ORIGINAL: rcdriver22

ET

When you have burnt 100ltrs (gross up for added oil thats nearly 1.5 hours between 100k to max) through a JJ1400 then after all the mods you get a different insight. Basically, engineering clearances are critical to good long life. On good turbines the rear O ring sits in its groove and "holds the outer race" forming a seal allowing oil in between the ceramic balls. On the JJ the fitting is so tight it can be an 'interference fit' between tunnel and bearing race outer, hence the pre load fails to operate and sticks. OK best to cut the O ring flush in the tunnel or deepen the O ring grove but if you remove the O ring completely to get the pre load to operate, then the outer race can turn or oscillate forming flats on the ceramic balls and hence rear bearing wear. Combine with too little oil or even too much oil (bad) causes wear due to flats forming at start up (hence suggesting 3% oil content but double flow rate). This non concentric operation at 160000 rpm without a 'complete full balancing' results in wear between shaft outer and the NGV (where again the clearances leaves a lot to be desired) this may form either galling on the shaft or turbine grounding on NGV due to clearances.

So you've bought your new JJ1400, altered the Combustion Chamber to inconel, refitted a new lube flow restrictor, checked the bearings, the O ring pre load, fuel manifold and paid for a full rebalancing. Stripped it and built it up some many many times, its only a few afternoons and you get to be as fast as Carlos at RTI. Its the non response to emails back from the factory[:-][:-] I think you are not really to run these turbines for very long or if you do then you want some spares to make regular repairs.

Paul