1	The Rattler® by TCI®
2	Award Winning Engine Vibration Control The Rattler® was voted “Best New Performance Racing Product” when introduced at the 1995 SEMA Show.
3	Why would you want a vibration absorber on your engine? Due to their inherent mechanical design, all internal combustion engines will display crankshaft torsional vibration. This is because torque cannot be applied to crankshafts from firing cylinders with steady pressure. As the piston rises and falls, so does cylinder pressure. The changing pressure, acting on the piston, results in forces being transmitted along the connecting rod and applied to the crankshaft journal. Engine speed slightly increases during power strokes and decreases during compression strokes. This is what causes twisting vibration of the crankshaft. In many instances, since the crankshaft drives the cam, crank vibrations can also cause instability in the valve-train. The Rattler® is designed to absorb these harmful vibrations.
4	What is crankshaft torsional vibration? In the operation of the crankshaft assembly, the aforementioned forces constantly reverse back and forth. The deflection and rebound of the crankshaft journal are indicative of crankshaft torsional vibration. In a multi-cylinder engine, this fluctuation in torque applied to the crankshaft from each cylinder makes the total torque applied to the crankshaft even more complex in time. Design constraints common to internal combustion engine crankshafts commonly cause these shafts to exhibit a resonant frequency, which when excited by the complex torque application, causes several critical speeds of engine operation.
5	What is crankshaft torsional vibration? What is resonant frequency? We have all seen the old Memorex^® commercial of a glass being shattered by the sound of a singer’s voice. What you were actually seeing was the point at which the glass was excited to its own natural frequency and at that moment, it shattered. This is a common example of resonance. All crankshafts have mass and a torsional spring rate. This means that all crankshaft assemblies will have a natural frequency. Inside an engine, the torque spikes from the firing cylinders excite the crankshaft at certain critical speeds to its own natural, or resonant, frequency. The vibration amplitudes at these critical speeds are commonly high enough to cause failures in the crankshaft, front-end accessory belts, gear train and cause valve timing problems.
6	What is crankshaft torsional vibration? As previously mentioned, in a multi-cylinder engine, the fluctuation in torque applied to the crankshaft from each cylinder makes the total torque applied to the crankshaft even more complex in time. Let’s consider a stock six-cylinder, four-cycle engine as an example. It will have three intake, compression, power & exhaust strokes per revolution. Because of this, the torsional vibration present in the system can be characterized as a complex wave made up of a series of simple sinusoidal components referred to as harmonics. These harmonics will be referred to as orders of vibration. An ‘order’, in the context of torsional vibration analysis, is a quantity representing a number of events or cycles per revolution.
7	What is crankshaft torsional vibration? These ‘orders of vibration’ can be used to determine which frequencies the crankshaft is subjected to through the speed range of the engine. This is done by utilizing the following equation. Frequency = (RPM X Order of Vibration) ÷ 60 Within an engine’s speed range, several ‘orders of vibration’ will be present.
8	What is crankshaft torsional vibration? This figure represents the overall level and dominant orders of crankshaft torsional displacement from a 350 CID Chevrolet V8 engine without any damping. It shows three predominant orders of vibration; 4^th, 5^th, and 8^th. Where the 5^th and 8^th orders peak, represent the critical speeds of operation. Using this information and the previous equation, we can determine the resonant frequency of the crankshaft. Knowing this, we can determine all critical speeds of operation.
9	What is crankshaft torsional vibration? This table represents the critical speeds of operation for an example 350 CID Chevrolet engine for the different orders of vibration. This information can be quite useful in determining orders of vibration that would be excited within the engine’s speed envelope. Remember, the critical speed is defined as when the input frequency is approximately equal to the resonant frequency of the crankshaft. Therefore, it should be clear that within the speed envelope of the engine, several critical speeds could be present depending upon the ‘harmonic content’ of the torsional vibration. It is at these critical speeds where crankshaft torsional vibration becomes a problem and must be controlled.
10	How is torsional vibration control achieved? Quite simply, an engine ‘balancer’ is used to control torsional vibration. Called a balancer because it often is counterweighted to offset an imbalance in the crankshaft assembly, it can be constructed in numerous ways so that it also can control damaging vibration present during engine operation. What’s not so simple is how the balancer goes about controlling vibration and protecting your engine from resonance. The balancer is going to be either an energy damper or an energy absorber.
11	What does resonance have to do with selecting an engine absorber or damper?
12	What is the difference between absorbers & dampers? There are fluid type, dry friction type and OEM, elastomer type dampers. And now there is The Rattlerâ absorber. The first three units have been readily available to the automotive market for years and in fact were the only types available. The fluid, dry friction and elastomer type devices are considered dampers and tend to reduce the amplitude vibration by using friction to dissipate energy. The Rattlerâ, an absorber, is a device that actually counteracts vibration by using internal rollers that automatically offset the twisting forces that cause vibration by alternately storing and releasing energy.
13	How does the TCI^® Rattler^® Work? The Rattler® is designed to attack the predominant orders of vibration for each specific application regardless of harmonic frequency. Unlike harmonic dampers, Rattlers are not 'frequency specific' but based, however, on the number of cylinders in the engine or 'events per revolution'. That is why they are so practical for drag racing, oval track as well as street driving applications; anywhere a modified engine is utilized.
14	Is this new technology?
15	Question: What are some of the other advantages the TCI^® Rattler^® has over other dampers on the market? Answer: The torque capability of The Rattler® to control vibration is huge. For example, the centrifugal force of one roller (of which The Rattler® has nine) at 7000 RPM creates 2407 pounds of force which is available to counteract vibration. In other words, the rollers move as needed to absorb vibration.
16	Question: What is the main advantage of the TCI^® Rattler^®? Answer: Modifying an engine can completely change its operational characteristics but the number of events per crankshaft revolution remains constant. By virtue of its design, The Rattler® is tied primarily to the number of cylinders (hence, orders of vibration) so it can easily be produced to match the specific needs of enthusiasts building engines from mild to wild. In order for a typical damper device to be effective, it must be carefully matched to each specific engine combination because each configuration yields a different natural frequency. An OE damper is effective on stock engines since engineers spend a great deal of time tuning for a specific engine configuration utilizing expensive analyzers and lots of dyno time. No independent engine builder or individual consumer can do the necessary testing to fully optimize a damper to a modified engine’s characteristics. Therefore, a damper placed on a modified engine becomes a compromise; better than nothing at all, but certainly not as effective as it could be were it custom tuned for that particular engine. To reiterate, The Rattler® is tuned primarily to the number of engine cylinders and retains maximum effectiveness at all engine speeds.
17	Question: The Rattler® makes noise. Does it have to make noise to work? Answer: The only time you may hear The Rattler® is when starting and stopping the engine. When you hear the slight “click”, you know The Rattler® is poised for action. Once rotating at speeds even lower than idle, the roller elements are forced to the outer edge of their pockets by centrifugal force and no longer make any noise. They then quietly roll back and forth imparting energy to the crankshaft to counteract torsional vibration.
18	Question: What is the life expectancy of the Rattler®?
19	Question: Stock type dampers have been known to have the timing mark slip relative to the crankshaft. Can the Rattler have the same problem? Answer: No. Another benefit of The Rattler’s® design is a CNC-machined, solid outer-body that does not move relative to the crankshaft position. This means that the timing marks that are etched into the perimeter of the balancer always stay properly indexed to your rotating assembly, ensuring that your ignition timing will be consistent. Also, the presence of the wide timing mark range on The Rattler® eliminate the necessity of using an expensive timing light with an advance dial on it…a less expensive standard timing light will work just fine.
20	The Rattler® Key Features Maintains maximum effectiveness at all engine speeds Reduced crankshaft fatigue over current designs Available in 6.25" and 7.25" diameters (external balance Chevrolet are 8" diameter) Integral timing marks that cannot move relative to the crankshaft SFI 18.1 Certified No fluids, elastomers or friction materials to harden, crystallize or deteriorate. No pulley or crank trigger shims required TCI pays contingency money to successful NHRA & IHRA racers using the Rattler®.
21	The Rattler® Application Chart
22	TCI Problem Solvers Telephone: 662-224-8972 Fax: 662-224-8255 Email: tech@tciauto.com Web Site: www.tciauto.com