Excellent information, THANK YOU VERY MUCH!
Chris

With ceramic balls or steel?
Chris

Ceramic Silicon Nitride

Bearing replacement
 

I just bought these bearing from xcioy a month ago.
https://cimg5.ibsrv.net/gimg/www.rcu...92199961f5.jpg
https://cimg6.ibsrv.net/gimg/www.rcu...4d5f1f53b2.jpg
https://cimg7.ibsrv.net/gimg/www.rcu...2547c07313.jpg

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

actually I never have a smallest problem with my jetjoe 1400 turbine specially after making my own program they usually sales with blank or not complete fadek program I’m pretty sure that this turbine still working perfect with the jet that I sold with , at the beginning of those turbines sales in USA not too many people knew about making the new program and they usually ended with blowtorch instead of a good working turbine, I’m pretty sure that if someone with better knowledge will take over the USA sales back days this could turn to today Kingtech class brand, I have like 3 of them and all of those turbines have a perfect working history.

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...

https://cimg2.ibsrv.net/gimg/www.rcu...5ad9b792e3.jpg

Not come across these in Model turbines yet. Are they 608 size ? How much do these go for ?

Cheers

Yes they are 8x22x7 mm
I am waiting a reply for the cost and if those are good at least for testing in a KJ66 turbine.
As soon as i get the response i will post it here.
Chris

AMT Turbine arent cheap, I suspect these bearings are not either however at least you can rest assured when it comes to quality for sure.

We will see!
I am waiting for their reply which probably will come tomorrow.
I will try one at least on the hot side!
Chris

OK the bearings cost 30 Euros each plus shipping, they are rated to 140,000 rpm and their precision is ABEC7
I will order two for testing them.
Chris.

I also found those from the manufacturer but no way to order them.
Notice the rpm limit and the wider ball grove.
Attachment 2271046

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.

Now if i tell you that i also did exactly the same by using regular 608 angular contact bearings and buying ceramic balls from Alixpress?
I didn't test them but they should be fine!

You should definitely test them!

With those i have 3 pairs of bearings that should outlive my tired turbine....
Chris

Almost all non-standard configuration bearings from all manufacturers are subject to MOQ's. I can tel you that GRW also makes similar bearings for a MOQ. The ones we buy for "model use" have never in 25 years of me buying them been the best you can buy. Just easily available.
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.

From what i can understand they will work with the axial loads presented in a KJ66, am i right?
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

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.

My kj66 clone has front preload and the gap between the compressor and the diffuser is non existent, it is a very good clone.
I am very anxious to try the gmn bearings with brass cage.
Chris

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.

Probably not Titanium but unobtainium for our hobby.
Chris

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?

Maybe some of the balls are not perfectly spherical and they find a high point?


Paul