Anti Vibration Handle Bars
For the Prevention of HAV
What Significance is HAV?
Briefly, HAV causes diminished sensory perception in several basic areas but one is of particular significance: Pressure Perception Threshold (PPT). What this means is that handling or holding onto vibrating equipment causes numbness and/or paresthesia (tingling) in the hands and wrist. In other words, after a length of time operating vibrating equipment such as a chain saw, grinders, or motorcycles for instance, you loose your ability to feel how tightly you’re gripping. To remedy this lack of grip sensation most people will instinctively increase grip pressure. With the added grip pressure HAV increases which in turn further diminishes PPT and so on. With the added grip pressure accelerated fatigue is assured.
Studies indicate certain frequencies of vibration are more likely to induce a reduction in PPT than others, oddly, 150 Hz (cycles per second) or about 7,500 rpm of a motorcycle engine has proven to be worse than say 30 Hz or 500 Hz. The study I’m citing didn’t specifically look at what frequencies are most detrimental. The study was focused on the affects of HAV on sensory input. Subjects (a polite way of saying volunteer college students trying to earn a little extra cash) were exposed to vibrations of specific amplitude at three different frequencies, 31.5Hz, 150Hz and 500Hz. It was discovered that 150 Hz was the most likely to induce numbness in the hand.
View HAV test results.
HAV, within the context of a motorcycle handle bar is obviously a bad thing and therefore reducing HAV should be of some importance to most riders and to someone plagued with arm-pump it would be of huge importance. Typically, gloves and grips do a tremendous amount to reduce the amount of impulse energy, transmitted from the bar into the hands. However, grips and gloves do very little to defeat or dampen energy in the form a vibration (bar movement) from the bars to the hands and wrists. Additionally, there is the obvious pit fall of diminishing returns with padded gloves and softer or thicker grips. The thicker the cushion the tighter the user will tend to grip to be able to adequately attain a normal grip sensation.
Why is HAV a Problem? (if I haven’t lost you yet)
Up'till now this entire explanation has been a bit technical so I’ll drop technical in favor of a little more light hearted explanation.
Your brain will eventually ignore mild input from nerve cells, if it didn’t you wouldn’t be able to wear eyeglasses for instance. It would be too annoying or painful. You ever notice how after a while, you don’t feel the glasses on your nose, hat on your head or gloves on your hands? I call it the outhouse principle – upon entering an outhouse things really reek, but after sitting a while things ain't so bad. Nature’s way of insuring you’re able to smell other things, fire smoke for instance. That’s why your Uncle Bob can’t smell his own B.O.
When operating vibrating machinery, jackhammers for instance, the same thing happens - after a while your brain ignores input from the vibrating jackhammer. A wonderful thing actually: in spite of all that vibration and jarring going on you’re still able to feel the sliver under your fingernail or the pebble in your glove. The bad thing is you can’t feel the jackhammer in your hands any more. Unfortunately, to regain sensation (tactile perception), most people will only grip harder, which flexes the forearms, which in turn restricts blood flow back to the heart and, well, the worse it gets – the worse it gets.
How Does One Prevent the Problems Associated with HAV?
A light grip is probably the most important key to avoiding arm pump, but even with a relaxed grip you will eventually suffer from outhouse syndrome (see the above paragraph for an explanation) and loose grip sensation. Therefore, a change in grip pressure is as important as a relaxed grip. Next time you go hard into a corner do a grip check, the adrenaline is up, your mind is screaming for all the sensory input in can find, which includes grip sensation, instinctively your brain will try to get you arms to place and extra bend you handle bars to achieve tactile perception.
My suggestion; instead of a focusing on grip pressure, focus on reducing outhouse syndrome by making slight alteration in grip pressure, from one finger to the next for instance, AND even more importantly, reduce the amount of input information the brain needs to deal with by placing the AV-Bars between your hands and the motorcycle.
How It Works
Before we continue with much of an explanation of how it works, we need to recognize that motion in a handlebar is simply energy, but in our everyday lives we have many names to define this motion: shock, sound, vibration, heat, to name a few, but all of these are a forms of the same molecular energy, distinguished only by the frequency (the rate something moves) and amplitude (how much it moves). In other words, sound and vibration are both molecular energy, just moving at a different rate.
Unlike light and radio energy which can travel through empty space, molecular energy needs a media, a molecular structure of some sort, to be transmitted from one place to another. Because we’re not using the handlebars to contact alien life forms or Bubba out on the Interstate, we need to focus on molecular energy. For reasons of simplicity we’ll ignore terms like “modulus of Elasticity” and “radiant Heat” and accept the following as generally true: The density of the molecular structure has everything to do with its ability to transmit energy. Sound will travel farther and faster in water than air, but not at all in a vacuum. A hardened steel ball, dropped onto a concrete floor will typically bounce higher than a rubber ball. Therefore, the tighter the molecular structure of a particular media (or structure), the farther, faster and more efficiently molecular energy can be transmitted. Ever thought about how hard handle bars are (Pretty dense molecular structure)?
Energy Through a Solid Media
We can easily recognize the dissipation of energy in the form of motion, a bell or tuning fork make noise as energy is dissipated into friction and therefore heat (although, neither one of these are even remotely efficient at transforming motion to heat). However, it is possible to transmit energy through solid media, purely at the molecular level, without any obvious motion. The desk-top toy called a Newton’s Cradle is the best example of this. Newton’s Cradle has a row of steel balls hanging on equal length strings which serve as pendulums. When one ball at the end of the row is dropped, the ball at the opposite end of the row will move, without any perceptible motion to the balls in the center. Obviously, it is possible for energy to travel through handle bars, without any obvious motion, as demonstrated by Newton’s Cradle. What this mean in more practical terms, someone’s hand, at the end of a handle bar could perform the same function as the last steel ball on Newton’s
Cradle and absorb the energy transmitted through a solid that seemingly doesn’t move.
View Motion Through Solid Media Principles
Refraction and Harmonics (Resonant Frequencies)
One of the things we had learned from our early years of study, vibration or energy as it travels through one media into another will refract. Much like the refraction of light observed in water; a pencil will appear to bend if half of it is submerged in a clear liquid. Sound or molecular energy will also refract just as light does as it passes from one media to another. Not only will the energy refract it will also change speed. The physics for this phenomenon is very well
and documented. In other words, the amount of refraction and the change in speed can be calculated if the “acoustic impedance” of a material is known. To apply this technology to a handle bar is quite simple: permit the energy induced into a bar to be transmitted through as many different materials, of different acoustic impedance as possible. The result will be energy traveling in many different directions and different speeds. With all this energy rattling around in different directions the likelihood harmonics, as a result of input energy from a motorcycle (achieving an input frequency where the handle bar naturally wants to vibrate) is all but eliminated. By eliminating harmonics, the likelihood of one energy wave building on another is also eliminated. Additionally, the likelihood of energy waves colliding; canceling each other, is increased.
View Resonance Principles
AVONE ™'s exclusive damping system reduces vibration up to 40% over conventional bars. Manufactured from 7075-T6 aircraft grade aluminum for strength and durability with 4.2mm wall thickness under patent #5,950,497.
The same technology that permits doctors to look into the human body with sound is also utilized in the Hav-Not. Molecular energy as it travels from one media to another will also reflect. What this means in practical terms is that a certain amount of energy will bounce back toward its source when hitting the boundary layer of two materials of different acoustic impendence. Or in other words, energy that would typically be dissipated into motion out to the end of handle bars is now reflected back toward its origin. Imagine an ocean wave hitting a chain-link fence, much of the water is permitted through the fence at a lower velocity while some will actually bounce backward towards the direction it came. Any subsequent waves will be affected, not only by the fence, but also by this return flow. The Hav-Not’s layers can be compared to this fence, several rows of fences as a mater of fact.
View Refraction and Mode Conversion Principles
In practical terms shock absorption is simply turning motion into friction and therefore heat. Nothing new here, shock absorbers and brakes on our automobiles operate on this same principal: taking stored energy in the form of momentum and turning it into heat; how quickly momentum can be converted, the greater the gains. The Hav-Not system has a rigid and relatively heavy inner-core surrounded by a soft outer layer. As the bar moves the inner core must translate axially through the center of the bar (moves back and fourth) this motion is resisted by the soft outer core, which turns this motion into heat.
Dynamic balancing is one of the most effective ways to control vibration (in this instance vibration is observable motion). Many competing anti-vibration technologies rely on this method and to their credit, a very good system. You may be familiar with the term: opposing forces of equal magnitude cancel each other. This is probably the best way to describe dynamic balancing. Imagine a balanced crank shaft on an automobile engine or motorcycle engine, or weights that balance automobile tires; an opposite but equal weight 180-degrees out of phase will balance a rotating mass. To apply this technology to an object that simply shakes instead of rotating: attach a weight, supported by a spring (or flexible mounting) to the object that shakes. If the spring rate and length and the counter weight have been correctly sized they will vibrate at an opposite but equal rate. However, the frequency of the vibration (speed at which it vibrates) must be very consistent for this dynamic balancing to have much affect.
A second part of a dynamic balancing system can be described with Newton’s second law of motion, which states that the heavier the mass of an object, the more energy is required to move it. Therefore, if a large weight was attached to the end of the handle bar, most of the energy that would normally be dissipated into motion by the bar vibrating like a tuning fork, would be diverted into moving the weight; a very effective way to remove unwanted vibration, but not practical if weight is an issue, such as it is on racing machines.
The Hav-Not technology also employs dynamic balancing by placing the heaviest material in the center of layers of soft outer core, but the Hav-Not system doesn’t rely solely on dynamic balancing as a means of reducing unwanted vibration.
View Dynamic Balancing Principles
Motion into the bars can actually be a good thing, just as the suspension keeps a car on the road or rider on the trail by permitting motion to be absorbed into heat , so does the bar. However bars have not typically been much better than a bell or a tuning fork at turning the motion to heat, until now. The Hav-Not system is unique because it encourages motion to the bars but doesn’t allow the tuning fork effect that would keep the bars moving. Simply attaching a weight to the bar will effectively keep it from moving, but the weight will also be effective at
transmitting energy into the operator’s hands forcing the hands to vibrate (turn motion into heat) instead of the bars.
Why it Works
Okay there you have it. Now we’ve defined terms and established a vernacular I can explain is much shorter amount of space why these work.
The Hav-Not system works because:
- Harmonics is stopped nearly completely by refraction
- Refraction due to multiple boundary layers moves energy in varying directions and different speeds causing them to collide.
- Boundary layers of different acoustic impedance cause refraction and mode conversion.
- Mode Conversion reflects energy toward is source interfering with subsequent waves of energy.
- Shock absorption due to axial translation, effectively transfers motion into heat.
- Dynamic balancing because heaviest mass is located and the center of a soft mobile core
- Motion is encourages but at the same time controlled.
(Hew, took us a long time to get here didn’t it.)
View HAV Test Results