Assembling the NOS 084

[blsnelling]

Tonight I begin assembling the NOS 084. I finally got the case yesterday.

First question. Normally I heat a case to 300F to install bearings and then the crank. The bearing's are already installed and ready for the crank. I don't want to take a chance blistering the coating on this NOS case, so what temp IS safe, guaranteed?

 

[lesorubcheek]

I can't comment on procedures for Stihls, but one thing that may help is to put the crank in the freezer (in a sealed bag helps prevent moisture problems). A cold crank will reduce the amount you need to heat the bearings (and case) to get it installed. I would think the paint on the case is safe to 200 degrees, maybe more. I'm sure you'll hear the real answer from some of the Stihl experts.

Dan

 

[blsnelling]

The crank is already in the freezer, in a ZipLock bag with the air sucked out of it

 

[Lakeside53]

You don't heat the case/bearings to put the crank in. If the cages are nylon, they will take it in the shorts if you heat them then push a crank though them.

Factory install on the 84 is to use the right tools to suck the slightly lubricated cranks onto the bearings at room temp. It's a tight press fit. You can use the techniques I showed on the 066 - suck the crank onto the flywheel side with the flywheel nut and some spacers, then the crank side with the clutch spyder and some spacers - combined with long 5mm screws to move the case on evenly.


BTW... the powdercoat OEM case is safe to temps way above what you use...

 

[blsnelling]

I fail to see where the cages are affected by heating and pushing the crank in. There's no stress on the cage. I heat the case and bearing assembly to 300F. The crank is in the freezer. The crank drops in with no pressure.

 

[Lakeside53]

Go ahead then. They are your bearings. I sure won't do it that way.

You might want to go to SKF, Nachi or other bearing manf sites and look at the engineering data on the max temp you are allow to heat a bearing for shaft installation. Most are about 165F... and you have to use an induction heater, not convection heating.

Heat the case to 300F and the bearings can fall out.


I think Stihl, Husky etc would use your method if it was safe...

 

[blsnelling]

So you're saying 300F is too hot for the cage? I would think it would get a lot hotter than 160F in normal operation.

 

[Stihl 041S]

Brad, reread his post.
Rob

 

[Lakeside53]

So you're saying 300F is too hot for the cage? I would think it would get a lot hotter than 160F in normal operation.

In normal opertion they are rotating, and the thrust is radial, not axial.

 

[blsnelling]

But without the heat, you're going to put a lot more axial thrust on it than without. Again, are you just saying the temp is too high for the nylon to withstand? As far as the bearing coming out, with both the case and bearing heated to the same temp, it's still locked in there.

 

[Lakeside53]

I have to go and split a guys 084 case. Be back later.

Brad - you might get any with any technique, or you might reduce the life of your long life bearing, but just because it appeared to work doesn't make it right.

Maybe I'm a bit to sensitive to shadetree techniques - having dealt with many aftermaths..

 

[blsnelling]

I'm just trying to understand what you're saying is at risk so that I can proceed carefully. I appreciate the discussion.

 

[Lakeside53]

But without the heat, you're going to put a lot more axial thrust on it than without. Again, are you just saying the temp is too high for the nylon to withstand? As far as the bearing coming out, with both the case and bearing heated to the same temp, it's still locked in there.

With the correct tool, axial thrust is via the inner core, so it's zero on the bearing race and outer ring.

Track down the reading material on the bearing sites. Basically two issue - cage material temperature and differential heating or cooling denting the races. You might get the heating even, but you have no control over the cooling.

And no.. the 5xxxx steel and mag expand at different rates to different end points.


Now I really have to go.

 

[Gumnuts]

mmmm...me too

Reached the same dilemna .
Andy had said 175* reco max for nylon cages.
Even go the safe side of.
In the process of making Stihl copies at the moment - groan/ time.
Although if you look under seals( forum search)there's a guy who used a C or G clamp.One guy even reco'd drill press arbor.

maybe extract the bearings -for the freeze fit.
Be interested what you decide.....


dang that styro....goes everywhere :biggrinbounce2:

 

[Stihl 041S]

Yo Luke, listen to Yoda. Or F%ked
be you will!

 

[blsnelling]

dang that styro....goes everywhere :biggrinbounce2:

:angry2::chainsawguy:

 

[blsnelling]

So heat is the issue. OK, so I'll heat it to 170F, lowest my oven will go, and see if it'll drop in. Can't hurt to try. Gots to be careful with these b e a u t i f u l NOS case halve you know

 

[Dan Forsh]

I'm just trying to understand what you're saying is at risk so that I can proceed carefully. I appreciate the discussion.

Where's the smilie for mule-headed.....

 

[blsnelling]

Where's the smilie for mule-headed.....

Mule-headed? Just trying to understand the issue so I can learn here I'm not going to just drop my head and have the dealer do something I can. THAT I am too mule-headed for

 

[RiverRat2]

Mule-headed? Just trying to understand the issue so I can learn here I'm not going to just drop my head and have the dealer do something I can. THAT I am too mule-headed for

Cant resist!!!!!!!!

Here ya go Brad!!!!!!

LOL!!!!!! Heee Hawwwwww!!!!!!!!!! Ya Mule Headed Beotch!!!!!!!

Where is Festus when ya need him???????