Harmonic Damper

[Jerry Irwin]

Hello Chaps...

Here;s a techy question for you all...
I have a 302 / 347 stroker with INTERNAL BALANCED Eagle crank.
Therefore not need a 25 / 50 oz/in or whatever flywheel or damper .
just a 'neutral' balance.

What are the pros / cons of running with NO Harmonic balancer ?

Thanks

Jerry

 

[Randy V]

With no harmonic balancer, your crankshaft is going to take a real beating. I wouldn’t think of doing it for very long (minutes) myself…

 

[Tom]

No personal experience with this but...1) timing chain will have shorter service life, and be more subject to catastrophic failure 2) crank more likely to break in use 3) idle will probably be slightly lumpier, and low speed drivability may impaired slightly. I think dirt track sprint cars run without a damper, so they run a gear drive on the cam. You can also tell a difference in use between a dual mass flywheel and a single mass flywheel.

 

[Jerry Irwin]

OK , let me expand a little further...

A neutral harmonic is in balance with it;s self ....ie it has no offset weights.
Taking another example...
flywheels come in various WEIGHTS.
Light weight allows faster spin up and spin down
heavy weight is the opposite but the extra weight makes engine 'appear' smoother.

Therfore the same applies to the other end of the crankshaft where the harmonic bit is ?
ie.. the lighter it is the faster spin up...therefore removing it will only have positive results ?

The reason for asking ....
Replace Harmonic with a set of ally pulleys ...

Jerry

 

[Neil]

Hello Chaps...

Here;s a techy question for you all...
I have a 302 / 347 stroker with INTERNAL BALANCED Eagle crank.
Therefore not need a 25 / 50 oz/in or whatever flywheel or damper .
just a 'neutral' balance.

What are the pros / cons of running with NO Harmonic balancer ?

Thanks

Jerry

A "harmonic balancer" is really a torsional damper for the crankshaft. Remove it and eventually your crankshaft will suffer a fatigue failure. Would anyone remove the shock absorbers and drive around that way? Same thing!

 

[Jerry Irwin]

Whilst that sort of makes sense...
There are NO harmonic balancers on straight 4 cylinders ? or straight 6 ( i think )
just a balance of crankshaft and away we go ......

Jerry

 

[Neil]

Whilst that sort of makes sense...
There are NO harmonic balancers on straight 4 cylinders ? or straight 6 ( i think )
just a balance of crankshaft and away we go ......

Jerry

I have never seen a 4 cyl or 6 cyl engine without a crank damper. You cannot balance a 4 cyl; it is inherently out of balance. A straight 6 or 12 is inherently in balance but a crank damper is still used.

 

[Jerry Irwin]

where is the crank damper on a 4 cylinder then ?
i have built many racing 4 cylinder motors with just flywheel and a drive pulley for the dry sump pump... never had a failure or vibration ?
zetec/lotus twin cam / 2.3 ecoboost turbo.
What am i missing here ?

Jerry

 

[Mike Pass]

Crank torsional resonance. The crank may be dynamically balanced but can torsionally "ring like a bell." If the firing pulses are sent intio the crank at a rate that matches the natural torsional frequency of the crank then it can resonate and this can create extreme vibration which needs to be damped out. The same principle is why many 4 cylinder diesels have dual mass flywheels.
Cheers
Mike

 

[Bill Kearley]

Zero balance is what you want. Find a Boss 302 , 1970 or equivalent. Yes you must use a balancer

 

[Neil]

where is the crank damper on a 4 cylinder then ?
i have built many racing 4 cylinder motors with just flywheel and a drive pulley for the dry sump pump... never had a failure or vibration ?
zetec/lotus twin cam / 2.3 ecoboost turbo.
What am i missing here ?

Jerry

The reason some 4 cyl engines get away without a crank damper is the very short length of their crankshaft. This shortness contributes to crank stiffness. A damper still helps control torsional vibration.

 

[Jerry Irwin]

Crank torsional resonance. The crank may be dynamically balanced but can torsionally "ring like a bell." If the firing pulses are sent intio the crank at a rate that matches the natural torsional frequency of the crank then it can resonate and this can create extreme vibration which needs to be damped out. The same principle is why many 4 cylinder diesels have dual mass flywheels.
Cheers
Mike

Thanks Mike....
That does make sense..

Jerry

 

[Howard Jones]

Pro: A correctly selected, high-quality harmonic dampener, in addition to a property-balanced rotating assembly, will contribute to a long life and high-reliability engine.

Con: lack of a quality harmonic dampener, or a damaged dampener will sooner or later cause catastrophic engine failure. I have no idea how long it would take but I bet an engine run on track would not last through the first several hours.........really.

 

[Jerry Irwin]

Pro: A correctly selected, high-quality harmonic dampener, in addition to a property-balanced rotating assembly, will contribute to a long life and high-reliability engine.

Con: lack of a quality harmonic dampener, or a damaged dampener will sooner or later cause catastrophic engine failure. I have no idea how long it would take but I bet an engine run on track would not last through the first several hours.........really.

Brilliant video......Answers all my questions.....
Thank you Howard... your a star !!!!!!!

Jerry