{"id":1789,"date":"2018-07-05T23:58:14","date_gmt":"2018-07-06T03:58:14","guid":{"rendered":"http:\/\/maxtorqueperformance.com\/?p=1789"},"modified":"2018-07-06T00:08:04","modified_gmt":"2018-07-06T04:08:04","slug":"harmonic-damper-a-key-source-for-lost-horsepower","status":"publish","type":"post","link":"https:\/\/maxtorqueperformance.com\/staging\/index.php\/2018\/07\/05\/harmonic-damper-a-key-source-for-lost-horsepower\/","title":{"rendered":"Harmonic Damper: A Key Source for Lost Horsepower"},"content":{"rendered":"
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Harmonic Damper: A Key Source for Lost Horsepower<\/h1>\n
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By Joe Palmer<\/a> <\/span> <\/span> August 17, 2017<\/span> <\/div>\n<\/header>\n

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We are all guilty of installing a flashy part on our hot rod or engine that doesn\u2019t add any power, but we\u2019re convinced the system \u201cruns better\u201d with it installed. Now imagine installing a part that doesn\u2019t directly build power, but its interaction with the engine\u2019s rotating assembly can release power that may have otherwise been wasted energy in the form of vibration, or maybe the part just reduces premature wear on bearings and associated components. This part\u2013the harmonic damper\u2013already exists on every street-driven engine, and is often overlooked as just a mounting point for accessory pulleys or a location for attaching weights for externally balanced engines. The harmonic damper presents a crucial opportunity to optimize your rotating assembly to insure longer life or to free up wasted energy that could be better applied to the tires.<\/p>\n

So is it a balancer, or is it a damper? The two terms are used interchangeably, but technically they have different functions. A balancer adds weight to help (externally) balance the lower rotating assembly of an engine, while a damper, quells the vibrations during crankshaft vibration which occur as a function of the combustion process. Keep in mind, while all harmonic balancers are dampers, all dampers are not balancers. Yet for purposes of bench racing, both terms are often used to mean the same part.<\/p>\n

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Romac elastomeric damper with laser engraved timing marks.<\/p>\n<\/p><\/div>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0
\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Keeping It Basic<\/strong> <\/p>\n

During the combustion process, each piston is forced to move down the cylinder as a result of an explosion contained within the combustion chamber. This stroke imparts a sudden rotational force to the crankshaft. Even though it is a very stout component, a crankshaft is not perfectly rigid. So during these combustion events, the crank will twist slightly in response to each explosion\/impact.<\/p>\n

This crank twist is analogous to a simple torsion bar with a lever arm at one end. Now assume you hit that lever arm with a hammer. You can imagine there will be some slight twist when you first hit the lever arm, but that would be followed by the arm springing back into place, maybe even vibrating for a short time before coming to rest.<\/p>\n

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Animation of a crankshaft with 108.476 Hz of harmonic distortion.<\/p>\n<\/p><\/div>\n

In this example, we have torsional twist followed by torsional vibration (during the spring back event). Torsional twist is a function of part length (inline engines will have a longer crankshaft than V-configurations) and thickness, material shear modulus (think: material stiffness), and Torque (force from combustion x crank throw). Similarly, torsional vibration is a function of part length, torsional stiffness, and polar moment of inertia (think: object\u2019s ability to resist torsion). For a detailed explanation of these phenomena, review Himmelstein\u2019s Technical Memo #8150<\/a>.<\/p>\n

What\u2019s the problem?<\/strong><\/p>\n

Torsional vibration has side effects that are rarely desirable. Because force is transmitted into a crankshaft at discrete points in its rotation (example: every 90 degrees of rotation in a V8 application), the output torque is not continuous, thus creating pulses and torsional vibrations. In the event that these pulses occur around the resonance frequency of a crankshaft, the effects can be multiplied. When this occurs, risk of component failure (broken crank) increases as well as the chance of premature wear of bearings. In some cases those vibrations can be transmitted to other points in the powertrain such as the valvetrain (via timing chain) or down the driveline towards the tires. Either direction isn\u2019t desirable as it can rob power in addition to potentially killing parts.<\/p>\n


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Technology Options<\/strong><\/p>\n

While a few methods to damping have been invented, the vast majority of automotive OEM and aftermarket companies point towards two solutions for controlling detrimental torsional vibration; elastomeric and viscous damping.<\/p>\n

\"\"<\/a>The method for elastomeric harmonic damper construction tends to make them the most cost-effective as an OEM replacement or upgrade. Romac Performance Products<\/a> specializes in elastomeric harmonic dampers and builds products for mild to full race applications. Construction is rather simple, and consists of four parts: a hub, elastomeric band, outer inertia ring, and snap ring. The hub is constructed to fit over the front of the crankshaft snout with a keyway. The hub will usually have a bolt pattern built into the front face which allows for attachment of accessory pulleys. The backside of the hub may have a cavity built for attaching weights to externally balance the rotating assembly. Applied around the hub is the elastomeric band which is constructed of a rubber polymer. Polymer durometer (hardness) gives Romac the ability to add or subtract damping ability, tune for engine frequency, and long term durability.<\/p>\n

Fit to the outside diameter of the elastomer band is the outer inertia ring. This outer inertia ring functions as a small flywheel that wants to remain at constant speed despite the acceleration and deceleration pulses that the crankshaft is experiencing. The elastomeric band between the hub and outer ring allows the outer ring to move slightly independently (or at a more constant speed), while the inner hub runs slightly faster and slower in response to torque pulses. A snap ring is inserted inside of the outer inertia ring in order to keep the band and inertia ring in their respective places.<\/p>\n

During operation, the band transmits only part of the vibrational forces from the hub to outer ring, while also converting some of that vibrational energy to heat which is dumped to atmosphere. Romac takes great pride in the fact that all of their harmonic dampers are hand assembled, giving technicians that ability to inspect each assembly for best results.<\/p>\n

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Romac elastomeric 5.8-liter Ford Mustang GT500 Damper with 15-percent supercharger overdrive pulley built-in. The elastomeric material rides between the silver center hub and the black outer ring.<\/p>\n<\/p><\/div>\n

A good example of viscous harmonic dampers are those offered by Fluidampr<\/a>. Speaking with Brian Lebarron at Fluidampr, he describes a viscous harmonic damper as \u201ccontain[ing] a free rotating inner inertia ring that shears through a thin layer of\u00a0proprietary\u00a0silicone. As it shears, destructive vibration is transformed to heat. Heat then radiates through the outer housing to atmosphere.\u201d More simply; the viscous damper includes an outer housing, an inner inertia ring (think free-rotating ring inside the housing), and the housing is filled with a THICK silicone fluid which fills in the gaps between the housing and ring.<\/p>\n

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Click to expand.<\/p>\n<\/p><\/div>\n

Under constant smooth torque applications, the housing and ring spin together. When torque pulses are introduced, the ring wants to continue spinning at a constant speed while the housing is in a constant state of acceleration and deceleration.<\/p>\n

The housing and ring speed differences apply a shear force against the silicone fluid between them. The silicone absorbs that shear force in the form of heat which is dumped to atmosphere.<\/p>\n

From an OEM perspective, an elastomeric damper covers the vast majority of engines being produced today. The primary reason for this choice is cost of manufacturing as the elastomeric option tends to be constructed of parts which have lower tolerances as well as utilizing raw materials which are more common and don\u2019t demand a premium price. Viscous dampers are often utilized by OEMs in high performance and luxury applications.<\/p>\n


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Do I Really Need One?<\/strong><\/p>\n

For those familiar with sprint car engines, they know that most sprint competitors don\u2019t utilize a damper at all. Similarly, a minority of drag racers have opted out of a damper with the theory that less rotating mass allows the engine to increase RPM quicker. We\u2019ll keep this discussion at a high level and just point out that sprint and drag engines aren\u2019t intended to see many miles. Careful component selection can help mitigate some overall vibration and ultimate component failures, but the benefits of a damper are undeniable for anybody looking for more than a few quarter-mile passes or a Saturday night main.<\/p>\n

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Here we can see how the Fluidampr viscous damper changes the large peaks and valleys of vibration the engine sees with an OEM rubber damper.<\/p>\n<\/p><\/div>\n

Selecting a Damper<\/strong><\/p>\n

Consider the following topics when choosing your next damper:<\/p>\n