[Fot] aftermarket crank dampeners and pullies for TR4's

[Michael Porter]

On 12/5/2013 4:54 PM, Randall wrote:
> ---- toodamnfunky at comcast.net wrote:
>> I second that. If a harmonic balancer isn't needed on the tr4 then why have
>> it?
> The problem is how do you define "needed" ?  I've seen the broken crankshafts, they do happen.  And although the breaks are sudden of course, I believe the damage happens over a long time, likely only when running at one particular (resonant) rpm.  If running a dampener (it's not really a balancer since the TRactor motor is already balanced without it) will lower the chances of a DNF and lost weekend from a broken crank, maybe it's worth sacrificing .01 second off your lap time.  (Or shaving that much more weight off the flywheel.)
>

Mostly in agreement with Randall on this one.  I'm going deep into 
memory (so, I may surface with sludge all over me), but weren't there 
stories of broken cranks quite a few years ago due to the removal of the 
long-nose crank adapters without replacing them with a damper or 
something of equal weight?

Beyond that, the wet-sleeve engine is a special case, I think. Fairly 
large piston area combined with the cylinder spacing required for 
wet-sleeves, along with three bearings, creates rather a large rocking 
couple, and those vibrations are very pronounced within the working 
range of the average race engine.  The engine may be in primary balance, 
but the amplitude of those second-order harmonics is pretty large until 
well beyond the maximum rpm of the engine.

Anything to dampen those vibrations seems to me to be a good thing. (On 
that note, had I the money for some serious experimentation, I'd be 
thinking about the crankshaft as two halves separated by the center 
journal and would be trying dampers on _both_ ends of the crankshaft....)


Cheers.



-- 


Michael Porter
Roswell, NM


Never let anyone drive you crazy when you know it's within walking distance....