- Chuck have you thought to go to 3mm?
George ( down under)
I finally got
time to get my failed 13b apart. The rear rotor was missing one apex seal,
the other 2 were intact but jammed due to the fragments of the broken one.
The rotor housing has the classic chatter marks all around. Doing a Google
of "13B apex seal chatter" results in plenty of examples of this failure
mode. Apparently the chatter is from the natural resonant frequency of the
seal, it eventually fatigues the seal causing failure.
The front rotor
was in good shape, but the housing had the same chatter marks, but not as
severe as the rear rotor. The front rotor housing was brand new 150 hours
ago when I rebuilt this motor after the Grand Canyon forced landing. At that
time the good rotor housing had slight chatter marks but I reused it. The
front rotor was destroyed at that time due to foreign object entering the
rotor.
Both rotors were
missing the corner seal rubber plugs on the side with the short apex
seal segment. Perhaps the small segment vibrated more, disintegrating the
rubber seals?
The first 260
hours of flying my rotary bird was with stock 3-piece seals, and I never saw
any chatter marks. The last 250 hours has been flown with 2 piece seals and
now I have chatter marks .
I now have
Tracy's 2 piece apex seals and I wonder how they will perform, it appears
that the heavier weight of the 2 piece seals puts the resonant frequency in
the cruising range of 6000RPM?
Chuck
Dunlap
RV6
13B
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