turbine bearing types
11-02-2021, 06:02 AM
#30
Yes i know Gaspar, he is very helpful and straight person.
If i decide to finally fit the GRW bearings after testing and hopefully surviving the tests i am going to buy them from him, did those bearings worked well?
So far i haven't found 8x22x7 angular bearings with brass cage it looks like a special order or a Unicorn but i also emailed AMT in case they have them.
Chris
If i decide to finally fit the GRW bearings after testing and hopefully surviving the tests i am going to buy them from him, did those bearings worked well?
So far i haven't found 8x22x7 angular bearings with brass cage it looks like a special order or a Unicorn but i also emailed AMT in case they have them.
Chris
Last edited by hendrix; 11-02-2021 at 06:11 AM.
11-02-2021, 06:17 AM
#31
I have lost 1700 dollars when i bought a JJ1400 if i remember correctly many years ago, it never worked more than 5 minutes and it ended up in the garbage bin because there is no way i could sell it to an unsuspected buyer and live with this thought.
JetJoe OWNERS thread
I only hope that the bearings i bought are not from them....
JetJoe OWNERS thread
I only hope that the bearings i bought are not from them....
11-02-2021, 09:04 AM
#32
You should have seen inside mine, screws with damaged threads, threads were stripped, the NGV was out of true etc.
It was like i bought a used one, i am talking about what i found the first time i stripped it down.
When i contacted Jetjoe i only got a cold answer. when i compared it to a used one i got (TREFZ TT66 from Germany) it was like i was comparing a Rolls-Royce with a Lada.
I decided that it was not worth it so i accepted my loss and moved on.
Btw i am about to buy 2 ANGULAR CONTACT bearings with brass cage and silicon nitride balls directly from AMT...
It was like i bought a used one, i am talking about what i found the first time i stripped it down.
When i contacted Jetjoe i only got a cold answer. when i compared it to a used one i got (TREFZ TT66 from Germany) it was like i was comparing a Rolls-Royce with a Lada.
I decided that it was not worth it so i accepted my loss and moved on.
Btw i am about to buy 2 ANGULAR CONTACT bearings with brass cage and silicon nitride balls directly from AMT...
Last edited by hendrix; 11-02-2021 at 09:14 AM.
11-02-2021, 09:30 AM
#33
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You should have seen inside mine, screws with damaged threads, threads were stripped, the NGV was out of true etc.
It was like i bought a used one, i am talking about what i found the first time i stripped it down.
When i contacted Jetjoe i only got a cold answer. when i compared it to a used one i got (TREFZ TT66 from Germany) it was like i was comparing a Rolls-Royce with a Lada.
I decided that it was not worth it so i accepted my loss and moved on.
Btw i am about to buy 2 ANGULAR CONTACT bearings with brass cage and silicon nitride balls directly from AMT...
It was like i bought a used one, i am talking about what i found the first time i stripped it down.
When i contacted Jetjoe i only got a cold answer. when i compared it to a used one i got (TREFZ TT66 from Germany) it was like i was comparing a Rolls-Royce with a Lada.
I decided that it was not worth it so i accepted my loss and moved on.
Btw i am about to buy 2 ANGULAR CONTACT bearings with brass cage and silicon nitride balls directly from AMT...
Not come across these in Model turbines yet. Are they 608 size ? How much do these go for ?
Cheers
11-03-2021, 08:55 AM
#38
I also found those from the manufacturer but no way to order them.
Notice the rpm limit and the wider ball grove.
sm608cta.pdf
Notice the rpm limit and the wider ball grove.
sm608cta.pdf
Last edited by hendrix; 11-03-2021 at 08:58 AM.
11-05-2021, 03:22 AM
#39
There was a lot of diy articles in Jetpower magazine, back in the days. They showed how to make hybrid bearings, from regular 608, and filling them up with balls from cheap ceramic bearings. The GRW bearings doesn't look a lot deeper than an ordinary deep groove bearing, with one of the shoulders turned down. Axial forces is not that big.
11-06-2021, 01:57 AM
#43
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I also found those from the manufacturer but no way to order them.
Notice the rpm limit and the wider ball grove.
Attachment 2271046
Notice the rpm limit and the wider ball grove.
Attachment 2271046
The Balls are perfect quality but the races are so-so with a less than perfect ground finishes. They do work and can last 50 hours plus in a well designed system kept clean. They do not handle the combo of high temp and high axial load well beyond certain limits.
11-06-2021, 02:30 AM
#44
The Balls are perfect quality but the races are so-so with a less than perfect ground finishes. They do work and can last 50 hours plus in a well designed system kept clean. They do not handle the combo of high temp and high axial load well beyond certain limits.
Of course i am not looking for a warranty just ideas to test, i like testing with a calculated risk after i decide on my own.
Chris
11-06-2021, 02:45 AM
#45
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No question they will work, GRW is used in majority of turbines on the market. The rear only preload of the KJ is not a good idea. You need to preload the front and not have it restricted in movement in axial direction. Full compliment bearings are very susceptible to ball oscillations that will cause outer ring to spin and if fit is not perfect will tend to rock the bearing to the point where the balls will bounce so much that they exit the inner race. Cages limit this. To reduce axial load the air pressure at the back of the compressor face should be as low as possible. A very small gap will generate a lot of air pumping and reduce pressure. There should be almost no air-gaps to the inside of engine where high pressure lives. I used the drive washer of compressor as a sort of seal by having an extremely tight running clearance.
11-06-2021, 04:33 AM
#46
The rear only preload of the KJ is not a good idea. You need to preload the front
I am very anxious to try the gmn bearings with brass cage.
Chris
Last edited by hendrix; 11-06-2021 at 04:38 AM.
11-08-2021, 03:01 AM
#47
Titanium have a similar appearance and function as steel bearings but have a longer life span due to better shields against rust and corrosions. but titanium balls were not easy for manufacturers as it is hard to put in the desired shape because of the strength of this material.
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Ruizmilton (11-22-2021)
11-22-2021, 07:11 AM
#49
bearing problem
I installed the first set of bearings of Ebay and i noticed a strange behavior, the shaft moves freely but sometimes it decelerates rapidly (not instantly) like there is friction somewhere but i am sure that nothing touches anywhere and there is no rubbing sound.
It feels like the bearings are getting tight occasionally and then free up.
The preload is working fine and the front bearing moves nicely as much as the preload washer allows.
Many times i an induce the problem by turning the shaft rapidly counterclockwise and then after it stops spin it in the opposite direction, then i can feel significant increase in friction.
Without preload the bearings spin for ever....
Any ideas?
It feels like the bearings are getting tight occasionally and then free up.
The preload is working fine and the front bearing moves nicely as much as the preload washer allows.
Many times i an induce the problem by turning the shaft rapidly counterclockwise and then after it stops spin it in the opposite direction, then i can feel significant increase in friction.
Without preload the bearings spin for ever....
Any ideas?
Last edited by hendrix; 11-22-2021 at 07:26 AM.
