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

[Joe Alexander]

On my street TR4A, the harmonics came in about 2800 RPM and again at 5600 RPM.

It was an interesting sensation. Hard to describe.

I never noticed it in any of the race engines.

Joe Alexander
4505 Donald Dr
Cedar Falls, IA 50613
The-vintage-racer.com
Gasketinnovations.com
Cell:  319.464.4711


> On May 21, 2020, at 6:14 PM, timmmurphh--- via Fot <fot at autox.team.net> wrote:
> 
> 
>  
>  
> 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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