During my preflight tests this morning I found the third failed
ignition coil in the last 150 hours so I finally got serious about dropping
the temps around my coils and alternator.
I've been concerned about this since the under-cowl temps are as
high as 180 deg F (delta T through rads is 70 - 90 deg F). The
attached photo shows the solution (hopefully). The alternator plenum
is made from a Tupperware container pirated from the kitchen with a skirt
made from sheet silicone rubber. A 5/8" ID vinyl hose routes cool air
from the oil cooler plenum to it. ( 3/8" ID hose was tried
first, not quite good enough) This was tried prior to today's
scrubbed flight and a temp probe shows that air inlet temps to the
alternator are only 3 - 5 degrees above ambient. Nice.
I had recently added a cooling plenum around the coils (also made of
tupperware) and fed by a 3/8" ID hose but it was pretty leaky and only
dropped temps about 10 - 15 degrees. After replacing the coil today I
built a better fitting plenum and fed it with 5/8" ID hose. This one
is made of space-age cardboard and I'll build a more permanent one from
fiberglass if it works OK. Will test tomorrow if wx allows.
Input shaft
Buly, got your input shaft today and checked it out. The thrust
bearing rollers & races look a little stressed but the roller cage has
been completely trashed. I do not think the .005" out of flatness on
your bellhousing would explain this and the odd wear pattern on the
plate. The marks and discoloration (heat) on the bearing and shaft
look as if there is misalignment between the E-shaft and the gear
drive. When you built the plate & bellhousing adapter for the
drive, how did you verify concentricity? This is much harder to do
than verifying the parallelism of the bellhousing and plate but is
absolutely vital. There is no question that the drive would have soon
failed if you had continued to run it. Glad this showed up
before flight.
Tracy (Happy to hear that Dave L. is safe! Good
flying. )