Why do you need an absorber or damper?
Simply put, to stop your crankshaft breaking in the long term, also to refine the noise and vibration from the engine. The big end of each con-rod slightly increases rotational speed during power strokes and decreases during compression strokes. This is what causes twisting vibration of the crankshaft. In some instances, since the crankshaft drives the camshaft and ignition timing, crank vibrations can also cause instability in the valve train and create spark scatter in the ignition timing. The dampers and absorbers are designed to reduce these vibrations.
All internal combustion engines will display crankshaft torsional vibration. This is because the accelerating torque from firing cylinders cannot be applied to crankshafts with steady pressures. It varies with the position of the crankshaft in relationship to each cylinder. As the piston rises and falls, so does cylinder pressure. The changing pressure, acting on the piston, results in forces transmitted along the connecting rod and applied to the crankshaft journal. In the operation of the crankshaft assembly, the forces reverse back and forth. The crankshaft reacts and transmits these forces that are indicative of crankshaft torsional vibration.
Each cheek of steel that joins the big end bearing journal to the main bearing journal has to carry the torque reaction between the firing cylinder and the rotating crankshaft. It cannot transfer this torque instantaneously and consequently flexes. For each forward flexing there is a reversal and this causes the crankshaft to “twist” back and forth along its length. This is the torsional vibration “a twisting action along its length as the crankshaft rotates”.
There are fluid type and stock type or elastomer dampers. Now available in the UK is The Sterling Damper Torsional Vibration absorber. The first two units have been readily available to the automotive market for many years and in fact were the only types available. The fluid type and elastomer type devices are dampers and tend to reduce vibration by using friction to dissipate energy. The Sterling Damper, an absorber, is a device that absorbs and controls vibration by using internal rollers that automatically offsets the twisting forces that cause vibration.
Inside the Sterling Damper are steel rollers that fit loosely into a specific number of cavities. By using an exact mathematical relationship, the rollers will roll forward during compression strokes and roll backward during the power stroke to keep the engine speed variations and vibration, to a minimum.
The concept is not new in fact it has its origins in airplane engines as far back as the 1920’s and is still being used today. What is new is that Vibration Free has applied this technology to the automotive aftermarket requirements of older and current internal combustion engines. This design concept permits the unit to be applied to front or rear mounted absorbers in the form of flywheels or pulleys and produced at a competitive price for the automotive industry.
The only time you may hear the Sterling Damper is when starting and stopping the engine, when you might hear the slight “click” of the rollers dropping within the cavities. Vibration Free are introducing quiet and (where space allows) Silent option
The Sterling Damper is a positive fit onto the nose of crankshafts, so you will need to use the same drawing and pulling tools and procedure that you would when installing a normally tight pulley.
No. The timing marks are integral to the body itself and cannot move relative to the crankshaft.
A bell if struck will “ring” at its natural frequency, just like a guitar string does. Everything has a natural frequency and a crankshaft is no different. Like the bell being struck with a hammer the firing power strokes of an engine at certain critical speeds excite the crankshaft to resonate at its natural frequency. It is not uncommon for these conditions to cause failures in crankshafts, front end accessory belts, gear train, and valve timing problems.
Resonance occurs when the exciting frequency is equal or close to the natural frequency of your crankshaft assembly or harmonics of it. The resonant crankshaft twisting action can be controlled by dissipating or absorbing that energy. Energy if dissipated is converted from mechanical energy into heat through friction, as is common to the elastomer and viscous type dampers. With an absorber type damper such as the Sterling Damper, torsional control is achieved by counteracting the forces at source that would if left unchecked initiate torsional vibration.
Through research and testing, detrimental engine harmonics have been identified. The absorber is designed to eliminate those specific harmonics which can cause failure. In other words, the absorber concentrates on eliminating the cause as opposed to reducing the effect of torsional vibration.
No, all objects have a natural or resonant frequency. Through research and testing, we can identify where resonance frequency is most harmful to an engine. The power stroke pulses of the piston firing are by far the principle forces that cause major damage to an engine.
The Sterling Damper is tuned to the number of firing cylinders per revolution and is effective at all engine speeds. It can be fitted to any even fire engine at the front or back and make use of the space available. It is important to remember that maximum efficiency is achieved at all engine speeds.
In order for the elastomer type to be effective, it must be carefully matched to each specific engine combination. It can be effective on stock engines since many of the OE and industry engineers spend a great deal of time tuning for a specific engine. No engine builder can do testing to match a modified engine to a damper’s characteristics. Because of the design, the Sterling Damper is tied primarily to the number of cylinders. It can easily be produced to match the specific needs of the enthusiast.
The torque capability of the Sterling Damper to control vibration is huge. For example, the centrifugal force of one roller (typically the Sterling Damper has a total of 9) at 7000 RPM creates 2407 pounds of force which is available as needed to control vibration. In other words, the rollers move as needed to control vibration.
Certainly, the principle reason for using a Sterling Damper is to protect the engine from torsional induced vibration fatigue. However, regarding potential increases in horsepower claims, every engine type has different responses. To date there have been many high performance engines built by astute engineers that do give a significant rise in horsepower and proven by back to back tests on the dyno.
The gains in power arrive by providing a stable and vibration free driving force for the camshaft and valve train.
Therefore on an average performance engine you’re rarely going to see a tremendous amount of horsepower gain unless something is wrong with the engine to begin with. The Sterling Damper has shown horsepower gains on the dyno but its primary function is extended durability due to reduced twist and fatigue.
Unlike some units, the Sterling Damper can be installed when balancing an engine assembly. The rotation of the crankshaft is sufficient to push the pucks inside the Sterling Damper into position. One of its benefits is that it has a solid billet machined one piece concentric hub, which means the residual imbalance levels are always very low.
To ensure that the Sterling Dampers are safe to operate at the high rpms associated with the performance industry, several measures were taken. Extensive finite element analysis was performed to ensure that the design could withstand extremely high rotational speeds without failure. Durability, SFI 18.1, and destruction tests have been run and the unit just keeps on going. Tests have surpassed the 100-million cycle mark with very little wear. The steel pucks inside steel cavities; roll very small amounts, not slide, in order to absorb torsional vibration. The Sterling Damper is unaffected by temperature, whereas the heat dissipating fluid and elastomer dampers will degrade if worked too hard and do require replacement in time.