Eliminate Handlebar Vibration, Kill It DEAD with a Fake Snake!

[TwoManyXS1Bs]

I like the idea of 'tuned mass', just can't wrap my head around having an adaptive system that would accomodate varying displacement magnitude and frequency. Thinking about a rotating eccentric mass, like phone vibrators, but would need an intelligent controller to maintain anti-phase, kinda like the Bose active noise-cancelling headsets.

Then again, having it statically tuned for our 'problem rpm', may suffice...

 

[FB71]

Then again, having it statically tuned for our 'problem rpm', may suffice...

and that's all it really is... The resonant frequency of the bars fall within range of the engine's second order vibration frequency at around 4500RPM. The tuned mass damper simply counters the vibrations at that particular frequency.

Ever used a sirometer tach for tuning single cylinder power equipment engines (Briggs & Stratton, etc)? http://www.treysit.com/9.html

its the same principle.

 

[the_nutt]

There was another recent post about vibration and oldbiker mentioned that someone he knew put solid bushings in place of the rubbers ones and it cured the vibration problem. This would be an easy lathe project but I wonder what the result would be. I know Hugh sells a kit for $75 on his site but have never heard of anyone using them or the result. You can buy a 12" piece of 1 3/4" 6061 alum for around $13, might be worth a shot.

My brother spun me a set of solid aluminum dampers one afternoon and I can attest to an immediate reduction in vibration. It's still not too fun to cruise at 70mph+ but it really helped with all lower speeds.

 

[TwoManyXS1Bs]

Sirometer tach, a new word, neat gadget. I have an old stationary engine tach, has several tuned fingers with little paddles that appear in a window (looks like hour-meter display). The 'paddle' that creates a vertical blur is your rpm.

If you could micro-observe the motion of the bar ends, what kind of pattern would you expect to see? Circular, oval, vertical, horizontal, figure-8, ...etc?

 

[FB71]

Sirometer tach, a new word, neat gadget. I have an old stationary engine tach, has several tuned fingers with little paddles that appear in a window (looks like hour-meter display). The 'paddle' that creates a vertical blur is your rpm.

If you could micro-observe the motion of the bar ends, what kind of pattern would you expect to see? Circular, oval, vertical, horizontal, figure-8, ...etc?

not sure about the motion, probably elliptical.

The device you have is called a reed tach, named for the individual tuned reeds in the window. Same idea as the sirometer.

 

[JP50515]

Wait is this what you're looking for? HAHAHAHA the videos still crack me up...old harley ladies gettin' it on with a motorcycle seat lol.


http://www.viberider.com/vibe_rider.asp

 

[TwoManyXS1Bs]

Viberider? Somebody's actually done this?

I suppose Hugh will have to start tooling up for 800 watt PMA's now...

 

[Jeeter]

A lot of you guys are missing the mark on vibration damping. It's not sheer mass that you should be after, but TUNED mass. Tom has it right, as do the bike manufacturers that put weights in only the end of the bar.

The goal is to provide a mass capable of vibrating at the same frequency as the bars, but in the opposite phase. Tom's idea is one of the better ones. The vinyl tubing does not fit tightly in the bars, and allows some movement. The lead shot adds mass. The tubing is then free to vibrate by itself, somewhat independent of the bars. If the mass is even close, it will tend to move with a delay, meaning; 1/the bar will push up on the tubing, 2/the tubing and shot will absorb that momentum, 3/the bar will reach its apex of movement and stop, 4/the tubing will use the absorbed momentum to begin moving up, 5/the bar will move down, and encounter the tubing and shot moving up against it. This cycle repeats. This is tuned mass damping.

Simply increasing the mass of the bars (solid steel stock, lead-cast inside bars, etc.) will not counteract the vibration of the bars. What it will do is move the resonant frequency of the bars outside of the range of vibrations present in engine. While it will help a good bit, its not as effective as a properly tuned mass damper.

Please don't take this as criticism of anyone's ideas or efforts. Just offering my limited insight.

oh, and the mass is most effective at the point in the bars that react the most, i.e., the ends of the bars. Mass near the center doesn't do much.

I gotta totally agree with this. The damping material in the bars has to be ~freely adjustable~ to counter the vibes made by the engine/road/bike. If the damping material/device is fixed within the bars it's effect will be minimal. Since the vibrations are varying all the time, the damping medium must be able to freely ~float~ (??) to allow counter frequencies to be generated. If "solid" handlebars were at all effective at reducing vibrations, they'd be all the rage and sold at your favorite online retailers for the paltry sum of no less than $250 bucks or so (hey, it's that "perceived value" thing, if you do not charge enough for it the public won't perceive it as ... well ... valuable.)

and that's all it really is... The resonant frequency of the bars fall within range of the engine's second order vibration frequency at around 4500RPM. The tuned mass damper simply counters the vibrations at that particular frequency.

Ever used a sirometer tach for tuning single cylinder power equipment engines (Briggs & Stratton, etc)? http://www.treysit.com/9.html

its the same principle.

Badda friggin bing!

not sure about the motion, probably elliptical.

The device you have is called a reed tach, named for the individual tuned reeds in the window. Same idea as the sirometer.

I'd agree, the motion is probably elliptical or it is orbital, like a guitar string is. The orbit actually sortof revolves and changes shape as the freqs alternate and continue in their normal state of flux.

I'm wondering if (perhaps) engine tuning and/or rephasing (or hell, just a good old fashioned "blueprinting" may be enough) may be a far more effective way to reduce vibrations? That's more of a rhetorical question as it is anything else. I mean I would think one may measure the difference in labor and time spent to address the issue between empirical testing with handlebar mounts and counterweights (which seems like it's kinda avoiding the actual problem) vs a solid carb sync and general state of tune or perhaps going long and doing a rephase.

I've had a few Harleys, and the lengths that company goes to when going about addressing vibration is pretty ridiculous. Rubber mounted everything (bars, pegs, engine, swingarm pivot .... yes, I said swingarm pivot, and more). The bars on my 1985 FXR were SO LOOSE (due to the manner that Harley Ferguson used to mount the bars) I could move them fore-and-aft at least four full inches (perhaps six?). No kidding. And after all of those efforts the magical Evolution engine still shook like a paint shaker at given revs. Why? All the rubber mounts in the world aren't going to counter the way the V-twin shakes. Those early FXRs were total Gumby bikes, everything on them was flexible, rubbery, moveable, and "anti-vibe". And none of it really worked very well. Most of us know the old addage of "you can polish a turd all you want, and when you're all done, all you have is a polished turd" (or some variation of that). So until Harley gets rid of that turd, it will always be a turd with polish on it. No matter how many rubber mounts it has.

So, I'm just showing my ignorance here (again) and wondering if there isn't a better way to chase that vibe demon down in the XS650? I mean rather than bar snakes. I'd guess that a bar snake would be a nice finishing touch, y'know like a final refinement or whatever. But isn't the main problem addressed better by attending to the engine?

Just asking, I've much to learn.

 

[Fndirtygreaser]

Fuck these vibes!!! Lol. I'm going 18t. Already have 30t to help reduce vibes lol

 

[fredintoon]

OK, antivibration tech is not science. It's an art form, just like cooking.
Here's my recipe.
Shove a plastic 12Ga shotgun shell wad down inside the bar as far as a straight 1/4" dowel will push it, probably just around the first bend.
The 12Ga wads happen to be a good fit inside a 7/8" bar.
Mix up a slurry of cold-set 2-part rubber mix and lead shot.
I used #7 shot from my trap loading stash but I doubt the shot size really matters.
Pour the slurry into the bar and let it hang while the rubber sets up.
Then flip the bar and do t'other end.
Should you later decide to fit bar-end mirrors the slurry/shot mix can be drilled out to the required depth with a 5/8" wood bit.

 

[Tomterrific]

I've had a Vibra Tach since 1975, very accurate.

The XS engine can be rephrased but the rocking couple will give a different vibration to deal with.

The VibeRider is too electronic. The 1970 solution is a half tennis ball under the passenger seat.

Tom

 

[DanW]

Here's what I did and seemed to help: I took a can of foam called "Great Stuff" and filled the bar completely so it was oozing out of both ends. The idea is to help soak some of the vibration. Once the foam was cured (takes a day or two) I carved the foam out about an inch from the ends and added handle bar weights (like you would see on any sport bike). I would guess it took about half the vibration out.

 

[Fndirtygreaser]

I have a springer front. I put some rubber in between where risers mount up. And wrapped a peice of inner tube around handle bar where it mounts to riser. Also filled bars with dirt and small crushed rocks. Helped dampen the vibes so it won't shake so bad that it hurts my hand especially over 75mph

 

[TwoManyXS1Bs]

Anybody have any experience with one of those mercury-filled recoil tamers installed in the stock of a shotgun or hi-power rifle? Interesting 'slosh' dynamics going on in there...

 

[Jeeter]

Anybody have any experience with one of those mercury-filled recoil tamers installed in the stock of a shotgun or hi-power rifle? Interesting 'slosh' dynamics going on in there...

I built .308s for a while (nothing super duper, holding 8 inches or so at 500 meters with factory ammo). I tried a few of those damper widgets. Hmmm, I wonder if that works because it's a one time thing going in one direction (damping a single shot that produces a motion that is always in the same direction). Engine/road vibes are so all over the place when it comes to frequency and even direction. So, I don't know, maybe it would work. But somehow it doesn't seem very intuitive.

I read about an XS650 streetracker that was featured in Barnetts a few months back. The owner had carbon fiber engine mount plates cut out (water jet? Laser? dunno) to replace the stock metal ones. He said it cut down on the buzzy-numbing vibration.

However Mark Barnett actually thought that rephasing would reduce the offensive vibration moreso than any other single modification. I don't recall if he specified which method (270 or 277), not sure either choice would make much of a difference over the other though. I suppose anything that would get those pistons out of their sync'd phase would at the very least change the vibe, if not reduce it's offensiveness.

 

[hairyboy]

ive got a 79sf,here in england, just replacing the 34 tooth rear sprocket with a 32, pushed the bad vibratin patch up to about 80mph.

 

[Jbinnington]

Jeeter: Harley Ferguson! LMFAO!!
Do they come in grey?