<VV> Harmonic Balancer

[kevin nash]

From: James Davis<mailto:hurricanehazel16 at gmail.com>
Sent: Saturday, March 21, 2020 4:40 PM
To: kevin nash<mailto:wrokit at hotmail.com>
Cc: virtualvairs at corvair.org<mailto:virtualvairs at corvair.org>
Subject: Re: <VV> Harmonic Balancer

If you look at the initial SAE engineering paper, the 140 cuin Corvair engine showed a huge crankshaft resonance at around 4,400 rpm, enough to propagate cracks in the crankshaft.   Thus only the engines with the ability to sustain operation at and above 4,400 rpm were equipped with a harmonic balancer initially.
Jim Davis

On Sat, Mar 21, 2020 at 11:32 AM kevin nash via VirtualVairs <virtualvairs at corvair.org<mailto:virtualvairs at corvair.org>> wrote:

Those earlier engines also broke cranks from time to time, and did it with greater frequency when stroked because of the loss of crank overlap. The Spyder cranks were made with a different material and were nitride…. “The new crank withstood over a half a million cycles in rotary fatigue testing without failure, wereas the old crank would develop cracks in about 100,00 cycles. Torsional vibrations in the crankshaft under full manifold boost at wide open throttle were found to  be comparable to the torsional vibrations in the naturally aspirated high performance Corvair engine. Consequently no harmonic vibration damper is needed.” This is from
Corvair, a complete guide, Car life special edition.
  Harmonic vibration dampers are always installed on engines when the crank will torsionally flex more than 1.5 degrees end to end, and if they don’t move that much, they don’t put them on. The long stroke engines need these, as there’s 2 rpms were the crank will exceed this 1.5 degree limit, both are in the range of normal driving. Both the late cranks and the earlier cranks are “somewhat” famous for breaking cranks but I’m not aware of anyone breaking a Spyder crank… all I know is if it was a matter of driving style and boost I should have broken one long time ago, as “mean” as I’ve been to it, and most of those miles were done without the harmonic balancer… 150000 miles on it.
Kevin Nash
63 Turbo EFI daily driver
Baddest fan on the planet!