Bearing help 3

[cancsco]

Hi,
I have a crankshaft which rotates with a 6000 rpm speed.
This crankshaft is driven by a motor and I have a setup where in the crankshaft is loaded both sides( motor in the center)
I have installed 2 bearings on each side to support the shaft. The ball bearings that I use are 12X24X6 on both sides.
Now the problem is with the bushing. I am using an aluminum bushing clamped to the motor assembly and the bearing is glued on its inner race to the shaft.
The problem is whatever I try to do, the bearing gets its outer race spun and gets damaged soon.
The temperature conditions is around 70 degrees Celcius.
I suspect it is because of the difference in thermal expansion of steel bearing and aluminum bushing.
My question is what is the regular practice in choosing the bearing and bushing materials.
Should I be using the same materials or of different kind.
Any help or suggestions is greatly appreciated.

 

[rnd2]

A steel bushing would thermally expand less than aluminium if indeed that is the problem.
Have you tried an interference fit between the bearing and the aluminium carrier? Is the wall thickness of the aluminium and general rigidity of the stucture adequate to carry the bearing with the type of loading it is experiencing?

 

[unclesyd]

I would try an AN type Tolerance Ring, either Rencol or USA.
We use them a lot in Al housings under some pretty high loads. If you have any ides of the loads either company can quickly tell you if they have a chance.

Sorry I don't have the URL's as my IE is malfunctioning for some reason and can't get to my favorites. A quick search will get both companies.

 

[DDRConsulting]

I am doing some research on a Main Bearing Failure on a Cooper Superior G2412 Natural Gas engine.

I am told Cooper has changed from the original Tri Metal bearing design to a Solid Aluminum type Main Bearing.
The Tri Metal bearing was replaced because the normal engine lubricating oil pressure on this engine of aprx. 80 PSI was causing the Lead overlay on the Tri Metal bearing to "Wash Away".
The Solid Aluminum bearing apparently is not affected by the high oil pressure.

My question is:
What are the advantages/disadvantages of Tri Metal over Aluminum?

Does anyone have experience with bearing failures on the Cooper Superior G2412 engine?

 

[rnd2]

DDRConsulting
Sounds like a hydrodynamic bearing problem.
Unless somone has specific hands on experience with this engine, suggest start a new thread and in addition, provide basic information such as shaft material, lube oil, shaft dia. rpm. bearing len and composition. etc etc.

 

[Tmoose]

From time to time I have heard of bearings being "washed" by too much oil pressure. Since the oil pressure in the hydrodynamic wedge is 1000s of psi I have a hard time understanding how 80 or 100 psi can cause a problem.
I'd be interested in seeing one of these "washed" bearings.

http://engineparts.com/products/bearingtech_files/frame.htm

http://www.engineparts.com/products/trimetal.html

 

[dwedel]

DDR, I agree with Rnd2, We really should be starting a new thread, instead of joining an old one.

I'm not sure how much I can help you, we only have GT and GTL series engines. I have done some research on Aluminum, Bronze and Trimetal bearings. For more information on the bearing materials themselves, ASM has a nice article in Volume 18, Friction, Lubrication, and Wear Metals.

http://products.asminternational.org/hbk/index.jsp

I have talked with several of our people about washed bearings. The issue would be in a genset that sat idle for long periods of time (years) with a hotstart pump maintaining the oil flow to the engine. I have heard of the issue, but haven’t seen any evidence yet. The mechanism for failure would be erosion if it is true.

Aluminum would probably be more preferable for its loading characteristics, than erosion resistance.

Once a manufacture sets up a block to run a specific type of bearings, most failures are mechanic or operator induced.

Is there a specific direction that you want to take this conversation, so we can give you better information?

I will not reply again, until a new thread is started.


dwedel
Hotrod Big Engines!
For site policies and guidelines
see faq731-376