Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
41
In theory a ruptured disc is
contained, I think that is part of certification, but in practice . .
. . .
Ooooh, I don’t think so. A broken blade is contained. If the casing
had to hold a ruptured disc, the plane would be unable to get off the
ground.
At P&WA they were once working up a “rotor dynamics rig”, basically
an arrangement of shafts and discs that would be spun up using an
electric motor to demonstrate a rather questionable theory called a
supercritical shaft. Pretty much everyone who understands what that
means expected it to come apart at 16,000 rpm. So the test stand was
fitted with “submarine netting” – basically a net consisting of 1"
steel cables in about a 1’ x 1’ mesh. Then somebody ran some
rudimentary calculations and determined that you’d be lucky to notice
the submarine netting flinch because the disc would go through it so
fast!
Airlines should put a red stripe there and sell cheaper seats in the
line of fire.
Well, let’s face it, if the disc comes through the cabin, pretty much
everyone on board is dead. Fortunately, modern commercial jet
engines don’t rupture discs. Period.
– Kirbert
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !On 23 Oct 2015 at 12:27, Richard Dowling wrote:
In reply to a message from Kirbert sent Thu 22 Oct 2015:
There is a UK eBay seller who supplies a flywheel puck
that is fitted over the flex plate as part of a manual
conversion. The other main part is a large adapter plate
to bolt the irregular Getrag bell to the rear face of a
V12 block.
I haven’t seen either part close up and have only fitted
detachable-bell style Getrag using a much smaller adapter
ring on the rear face of a Jag bell.
Didn’t that recent Las Vegas jet grenade its port engine
and damage the fuselage before aborting at McCarran?–
1E75339 66 D, 1R27190 70 FHC, 79 S2 XJ12L
Gaithersburg, Maryland, United States
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Well, let’s face it, if the disc comes through the cabin, pretty much
everyone on board is dead. Fortunately, modern commercial jet
engines don’t rupture discs. Period.
If you search the subject line “Its the chain tensioner” around April
2014 it must have been a very quiet time on the V12 front.
The mention of a QANTAS A380 severely damaged by a ruptured disc led
to a large input of related stories.
V12 events took a back seat for a while.
You entertained us with a number of interesting war stories, always
appreciated by the audience.
Richard Dowling, Melbourne, Australia. 1979 coupe + HE V12 + manual;
1989 convertible; 2003 XJ350.
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Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
44
Didn’t that recent Las Vegas jet grenade its port engine
and damage the fuselage before aborting at McCarran?
It did something, but as usual the news reports didn’t provide any
pertinent details. Mighta just chucked some blades, I dunno.
– Kirbert
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !On 23 Oct 2015 at 11:25, PeterCrespin wrote:
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
45
If you search the subject line “Its the chain tensioner” around April
2014 it must have been a very quiet time on the V12 front. The mention
of a QANTAS A380 severely damaged by a ruptured disc led to a large
input of related stories.
Who makes the engines in the Qantas A380?
– Kirbert
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !On 24 Oct 2015 at 8:18, Richard Dowling wrote:
You already know that, it gave you great satisfaction.
Richard Dowling, Melbourne, Australia. 1979 coupe + HE V12 + manual;
1989 convertible; 2003 XJ350.
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Richard Dowling sent Sat 24 Oct 2015:
Word’s not completely out on that, but Av Week intimates a
disk, I believe I read.
Not the first time in recent memory that a disk let go on a
commercial airliner.
And I agree on seating- I always sit fore or aft of those
beasties.
Biggest threat is on roll out where max power is called
for. I have been on a plane that lost an engine on take
off, and in my case we had a military-trained test pilot at
the helm and I suspect this is what saved the day.
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In reply to a message from Richard Dowling sent Sat 24 Oct 2015:
Who made the engine in the Britsh Airways McCarran
incident? Yup, Kirby’s old firm but the meeja in the US
left that bit out. Somehow, had it been a non-US engine I
think they would have included the name…–
The original message included these comments:
Who makes the engines in the Qantas A380?
– Kirbert
You already know that, it gave you great satisfaction.
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
Who made the engine in the Britsh Airways McCarran
incident? Yup, Kirby’s old firm but the meeja in the US
left that bit out. Somehow, had it been a non-US engine I
think they would have included the name…
Gaithersburg, Maryland, United States--------------------------------------------------------------------------------
Ease up Pete, it was reported as a GE engine, and the media took great
delight in digging into the past history of failures with this
particular engine type, of which there have been a number but nothing
out of the ordinary.
When the dust settles, no matter who makes the engines, they are
extremely reliable and failures are very rare indeed.
For those puzzled about where this thread is heading, the jet engine
debate started over a year ago with a long and heated discussion about
the V12 chain tensioner.
Many forum members took Jaguar engineers to task for choosing to put
such a device, mostly made of plastic, into an engine.
Of course, in hindsight you probably would not do such a thing but it
is hard to say what information was to hand when the decision was made
back in the late 60s.
From this discussion of engineering choice in a modest $5k engine we
progressed to what turned out to be an equally heated discussion about
the relative merits of British built jet engines versus US built ones.
The latter types of engine are more likely to be a $20M item in your
shopping basket, but the idea was to draw parallels about engineering
choice and reliability.
I think at the time we exhausted just about everything you could ever
say about the tensioner question, and a fair percentage of what you
could say about jet engine design and reliability.
Discussion closed ?
Richard Dowling, Melbourne, Australia. 1979 coupe + HE V12 + manual;
1989 convertible; 2003 XJ350.
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Richard Dowling sent Sat 24 Oct 2015:
My post was tongue in cheek Richard, and wrong it seems!
I onew it was American buy mis-remembered as P&W. Since I
live in the US but see alot of UK news it was noticeable
how the ‘British’ word was applied/implied in the US
coverage whereas the engine make was stated matter-of-
factly in the BBC report and seemingly Australia too.
Sensitive? Moi?
I remember the debate about the Morse tensioner (another
American company) :-)–
The original message included these comments:
Ease up Pete, it was reported as a GE engine, and the media took great
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In reply to a message from Mark Eaton sent Thu 22 Oct 2015:
Mark
That’s bad news. It’s a bit of a misnomer to have a
‘‘Factor of Safety’’ LESS THAN 1…!!!
Depends of course on where you set your definition of 1.
I have my Fidanza flywheel ready to go back on because my
engine in going back in soon.
This news makes me nervous…was it a Fidanza you
analysed??? Mine is a Fidanza and I would be pretty sure
they would have done the necessary analysis on these
things before selling them to the public…
And a testing program…surely…!!
Your information is telling me that even at red line in
our engines the flywheel is over stressed…
Are you sure …???
Regards
Matt–
The original message included these comments:
I just ran a quick FEA on the alloy flywheel and the Factor Of Safety is
0.57 at 8000rpm. That is NOT GOOD. It should preferably be better than 1.5
and ideally 3 or more.
At 6,500 rpm the FOS is 0.86. Still very bad.
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In reply to a message from Mark Eaton sent Thu 22 Oct 2015:
Mark
I just looked on the Fidanza webpage and my confidence has
taken a hit. They talk about yields stress for the
aluminium they use which is not ‘‘Engineer’’ speak at all.
Steels exhibit a yield stress but aluminium is designed to
0.2% proof stress.
Nowhere could I find any info on any testing…or RPM
limits…surely an important parameter??
Matt–
The original message included these comments:
I just ran a quick FEA on the alloy flywheel and the Factor Of Safety is
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In reply to a message from PeterCrespin sent Sat 24 Oct 2015:
Interesting…I remember my news organization here (Eastern
US) reported that engine as a Rolls-Royce Trent 900.–
The original message included these comments:
I onew it was American buy mis-remembered as P&W. Since I
Ease up Pete, it was reported as a GE engine, and the media took great
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
I am not sure who manufactured this flywheel. It looks very well made and is
nicely finished. But it is over stressed in the area around the crank
flange, mainly because there is a steel friction plate bolted into the
flywheel for a 7 1/4" triple plate clutch, and the bolt holes supporting the
plate are right in the middle of the highest stressed areas around the crank
flange. It is possible that a similar flywheel with a larger dia friction
plate would position those holes safely away from this area.
Some years ago I had a steel flywheel lightened for an XK engine. The
machinist did a thumb suck and suggested removing “about this much”
material. The flywheel worked fine, but I never red lined that engine (carb
issues). The difference between too much and not enough was based upon his
gut feeling. I never questioned it at the time, but I was a lot younger then
Now that I have the tools available, I spend most of my business day
simulating designs before anything is put into production. Simulations
aren’t gospel, but they do show trends very well. But these tools are
designed for idiots like me to use, so that doesn’t necessarily mean the
answer is correct. Garbage in / garbage out. But in my experience it is very
likely to be correct, if you have taken the time to build an accurate model,
and they have an uncanny ability to educate a user as to what is actually
happening in a given situation. I can’t think of a time when an optimised
design (based upon simulation) didn’t deliver the promised value in the real
world.
You can also “CAD Design” something and not do a stress analysis on it. That
is additional software that costs an arm and a leg and is probably outside
the bounds of a normal machine shop.
Do they not, in America, have a testing standard for flywheels (SFI?)? There
also seems to be a test procedure defined in SAE J-1240. SFI testing
requires the manufacturer to nominate a maximum RPM, where upon the flywheel
will be spun for 1 hr at 150% of the nominated RPM and then tested for
cracks or elongation. The cynic in me thinks “Ah ha! Submit a flywheel with
a max RPM of 3,000 rpm and you will happily pass SFI testing!” I note that
the SFI label does not show the max rpm tested, nor does the manufacturer
seem to declare it! Nor are manufacturers required to provide this testing
and only do so on demand from racing sanctioning bodies.
Regards
Mark-----Original Message-----
Nowhere could I find any info on any testing…or RPM
limits…surely an important parameter??
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Interesting…I remember my news organization here (Eastern
US) reported that engine as a Rolls-Royce Trent 900.------------------------------------------------------------------
From a Guardian article re engine failure:
" The twin-engine Boeing 777 was built in 1998 and registered to
British Airways a year later. By the end of 2013 it had flown nearly
77,000 hours, according to the British Civil Aviation Authority. GE90
engines are used in most Boeing 777s.
GE Aviation said that the spool, which holds the blades in the
GE90-85B engine, was among the first ever made for that model in 1995.
"
No mention of RR in any Google hits, of which there are many on the subject.
I guess a reporter jumped the gun before finding the facts.
Richard Dowling, Melbourne, Australia. 1979 coupe + HE V12 + manual;
1989 convertible; 2003 XJ350.
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Mark Eaton sent Mon 26 Oct 2015:
Hi Mark
Hopefully this is where the Fidanza sits. It is used with
a 10.5’’ Chevrolet clutch plate so perhaps the holes are in
a suitably stressed location.
I see they quote an SFI number for my flywheel which I
checked is a testing organisation as you said. But the
design RPM should be explicitly stated…because the
centripetal acceleration is a speed squared relationship
so the design speed is important.
Yes…interesting point…‘‘Design’’ has many meanings.
Without analysis it is more ‘‘styling’’…and anyone can
‘‘style’’ something. But if the object is going to be
subject to any of the laws that govern the planet then
analysis is also necessary. My damned engine stand was
‘‘styled’’ by someone in China whereas it should have been
‘‘designed’’ to support the mass of the Engine.
Regards
Matt–
The original message included these comments:
flange. It is possible that a similar flywheel with a larger dia friction
plate would position those holes safely away from this area.
You can also ‘‘CAD Design’’ something and not do a stress analysis on it. That
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
57
I am not sure who manufactured this flywheel. It looks very well made
and is nicely finished. But it is over stressed in the area around the
crank flange, mainly because there is a steel friction plate bolted
into the flywheel for a 7 1/4" triple plate clutch, and the bolt holes
supporting the plate are right in the middle of the highest stressed
areas around the crank flange.
The bolt holes for the face plate are at the ID of the face
plate? I wouldn’t have done that, as of course they’ll end up in a
highly stressed area. Better to fasten using bolts at the OD, or
perhaps use the same bolts that hold the pressure plate to the
flywheel.
This flywheel came with the mounting holes for the triple plate
clutch?
Simulations
aren’t gospel, but they do show trends very well.
Simulations are GREAT for showing you where the areas of concern lie!
Hence, where would be a good place to drill mounting holes and where
would NOT. And where would be a good place to machine metal away and
where would not.
There also seems to be a test procedure defined in SAE J-1240. SFI
testing requires the manufacturer to nominate a maximum RPM, where
upon the flywheel will be spun for 1 hr at 150% of the nominated RPM
and then tested for cracks or elongation.
Dumb test. Better to run it from 0 to 150% and back, over and over,
for that hour.
I note that the SFI label does not show the max rpm
tested, nor does the manufacturer seem to declare it!
Doesn’t the redline on the tach count?
Nor are
manufacturers required to provide this testing and only do so on
demand from racing sanctioning bodies.
Nobody in the US cares about manual transmissions.
– Kirbert
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !On 27 Oct 2015 at 17:21, Mark Eaton wrote:
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
58
Here’s the thing: Aluminum is fundamentally different from steel in
applications like this, because steel has a yield point and if you
design to stay below that yield point you can theoretically design a
part to last forever. Aluminum has no such potential; theoretically,
no matter how much you baby it, eventually it will fail in fatigue.
Hence, an aluminum flywheel should come with some guidance on its
projected lifespan, how long you can confidently leave it in there
before you really should consider replacing it with a new one. I
would presume that, if you just drive around on the street and only
approach redline on rare occasions when you’re showing off to a girl,
a well-designed aluminum flywheel would last longer than most of the
rest of the car, so it might as well be “the life of the car.” If
you’re using the car competitively, though, you really need to pay
attention to the amount of time that flywheel spends at high RPM. It
might be wise to replace it every racing season.
– Kirbert
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In reply to a message from Richard Dowling sent Mon 26 Oct 2015:
Sorry my mistake…I didn’t realize you were referring to BA
Flight 2276. I thought it was still about Qantas Flight 32.–
The original message included these comments:
I guess a reporter jumped the gun before finding the facts.
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As you know, old posts show up as suggested topics, so here I am reading through all the posts with a lot of information that I really have to think about to understand. If I can at all.
Here’s the thing, I weighed the steel flywheel a few weeks ago and it weighs in at 29lbs. The new Fidanza flywheel which is still not on the engine, which is still not in the car, which is at the paint shop, weighs in at 14lbs.
Now I have a new question. With everything apart, would you invest the time and money to have the flywheel and clutch pressure plate balanced ?
