A cure for vibration white finger

[sbrumby]

For some time now my big bike gives vibration to the handlebars which in turn makes my right hand go numb. Wing mirrors are ok as they are rubber mounted, left hand ok as you dont have to hold so tight. Then sunday returning from ralley brainwave 1 1/2" o ring in gap between twisgrip and right controls, bingo dont have to hang on for dear life and got built in cruise control.

[oilburner]

You didn't mention if your big bike was gas or diesel, but if it's gas, particularly a twin, and the vibration wasn't always there, check carb sync and valve clearance.

[Fiddler]

Sam,

Really pleased youve solved that one cos you could have been storing up a whole host of problems for later in life.
I worked with a guy briefly who had a bad case of white finger from being a stone mason and using vibrating tools, absolutley ruined his life both employment wise and at home. An absolute giant of man who I watched break down in tears of frustration when he couldnt feel his fingers to fix his lads push bike.

I dont want to harm anyones enjoyment of there machine, or sound like the dreaded Health and Safety Executive but I do urge anyone suffering odd symptoms to do a bit of research and take it seriously.

[sbrumby]

Yes its diesel 950 twin, dont do petrol, OK for a chainsaw & washing paint brushes in.

[LocomotiveBreath]

I have the same problem, also had it with my Harley (ick), My cure was to put a manual friction throttle over-ride (cruse control) in the throttle so I could take my hand off the throttle at times to let the blood flow back to my hand.

It's great, by locking the RPM setting, the govoner will act just like an expencive cruse control the petrol bikes only dream about.

Dave

[Trackrider]

Maybe something lika a Throttle Rocker would be a solution. Attach it to the end of your gasgrip, it extends to outer side of your hand palm. That way you can keep the gas grip in position without gripping it tightly. I've had one for years now and it really helps in keeping your right hand relaxed on long trips.

[Stuart]

I've been reading some other forums out there lately and seeing how many riders of big petrol powered bikes suffer from vibration. My old Ducati gives me a tingle as well I've done the following...

Luckily I now ride a triple and so not much of a problem but I have managed to wipe it out almost completely and at little cost. Here's how...

Basically I used the (quite) heavy bar ends as a counter weight to the vibration. I enlarged the centre screw hole by about .3mm (but screw was already quite loose in there) then I put a chamfer on only half the end that fits into the bar, covering the other half with an O ring.

At the (countersunk) screw head end I inserted a 9mm drill (that was the diameter of the small O ring once it was over the screw) and lightly touched it to create a seating bed for said O ring.

When I assembled to whole thing I tightened the screw almost but not quite, all the way in thus leaving the bar end with both front & back movement against the two O rings. This alters the dynamic at the end of the handlebars meaning the bar end can move and dampen the vibration. It works better than I thought
And the bonus is, of course, that it can be put back as was by simply removing the O rings

[Sibbo]

Another quick and dirty semi cure is foam hand grips as against hard ones . Pretty standard for Norton twin riders

[mark_in_manchester]

Hey Stuart, you re-invented the dynamic absorber!

This is a standard vibration control technique, where a system with a resonance at a given freq is controlled by the addition of a sub-system with resonance designed to occur at the same frequency. If you do it right, the new sub-system generates large reaction forces against excitation at the frequency of interest, effectively stiffening the whole thing up. You can think of it as presenting a high mechanical impedance (Force/velocity) at the design frequency; this puts a big dip in the velocity response of the main system, right at the original system resonance - effectively splitting it into two subsidiary resonances, both of lower amplitude.

Some bike footrests and bars come with this stuff installed. As part of my job I once tried to design an impact drill on the same basis, but frequency turned out to be much too high for an effective solution.

Getting the frequency right is tricky without access to accelerometers and frequency analysis equipment...

Vibration white finger is exacerbated by low temperatures, so if you find yourself suffering, in addition to the suggestions made above heated grips and bar muffs will also be a good idea.

cheers

Mark

[XLerate]

Gloves with gel-filled palms can help a lot. Many different online vendors sell them, here's one example:

http://www.chilhowee.net/motorcycle-glo ... IM013.html

[Stuart]

Mark, thanks for the technical explanation I knew I was doing something like that. It has made the ride spookily smooth

[Sibbo]

Stuart , what would you estimate the weight of those bar ends at ? 50 gms each ? I'm assuming no more than .5 mm movement ?

I've been reading some other forums out there lately and seeing how many riders of big petrol powered bikes suffer from vibration. My old Ducati gives me a tingle as well I've done the following...

Luckily I now ride a triple and so not much of a problem but I have managed to wipe it out almost completely and at little cost. Here's how...

Basically I used the (quite) heavy bar ends as a counter weight to the vibration. I enlarged the centre screw hole by about .3mm (but screw was already quite loose in there) then I put a chamfer on only half the end that fits into the bar, covering the other half with an O ring.

At the (countersunk) screw head end I inserted a 9mm drill (that was the diameter of the small O ring once it was over the screw) and lightly touched it to create a seating bed for said O ring.

When I assembled to whole thing I tightened the screw almost but not quite, all the way in thus leaving the bar end with both front & back movement against the two O rings. This alters the dynamic at the end of the handlebars meaning the bar end can move and dampen the vibration. It works better than I thought
And the bonus is, of course, that it can be put back as was by simply removing the O rings

[XLerate]

Just offhand I'd say the cleverness of Stuart's design isn't in the specific weight, but is in the o-rings. That way the weighted ends can absorb the harmonics through the screw & cancel them by the rubber.

That is, a vibration wave comes down the tube and through screw, into bar end, which is a different sort of mass causing vibration wave form to change in bar end. The rubber then delays the time when it would begin to be in sympathetic vibration to the tube's vibration wave, so it upsets the wave harmonics, in effect absorbing & cancelling vibration wave form. More the fact that it's a solid steel or aluminum slug isolated by rubber, changing vibration wave, instead of continuance of wave form in the tube.

Not sure if that's why you asked about the weight, just my observations on why it works.

[Sibbo]

Your explanations of how it all works are great ! and .no I hadn't realised the O rings function in the mechanism although I would have followed instructions and included them but only so the things wouldn't rattle ! I was under the impression that there would be an optimal mass for damping the vibration but hadn't quite picked up on the rubber's part in the process .

Much appreciated!

[XLerate]

Glad it helped!

I suspect there would be an optimal mass, and also the relative length of end plugs would have different effects. About the only way to discover the best is some serious trial & error. So I'd say Stuart's experiment & reported results is the best to go by, unless you felt like starting out long & shortening by tiny increments.

[mark_in_manchester]

The frequency the dynamic absorber will operate at is found from f (Hz) = 1/(2*pi) * sqroot( stiffness K / mass M). K is in N/m and M in kg. So - it depends on both stiffness and mass. In many situations the vibration of an object will be constrained to only one degree of freedom - perhaps in-line with the bar itself, end on - but a solid body can have up to 6 degrees of freedom (3 translation, 3 rotation) which create 6 'pure' resonances plus a bunch of coupled ones.

Problematic handlebar motion is probably transverse (bending) as opposed to longitudinal - so though the mass will be easy to calculate, the stiffness in this direction will be less so. But since my guess is that no accelerometers or freq anaysis kit is available, the only recourse is trial and error - and subjective data in acoustics or vibration is notoriously unreliable / unrepeatable. Good luck!

(If anyone is REALLY into this stuff, a cheapo accelerometer can be made from a record player pickup - shite ones are very cheap on ebay - and freeware freq analysis programs are available which will capture a signal via a soundcard - try looking for 'ARTA', for example, and feel free to PM me. But I do this for work, so in free time I'd rather think about upholstering my sidecar...now searching for a knackered red-leather sofa...)

cheers
Mark, Manchester

[XLerate]

Thanks for the explanation, Mark!

I'm just a plain old uneducated country hick. I was interested at one time in sinusoidal wave harmonics, meaning study of sympathetic waves & stuff [explaining for those that don't know] and found it fascinating but got well beyond my skill levels. I got the theory & real world part but weak on the mathematics required. Most I use now is simple sound wave calculations related to tuned length exhaust, wave reversions etc. but of course a wave is a wave in a certain sense.

I'm sure it's entirely brain-drain complex trying to measure & calculate all the assorted frequencies generated by the engine, chassis & components in a bike.

[Sibbo]

Thanks all, this thread is a keeper. You never know who is going to happen along and give you the gift of their knowledge and experience .

[Stuart]

This took some finding but worth it I think The Vibranator seems to do the same as my floating bar ends fix only it does it slightly differently. The ends appear to fix solid and support the narrow (and I presume weighty) floating insert.
http://www.vibranator.com/default.asp
I knew someone must make something like this An ideal device for use on some our machines



I'm sure some of the big manufacturers employ this technology only the don't shout about it. I saw a bike the other day that had a clear gap between screw head/washer and the rest of the bar end but I was distracted and didn't get the make or model. Must make a point of asking more questions of owners in the bike park come the weekends
Maybe we could all do this and if we identify a stock bike using rubber mounted bar ends post it up. Then all we have to do is phone up the breakers yard

[mark_in_manchester]

[quote="XLerate"]I'm just a plain old uneducated country hick[/quote]

Hey XLerate, don't do yourself down - you seem to have got a long way without the maths...which usually takes you further, but not always.

I learned about the technique whilst working in industrial vibration control 20 years ago, but did not apply it until noticing it employed in my mate's bike's footrests (a touring Kwak of about 1000cc...maybe 10 years ago). Then I persuaded a large industrial outfit to fund a study into using the idea for a vibration-reduced power tool. A more practical engineer might have said (and did, at work) - 'that things going to have to be far too stiff since the frequency you need to control is pretty high'. But I thought - 'no, look at this nice math model I've made with the big notch in the frequency response'. So we built an expensive prototype. Which didn't work.

urrrp. Oh well.

[XLerate]

I'm just a plain old uneducated country hick

Hey XLerate, don't do yourself down - you seem to have got a long way without the maths...which usually takes you further, but not always.

I learned about the technique whilst working in industrial vibration control 20 years ago, but did not apply it until noticing it employed in my mate's bike's footrests (a touring Kwak of about 1000cc...maybe 10 years ago). Then I persuaded a large industrial outfit to fund a study into using the idea for a vibration-reduced power tool. A more practical engineer might have said (and did, at work) - 'that things going to have to be far too stiff since the frequency you need to control is pretty high'. But I thought - 'no, look at this nice math model I've made with the big notch in the frequency response'. So we built an expensive prototype. Which didn't work.

urrrp. Oh well.

Thanks, Mark, got a real good laugh here hah! I've been a tinker inventor for years and more than a few times found that there was just too much I didn't know, going hand in hand with what I do know! Wooops...

But, ever optimistic! Maybe next time, huh?

[Sibbo]

Yep ,you don't need to know the answers but you do need to know the questions !

[Anorak_ian]

It may be worth asking the tyre centre to balance the wheels absolutely spot on?

Nice find Stuart, I'll need something like this on a future project.

[Stuart]

It's taken a while but I talked to a guy today who told me his Triumph Sprint has these 'isolator' style bar ends as standard. He said they were 'well flexible'. I can only presume Triumph fitted these for a reason

Anyway, next time you're in the bike park somewhere and see a Sprint, home in on it to confirm

[Stuart]

Here's a closeup of a Sprint Bar-end. Looks promising

[XLerate]

Motocross & dirt bikes all have another bar across top of handlebars, from one side to the other. I imagine that little extra bar would also break up the harmonics in the bar set to help balance vibrations. Vibration coming up from mounting would then move through this bar first, right/left before it got to bar ends, acting as a vibration balance bar to cancel vibrations? Seems possible.

I don't have a running diesel bike or else I'd do a bolt-on bar like that to test the theory.

[mark_in_manchester]

The brace on the dirtbike bars will stiffen them up - the first vibration mode will still happen (it always does) but at a higher frequency than before.

I think the bars on dirtbikes take this form since they tend to be 'sit up and beg' raised things - not least you need these to ride whilst standing on foot pegs - and such raised, bendy efforts are pretty flexible without the brace. As I know from my diesel-ural, which uses a silly pair of raised custom bars which flaggle around a whole lot. When wamth and light return in the evenings I may even change them.

(Who ever really does 'winter projects'? The young? Those with heated sheds? My only inclination at the moment is to get home early evening and sleep...)

[XLerate]

I detest winter!

I was thinking that vibrations would travel from bar mounting [which I think should have a rubber isolater] through main bars and up to cross bar, then scatter out along cross bar and also toward ends of main bar. I was imagining the cross bar as somewhat breaking up the travel of a wave but maybe your thought is better.

Didn't post it but also thought about that crossbar being cut in center [it's not needed for strength or support] with a rubber coupling between the two cut ends. Possibly this bar would act as a tuning fork to absorb a good bit of vibrations and then ring it out, to somewhat cancel some frequencies and dissipate the vibration into that rubber coupling. It's possible one could tune this activity by wall thickness & length of cross bar pieces?

Rubber coupling could be hidden within another outer tube with that further disrupting the flow of the waves? This cut cross bar seems most likely to achieve the intended result of cancelation far as I can see [which is progressively less & less as the years march on!].

[Stuart]

Actually got my hands on a Sprint barend today and yes, they are exactly just what we thought Owner tells me Triumph did have a vibration problem with that bike. I may try and get a pair from the breakers.

[Stuart]

These just turned up from eBay (minus one insert ). They weigh 250g each and have a 22mm dia recess handlebar side. The rubber inserts look in good condition and up to the job. A little something to play with anyway