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

[barry rosenberg]

 Back in 1980, Fred Baker won the run-offs at Road Atlanta in a Jag XKE. One thing that he said helped was making the flywheel and harmonic damper as close to the same weight as possible. He used some big American car damper. They had trouble making maximum RPM and ran the engine on a dyno with a strobe light on the flywheel and noticed a severe flex to the crank. They increased the damper weight and the vibration was reduced giving close to 1,000 more RPM. The cranks "wiggle" at high RPM. Matching the weight at both ends reduced that. They did blow the engine the next week when giving writers a test ride. I used this theory on my TR4A using a factory crank that I modified and lightened, I used an ATI custom damper and a lightened aluminum flywheel (less than 18 lbs for flywheel, PP and disc) and was able to turn the engine to 7,300. I also used a custom 1/4" plate bolted to the oil pan rail and across to the center main caps. Maybe some one can get more info on this theory.
Barry Rosenberg
    On Friday, May 22, 2020, 07:32:38 AM EDT, fubog1 via Fot <fot at autox.team.net> wrote:  
 
  

Note that lighter pistons and connecting rods 
 That's a BIG gain, it gets some of that recip/bending load out of the mains. 
Glen
 
 
-----Original Message-----
From: timmmurphh--- via Fot <fot at autox.team.net>
To: fot at autox.team.net
Sent: Thu, May 21, 2020 7:07 pm
Subject: [Fot] FW: Flywheel wt & crank harmonics -TR3/4

   From: timmmurphh at gmail.com <timmmurphh at gmail.com> 
Sent: Thursday, May 21, 2020 6:06 PM
To: 'TeriAnn J. Wakeman' <tjwakeman at gmail.com>
Subject: RE: [Fot] Flywheel wt & crank harmonics -TR3/4  The weight of the flywheel will definitely affect the harmonic frequency.  The heavier the flywheel, the lower the harmonic frequency will be.  The flywheel contributes a significant amount to the total rotating inertia due to its weight and that the weight is at greater radius than the other rotating masses.  Inertia increases as the square of the radius.  It is not a linear function of the radius.  An RPM of 5200 was mentioned as the harmonic resonance.  I had always heard that it was more like 6300 RPM.  I have never seen a calculation for it.  It would be complex.  Note that lighter pistons and connecting rods would tend to lower the harmonic frequency as they would reduce the inertia in the engine.  Tim Murphy  From: Fot <fot-bounces at autox.team.net> On Behalf Of TeriAnn J. Wakeman via Fot
Sent: Thursday, May 21, 2020 2:44 PM
To: FOT <fot at autox.team.net>
Subject: [Fot] Flywheel wt & crank harmonics -TR3/4  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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