Bar end weights - asymmetric, why, help?

[Ali-bear]

Got most of the way through the operation to narrow my handlebars, then got the the bit where I have to cut the bar end weights. Then noticed, they are different lengths! See picture.

I measured the bars and they are symmetrical (centre clamp to bar end equal both sides). By comparing the two hand guards, I was able to work out its the right-hand one (throttle side) that's longer. At least I think so.

But, WHY?

 

[karnevil]

But, WHY? [/QUOTE]

When BMW designed the 1200 they thought that it would be so boringly reliable that we owners would have nothing to talk about so they designed in these little quirky features for us all to discuss...................!


Well they may have




prehaps









you dont know for sure they didnt

 

[Owen Snell]

No doubt there is a weight difference in the equipment mounted on each end of the bars - clutch one end, brake and throttle on the other. The different bar end weights will even this out.

 

[alimey4u2]

No doubt there is a weight difference in the equipment mounted on each end of the bars - clutch one end, brake and throttle on the other. The different bar end weights will even this out.

Indeed correct, the term is kinetic damping.....

 

[Ali-bear]

Indeed correct, the term is kinetic damping.....

As opposed to static damping?

I can confirm the bars swing round to the left, if the weights are removed, when the rear end is weighted and the bike is on the centre stand.

 

[alimey4u2]

Consider the handlebar as a tuning fork. At a certain frequency it becomes resonant. By adding weights to the end of the tuning fork you can reduce the oscillation (vibration) & indeed "tune" an annoying frequency out...

 

[Owen Snell]

Consider the handlebar as a tuning fork. At a certain frequency it becomes resonant. By adding weights to the end of the tuning fork you can reduce the oscillation (vibration) & indeed "tune" an annoying frequency out...

Yes, the bar end weights are there in the first place as a kinetic damper to reduce vibrations. Additionally, the extra rotational inertia will damp / slow down the steering, but looking at the size of the weights I am not sure how big this effect will be.

The static balancing is the difference in the size of the weights.

Changing the bars will introduce a different dynamic effect as the weight and stiffness of the new bars will not be the same as the old bars. Whether this needs a different end weight will probably be a matter of trial and error.

However, the difference between the 2 end weights will need to be maintained in order to keep the correct static balance, as you will be refitting the same kit onto the new bars.

 

[alimey4u2]

Additionally, the extra rotational inertia will damp / slow down the steering, but looking at the size of the weights I am not sure how big this effect will be.

In relationship to the gyroscopic effect & mass of the front wheel assy. I would "think" negligible..

 

[Ali-bear]

I think you're getting a bit beyond yourselves, there.

I accept that the purpose of bar end weights is to damp vibrations by absorbing kinetic energy. But these BuMW ones are solid metal. My old Triumph ones had a "two bits of metal joined by rubber" design which I can believe would absorb some energy. The BuMW ones will merely change the resonant frequency and node/anti-node distribution.

Maybe moving the anti-node away from the bit where the hand grips is all thats needed

But the throttle side one sticks out - surely this will upset my aerodynamics

 

[Owen Snell]

I think you're getting a bit beyond yourselves, there.

I accept that the purpose of bar end weights is to damp vibrations by absorbing kinetic energy. But these BuMW ones are solid metal. My old Triumph ones had a "two bits of metal joined by rubber" design which I can believe would absorb some energy. The BuMW ones will merely change the resonant frequency and node/anti-node distribution.

Maybe moving the anti-node away from the bit where the hand grips is all thats needed

But the throttle side one sticks out - surely this will upset my aerodynamics

Changing the frequency is correct, to move the resonant frequency of the bars away from the bike's vibration frequencies (engine, box, shaft etc.).

 

[wilbjr21]

Well ... they seem to work !!!!

 

[alimey4u2]

All you want to know HERE

In relationship to the gyroscopic effect & mass of the front wheel assy. I would "think" negligible..

Looks like I thunk wrong....

 

[Ali-bear]

I went for a ride with the shortened bars and no end weights and suffered neither white-finger inducing vibrations nor tank slappers.

But I cut them down and bolted them back on anyway.

Job done!

 

[talonfs]

Did as above when I fitted Renthal Twinwalls to my GS.

It is interesting though, that the end weights on my 04 1200GS were the same size both sides, but on my 07 the are asymmetric.

 

[luckylucian]

2004 model has 80g, 2005 onward has 90g end weight on throttle side.

No idea why they changed tho'

 

[Steve E]

Out of curiosity I checked my bar weights today. Both left and right are identical. The weighty part on the ends are 27mm long and 30mm in diameter. They weigh 150grams each. Bike is a 2005 1200.

Are mine different to everyone elses?

Steve

 

[Captain GSA]

Are we saying then that if we attach things like Sat-Nav to one side of the bars we 'should' have them balanced....

Is it that critical?

 

[Ali-bear]

Nah .