My own opinion is that a very heavy 31# flywheel has more to do with cranks
cracking than the absense of a dampener. These flywheels should have never been
31#.
I use an MGB harmonic balancer on #197, but seriously doubt it does very
much, outside of provide me with a pulley for a narrow belt.
I have used flywheels from 10-20# in 16 years of racing, sometimes exceeding
6,000 RPM and have never broken a crankshaft. And I use a stock crankshaft
with no preparation beyond balancing.
It is my understanding that harmonic balancers have to be carefully
engineered to the specific engine characteristics. I doubt that Triumph studied
this in
very great depth for this particular engine. Mostly my opinion, but I have
some history, both empirically and by asscociations.
Joe A
> Pardon my ignorance, but I have a question. Do the eliminated parts
> contribute in any way to balancing or
> > dampening vibrations on the crankshaft?
>
> On the TR2-4; I've been told by those who should know that the stock fan
> itself, and the rubber bushings it mounts on, acts as a harmonic dampener.
> This has nothing to do with engine balance (although the fan assembly is
> balanced by itself), but with reducing vibrations in the crankshaft that add
> to it's stress.
>
> However, based both on personal experience and what I've been told, this
> doesn't appear to be too important for nearly stock, street-driven engines.
> It's the people who consistently run over 5000 rpm that seem to need the
> dampening. To that end, most of the racing TR parts suppliers offer a
> harmonic dampener to fit the TRactor motor. It's also usually alloy, and
> usually part of a narrow belt conversion, and quite pricey. TriumphTune
> used to sell the parts to allow using the dampener from a BMC motor, but
> AFAIK that kit has been NLA for a long time.
>
> I've run over 100,000 miles on the street with no mechanical fan or
> extension, even exceeding 5000 rpm on occasion (once had a passenger ask me
> if the tach was supposed to hit the stop like that <g>), and never broken a
> crank. I have seen the cranks others broke, but AFAIK every one of them was
> on the race track, not on the street. YMMV of course.
>
> Randall
>
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