Harmonic balancer?? Why have one??
Thread Starter
Race Director
Joined: Nov 2000
Posts: 11,872
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From: Waterloo ontario Canada
Harmonic balancer?? Why have one??
I had to replace my harmonic balancer because my old 454 required the external balance of one. The one I traded for is for an internal balanced motor.
While picking it up from the speed shop the old owner asked my why I bother running one at all? He raced internal balanced engines and only used the internal hub.
Well today I cut the outer ring off. It is just a heavy ring of steel with a very slim elastic band between the center hub and outer ring.
I checked with Weiand who sold me the blower as well as BDS and both agree that other then a hub for attach the accessories too there is no need for harmonic balancer with an internal motor.
While picking it up from the speed shop the old owner asked my why I bother running one at all? He raced internal balanced engines and only used the internal hub.
Well today I cut the outer ring off. It is just a heavy ring of steel with a very slim elastic band between the center hub and outer ring.
I checked with Weiand who sold me the blower as well as BDS and both agree that other then a hub for attach the accessories too there is no need for harmonic balancer with an internal motor.
Melting Slicks
Joined: Feb 2003
Posts: 3,053
Likes: 4
St. Jude Donor '03,'11
Originally Posted by norvalwilhelm
I had to replace my harmonic balancer because my old 454 required the external balance of one. The one I traded for is for an internal balanced motor.
While picking it up from the speed shop the old owner asked my why I bother running one at all? He raced internal balanced engines and only used the internal hub.
Well today I cut the outer ring off. It is just a heavy ring of steel with a very slim elastic band between the center hub and outer ring.
I checked with Weiand who sold me the blower as well as BDS and both agree that other then a hub for attach the accessories too there is no need for harmonic balancer with an internal motor.
While picking it up from the speed shop the old owner asked my why I bother running one at all? He raced internal balanced engines and only used the internal hub.
Well today I cut the outer ring off. It is just a heavy ring of steel with a very slim elastic band between the center hub and outer ring.
I checked with Weiand who sold me the blower as well as BDS and both agree that other then a hub for attach the accessories too there is no need for harmonic balancer with an internal motor.
I'm guessing some kid broke into you CF account and is posting this.
As an engineer i'm sure you know the importance of damping harmonics on a long piece of metal under severe stress.
You might be able to get away with not having one on a race engine that isnt expected to have lots of hours. A street motor will eventually develop stress cracks in the crank and fail.
Unbelievable the reputable aftermarket performance companies told you a balancer isn't necessary.
Last edited by turtlevette; Nov 4, 2006 at 04:30 PM.
Le Mans Master
Joined: Apr 2000
Posts: 5,202
Likes: 10
From: cincinnati ohio
St. Jude Donor '09
The harmonic balancer, or vibration damper, is a device connected to the crankshaft to lessen the torsional vibration. When the cylinders fire, power gets transmitted through the crankshaft. The front of the crankshaft takes the brunt of this power, so it often moves before the rear of the crankshaft. This causes a twisting motion. Then, when the power is removed from the front, the halfway twisted shaft unwinds and snaps back in the opposite direction. Although this unwinding process is quite small, it causes "torsional vibration." To prevent this vibration, a harmonic balancer is attached to the front part of the crankshaft that's causing all the trouble. The balancer is made of two pieces connected by rubber plugs, spring loaded friction discs, or both. When the power from the cylinder hits the front of the crankshaft, it tries to twist the heavy part of the damper, but ends up twisting the rubber or discs connecting the two parts of the damper. The front of the crank can't speed up as much with the damper attached; the force is used to twist the rubber and speed up the damper wheel. This keeps the crankshaft operation calm.
Thread Starter
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Originally Posted by turtlevette
Norval,
I'm guessing some kid broke into you CF account and is posting this.
As an engineer i'm sure you know the importance of damping harmonics on a long piece of metal under severe stress.
You might be able to get away with not having one on a race engine that isnt expected to have lots of hours. A street motor will eventually develop stress cracks in the crank and fail.
Unbelievable the reputable aftermarket performance companies told you a balancer isn't necessary.
I'm guessing some kid broke into you CF account and is posting this.
As an engineer i'm sure you know the importance of damping harmonics on a long piece of metal under severe stress.
You might be able to get away with not having one on a race engine that isnt expected to have lots of hours. A street motor will eventually develop stress cracks in the crank and fail.
Unbelievable the reputable aftermarket performance companies told you a balancer isn't necessary.
BDS a well know blower company has a wide range of simple hubs to bolt accessory pulleys too and forget the harmonic balancer.
I emailed them asking if I needed one for my street motor and they said NO a simple hub is all you need.
I cut mine apart this morning and discarded the heavy outer ring. I will run WITHOUT one.
Thread Starter
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Yellow 72 that is a good explantation but why does the front of the motor accelerate more then the back? The crank should see equal power strokes all along it's length?
Doesn't alot of 4 bolt mains sometimes use 2 bolt on the front??
Maybe the fact that I am running a big blower belt under load takes the torsional twist out of the crank but honestly blower companies say you can run fine with just a hub it the motor is internally balanced
I also broke down and dropped the 38 pound steel flywheel and went with a 15 pound aluminum one.
Doesn't alot of 4 bolt mains sometimes use 2 bolt on the front??
Maybe the fact that I am running a big blower belt under load takes the torsional twist out of the crank but honestly blower companies say you can run fine with just a hub it the motor is internally balanced
I also broke down and dropped the 38 pound steel flywheel and went with a 15 pound aluminum one.
Melting Slicks
Joined: Dec 2005
Posts: 2,441
Likes: 0
All the factory V8 engines I've seen came with dampeners, regardless of being internally or externally balanced. Maybe the modern factory blower equipped motors produced today are without that piece, I've never noticed.
Great opportunity for an "outside of the box" debate/discussion.
Great opportunity for an "outside of the box" debate/discussion.
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Burning Brakes
Joined: Mar 2006
Posts: 1,036
Likes: 2
From: Huntingburg Indiana
Originally Posted by norvalwilhelm
Yellow 72 that is a good explantation but why does the front of the motor accelerate more then the back? The crank should see equal power strokes all along it's length?
Doesn't alot of 4 bolt mains sometimes use 2 bolt on the front??
Maybe the fact that I am running a big blower belt under load takes the torsional twist out of the crank but honestly blower companies say you can run fine with just a hub it the motor is internally balanced
I also broke down and dropped the 38 pound steel flywheel and went with a 15 pound aluminum one.
Doesn't alot of 4 bolt mains sometimes use 2 bolt on the front??
Maybe the fact that I am running a big blower belt under load takes the torsional twist out of the crank but honestly blower companies say you can run fine with just a hub it the motor is internally balanced
I also broke down and dropped the 38 pound steel flywheel and went with a 15 pound aluminum one.
Melting Slicks
Joined: Nov 2003
Posts: 2,362
Likes: 1
From: San Antonio TX
A little more info here. http://www.blowerdriveservice.com/ca...pany_id=101011
They have some great set ups.
They have some great set ups.
Le Mans Master
Joined: Apr 2000
Posts: 5,202
Likes: 10
From: cincinnati ohio
St. Jude Donor '09
Originally Posted by bondoboy
I would say the front of the crank accelerates faster because there is little load there. The transmission and drive train are putting a load on the rear.
The torsional motion of the crank would logically be toward the front farthest away from the "fixed end"I'm using one of those budget aftermarket performance dampeners with my blower drive and may end up with more problems than running a just a hub
I'll agree that there are many high end motors on the street and tracks running no crank dampeners with apparently no ill effects
Race Director
Joined: Apr 2000
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
I think we are talking about 2 different kinds of motors here. It appears you don't need to ( or shouldn't ) run a traditional balancer on a blower motor, I would not run an ordinary normally asperated motor without one attached 
Le Mans Master
Joined: Apr 2000
Posts: 5,202
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From: cincinnati ohio
St. Jude Donor '09
Originally Posted by DWncchs
Doesnt the balancer also deaden vibrations in the valve train ?
Team Owner
Joined: Jul 2004
Posts: 40,368
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From: Redondo Beach, California
I think that because the crank and rods are pretty much assymetrical, the engine can only be balanced for a narrow band of RPM's. The vibration damper helps with vibration at RPM's different than the engine was really balanced for. Previous posts talking about harmonics is basically another way of saying the same thing. Anyhow a vibration damper is a good thing, it's at least like insurance. It certainly won't harm your engine. I would think it's really necessary.
Melting Slicks
Joined: Feb 2003
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Likes: 4
St. Jude Donor '03,'11
i'm an electrical engineer so i don't know what i'm talking about, but i always thought harmonic frequencies cause travelling stresses within metal to bounce off each other and actually build. Like the bridge in WA that collapsed in the wind. The oscillations got bigger and bigger because it was oscillating at a harmonic until it couldn't take it anymore and collapsed.
When the cylinder fires there is an impulse of torque applied to the crankshaft ( like somone hitting the throw with a sledge hammer) causing a ringing in the metal. At certain frequencies this would cause stress cracking of the metal over time. If the stresses weren't dampened by some method.
Large steam turbine power plant's blades can crack from harmonics if operated too long at certain speeds where harmonics are generated.
So they're saying the huge rubber belt on the front of a blower motor acts as the damper?
When the cylinder fires there is an impulse of torque applied to the crankshaft ( like somone hitting the throw with a sledge hammer) causing a ringing in the metal. At certain frequencies this would cause stress cracking of the metal over time. If the stresses weren't dampened by some method.
Large steam turbine power plant's blades can crack from harmonics if operated too long at certain speeds where harmonics are generated.
So they're saying the huge rubber belt on the front of a blower motor acts as the damper?
Last edited by turtlevette; Nov 4, 2006 at 11:09 PM.
Le Mans Master
Joined: Jul 2005
Posts: 5,752
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From: Austin Texas
Here is a little info. for you all to ponder. On some C-1's, especially the later models, had no harmonic balancer, just a solid thin hub just large enough to bolt a pulley to. No balancing function or outer ring at all. Hmmmm
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
This is a highly interesting thread to me, as for about 45 years now, the way I thought I unnersood the thang wuz those harminicas needed cancelling or surely the vibrations of twist would combine to toss Chubby Checker's back out....at some rate or frequency, take you pick....
and yes, that heavy loaded belt/pulley being rubber would with it's load act the same as the rubber isolated damper....
IMO, of course.....but then again, I don't have a degree...
and yes, that heavy loaded belt/pulley being rubber would with it's load act the same as the rubber isolated damper....
IMO, of course.....but then again, I don't have a degree...