IMS - Going with SKF hybrid

[edc]

Originally Posted by Gelbster

Do you mean to say Hartech?
I have the hard copy of the Magnum Opus by Baz.
https://www.hartech.org/images/downloads/Hartech%20Engine%20Guide%20(interim).pdf
this is fun:
https://www.hartech.org/hartech-videos

Yes I do mean Hartech.

[Smallblock454]

Hello Silber,

concerning the SKF 6204 2RSLTN9 hybrid bearing. Please read the recommendations from SKF for that bearing.

Sorry i coudn''t find an english version of that product catalogue: Medienbibliothek

Read chapter 15F Hybridlager

This bearing series is designes for electric motors. Not shure if this bearing is really recommendable for an IMSB application.

Regards, Markus

[Gelbster]

Brilliant research Markus.
The CH does nothing to solve the seal issue nor the out of round,nor the run out problems that bedevil the generic deep groove ball bearing for IMSB.
The surprising success of the modified roller bearing for IMSB may be that it is more tolerant of slight alignment problems.
If the original bearing has survived 100K miles, a generic 1RS $3 bearing would probably perform just as well. It would be more tolerant of clumsy Installation.
But without the results of a Pre-Qualification Inspection much of this chatter is meaningless.......
Anyway, it is easy to replace the IMSB whenever you replace the clutch (per Markus). So ultimate life span is a curious goal.
Minimizing the risk of premature failure with a more fault tolerant design - now that may be a more useful goal in the M96 real world. That is what an oil fed, plain bearing with all kinds of modifications achieves - at a price. But only if the engine passes Pre-Qualification.

[Smallblock454]

Hello,

this might chart be also helpful. It shows the specs and abbreviations for SKF bearings. Sorry, i have it only in german language. But it may help and also it might show that there are more things to consider than width, height and rpm.

@ Gelbster: i think the main problem is that this specific SKF 6204 2RSLTN9 bearing wasn't designed for an application in an engine oil bath. It was designed for a dry environment as a electric motor bearing. Also it isn't very heat resistant. For example it is not allowed to be heated up over 80 degrees celsius (176 degree fahrenheit) when you install it. No problem when you install it as an ISMB, because you have to cool it down, but it shows that it is not very heat resistant. In an inner engine enviroment you can have 150 degrees celsius (300 degree fahrenheit) very easily.

Regards, Markus

[Silber]

This is where i got my temperature data:

Temperature limits

If it turns out the skf bearing is a no-go thats OK. If my analysis of the root cause is good, the pelican bearing shouldbe just fine with a freeze plug behind it to stop grease washout.

Silber

[Smallblock454]

Hello,

for those that are interested in i found the english version of the SKF bearing catalogue. Lots of infos:
Library

Overview of all 6204 SKF bearings available:
SearchResult

And this might be interesting for all that want to go deeper in this topic:
SearchResult

@ Silber: think the pelican bearing is OK for shure. Most important part is very careful de- / installation.

@ Gelbster: I recommend to read the introduction of the SKF catalogue about what types of bearings are available and what are the differences in detail. Chapter A to H. I'm pretty shure you'll find some interesting facts.

Regards, Markus

[Smallblock454]

Sorry, double posting.

[Gelbster]

Originally Posted by Silber

This is where i got my temperature data:

Temperature limits

If it turns out the skf bearing is a no-go thats OK. If my analysis of the root cause is good, the pelican bearing shouldbe just fine with a freeze plug behind it to stop grease washout.

Silber

The freeze plug & grease washout.I don't understand.
The fundamental problem is that conventional IMSB wisdom suggests the bearing seals deteriorate because of heat.(BTW, the same problem affects a similar bearing in the 6 speed gearbox.) Then the grease washes out because the bearing is partially(1/3) immersed in engine oil.
How will a freeze plug solve the heat deterioration problem for the bearing seals ?
If you fit a Freeze plug and remove one or both seals, that is different.
If you remove both seals ,the logic of a freeze plug is obvious.You avoid partial filling the IMS tube with oil
If you remove just the outer seal, the freeze plug seems unnecessary.
So what does the freeze plug achieve exactly and with which seals remaining/removed?
Assuming it is a good interference fit & doesn't distort the tube during install.

[Smallblock454]

I think there are more parameters than seal deterioration.

Type of bearing and capability to handle axial force, torsion and vibrations.
Type of cage.
Type of grease if you have a sealed one - heat resistancy.
Type of sealing and seal material.
Misalignment IMS and ISMB.
Rotation Per Minute / Friction inside the IMSB.
Amount of contamination the IMSB can handle. hc
Heat and heat cycles.
Maybe fast up and downcycling when motor revs up or down.

And again. If you have a bearing that was designed to run as a sealed bearing and you remove the sealing, you have no specification, because the bearing wasn't designed for that.

There are bearings that are designed to run in oil. These might be the right choice if you want to run an open bearing,

Regards, Markus

[Silber]

Originally Posted by Gelbster

The freeze plug & grease washout.I don't understand.
The fundamental problem is that conventional IMSB wisdom suggests the bearing seals deteriorate because of heat.

I am not sure this is entirely right, I think the main problem is the heat cycles of the air in the IMS tube sucking oil past the seals. I am trying to solve that issue.

So, I am correcting the problem I think to be the root cause of the issue. I can see heat deteriorating the seals to some degree, perhaps a bearing with Viton seals would be ideal. If heat deterioration was the only issue, why would the oil run into the IMS tube, but not come back out?

I am leaning toward the pelican bearing with the freeze plug rather than a fancy ceramic bearing, not sure if I really believe ceramic is needed at this point especially if I change them every time I change the clutch. Standard 6204's are around US $6-10 each. Porsche thought they were a lifetime solution and if I can fix the oil ingress issue, I can probably make 75k miles or so.

Silber

P.S. - Here was where I explain my theory IMS - Going with SKF hybrid

[Silber]

Great points Markus, I answer below

Originally Posted by Smallblock454

Make shure it can't move.

Freeze plug is designed to hold back heated engine coolant at a high pressure, should be more than up to this task.

Originally Posted by Smallblock454

Make shure it doesn't put too much pressure on the IMS tube and that the pressure is evenly.

The place where it will be driven into IMS tube is at the very most supported point in the entire IMS assembly. Deep inside all the reinforcement around the sprocket. It can push against that casting, same as the bearing just with a tube in between.

Originally Posted by Smallblock454

Make shure it doesn't influence the balancing of the IMS tube.

It is a very lightweight and symmetrical part, I am not worried of this.

Originally Posted by Smallblock454

Make shure it is removable – just in case

.
Freeze plugs are removeable HOWEVER I would not use a freeze plug with anything other than an uprated center bolt. If the center bolt fails you will have to drive the freeze plug deep into the shaft to remove the broken bolt OR come up with a way to pull via the stub of the original broken bolt.

With an uprated center bolt, I cannot see it snapping when you pull, so not really a concern.

Rather than calculating pressures, I am trying to source a damaged Intermediate shaft to plug, and then put an air pressure gauge onto, then just stick it in an oven at 300f and see what we get.

regards,

Silber

[Smallblock454]

Hello Silber,

there are 3 different types of IMS for the 986 available - depends on bearing and engine type. Make shure you get the right one for you car, because there are differences.

Regards, Markus

[Silber]

Markus,

I am just planning to plug the end of the spare IMS and test how much pressure is generated by heating it up. Will not actually be installed on my car, so doesn't really matter which version it is.

Steve

[Silber]

Thought I would update this thread with what I finally decided to do.

Since I ultimately decided to prepare my car to SCCA STR class rules, I am only allowed to put in the part that is either the Porsche original part, or the most closely similar available part. Since Porsche does not offer an IMS bearing separately, the most similar part available that I could find was the pelican parts IMS kit. Any other part would likely get me protested and I would lose.

If I had not been preparing to autocross class rules I would’ve put in a freeze plug, but since I am that is not an option.

Regards,

Silber