Harmonic balancer
Encyclopedia
A harmonic balancer is a device connected to the crankshaft
of an engine to reduce torsional vibration
and serves as a pulley for drive belts.
Every time the cylinders fire, torque is imparted to the crankshaft. The crankshaft deflects under this torque, which sets up vibrations when the torque is released. At certain engine speeds the torques imparted by the cylinders are in synch with the vibrations in the crankshaft, which results in a phenomenon called resonance
. This resonance causes stress beyond what the crankshaft can withstand, resulting in crankshaft failure.
To prevent this vibration, a harmonic balancer is attached to the front part of the crankshaft. The damper is composed of two elements: a mass
and an energy dissipating element. The mass resists the acceleration of the vibration and the energy dissipating (rubber/clutch/fluid) element absorbs the vibrations.
Additionally the energy transferred from the piston
to the crankshaft
can induce as much as 2 degrees of twist in the crankshaft
, which has many follow-on effects on all engine elements that require adequate timing such as valve opening, cam timing, ignition timing
etc.
Over time, the energy dissipating (rubber/clutch/fluid) element can deteriorate from age, heat, cold, or exposure to oil or chemicals. Unless rebuilt or replaced, this can cause the crankshaft to develop cracks, resulting in crankshaft failure.
Performance enthusiasts have been known to remove harmonic balancers, usually when the balancer is attached to the crank pulley, deciding that they aren't necessary and their mass reduces the performance of the engine. However, this is unproven and potentially very risky because the danger of damage to the engine from the vibrations the damper is intended to prevent is too high.
Certain cars, however, do not come equipped with an external balancer on the crank pulley, and as such, can have the pulley replaced with a performance oriented product which counter-acts these resonance
frequencies.
Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...
of an engine to reduce torsional vibration
Torsional vibration
Torsional vibration is angular vibration of an object—commonly a shaft along its axis of rotation. Torsional vibration is often a concern in power transmission systems using rotating shafts or couplings where it can cause failures if not controlled....
and serves as a pulley for drive belts.
Every time the cylinders fire, torque is imparted to the crankshaft. The crankshaft deflects under this torque, which sets up vibrations when the torque is released. At certain engine speeds the torques imparted by the cylinders are in synch with the vibrations in the crankshaft, which results in a phenomenon called resonance
Resonance
In physics, resonance is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. These are known as the system's resonant frequencies...
. This resonance causes stress beyond what the crankshaft can withstand, resulting in crankshaft failure.
To prevent this vibration, a harmonic balancer is attached to the front part of the crankshaft. The damper is composed of two elements: a mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
and an energy dissipating element. The mass resists the acceleration of the vibration and the energy dissipating (rubber/clutch/fluid) element absorbs the vibrations.
Additionally the energy transferred from the piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...
to the crankshaft
Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...
can induce as much as 2 degrees of twist in the crankshaft
Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...
, which has many follow-on effects on all engine elements that require adequate timing such as valve opening, cam timing, ignition timing
Ignition timing
Ignition timing, in a spark ignition internal combustion engine , is the process of setting the angle relative to piston position and crankshaft angular velocity that a spark will occur in the combustion chamber near the end of the compression stroke...
etc.
Over time, the energy dissipating (rubber/clutch/fluid) element can deteriorate from age, heat, cold, or exposure to oil or chemicals. Unless rebuilt or replaced, this can cause the crankshaft to develop cracks, resulting in crankshaft failure.
Performance enthusiasts have been known to remove harmonic balancers, usually when the balancer is attached to the crank pulley, deciding that they aren't necessary and their mass reduces the performance of the engine. However, this is unproven and potentially very risky because the danger of damage to the engine from the vibrations the damper is intended to prevent is too high.
Certain cars, however, do not come equipped with an external balancer on the crank pulley, and as such, can have the pulley replaced with a performance oriented product which counter-acts these resonance
Resonance
In physics, resonance is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. These are known as the system's resonant frequencies...
frequencies.