Oh those CERTIFIED plane engines !!!!!!!!!!!!!!!!!

("stol" wrote)
So here comes round number three. Too bad they don't have the three
strike rule in aviation.

http://www.lycoming.textron.com/support/publications/maintenancePublications/serviceBulletins/SB569.pdf


Today's AvWeb lead story:

http://www.avweb.com/eletter/archives/avflash/586-full.html#191678
Lycoming Woes Continue: 5100 Crankshafts To Be "Retired"

(From the link)
"In previous recalls totaling some 2400 crankshafts, Lycoming has paid for
the engine work to various degrees, even reimbursing owners for hangar
expenses and loss of use in the 2003 recalls. Not this time. Owners affected
by the crank retirement will get a discount deal on the replacement
crankshaft -- $2000 for the shaft, plus a box full of free parts such as
gears, bearings, piston ring sets, connecting rod bolts and nuts and seals.
But they're on their own for engine assembly, repair and reinstallation,
which field overhaul shops tell us will add another $4000 to $5000 to the
job if the crank is replaced proactively or before the engine reaches
routine TBO. Further, owners will have to ship the retired crankshaft back
to Lycoming to obtain the discount price, also at their own expense. The
$2000 offer applies to crankshafts for any engine and is substantially below
list price for a new part, especially for six-cylinder engines."

"Lycoming says it will ramp up production of replacement crankshafts but as
in previous recalls, priority will go to government operators and Part 121
and Part 135 operators, with private owners last. What's not known is if
this recall withdraws all of the potentially defective crankshafts from the
market. (We queried Lycoming about this but haven't received a reply yet.)
The crankshafts in question were manufactured between March of 1997 and
March of 2002."


Montblack

"Montblack" wrote in message
...
("stol" wrote)
So here comes round number three. Too bad they don't have the three
strike rule in aviation.


http://www.lycoming.textron.com/supp...ncePublication
s/serviceBulletins/SB569.pdf


Today's AvWeb lead story:

http://www.avweb.com/eletter/archives/avflash/586-full.html#191678
Lycoming Woes Continue: 5100 Crankshafts To Be "Retired"



But the mandatory service bulletin leaves out O-320's and O-235's.

One wonders if Teledyne is getting its alloys from the same source. I doubt
it.

And where are the reports of deaths or personal injury caused by the bad
cranks? Do we have a cite from a Lycophobe?

jls wrote:

"Montblack" wrote in message
...

("stol" wrote)

So here comes round number three. Too bad they don't have the three
strike rule in aviation.


http://www.lycoming.textron.com/supp...ncePublication
s/serviceBulletins/SB569.pdf


Today's AvWeb lead story:

http://www.avweb.com/eletter/archives/avflash/586-full.html#191678
Lycoming Woes Continue: 5100 Crankshafts To Be "Retired"




But the mandatory service bulletin leaves out O-320's and O-235's.

One wonders if Teledyne is getting its alloys from the same source. I doubt
it.


Just guessing here, but aren't the O-235 adn O-320 cranks solid rather than
hollow (for constant speed props)?

Just guessing here, but aren't the O-235 adn O-320 cranks solid rather than
hollow (for constant speed props)?

They are hollow, and some models of the engines have
provision for a governor. That hollow crank has been the subject of an
AD; the front end of the crank gets cold in flight due to the prop's
heat loss and the hollow bore, open to the case, gets condensation and
oil in it. Those mix and form sludge and acids that eat away at the
inside of the bore and weaken the crank. See:

http://www.airweb.faa.gov/Regulatory...5?OpenDocument

Hollow shafts are stiffer than solid shafts. The stresses are
all concentrated in the outside wall, with no central material to act
as a fulcrum to stretch the outside on bends. Try bending a piece of
5/8" bar and one of 5/8" tube sometime (same material, of course) and
see the difference. The bar will bend, but the tube will resist bending
until it suddenly kinks. Cranks need to be stiff, especially where they
are loaded with gyroscopic forces, and need to be light, so they're
mostly hollow.

Dan

wrote:

...

Hollow shafts are stiffer than solid shafts. The stresses are
all concentrated in the outside wall, with no central material to act
as a fulcrum to stretch the outside on bends. Try bending a piece of
5/8" bar and one of 5/8" tube sometime (same material, of course) and
see the difference. The bar will bend, but the tube will resist bending
until it suddenly kinks. Cranks need to be stiff, especially where they
are loaded with gyroscopic forces, and need to be light, so they're
mostly hollow.


More importantly a hollow shaft that is the same weight as a solid
one will have a larger diameter which gives you much better
stiffness, especially in torsion, for the same weight.

--

FF

wrote:
wrote:
...

Hollow shafts are stiffer than solid shafts. The stresses are
all concentrated in the outside wall, with no central material to act
as a fulcrum to stretch the outside on bends. Try bending a piece of
5/8" bar and one of 5/8" tube sometime (same material, of course) and
see the difference. The bar will bend, but the tube will resist bending
until it suddenly kinks. Cranks need to be stiff, especially where they
are loaded with gyroscopic forces, and need to be light, so they're
mostly hollow.


More importantly a hollow shaft that is the same weight as a solid
one will have a larger diameter which gives you much better
stiffness, especially in torsion, for the same weight.

Yes. The outer diameter of the hollow tube will be slightly larger than
the solid rod. On the drawing board, if the outer diameter is strictly
limited (by crank journal diameter), or slightly limited (if the block
allows slightly larger journals), then changing the crankshaft from
solid for hollow this may or may not be an issue. (Pretty wordy!)

In reality, swapping out a solid crankshaft for a hollow one of equal or
at least sufficient strength and stiffness is not always simple,
prudent, or even possible. (Pretty wordy again!)

Here is a good reference for anyone (regardless of their level of
engineering knowledge):

http://www.engineersedge.com/calcula...re_case_12.htm

You can play with the numbers a bit. Moment of inertia is directly
related to stiffness (in torsion) while (cross section) area is directly
related to weight. Section modulus is directly related to bending strength.


PS- Fred, you (and others in this thread) obviously have a good handle
on this stuff. My post is mostly directed to the audience. Disclaimer,
I'm 99% sure I got the working definitions right. Corrections are
welcome