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Thanks for a second data point, Mark.
I strongly suspect that you are correct, we simply are
driving coils designed for start/stop slow go automobiles rather than constant
hour after hour of 6000+ rpm operations.
But, I suspect that excess heat is still the core of
the problem whether under cowl heat or internal heat due to electrical power use
at high rpms.
Ed
----- Original Message -----
Sent: Wednesday, January 18, 2006 11:27
AM
Subject: [FlyRotary] Re: LS1 Coil
Failures
Ed,
I was thinking about
this a while back and was astounded at how many “firings” per second these
coils are producing. Each rotor fires once/revolution of the eccentric
shaft. Cruising along at 6000rpm, that’s 600 sparks/second/coil.
My 5.3L Chevy truck (with LS1 coils), cruising down the highway at 1500 rpm,
each coil fires once every other revolution, or 750 times/minute, or 12.5
times/second. So, we’re really pushing these coils to the limit. I
find it amazing that they don’t fail more often than this. By the way,
in 126,000 miles, I have yet to have a coil fail on my LS1.
Mark
S.
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Ed Anderson
Sent: Wednesday, January 18, 2006 9:09
AM
To: Rotary motors in aircraft
Subject: [FlyRotary] LS1 Coil
Failures
Hummm, think I will
hold off swapping my stock Mazda Coils for the LS1s sitting on my work bench
until we have a better handle on the coil "problem". Have now flow for
300 + hours and over six years with the stock coils with the only problem
being the early failure of the leading module because of a resistor opening in
its base.
The wattage of the
resistor is apparently too low to carry the load of the ignition continuously
running at 6000+ rpm. Replaced the resistor with a higher wattage one
and no more problem. At least three people have had this resistor fail
using the stock coils - it may well be that the auto folks don't design for
their coils to be run at high continuous rpms unlike the MSD type ignitions
for racing.
I wonder what the
automobile circle are experiencing with their LS1 coils - anyone
know?
----- Original
Message -----
Sent: Wednesday,
January 18, 2006 9:57 AM
Subject: [FlyRotary] Re:
Coil & Alt cooling, Buly's input
shaft
I'm wondering if
180f under hood is really the main cause for coil fail? Auto's shut off hot
in desert, black steel hood, must see temps way beyond anything we can throw
at them. You can't get those puppies to fail regardless of environment.
Perhaps there are one or two other significant causes. I'd be real quick to
abandon that manufacturer.
On Tue, 17 Jan
2006 22:39:15 -0500 "Tracy Crook" <lors01@msn.com>
writes:
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.
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. )
-al
wick
Artificial intelligence in cockpit, Cozy IV powered by stock Subaru
2.5
N9032U 200+ hours on engine/airframe from Portland, Oregon
Prop construct, Subaru install,
Risk assessment, Glass panel design
info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
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