In message <67@smyers.demon.co.uk> writes:
> This subject may have been brought up before, and if so please accept my
> apologies as a newcomer, and point me in the direction of suitable info.
>
> Triumph 4 cylinder engines have a fan fitted to the crankshaft as standard
> for
> cooling purposes. I have heard that this also acts as a damper for vibrations
>
> in the (3 main bearing) crankshaft, and without it, it is possible for the
> vibrations to actually break the crankshaft. A number of people sell
> electric
> fans to replace the mechanical one (my TR4A has one fitted and the crankshaft
>
> has indeed broken in the past). Any thoughts on this from anyone? If it is
> true what suggestions does anyone have as to an alternative method of
> damping?
>
> --
> Matthew Adams, (1966 TR4A)
>
> email: matt@smyers.demon.co.uk
The engine used in the TR2->4A does not have a real harmonic dampener. The
crank harmonics are such that they can break ( I believe at the flywheel end) in
the 5200->5500 RPM range. This is why even the factory race/rally cars were not
allowed to rev abouve 5000 RPM.
Someone who had access to British Lealand's crank harmonic records (collected
from the camponys they gobbled up) compaired the TR crank's harmonic pattern
aginst all the other engines and found one that had almost identical
characteristics without a harmonic damponer.
There is a kit available that uses the harmonic dampener from the other crank, a
narrower fan belt (The harmonic dampener's pully took a standard width belt),
and a narrower pully for the water pump. You can scrounge a generator pully
from most any other generator. This kit was ment to be used in race cars
without fans, or street cars with an electric fan. It is available in the US
from British Frame and Engine, and I believe in the UK from Racetorations.
If you plan to rev your engine much, I would also suggest nitriding the crank
during its next rebuild. This process takes a while, so you might schedule it
as soon as it comes out of the engine. In mine, the nitriding, turning and
balancing was the longest serial set of rebuild operations. Be sure the oil
plugs are removed from the crank before nitriding.
TeriAnn Wakeman Large format photographers look at the world
twakeman@apple.com upside down and backwards
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