[Fot] Flywheel wt & crank harmonics -TR3/4

[Rick Parent]

Everything resonates at it own natural frequency including us haha, and if your crank and flywheel are close in that particular freq you will have a problem so changing the weight will change the freq. subtracting weight does help but to what measure on your application I can't say, adding weight may help but it could also have the effect of compounding the problem. I am partial to using a front pulley as light and small as possible (no damper) and also a huge fan of light weight flywheels and small diameter clutches for this very reason. The most expensive thing you can do to help your the problem is a super light crankshaft. I recently build a motor for a guy with a custom crank that knocked off 12 lbs and I could tell the difference on the dyno before it ever went in the car, the typical vibrations were gone. I asked the driver after his first session how he liked the motor and the only thing he kept saying was "it's so smooth" over and over, it audibly sounded different on track as well, crazy. The really bad part is when the Harmonic frequency gets transferred to the valve train, then you will have a serious disaster. 4 cylinders are known for this problem and some guys won't even run one on their Dyno and I personally have thrown more flywheels off on the Dyno than I would care to admit and this very problem has forced me to look at the options if for no other reason than to make my life easier. Not looking for work here but I would be willing to build a crank for anyone wanting to take their stuff to the next level but it would cost about $3000.
Thanks, Rick
General (Mad Dog) Mattis"Be prepared to reverse decisions as new data comes in, then replace assumptions with knowledge"
 

    On Thursday, May 21, 2020, 03:43:54 PM EDT, TeriAnn J. Wakeman via Fot <fot at autox.team.net> wrote:  
 
   
Something I have wondered about for years.
 
Does the weight of the flywheel affect the RPM and intensity of harmonics inherent in a TR3/4 stock crank? I've never found an answer to that question.
 
TeriAnn
 
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