Hi Tom!
Very interesting notes. What I did with my original metal fan, after
cleaning it up during the restoration, and before painting the fan, was
this:
I removed the 'burs' on the outer tips/edges of the blades (certainly not
enough mass removed to make a difference, this I know from working with
aircraft propellors- where balance is even more critical).
I placed the blade, one side at a time, on the flat clean workbench. I noted
blade tips that were 'higher than others'. I flipped the fan, did the same
thing. I 'tweeked' the blades till they were all in 'the same plane'. I did
this by gently pushing to have all the tips rest evenly on the bench. Did
this both ways. I installed the fan on the hub with the balance piece - From
whence it came off. After start up I watched the 'plane' of the diagonal
blades in reference to the radiator. As one accelerates the engine, one can
see a fine change of plane. I measured with a micrometer the fine
differences. Each tweek made the high rpm balance 'better', but it is still
far from acceptable to me.
I know from my early years with the car (1970-71)driving across Oklahoma,
Texas and New Mexico at 5000-5500 rpm (valves adjusted per Kasters 'blue
tuning manual) - I had no vibrations then that were 'anoying or clearly
'unacceptable'.
As you say- with the age of the fan - it just seems the logical next step
for practical driving and occassional bursts thru the the mid 4,000 rpm
range - is a plastic fan or an electric fan conversion, which seems most
practical to me. After all, this is what TRiumph did for the TR-6 - better
technoogy.
I'm not about to pull the engine & tranny for this problem. I have no
'abnormal vibrations'at 3800 RPM or below- where most cruising is done,
despite my Panasports with 165 x15 tires which have the effect of 'low
profile tires (1/2" wider rim than stock discs). The GPS confirms the car
runs about 5mph slower at 3500 RPM (65mph real speed vs 70mph indicated).
This is a NON-overdrive car. Another someday project!
Interesting about the tranny balance piece, I'll look for that next time
I'm under there. For me, originality is not a issue vs practicality. Another
thing, I recently learned there is some minor play in the crank with the
'thrust washer test'. Don't know if this has anything to do with this
crank/fan imbalance or not.
All these are Interesting technical questions in our search for 'Triumph
Perfection'! I'll report back in the spring,when I get the conversion
completed.
Hope to see you in Ohio for the TRA National next year!
Sherman
-----Original Message-----
From: T.R. Householder [mailto:trhouse@greenapple.com]
Sent: Thursday, January 31, 2002 7:58 PM
To: Taffel, Sherman
Subject: Re: TR3 fan balance
FYI.
Tom
There is a system of balance weights mounted on the fan
assembly. These however
do not balance the engine in my opinion. Somewhere I saw a
photo in a manual of
how the fan and hub assembly were balanced on a bench jig.
Once the assembly was
balanced holes were drilled to mark the correct location
of the weight. If you
have the original fan assembly it should go back together
with out much
difficulty. hard to say how accurate it is after all these
years. The jig was
nothing more than a couple of rails that ran parallel to
each other probably
about ten inches apart. a machined shaft was inserted
through the assembly and
the ends of the shaft were placed on the rails. it
appeared as though the
assembly would be rolled along the rails and then when it
settled out the heavy
side was marked. The weights were probably then adjusted
and the procedure
repeated until the assembly rolled without stopping in any
certain spot.
Technology is far more advanced I'm sure that your shop
will be able to sort
this out. the only other balancing mechanism added was a
weight ti the end of
the four speed syncro box. this was attached to the tail
shaft of the trans.
there was an archive tread on this a couple of years ago.
it sort of surprised
me i always thought the large cast Ball worked more as a
heat sink to keep the
exhaust heat off of the rear seal. Your Clutch disc and
pressure plate should
surely accompany the engine to the shop.
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