The harmonic balancer is the term given to the crankshaft pulley when it includes an external metal ring (usually made of cast iron). This ring may contain flat or V-belt grooves or just be a plain weight.
Chevrolet only put a harmonic balancer ring on in engine designs where the crankshaft twists more than 1/2 of one degree (from the front of the crankshaft to the back of the crankshaft) at any engine condition. Problem areas are smetimes at idle or at several rpm's under full throttle. The crankshaft has a natural freqouency when struck with a hammer you will hear a ringing sound. You could go to a piano and pick out that frequency. Whenever the cylinders fire at that frequency (RPM/2), or multipuls of that frequency, then the crankshaft vibration is amplified and excessive twisting may occur. The crankshaft rotation motion actually becomes jerky instead of a smooth rotation. This vibration is passed along to other parts of the engine as well as to the transmission and driven wheels. The crankshaft can develop cracks overtime. To protect the engine and crankshaft for this vibration damage, the factory measures vibration in an engine test stand and selects a harmonic balanacer design to dampen this unwanted motion to less than 1/2 degree maximum. The primary design features that regulate this tuned frequency (kind of like a radial tuning fork!) are the thickness of the rubber strip, its hardness (durometer), and the inertial mass (apparent rotating weight) of the harmonic balancer ring.
Everything is fine until the rubber strip begins to change over time with heat and wear. When the rubber strip begins to harden (change durometer ) its tuned frequency changes and it no longer works to properly dampen the unwanted crankshaft twisting motion.
A 'rule of thumb' test of the condition of the rubber strip's health is to push your thumbnail into the rubber strip of the harmonic balancer. Originally it was about a 60 durometer hardness, which would feel very firm but flexible, without hurting your tumbnail. When the rubber still feels somewhat flexible but it hurts your thumbnail, it has begun to harden and change the frequency. The rubber can actually harden into a solid mass before the rubber bond breaks and the harmonic balancer ring shifts out of position or slips out of position. The harmonic balancer has practically failed, however, when the rubber durometer begins to change significantly.
If you want to keep your original harmonic balancer rather than replace with a new replacement unit, there are several firms that can rebuild your original harmonic balancer. The three that I am aware of are Winslow Manufacturing (North Carolina), Damper Doctor (Northern California), and my business: Dale Manufacturing (Salem, Oregon).
Most customers ship using the post office medium sized 'flat rate box'. The key to safe shipping is to reinforce your shipping box inside on the bottom and sides with heavy hardboard and then to put the flat side down on the bottom of the box. Next for packing, take old newspaper two layers think and crumple into tight balls and pack all around tightly, leaving no emply space in side the box so when closed and securely taped shut, your part can not shake or rattle. You can contact the other rebuilders for their service details.
I would be glad to answer any specific questiosn relating to harmonic balancers that I might know.
There is some more general information, including two Chevrolet engine test lab results on harmonic balancer testing on another Chevrolet engine on our web site (www.dalemfg.com)
Chevrolet only put a harmonic balancer ring on in engine designs where the crankshaft twists more than 1/2 of one degree (from the front of the crankshaft to the back of the crankshaft) at any engine condition. Problem areas are smetimes at idle or at several rpm's under full throttle. The crankshaft has a natural freqouency when struck with a hammer you will hear a ringing sound. You could go to a piano and pick out that frequency. Whenever the cylinders fire at that frequency (RPM/2), or multipuls of that frequency, then the crankshaft vibration is amplified and excessive twisting may occur. The crankshaft rotation motion actually becomes jerky instead of a smooth rotation. This vibration is passed along to other parts of the engine as well as to the transmission and driven wheels. The crankshaft can develop cracks overtime. To protect the engine and crankshaft for this vibration damage, the factory measures vibration in an engine test stand and selects a harmonic balanacer design to dampen this unwanted motion to less than 1/2 degree maximum. The primary design features that regulate this tuned frequency (kind of like a radial tuning fork!) are the thickness of the rubber strip, its hardness (durometer), and the inertial mass (apparent rotating weight) of the harmonic balancer ring.
Everything is fine until the rubber strip begins to change over time with heat and wear. When the rubber strip begins to harden (change durometer ) its tuned frequency changes and it no longer works to properly dampen the unwanted crankshaft twisting motion.
A 'rule of thumb' test of the condition of the rubber strip's health is to push your thumbnail into the rubber strip of the harmonic balancer. Originally it was about a 60 durometer hardness, which would feel very firm but flexible, without hurting your tumbnail. When the rubber still feels somewhat flexible but it hurts your thumbnail, it has begun to harden and change the frequency. The rubber can actually harden into a solid mass before the rubber bond breaks and the harmonic balancer ring shifts out of position or slips out of position. The harmonic balancer has practically failed, however, when the rubber durometer begins to change significantly.
If you want to keep your original harmonic balancer rather than replace with a new replacement unit, there are several firms that can rebuild your original harmonic balancer. The three that I am aware of are Winslow Manufacturing (North Carolina), Damper Doctor (Northern California), and my business: Dale Manufacturing (Salem, Oregon).
Most customers ship using the post office medium sized 'flat rate box'. The key to safe shipping is to reinforce your shipping box inside on the bottom and sides with heavy hardboard and then to put the flat side down on the bottom of the box. Next for packing, take old newspaper two layers think and crumple into tight balls and pack all around tightly, leaving no emply space in side the box so when closed and securely taped shut, your part can not shake or rattle. You can contact the other rebuilders for their service details.
I would be glad to answer any specific questiosn relating to harmonic balancers that I might know.
There is some more general information, including two Chevrolet engine test lab results on harmonic balancer testing on another Chevrolet engine on our web site (www.dalemfg.com)
Comment