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Old Mar 10, 2013, 09:11 PM
Registered User
USA, NY, East Aurora
Joined Jul 2006
36 Posts
Motor balance

The bearings in all of these motors are GRW German made hybrid ceramic bearings. There are three things that will shorten the life of the bearings or destroy them

Imbalance - These bearings do not tolerate imbalance
Overheat - Overheating the motor will kill any bearing
Lubrication issues - Failure to lubricate or insufficient lubrication will destroy the bearing(s) in short order

I can demonstrate this on a cheap or expensive motor. They all work on the same principle.

As for replacing bearings without rebalancing, sometimes you can get away without a balance but often you will need to rebalance the motor. If you detect any vibration after reassembly do not run the motor. If a bearing does fail (usually tail bearing) the result is almost always catastrophic.

Quote:
Originally Posted by mr_matt_II View Post
On a high performance turbine they have to be balanced after assembly.

On a lower performance turbine or one that you don't need top performance or reliability you can do without an assembled balance.
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Last edited by afioretti; Mar 11, 2013 at 01:30 PM. Reason: grammar
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Old Mar 13, 2013, 11:09 AM
Registered User
Joined Oct 2004
171 Posts
Quote:
Originally Posted by afioretti View Post

As for replacing bearings without rebalancing, sometimes you can get away without a balance but often you will need to rebalance the motor. If you detect any vibration after reassembly do not run the motor. If a bearing does fail (usually tail bearing) the result is almost always catastrophic.

Yes, but I would add that any out of balanced condition that is remedied with the final balancing(now done on the completed turbine or core) cannot be felt by hand, so you would not know if you had any out of balance condition or not.

I commented originally because it seems some people would like to repair their own turbine, and if they do not have a balance machine, they cannot balance it (balance after assembly I mean). The best they can do is mark the component relationships and then carefully reassemble.

In my experience this is marginally acceptable on lower performance turbines only, and will not result in optimal reliability or performance...will it result in ACCEPTABLE reliability and performance?..... well that is up to the individual.

If the alternative is NOT being able to take apart and reassemble the turbine, well I guess by definition the resulting reliability and performance is acceptable!
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Old Mar 14, 2013, 07:16 PM
Registered User
USA, NY, East Aurora
Joined Jul 2006
36 Posts
Balancing

Hi Matt,

I do not recommend replacing bearings without balancing but I see people do this all of the time. It is a chance that people take.

Andy

Quote:
Originally Posted by mr_matt_II View Post
Yes, but I would add that any out of balanced condition that is remedied with the final balancing(now done on the completed turbine or core) cannot be felt by hand, so you would not know if you had any out of balance condition or not.

I commented originally because it seems some people would like to repair their own turbine, and if they do not have a balance machine, they cannot balance it (balance after assembly I mean). The best they can do is mark the component relationships and then carefully reassemble.

In my experience this is marginally acceptable on lower performance turbines only, and will not result in optimal reliability or performance...will it result in ACCEPTABLE reliability and performance?..... well that is up to the individual.

If the alternative is NOT being able to take apart and reassemble the turbine, well I guess by definition the resulting reliability and performance is acceptable!
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Last edited by afioretti; Mar 14, 2013 at 11:03 PM.
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Old May 18, 2013, 03:58 PM
Brooklynite In Texas
Manor, TX. USA,
Joined Jul 2008
579 Posts
I don't want to steal any thunder and such but I built and repaired jet engines for many years and it is not rocket science. But It does take good common sense.

If you don,t have the tools and a working knowledge of the subject you best send it to someone who does. On the other hand I have disassembled engines and replaced bearings without doing any form of balancing. a bearing will not put a engine out of balance but poor assembly will.

The marking of component placement is paramount on all moving components. Any damaged spinning component must be rebalanced by itself and as part of the assembly.

If you haven't acquired the knowledge to do the job you could be the cause of much grief.........................A word to the wise. OH yeah ..buy cheap and pay the price!
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Old May 28, 2013, 01:50 PM
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mikes68charger's Avatar
United States, OH, Columbus
Joined Jul 2010
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I have not gotten a turbine yet but Im saveing for a KingTech

How much do these 25 hour rebuilds cost anyway??
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Old May 28, 2013, 04:25 PM
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Tampa FL
Joined Apr 2009
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Quote:
Originally Posted by mikes68charger View Post
I have not gotten a turbine yet but Im saveing for a KingTech

How much do these 25 hour rebuilds cost anyway??
With kingtech not much at all. With the lifetime warranty it covers the expensive stuff. I thought I saw around 200.00 or so. If you have any problems you get it fixed for free of course. They pretty much get everything out same day or next day. And the turnaround on engine service is a week or less.
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Old May 28, 2013, 06:42 PM
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Pittsburgh Allegheny, Pennsylvania, United States
Joined May 2004
1,188 Posts
Quote:
Originally Posted by mikes68charger View Post
I have not gotten a turbine yet but Im saveing for a KingTech

How much do these 25 hour rebuilds cost anyway??
Quote:
Originally Posted by gunradd View Post
With kingtech not much at all. With the lifetime warranty it covers the expensive stuff. I thought I saw around 200.00 or so. If you have any problems you get it fixed for free of course. They pretty much get everything out same day or next day. And the turnaround on engine service is a week or less.


The warranty doesn't cover maintenance. But... as long as you keep up on the service... if you burn out a fuel pump, or chuck a wheel... they will fix it.


Last time I talked to Berry... I think it was $350 for the 25 hr service. (Still cheaper than most other's)
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Old Jun 03, 2013, 10:41 AM
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United States, TX, Leander
Joined Sep 2003
2,592 Posts
The TBM website says $300 for the K80. I've been talking to the jet jocks in the club to come up to speed on turbines. I want to do a jet before I retire. The K80 looks like the ticket.
Edwin
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