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david mccandless wrote:
Hi to all, has anyone ever considered ball-milling out the apex seal grooves and pressing in a round tough steel insert and then milling the seal slot in the steel insert. This would then be' horse shoe' cross section, so to speak. The corner button seals could also fit into the ends. Maybe a new rotor would be cheaper, but this may have better reliability and longer life. FWIW, Dave Mc
On 24/04/2005, at 5:24 AM, Ed Anderson wrote:
Sounds expensive. And how will you keep the insert from flying out of the rotor as centripetal force tries to fling it out at 2000RPM?
As for reliablility and long life, unless your flying for a living, 400 hours IS a long life. If you fly 2 hours a weekend, every weekend, it will take nearly 4yrs to reach that number. It may just be me, but I don't see the point in expecting any of the components to last more that 5yrs. All the hard parts may be doing just fine, but how can you bet your life on old rubber seals and gaskets (and they will be old after that much running). As for the 2000 TBO that the certified guys like to talk about but never see with a Lycoming, it just doesn't make sense to even use those numbers in an experimental airplane. That is 20yrs for the typical, non-commercial, GA airplane. I ask myself, "Do I really want to fly behind an engine that hasn't been opened up since I graduated from high school?" I always get a resounding, "NO!" The engine comes apart for a rebuild in 5yrs whether it has 100hrs or 2000, and whether it's running like a top or smoking up half the town.
I just don't think any exotic solutions are called for with the apex seals. The cost to benefit ratio isn't right. Mill them out to 3mm or use the 'press-back-into-place' solution suggest by Bruce and expect to replace the engine in 5yrs. If all the other systems are running well, you'll be able to have a new engine then for what you shell out on machining cost now.
--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."
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