Engine speed slightly increases 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 cam, crank vibrations can also cause instability in
the valve train. The dampers and absorbers are designed to reduce these
vibrations.
What is crankshaft
torsional vibration?
Answer:
Due to their mechanical design, all internal combustion engines will
display crankshaft torsional vibration. This is due to the fact that
torque cannot be applied to crankshafts from firing cylinders with steady
pressure. 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.
What is resonance
frequency?
Answer:
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 exposed to its own natural frequency and at that
moment it shattered. This is a common example of resonance. Inside the
engine the torque spikes from the firing cylinders excite the crankshaft
at certain critical speeds to its own natural frequency. It is not
uncommon for these conditions to cause failures in crankshafts, front end
accessory belts, gear train, and valve timing problems.
What does resonance
have to do with selecting an engine damper/absorber?
Answer:
Remember, resonance occurs when the exciting frequency is equal or close
to the natural frequency of your crankshaft assembly. Resonance can be
controlled either by dissipating the energy causing the crankshaft to
twist or by absorbing that energy. Energy dissipation, common to the
elastomer and viscous type dampers, convert mechanical energy into heat
energy through friction. Energy absorption, common to the Rattler®,
provides torsional control by providing counteracting forces to the forces
that actually cause 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.
Does just the
crankshaft have a resonance frequency?
Answer:
No, all objects have a natural or resonance frequency. Through research
and testing, we can identify where resonance frequency is most harmful to
an engine. Piston firing, by far, is the force that causes major damage to
an engine.
What
is the Rattler®?
Answer:
It is a torsional vibration absorber that controls twisting (torsional)
vibration of the crankshaft. Engineers call it a pendulum type of
absorber.
What
is the difference between dampers and absorbers?
Answer:
There are fluid type and stock type or elastomer dampers. Newest to the
market is the RattlerŽ 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 Rattler®, an absorber, is a device that absorbs and controls vibration
by using internal rollers that automatically offsets the twisting forces
that cause vibration.
How
does the RattlerŽ work?
Answer:
Inside the RattlerŽ are steel rollers that fit loosely into a
specific number of holes. 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.
Is
this new technology?
Answer:
The concept is not new. In fact it has and is currently being used in
airplane engines where cost is not an important consideration. What is new
is that TCIŽ was able to apply this technology to the internal combustion
engine and obtain a U.S. patent for the design of the Rattler®.
This design and concept permits the unit to be produced at a competitive
price for the automotive industry.
What
is the main advantage of the Rattler®?
Answer:
The RattlerŽ is tuned to the number of cylinders and is effective
at all engine speeds. 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 RattlerŽ is
tied primarily to the number of cylinders. It can easily be produced to
match the specific needs of the enthusiast.
What
are some of the other advantages and differences the RattlerŽ has
over other units on the market?
Answer:
The torque capability of the RattlerŽ to control vibration is huge.
For example, the centrifugal force of one roller (the RattlerŽ 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.
What
about horsepower? A lot of claims have been made regarding increase in
horsepower.
Answer:
In high performance motors where crankshaft vibration can be excessive, it
can provide increased power by providing a stable and vibration free
driving force for the camshaft and valve train.
So
what are you saying?
Answer:
We have data that show horsepower gains but according to engine builders
and results from dyno information, on an average performance engine you
actually are not going to see a tremendous amount of horsepower gain
unless something is wrong with the engine to begin with. The RattlerŽ has shown horsepower gains on the dyno but its primary function is
extended durability due to reduced twist and fatigue.
Can an engine dyno
show torsional vibration twist?
Answer:
No. To test torsional vibration twist you need monitoring equipment that
you will not find at your average engine builder/dyno facility. TCIŽ
initially contracted a highly specialized facility to do testing in their
torsional vibration testing labs. In fact, we also did actual on track
testing with a variety of race cars to see if in-house dyno cell results
and on-track testing were consistent with the mathematical theory that was
patented. This is a very costly type of testing and very few units sold in
the aftermarket have ever been exposed to this type of testing.
The RattlerŽ makes noise. Does it have to make noise to work?
Answer:
The only time you may hear the RattlerŽ is when starting and
stopping the engine. When you hear the slight "click" you know the RattlerŽ
is ready to work. The slight noise could have been eliminated but TCIŽ decided to keep it as a distinguishing trademark.
Do you have to have
special tools to install the Rattler®?
Answer:
You use the same tools and procedure that you would when installing a
balancer.
Can you balance a
crankshaft with a RattlerŽ installed on the assembly?
Answer:
Unlike some units, the RattlerŽ can be installed when balancing an
engine assembly. The rotation of the crankshaft is sufficient to push the
pucks inside the RattlerŽ into position. Some aftermarket brands
recommend using a stock balancer when using an external unit to balance
the assembly, some recommend removing part of their damper before
balancing the crankshaft due to certain elements not being properly
centered.
What is the life of
the RattlerŽ?
Answer:
To ensure that the RattlerŽ was 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. TCIŽ has run durability,
SFI 18.1, and destruction tests and the unit just keeps
on going. Test Rattlers® have surpassed the
100-million cycle mark with very little wear. Steel pucks roll, not slide,
very small amounts inside steel holes to absorb torsional vibration. RattlerŽ
is unaffected by temperature. Fluid and elastomer dampers do
require replacement in time.
In the past, stock
type units have been known to have had timing marks that have slipped
relative to the crankshaft. Can the RattlerŽ have the same problem?
Answer:
No. The timing marks are integral to the body itself and cannot move
relative to the crankshaft.
Please DO
NOT hesitate to call TCIŽ at (662) 224-8972 or E-mail
us if you have any additional questions.
