert the bearing is with a bearing press.

The 'homebrew' way is to put it in the oven.

You think the factory puts bearings in the oven?


Quote:
> Hello,

> A friend of mine replaced the front bearing on his Supertigre S61
> by force(used a bearing puller), I subsequently discovered
> that the proper way was to heat the case in an oven and it would easily
drop out.

> What are the implications now ? The engine has not been started and
appears
> to turn ar normal.

> Thanks,

> J


 
 
 

Bearing replacement

Post by WFTE » Sun, 21 Oct 2001 13:44:21


Actually when you remove certain bearings in an R/C engine you do heat it. That
is the way the factory repair centers do it.

Ken

Quote:
>The proper way to remove a bearing is with a bearing puller. And the proper
>way to insert the bearing is with a bearing press.

>The 'homebrew' way is to put it in the oven.

>You think the factory puts bearings in the oven?



>> Hello,

>> A friend of mine replaced the front bearing on his Supertigre S61
>> by force(used a bearing puller), I subsequently discovered
>> that the proper way was to heat the case in an oven and it would easily
>drop out.

>> What are the implications now ? The engine has not been started and
>appears
>> to turn ar normal.

>> Thanks,

>> J

 
 
 

Bearing replacement

Post by CK » Sun, 21 Oct 2001 15:56:23


Actually different "Factory authorized" repair facilities do it different
ways.

SOME use heat when heat is called for and some do not.

Take a look at what Clarence Lee has to say on this very subject.

He states that heat should be used when needed if the bearing will not come
out easily when using just a puller alone. UNLESS the factory instructions
specifically indicate that you should apply heat.

The bearing is held in place on the crankshaft by an interference fit. It is
also held in the actual engine case by this very same interference fit.

My only concern would be just how "secure" the bearing is on both the crank
and in the case. In most circumstances even a slight interference fit will
suffice.

What CAN happen when these interference fits become too loose is either the
bearing outer race will spin in the case or the inner race will become loose
enough for the crankshaft to begin spinning inside the inner race.

These are a couple of fairly easy and usually successful "fix's" to remedy
either problem.

BTW: Some years back we would modify cheap (at the time) engines for high
RPM use. Some were used in model boats, some in model cars and some for
pylon racing. The crank spinning inside the inner race used to be one of the
first failure points on these highly stressed engines. Application of the
above mentioned "fixes" would allow us to use the engine for a "few" more
runs before they would self destruct!!

CK


Quote:
> Actually when you remove certain bearings in an R/C engine you do heat it.
That
> is the way the factory repair centers do it.

> Ken

 
 
 

Bearing replacement

Post by Bill Vai » Sun, 21 Oct 2001 22:07:17


Careful here John,

There is some really bum gouge in this thread....

Bill Vail


Quote:
> Hello,

> A friend of mine replaced the front bearing on his Supertigre S61
> by force(used a bearing puller), I subsequently discovered
> that the proper way was to heat the case in an oven and it would easily
drop out.

> What are the implications now ? The engine has not been started and
appears
> to turn ar normal.

> Thanks,

> J

 
 
 

Bearing replacement

Post by CK » Mon, 22 Oct 2001 04:35:11


Bill,

Could you be a little more vague?


Quote:
> Careful here John,

> There is some really bum gouge in this thread....

> Bill Vail

 
 
 

Bearing replacement

Post by Paul McIntos » Mon, 22 Oct 2001 08:38:24


Did he use the bearing puller to INSTALL the bearing?  How?  If enough
pressure was placed on the center race to install the bearing into a cold
crankcase, the races were likely damaged and the bearing will not last as
long.

--
Paul McIntosh
Desert Sky Model Aviation
Engines, planes, bearings and boats
http://fly.mcintoshcentral.com
.

Quote:
> Hello,

> A friend of mine replaced the front bearing on his Supertigre S61
> by force(used a bearing puller), I subsequently discovered
> that the proper way was to heat the case in an oven and it would easily
drop out.

> What are the implications now ? The engine has not been started and
appears
> to turn ar normal.

> Thanks,

> J

 
 
 

Bearing replacement

Post by JP » Mon, 22 Oct 2001 08:51:08


Installing a single bearing cold (force fit) can be done successfully (with
great care).  In most "ball bearing" model aircraft engines, though, the
crankshaft is supported by two bearings, and it's important that the two
bearings and the crankshaft be colinear, to prevent or at least minimize
binding.  Without _very_ precise tooling, it would be difficult to get accurate
alignment if the job is done cold.

Success is much more likely if the case is heated just enough to allow both
bearings to be slipped in at the same time, with the crankshaft serving as the
alignment jig and holding the bearing alignment while the case cools.

Your mileage (and opinion) may vary.

John P.

 
 
 

Bearing replacement

Post by Bill Vai » Tue, 23 Oct 2001 00:02:18


Sorry Ck,

I was feeling cranky:-)  Here is a little more....

Quote:
>The proper way to remove a bearing is with a bearing puller. And the proper
>way to insert the bearing is with a bearing press.
>You think the factory puts bearings in the oven?

This is just plain wrong.... While the factory may or may not heat the case
to install the bearings I (and anyone else I've raced with in 30+ years)
always reinstall the bearings on all my performance engines by heating the
case.  Bearings are a sweat fit in the case and should be perfectly aligned
with the case/crank bore.  The easiest way to do this is to heat the case
and use the crank itself as an alignment "tool".

Quote:
>Take a look at what Clarence Lee has to say on this very subject.
>He states that heat should be used when needed if the bearing will not come
>out easily when using just a puller alone. UNLESS the factory instructions
>specifically indicate that you should apply heat.
>The bearing is held in place on the crankshaft by an interference fit. It

is also held in the actual engine case by this very same interference fit.

Clarence was a great engine man and still very knowledgeable if not somewhat
dated. He is now (and has been for years) a very respected engine collector.

He was also very involved in the development of the K&B/Veco line of engines
30+years ago and to my knowledge K&B's were the only engine that the bearing
was not a slip fit on the crank. They were press fit.

Bearings should NOT be held in place on the crankshaft by an interference
fit!  They were in some K&B's and  it was a nightmare. On K&B's where the
main bearing was press fit on the crank I would remove the crank and stuck
bearing from the engine, chuck the bearing in a vise and hammer the end of
the crank until the bearing slipped off.  That of course destroyed the
bearing.  I would then polish the crank until the bearing was a tight slip
fit and put in a new bearing.  I own 300+ engines from Nelsons to Nova
Rossi's, 40+ K&B's to OS and Fitzpatricks and with the exception of some
older K&B's, the bearings are NOT and should NOT be a press fit on the
crank.

Now to answer the original question. "What are the implications now (of cold
pressing the bearings in place)?"  In all likelihood nothing.  Just run the
thing.  I've seen folks run engines orange with rust and while I don't
recommend it and performance and life may suffer, it will be fine.  If you
are running your engine in the 30,000 rpm range it would matter but for the
average OS, TT, GMS, ASP... turning 12,000 rpm and making 1.2ish horsepower
it just doesn't matter. Any possible damage to the balls or races (if the
cage is damage, that matter!), or any misalignment will not be a factor in
sport flying.  VERY few model engines are flown enough to find the service
life of the bearings even if poorly installed and misaligned.  Look back at
the years of SPORT flying at your club...when was the last time you saw a
bearing failure?

My guess is that we will disagree but that is OK...

Bill Vail


Quote:
> Bill,

> Could you be a little more vague?



> > Careful here John,

> > There is some really bum gouge in this thread....

> > Bill Vail

 
 
 

Bearing replacement

Post by Brian Hampto » Tue, 23 Oct 2001 09:09:59


For anyone interested in a rather technical explanation of just what is involved
with correctly fitting bearings to an engine go to this link
http://home.wxs.nl/~wakke007/fmv/fmv_1.htm
This article was written back in the late 70's for a world class FAI T/R diesel
engine where perfection of fit was absolutely necessary. The bearing section
begins on the second page but I would highly recommend reading through the
entire article.

Brian Hampton
Adelaide, South Oz

 
 
 

Bearing replacement

Post by Paul McIntos » Wed, 24 Oct 2001 00:39:19


That was a very interesting article.  It confirms that heating the crankcase
to install the bearings is the most economical way for sport engines.

One of the statements made puzzles me.  They state that heating the bearings
to 100-150C would damage them.  I can't see this happening to properly heat
treated materials and modern lubricants.  Most all bearings are supplied
with light greases that can easily withstand those temperatures.

--
Paul McIntosh
Desert Sky Model Aviation
Engines, planes, bearings and boats
http://fly.mcintoshcentral.com
.

Quote:
> For anyone interested in a rather technical explanation of just what is
involved
> with correctly fitting bearings to an engine go to this link
> http://home.wxs.nl/~wakke007/fmv/fmv_1.htm
> This article was written back in the late 70's for a world class FAI T/R
diesel
> engine where perfection of fit was absolutely necessary. The bearing
section
> begins on the second page but I would highly recommend reading through the
> entire article.

> Brian Hampton
> Adelaide, South Oz

 
 
 

Bearing replacement

Post by Brian Hampto » Wed, 24 Oct 2001 08:34:50


Quote:

> That was a very interesting article.  It confirms that heating the crankcase
> to install the bearings is the most economical way for sport engines.

> One of the statements made puzzles me.  They state that heating the bearings
> to 100-150C would damage them.

That puzzled me too...that sort of temperature wouldn't even affect aluminium
let alone steel. However the article mentioned leaving it to Henry Nelson so
presumably he could throw some light on it? My only guess is that they had been
discussing the strong interference fits used by Henry Nelson and the special
requirements for it and that if a normal clearance bearing was substituted then
the compression of the outer race on cooling would ruin it.

Brian Hampton
Adelaide, South Oz

 
 
 

Bearing replacement

Post by Bill Vai » Wed, 24 Oct 2001 09:38:13


Paul,

I didn't read the entire article but I would guess they are worried about
the bearing retainer.  Just the other day I was removing a set of ceramic
bearings and without thinking, damaged the nylon bearing retainer with too
much heat.  Doh!  Most if not all bearings fail because the retainer fails.
Low cost low speed bearings usually have a retainer that is riveted or has
bent tabs which work loose.

Just a guess

Bill Vail


Quote:
> That was a very interesting article.  It confirms that heating the
crankcase
> to install the bearings is the most economical way for sport engines.

> One of the statements made puzzles me.  They state that heating the
bearings
> to 100-150C would damage them.  I can't see this happening to properly
heat
> treated materials and modern lubricants.  Most all bearings are supplied
> with light greases that can easily withstand those temperatures.

> --
> Paul McIntosh
> Desert Sky Model Aviation
> Engines, planes, bearings and boats
> http://fly.mcintoshcentral.com
> .


> > For anyone interested in a rather technical explanation of just what is
> involved
> > with correctly fitting bearings to an engine go to this link
> > http://home.wxs.nl/~wakke007/fmv/fmv_1.htm
> > This article was written back in the late 70's for a world class FAI T/R
> diesel
> > engine where perfection of fit was absolutely necessary. The bearing
> section
> > begins on the second page but I would highly recommend reading through
the
> > entire article.

> > Brian Hampton
> > Adelaide, South Oz

 
 
 

Bearing replacement

Post by Paul McIntos » Thu, 25 Oct 2001 01:13:55


I was kind of confused about the timeline of a lot of the things mentioned.
They seemed to jump back and forth from the '70s to present (whenever the
article was written).  The only Nelson engines mentioned (IIRC) were a
decade or more ago when nylon retainers were not very common.  There were
other non-metallic retainers that would not be too bothered by heat at that
time.  I am with Brian in that they were also talking about extreme
interference fits.

--
Paul McIntosh
Desert Sky Model Aviation
Engines, planes, bearings and boats
http://fly.mcintoshcentral.com
.

Quote:
> Paul,

> I didn't read the entire article but I would guess they are worried about
> the bearing retainer.  Just the other day I was removing a set of ceramic
> bearings and without thinking, damaged the nylon bearing retainer with too
> much heat.  Doh!  Most if not all bearings fail because the retainer
fails.
> Low cost low speed bearings usually have a retainer that is riveted or has
> bent tabs which work loose.

> Just a guess

> Bill Vail



> > That was a very interesting article.  It confirms that heating the
> crankcase
> > to install the bearings is the most economical way for sport engines.

> > One of the statements made puzzles me.  They state that heating the
> bearings
> > to 100-150C would damage them.  I can't see this happening to properly
> heat
> > treated materials and modern lubricants.  Most all bearings are supplied
> > with light greases that can easily withstand those temperatures.

> > --
> > Paul McIntosh
> > Desert Sky Model Aviation
> > Engines, planes, bearings and boats
> > http://fly.mcintoshcentral.com
> > .


> > > For anyone interested in a rather technical explanation of just what
is
> > involved
> > > with correctly fitting bearings to an engine go to this link
> > > http://home.wxs.nl/~wakke007/fmv/fmv_1.htm
> > > This article was written back in the late 70's for a world class FAI
T/R
> > diesel
> > > engine where perfection of fit was absolutely necessary. The bearing
> > section
> > > begins on the second page but I would highly recommend reading through
> the
> > > entire article.

> > > Brian Hampton
> > > Adelaide, South Oz

 
 
 

Bearing replacement

Post by Charles & Peggy Robinso » Sat, 27 Oct 2001 09:44:43


  Don't worry about it.

  CR

Quote:

> Hello,

> A friend of mine replaced the front bearing on his Supertigre S61
> by force(used a bearing puller), I subsequently discovered
> that the proper way was to heat the case in an oven and it would easily drop out.

> What are the implications now ? The engine has not been started and appears
> to turn ar normal.

> Thanks,

> J