OS 70 Surpass bearing replacement

OS 70 Surpass bearing replacement

Post by Alan Harrima » Tue, 27 May 2003 22:50:32



Hi all,

This is my first attempt at replacing the bearings (both front and
rear) on my OS 70 Surpass. I pretty much followed the directions in
Harry Higley's book, "All About Engines"  All went well, except it
took considerable force to remove the crankshaft. After the front and
rear bearings were installed, I performed a spin test. While it spins
very easily, I can hear and feel a very slight roughness. I have to
listen closely, but it's there, especially when the motor is pointed
bottom side down. Is this cause for concern? I had expected it would
be silky smooth quiet.

One possibility, when I tried to install the new rear bearing onto the
crankshaft, it wouldn't go on easily. So I positioned the crankshaft
squarely over a piece of wood with a hole drilled just large enough to
accommodate the shaft. After a couple of taps the bearing was in
place. Now I'm wondering if perhaps the bearing was damaged during
this process? Any thoughts or suggestions?

Thanks,
Alan Harriman

 
 
 

OS 70 Surpass bearing replacement

Post by Paul McIntos » Tue, 27 May 2003 23:22:10


Yes, the rear bearing was damaged.  It will run but will never be like new
and may come apart rather quickly.  What happened is you tapped on the
crankshaft and that transferred all the force from the inner race to the
outer race through the balls.  This dented probably both races.

Go to my web site and look up the bearing replacement FAQ for a preferred
way to install bearings.

http://rc-bearings.com


Quote:
> Hi all,

> This is my first attempt at replacing the bearings (both front and
> rear) on my OS 70 Surpass. I pretty much followed the directions in
> Harry Higley's book, "All About Engines"  All went well, except it
> took considerable force to remove the crankshaft. After the front and
> rear bearings were installed, I performed a spin test. While it spins
> very easily, I can hear and feel a very slight roughness. I have to
> listen closely, but it's there, especially when the motor is pointed
> bottom side down. Is this cause for concern? I had expected it would
> be silky smooth quiet.

> One possibility, when I tried to install the new rear bearing onto the
> crankshaft, it wouldn't go on easily. So I positioned the crankshaft
> squarely over a piece of wood with a hole drilled just large enough to
> accommodate the shaft. After a couple of taps the bearing was in
> place. Now I'm wondering if perhaps the bearing was damaged during
> this process? Any thoughts or suggestions?

> Thanks,
> Alan Harriman


 
 
 

OS 70 Surpass bearing replacement

Post by Alan Harrima » Wed, 28 May 2003 02:23:54


On Mon, 26 May 2003 14:22:10 +0000 (UTC), "Paul McIntosh"

Quote:

>Yes, the rear bearing was damaged.  It will run but will never be like new
>and may come apart rather quickly.  What happened is you tapped on the
>crankshaft and that transferred all the force from the inner race to the
>outer race through the balls.  This dented probably both races.

Thanks for the reply and the great info. Looks like I'll be ordering
another bearing. From what I understand now, it's important not to
allow uneven side force to be applied from one race to the other.
Perhaps if I had a hollowed dowel, sized in such a way as to only
contact the inner race, it wouldn't have damaged the bearing as I
tapped it into place. Or maybe I need a new crankshaft?

I'm curious, you have great prices on replacement bearings. Are these
shipping from the UK? I paid $20 for a stock OS replacement. Also, do
they include front, rear and cam bearings? (OS 70 Surpass)

Thanks,
Alan Harriman
Rochester Hills, Mich

Quote:

>Go to my web site and look up the bearing replacement FAQ for a preferred
>way to install bearings.

>http://rc-bearings.com



>> Hi all,

>> This is my first attempt at replacing the bearings (both front and
>> rear) on my OS 70 Surpass. I pretty much followed the directions in
>> Harry Higley's book, "All About Engines"  All went well, except it
>> took considerable force to remove the crankshaft. After the front and
>> rear bearings were installed, I performed a spin test. While it spins
>> very easily, I can hear and feel a very slight roughness. I have to
>> listen closely, but it's there, especially when the motor is pointed
>> bottom side down. Is this cause for concern? I had expected it would
>> be silky smooth quiet.

>> One possibility, when I tried to install the new rear bearing onto the
>> crankshaft, it wouldn't go on easily. So I positioned the crankshaft
>> squarely over a piece of wood with a hole drilled just large enough to
>> accommodate the shaft. After a couple of taps the bearing was in
>> place. Now I'm wondering if perhaps the bearing was damaged during
>> this process? Any thoughts or suggestions?

 
 
 

OS 70 Surpass bearing replacement

Post by Paul McIntos » Wed, 28 May 2003 04:56:12


When you install the bearing it is VERY important not to use the inner race
to force the bearing into place.  The  forces generated on the balls and
races by doing that are many times the amount of force you are applying to
the bearing.  The ideal bearing inserton tool would be a slip fit into the
inner race with the outer diameter just under the size of the outer race.
It would also have a recess so that it would not push on the inner race
during installation.

Machining of model engine crankcases is very accurate and if you get the
bearing in straight, there will not be any appreciable off-axis loading.

I ship from either the US or UK depending on where I have the particular
bearings stocked.  I am opening a shipping point in Phoenix, AZ to handle
the US customers.

My bearing sets contain front, rear and cam bearings for most four strokes.
Some, like the smaller Saitos, don't have separate cam bearings.


Quote:
> On Mon, 26 May 2003 14:22:10 +0000 (UTC), "Paul McIntosh"

> >Yes, the rear bearing was damaged.  It will run but will never be like
new
> >and may come apart rather quickly.  What happened is you tapped on the
> >crankshaft and that transferred all the force from the inner race to the
> >outer race through the balls.  This dented probably both races.

> Thanks for the reply and the great info. Looks like I'll be ordering
> another bearing. From what I understand now, it's important not to
> allow uneven side force to be applied from one race to the other.
> Perhaps if I had a hollowed dowel, sized in such a way as to only
> contact the inner race, it wouldn't have damaged the bearing as I
> tapped it into place. Or maybe I need a new crankshaft?

> I'm curious, you have great prices on replacement bearings. Are these
> shipping from the UK? I paid $20 for a stock OS replacement. Also, do
> they include front, rear and cam bearings? (OS 70 Surpass)

> Thanks,
> Alan Harriman
> Rochester Hills, Mich

> >Go to my web site and look up the bearing replacement FAQ for a preferred
> >way to install bearings.

> >http://rc-bearings.com



> >> Hi all,

> >> This is my first attempt at replacing the bearings (both front and
> >> rear) on my OS 70 Surpass. I pretty much followed the directions in
> >> Harry Higley's book, "All About Engines"  All went well, except it
> >> took considerable force to remove the crankshaft. After the front and
> >> rear bearings were installed, I performed a spin test. While it spins
> >> very easily, I can hear and feel a very slight roughness. I have to
> >> listen closely, but it's there, especially when the motor is pointed
> >> bottom side down. Is this cause for concern? I had expected it would
> >> be silky smooth quiet.

> >> One possibility, when I tried to install the new rear bearing onto the
> >> crankshaft, it wouldn't go on easily. So I positioned the crankshaft
> >> squarely over a piece of wood with a hole drilled just large enough to
> >> accommodate the shaft. After a couple of taps the bearing was in
> >> place. Now I'm wondering if perhaps the bearing was damaged during
> >> this process? Any thoughts or suggestions?

 
 
 

OS 70 Surpass bearing replacement

Post by Tom Wale » Wed, 28 May 2003 09:07:38


Paul, here is what I have done in the past with my Super Tigres: I heat the
crank case in the oven and put the bearing in the freezer just long enough
to give it a good chill, the bearing just falls in place. Never had a
problem with that but is it a safe practice?

Tom Wales
AMA 435536

 
 
 

OS 70 Surpass bearing replacement

Post by Paul McIntos » Wed, 28 May 2003 15:33:04


Yes, that is the preferred way.  Putting the bearing in a freezer isn't
always necessary, though.


Quote:
> Paul, here is what I have done in the past with my Super Tigres: I heat
the
> crank case in the oven and put the bearing in the freezer just long enough
> to give it a good chill, the bearing just falls in place. Never had a
> problem with that but is it a safe practice?

> Tom Wales
> AMA 435536