PDA

View Full Version : Settle a debate: ball bearing vs journal bearing



doggunracing
11-15-2005, 02:55 PM
I'm leaving out my ideas/opinions for now. Which will cope with surge damage better and why? I looked for solid proof in Max Boost and Garrett websites but found nothing solid. Ideas and opinions are welcomed, but printed fact is preferred.

vosko
11-15-2005, 03:37 PM
a friend showed me this from the garret website...

http://www.vosko.net/photos/garrett/Tech101_speed.jpg

flip240
11-15-2005, 06:22 PM
How does that prove one is better than the other in protecting against damage from surging? http://forums.freshalloy.com/images/graemlins/confused.gif

ILikeMy240sx
11-15-2005, 09:30 PM
With journal bearings, there is no reacting load on the bearings from an axial load on the thurbocharger shaft. On the other hand, ball bearings will "see" the axial load on the turbocharger shaft from a compressor surge. Now, depending on the type of bearings (whether its deep grooved ball bearing or angular contact ball bearing, the capability of the ball bearing to withstand axial load varies)

Just looking at the bearings alone... without the regard to the turbocharger components. It is my opinion that the journal bearings will survive axial loads better because it does not "see" the axial load on the shaft since it is not preventing the shaft from translating in axial direction.

_Def_
11-15-2005, 10:41 PM
With journal bearings, there is no reacting load on the bearings from an axial load on the thurbocharger shaft. On the other hand, ball bearings will "see" the axial load on the turbocharger shaft from a compressor surge. Now, depending on the type of bearings (whether its deep grooved ball bearing or angular contact ball bearing, the capability of the ball bearing to withstand axial load varies)

Just looking at the bearings alone... without the regard to the turbocharger components. It is my opinion that the journal bearings will survive axial loads better because it does not "see" the axial load on the shaft since it is not preventing the shaft from translating in axial direction.




http://forums.freshalloy.com/images/graemlins/confused.gif

I have no idea what you are talking about...


Journal bearing turbos have a hydrodynamic thrust bearing that provides axial stability.

From what I know of tribology, I'd say the ball bearing turbo would survive longer from the low frequency "chattering" the bearings will see from surging.

ILikeMy240sx
11-15-2005, 10:49 PM
Hmm I didnt know that the journal bearings on turbos were thrust bearings... I thought they were just axial bearings. Well I guess there goes my statement out the door

ItzGenX
11-16-2005, 12:32 AM
Journal bearings will not see thrust motions. All thrust forces will be directed at the thrust bearing itself. Journal bearings are basically a sleeve that the shaft slips through. During surge, the shaft will encounter loads in all directions randomly. As someone earlier pointed out, this causes a 'chatter' like motion throughout the shaft which the journal bearings will see and aren't designed to cope with causing additional wear and flat spots. Ball bearing turbos are kind of locked in place with the shaft eliminating a thrust type bearing. During surge in a ball bearing type turbo, the shaft will 'try' to chatter along the bearing, but the ball bearing rollers are constantly in orbit. This means the ball bearing evenly distributes this surging force preventing flat spots and gaps producing even bearing wear. Ball bearing turbos also have a 'gyro' effect, stabilizing any sudden change in direction or force and will actually have shorter amounts of surge. Ball bearing turbos handle surge quite well due to these reasons. However, journal bearing turbos can be upgraded (or as a common option) to get the 360 degree thrust bearing. The 360 degree thrust bearing helps nullify this force in a full circle, preventing shaft chatter and adds greater lifespan and reliability. So when it comes down to it, a ball bearing naturally lasts and handles surge depending on bearing design, but like both turbos, they can only handle so much before major signs of wear destroys them. Out the box, a ball bearing turbo should be able to handle a larger amount of surge then the traditional journal types. Selecting the correct size turbo for the application and correct sized bypass valve to handle the amount of air should not see any major surging problems to worry about bearing failures in the first place.

asad
11-16-2005, 06:54 AM
Hmm I didnt know that the journal bearings on turbos were thrust bearings...



There is a separate thrust bearing and shaft bearings.

Asad

gt3071r240
11-16-2005, 11:55 AM
can we make this a sticky or put it in the faq please? Lots of good info

shane_B
11-17-2005, 09:19 AM
Is there is no thrust bearing in the ball bearing turbos? Or are the ball bearings designed to handle axial thrust?

fenge
11-17-2005, 12:09 PM
I believe most ball-bearing turbos use a pair of angular contact bearings to handle thrust loads in either direction. So no, there isn't a dedicated thrust bearing in a ball bearing turbo.

_Def_
11-17-2005, 05:28 PM
I believe most ball-bearing turbos use a pair of angular contact bearings to handle thrust loads in either direction. So no, there isn't a dedicated thrust bearing in a ball bearing turbo.



Correct, they use two ball bearings that have the race and shell at some angle to each other such that they handle both the axial and radial loads.