[TR] Dampener or no Dampener on Tractor Engines

[N197TR4 at cs.com]

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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