Finally! a fix for handle bar vibration

Discussion in 'User Mods' started by racerboy, Mar 24, 2020 at 11:00 AM.

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  1. Mar 24, 2020 at 11:00 AM #1

    racerboy

    racerboy

    racerboy

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    my 07 has the OEM handle bars which eventually over time, started to vibrate really bad. Mang! I chkd the usual culprits, those chkd out. So, I opted to try a set of Renthal Street fighter bars. Wow.. ZERO, I mean ZERO vibration, meaning, the mirrors are clear, no fuzzy shaking vibration which is common. The measurements were spot on, 755mm is 29" and 7/8" . I like the leverage, and the cross bar pad is cool.
     

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  2. Mar 25, 2020 at 10:17 AM #2

    Fire-medic

    Fire-medic

    Fire-medic

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    Boy, that's a new one on me, vibrating bars worsening over time. I could see that being the case if you got a crack in the bar somehow. V-4's generally aren't-known for vibration such-as other engine configurations are. Singles, parallel-twins (pistons together or 180 degrees apart) V-twins (90 degree engines are supposed to be better), triples all have their known vibration patterns. The frequency at-which the bars resonate, and the distance (height or amplitude) of the vibration come-into play. Think of a single, no counterbalance, at higher rpm's, are well-known to have significant issues, which adds to rider fatigue over time. Add to that a poorly-muffled exhaust, and the bike becomes no-fun after the rider's threshold is met, and exceeded. This puts the rider at-risk for being able to make split-second decisions about bike control. Numb hands and wrists are a sign that the best thing to-do is to take a break, change your bike's speed, to change the frequency/amplitude of the handlebar vibrations.

    Twins can be like a single, if the crankshaft is designed so the pistons rise and fall together, or if the piston throws are 180 degrees apart, the harmonics change. The Laverda parallel-twins in their larger displacements were known to be punishing to their riders because of the engine vibration transmitted to the handlebars.

    The Norton 'Isolastic' engine bracket system proved to reduce the rider's sensation of vibration in an effective fashion. It took the Norton Atlas from being a known candidate for producing fatiguing vibration to the Commando, where vibration was minimized onto one plane, due-to the rubber engine mount brackets. Buell also did extensive research into engine mounting bracketry, while allowing the frame to provide precision degrees of handling, on the Harley-Davidson V-twins they used.

    One of the simplest ways to isolate the handlebars is to provide rubber biscuits in the steering triple tree to house the handlebar mounts, thereby allowing the rubber biscuits to provide isolation from engine-induced harmonics from reaching the handlebars. One unfortunate byproduct of this was that such a system, if not properly engineered, caused a noticeable imprecision in handling, usually described according to the insulation material's composition: "rubbery." Holding onto the handlebars as they noticeably-moved in your hands, while trying to hold a line at-speed, on a rain-slicked pavement, is not a confidence-inducing experience!

    This meant that ride engineers had to choose the appropriate durometer-rating of the rubber insulator. Too-soft, and the steering characteristics suffer from rider-perceived imprecision. Too-stiff, and the vibration returns. In the words of famed off-road rider JN Roberts, "what's a mother to-do?"

    V-twins have their own set of issues, generally high-amplitude, low-frequency vibrations when you have something like the 45 degree separation of a Harley-Davidson, and a low-revving engine. It's entertaining to-watch the front wheel of a Harley at a traffic light, doing the 'Jitterbug,' and then once underway, that jumping up and down subsides, with the amplitude returning further up the rev band. It's like a throbbing, stay-away from being close-to redline, or your sensation of power impulses through the bars will return, a throbbing of the bars, not a 'buzz.' This is very-fatiguing for any prolonged period!

    Triples, anyone who's ridden an air-cooled Kawasaki 2-stroke triple in the 500 cc or 750 cc sizes will know exactly the difference between the Harley's low-frequency/high-amplitude vibration and the Kawasaki's high-frequency/low-amplitude sensation. The triple's characteristic is usually referred to as 'buzziness.' The bars can numb your hands in a more-subtle way because you aren't experiencing the 'jumping' of the bars, like a V-twin gives you. Over-time, however, the high-frequency/low-amplitude 2-stroke triple's can and will numb your hands into not necessarily a painful sensation, but one in-which the nerves become numbed-to their primary sensation of touch, and you may-find that your hands' response to quickness of movement has become compromised. You want to squeeze the front brake lever, but your hand is slow to-respond, not good!

    With the passage of time, manufacturers have tried a variety of things to alter the frequency/amplitude conundrum. Primary among these is probably the crankshaft's balance-factor. This 'sets the stage' for the vibration characteristics displayed by the engine, and plays an important part in such things as metal fatigue for the engine and various parts of the engine. Kevin Cameron once mentioned about racing the 2-stroke triples and fours, and how with the passage of time, the experienced mechanic would know that it was time to check the motor mounts because the vibrations would cause metal fatigue and failure. "Why-not make the brackets thicker?" Because that adds weight, and it's easier to keep an eye on the brackets for their propensity to developing cracks. Even the crankshafts were part of the equation. After a certain amount of run-time, the crankshafts/rods needed to be replaced because of metal fatigue. Failure to do this would result in a broken crankshaft or rod which would destroy the cases, not something that you want on Daytona's Turn 1, heading onto that high-speed banking.

    Singles and twins, with their higher amplitude vibrations, could quickly make a rider uncomfortable. Different crankshaft spacings for twins could mean different characteristics perceived through the handlebar's vibrations: the pistons rising and falling together (a 360-degree crankshaft) would be more-punishing to the rider than would the crank throws being spaced apart 180 degrees.

    With time, manufacturers decided to tackle the vibrations by adding weights running the opposite of the engine's vibration patterns. The use of these balance shafts has become popular in both cars and motorcycles, and has resulted in a significant reduction in rider-perceived vibration. They are run off of the crankshaft by gear or by chain, and have proven to be of great value in reducing the rider's fatigue-factor.

    'Bar snakes,' shot-filled handlebars, tapered-thickness aluminum handlebars, and even home-made remedies like injecting silicone into the hollow bars all have been used with varying degrees of success to lessen handlebar-produced vibration. Of course, the easiest method is to add bar-end weights, an OEM product for many manufacturers, on many models of motorcycles, over the years.

    Your success in locating an easily-substituted product for the OEM handlebar which apparently has lessened the individual perception of vibration to the rider at that point, holds promise for those who wish to-lessen their handlebar vibration in an easily-applied fashion. Anyone who suffers from carpal tunnel syndrome and who rides, may choose to investigate this further as a way of allowing them to ride for longer periods, or in extreme cases, ride at-all.
     

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