Pat B schrieb:
>
> DANMAS@aol.com wrote:
> >
> > In a message dated 98-06-29 05:55:29 EDT, jmccarr@ibm.net writes:
> >
> > > Bill Piggot's, Original Triumph (New Edition, 1998) on page 71 talks
> > > about the original fan as a crankshaft vibration damper. He makes the
> > > following comment "Owners who have substituted an electric fan sometimes
> > > experienced broken crankshafts owing to the loss of this damping
> > > effect. Careful engine balancing appears to prevent this occurance."
> >
> > Jack,
> >
> > Piggot did a pretty good job with his book, but he does have a few errors.
> I'm
> > afraid I will have to disagree with him on this one. In fact, if any thing,
> I
> > beleive the opposite is true.
> >
> > Consider the construction of the crank damper, to which the fan is attached.
> > It consists of three pieces - an inner hub, an outer ring, and a rubber fill
> > holding the two pieces together. The fan attaches to the inner hub, which is
> > bolted directly to the crank.
> >
> > Now, conside the operation of a piston type engine. On the power stroke, the
> > piston drives the crank throw, and puts power to the crank. On the
> Compression
> > stroke, just the opposite occurs - the crank throw is forcing the piston up
> in
> > the cylinder. For each cylinder, the crank is alternating between these two
> > forces, which produces vibration. The rubber between the two pieces of the
> > damper tries to absorb these vibrations, and smooth out the crank forces.
> >
> > The more rotating mass there is to the crank, the harder it will be for the
> > damper to perform its function. On the power stroke, any additional mass
> will
> > resist the downward motion of the piston, and on the compression stroke, it
> > will tend to "flywheel" the piston upwards. The difference between the
> > opposing forces will be greater, the larger the rotating mass.
> >
> > Every book or magazine that I have read that touched on the subject advise
> > putting as little weight on the crank snout as possible, just for the
> purpose
> > of reducing the odds of the crank breaking.
> >
> > Additionally, if the fan blades are a little off balance, which I bet most
> > are, as old as they are and as many knocks as they've had over the years,
> they
> > will contribute even more to crank vibration.
> >
> > There is a whole lot more to the overall function of the damper, but this
> > covers the basics.
> >
> > I may be all wet, but at least that's my opinion. Perhaps the TR3 uses a
> > totally different damper construction than nearly any other car ever made?
> >
> > Dan Masters,
> > Alcoa, TN
> >
> > '71 TR6---------3000mile/year driver, fully restored
> > '71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
> > http://www.sky.net/~boballen/mg/Masters/
> > '74 MGBGT---3000mile/year driver, original condition - slated for a V8 soon
> > '68 MGBGT---organ donor for the '74
> Here's My 2 cents...
> The reason dampers are used is to reduce amplitudes of items which are
> resonating. If a crankshaft damper is being used, then the crank shaft
> has a resonant frequency which is either excited by the firing frequency
> or the rotational frequency of the engine. I assume that the TR6 has
> inline six cylinder engine which is inheriently balanced for both shake
> and couples. Since the Inline 6's have one of longest crankshafts made,
> I would assume that there is a torsional resonance of the crankshaft,
> somewhere below 300 Hz. If the engine were to operate at this resonant
> frequency without the damper, the amount of time needed to fail the
> crank would be rather short.
>
> My suggestion... Do whatever you want with the fan. Be sure that the
> damper is left intact and the rubber is in good shape.
>
> BTW, in a modern inline 4 cyl or V6 engine, inertial forces can exceed
> 6000 lb. at redline.
>
> --
> Patrick Barber
> 74 Spitfire 1500 (FM14774U)
> "Go Red Wings" ... 1998 Stanley Cup Champions!!!
>
>
Where exactly is this said crankshaft damper ?????? All I found bolted on
the crankshaft of my TR 6 was a pulley(without any rubber), a extension and a
plastic fan but nothing like a inner hub, outer ring and rubber filling. Can
anyone explain where this dam per is ?
The other thing is that if it is right that the crankshaft of the TR 6 engine
has a resonant frequency somewhere close 300 hz the Triumph engineers did a
good
job. 300 hz eaquals 300 RPM and all an engine designer needs is a resonant
frequency at an engine speed higher or lower than normal operating engine
speed.
Operating a TR engine at 300 RPM sounds hard to do and there should be no
touble
without a damper.
Gerhard
CC 31998 LO
Interesting quote I found in a motor magazin interview with my former next
house
neighbour Ferry Porsche jr. who recently died.
Question: "Why is the ignition key on a (lhd)Porsche always on the left side of
the steering wheel?"
Answer: "Because I didnīt like the idea that not the driver alone has
complete control on the car"
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