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Discussion Starter #1
These crashbars, are both inexpensive, and provide the most coverage for the $400 dollar side panels. but they do tend to vibrate some in the 4800-5300rpm range(ie a really sweet cruising range for the wee). I have not really been bothered by this much but I had a brain wave yesterday. And the beta version was tested today. I have found a soloution that will not eliminate the vibes but will reduce them to the level of no crash bars installed within 8-10%(this is from a displacement accelerometer on a vibescanner used to monitor industrial machinery)

here is a pic of the Beta version of the damper:



This came to me while cleaning a shotgun that had a mercury recoil suppressor fitted into the stock.

I did not want to pull the recoil pad on the shotgun(it is epoxied on) but I found a 3"long 3/4" pipe nipple in my junk drawer and some caps. I also have about 30 lbs of mercury left over from my shop (used for removing lead from gun bbls., and also in making Daguerreotypes) so I sealed a cap on one end filled the tube to within 1/4" of the top and sealed the second cap on. I now had the recoil supressor(uh damper) built and since I wanted to do a concept test I wrapped it in tape to build up the body dia larger than the caps. two worm clamps around the vibe damper after I padded the crash bar tube with masking tape.

I had measured the amplitude of the bar vibrations before the install, and after, and the motor mount vibrations, without the CBs installed.

the motor mount test spot yielded a displacement of right at.014"
the crash bar end showed a displacement of .112" without the damper.
the crash bar end showed a displacement of .006" with the damper on the damper mt side and a displacement of.011" on the opposite side. (these measurements were taken in fifth gear on the interstate on level ground with the throttle held with the rosta cruise at 4900, 5000,5100,5200, and 5300rpm the displacement numbers above are avgs. of each rpm point)

the seat of the feet and hands vibe scanner said holy shit this is just like no crash bars!!!

I installed the damper on one side only, hoping that it would cause the 2 sides to vibrate at non-sympathetic frequencies, thus producing destructive interferance transfered through the spreader bar from one side to the other to help reduce the vibrations even more. I will let you know in a few days if there is any benefit in running one on each side(the danger is that they may sync the vibes on both sides and produce sympathetic interference and make the vibes worse!) but a test is still in order.

Another nice thing about this rig is acts on all nodes of vibration (even though verticle is the primary node) It reduces the side to side shake as well.

OK I hear it now I don't have any Mercury laying around, go to Ebay and look for C&H or Break-o MERCURY TYPE shotgun recoil suppressors. and mount as per my pictures.

link to C&H: http://www.mercuryrecoil.com/#top

And by the way this works many many times better than filling the bars with bbs or lead shot (and winds up being lighter)

IMPORTANT, The more rigid your mt. is the better it will work, the commercial units should work even better than mine has, as they have a number of internal baffles, that give the mercury more surface area to push against. (I would look for the 7/8" dia 5 " long 16 oz model) my home brew has 10 oz of mercury in it. and is 4" long

I have tried just weights up to about 3 lbs, set about every where on the bars and the right amount in the right place works well but this works much better and is cake to install, it also dampens across the rpm range not just at a sweet sport like tuning with weights.

It really was like taking the bars off.

Now I am making no bs here this will not NOT make the strom bmw boxer smooth, but it will get you very close to the bikes feel without the crash bars, even when you have them on!:)
 

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Not so good vibrations

I have increased engine vibration on my 03 DL1000 around 5K on my bike with SW-MOTECH Crashbars/Engine Guards installed. Now I bought the bike that way so I don't know what it is like without the bars.

As a rule do crash bars enhance the passing of engine vibration to the frame? This is the only bike I've had them on.
So if I take them off will this likely reduce the 5K vibrations?
 

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This phenomenon must vary depending on the model of crash bars. I have H&B bars on my DL1000, and I have no increased vibration at any rpm . The H&B bars are built very differently for the DL650. It seems that I have seen the most complaints about vibration from folks who have the SW Motech and Givi bars.

Uzidzit,
A couple of questions: Have you tried your damper on the vertical bar behind the one you have it mounted on in the picture? Any plans to try to make it look a bit better? I imagine you could use a similar pipe with plugs rather than caps to improve the look and negate the need for the wrapping to increase the diameter of the body. As for mounting, what about a couple of shotgun mag tube clamps? (Hey, this whole idea started with a shotgun!)


Man, those mercury filled recoil reducers aren't cheap! The cheapest one I could find is $53, and you'd need two of them to dampen both engine guards. Hey, Uzi, have you thought of trying this same thing on the handlebars to see what it would do to reduce vibration?
 

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Discussion Starter #5 (Edited)
my bars are the Hepco bars.

the vibes did not bother me but they were there (put a hand on the bars while you are riding in the 5 k range you will feel it run through the range you will feel the bad spot). and yes I will paint it black and machine a nice alum. bracket for it in a while. I tried two today and it was not really any better than the single on one side, from a rider perspective, the vibescanner however showed a smaller displacement on the right bar.

yea they are not cheap that is why I mentioned finding them used on ebay.

I found it difficult to ride at that rpm actually out of habit I ride above 5500rpm, or slow cruise at 4500 this probably and adaptation I made without thinking about it. I will keep the fix on though because it does work and may decrease the speeding ticket chances at times from riding a bit faster to keep the revs in the smooth range.


mercury filled bar end weights may be just the ticket for the handle bars.
 

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How did you measure those displacements? I'd think I'd rather use lead instead of something containing mercury. While both metals are potent toxins, the safer metal to use is lead since it is a solid. Also, since mercury is not that much denser than lead I think I'd stay away from anything containing mercury. I have filled my Givi bars with BB's and that reduced the vibrations, I think I will experiment with adding some lead weights too.
 

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How did you measure those displacements? I'd think I'd rather use lead instead of something containing mercury. While both metals are potent toxins, the safer metal to use is lead since it is a solid. Also, since mercury is not that much denser than lead I think I'd stay away from anything containing mercury. I have filled my Givi bars with BB's and that reduced the vibrations, I think I will experiment with adding some lead weights too.
Uh...yeah. +1 to Arne.

I also have filled the bars with BB's. $4 for one thing of BB's seems a little cheaper than buying those things.
 

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Discussion Starter #9 (Edited)
How did you measure those displacements? I'd think I'd rather use lead instead of something containing mercury. While both metals are potent toxins, the safer metal to use is lead since it is a solid. Also, since mercury is not that much denser than lead I think I'd stay away from anything containing mercury. I have filled my Givi bars with BB's and that reduced the vibrations, I think I will experiment with adding some lead weights too.
Uh...yeah. +1 to Arne.

I also have filled the bars with BB's. $4 for one thing of BB's seems a little cheaper than buying those things.
the mercury recoil suppressors are sealed for life, and the solid lead will not work as well, it is not a matter of mass alone it is a matter of mass impacting a working surface, beyond the simple inertia.

this is the tool I used for reading the displacements:
http://www.pruftechnik.com/en/condi...table-data-collectors/product/vibscanner.html

you have to be in contact with the mercury for it to be a health and safety issue, and in its metallic form it is not as readily absorb able as most think, the oxide and vapors are what you really need to avoid and there is no contact in a permanently sealed container, kind of like lead unless you are inhaling vapors, ingesting dust, or eating oxides, metallic lead is much more benign than many think. (it has the same hysteria that motor bikes do oh god those things will kill you!!!!!!!!!!!!!) The biggest danger from lead is running into a piece of it weighing about 250grains being about .452" in diameter and traveling 700-1000feet per second!
 

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the mercury recoil suppressors are sealed for life, and the solid lead will not work as well, it is not a matter of mass alone it is a matter of mass impacting a working surface, beyond the simple inertia.

this is the tool I used for reading the displacements:
http://www.pruftechnik.com/en/condi...table-data-collectors/product/vibscanner.html

you have to be in contact with the mercury for it to be a health and safety issue, and in its metallic form it is not as readily absorb able as most think, the oxide and vapors are what you really need to avoid and there is no contact in a permanently sealed container, kind of like lead unless you are inhaling vapors, ingesting dust, or eating oxides, metallic lead is much more benign than many think. (it has the same hysteria that motor bikes do oh god those things will kill you!!!!!!!!!!!!!) The biggest danger from lead is running into a piece of it weighing about 250grains being about .452" in diameter and traveling 700-1000feet per second!
Yes, under normal operating conditions I'm sure the mercury is contained perfectly fine. I was more thinking -non normal working conditions-, i.e. accident. That might be a very different story.

Also, I see no good physical reason why this would work any better or worse than adding the same amount of weight in lead. The two properties that determine the main (the setup could potentially vibrate at multiples of this main frequency) resonant frequency of the bike-crash bar setup are geometry and mass. Adding the same weight in the form of lead in a similar container should yield the same results. Now, if you were to fill this tubes only halfway with Hg I might, potentially, expect different results.

the mercury recoil suppressors are sealed for life, and the solid lead will not work as well, it is not a matter of mass alone it is a matter of mass impacting a working surface, beyond the simple inertia.

Could you explain this?
 

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I wrote up my solution to the Givi bars vibration problem earlier this year, it's simpler and works well for me.

The plug that is fitted between the two halves of the bars in front of the engine fits quite loosely in the bars. This makes for easier assembly, but is a source of vibration. I found that I could remove the sloppy fit by using pieces of 12 ga shotgun shell casings as shims--they work perfectly to make a "press fit" plug between the two bar halves.

Assembling the bars on the bike is marginally more difficult, but the end result is no vibration, and no "add-ons" hanging on the bars.

George
 

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I wrote up my solution to the Givi bars vibration problem earlier this year, it's simpler and works well for me.

The plug that is fitted between the two halves of the bars in front of the engine fits quite loosely in the bars. This makes for easier assembly, but is a source of vibration. I found that I could remove the sloppy fit by using pieces of 12 ga shotgun shell casings as shims--they work perfectly to make a "press fit" plug between the two bar halves.

Assembling the bars on the bike is marginally more difficult, but the end result is no vibration, and no "add-ons" hanging on the bars.

George
I did what you described. Unfortunately it did not solve the vibration issue for me.
 

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Discussion Starter #14
Yes, under normal operating conditions I'm sure the mercury is contained perfectly fine. I was more thinking -non normal working conditions-, i.e. accident. That might be a very different story.

Also, I see no good physical reason why this would work any better or worse than adding the same amount of weight in lead. The two properties that determine the main (the setup could potentially vibrate at multiples of this main frequency) resonant frequency of the bike-crash bar setup are geometry and mass. Adding the same weight in the form of lead in a similar container should yield the same results. Now, if you were to fill this tubes only halfway with Hg I might, potentially, expect different results.

the mercury recoil suppressors are sealed for life, and the solid lead will not work as well, it is not a matter of mass alone it is a matter of mass impacting a working surface, beyond the simple inertia.

Could you explain this?
first the recoil suppressors are steel bodied and I could put many of you beating on them with a mallet and they will not fail, the force required to break one is simply not available in a crash, short of firing one out of a cannon at a hard target at say 2,000ft/sec they will not break will not leak. if they did the epa would have banned them years ago. They will fail by accident if you consider sawing one in half an accident.

the internal design of the suppressor has what looks like a series of washers spaced through its length. each of these washers acts as a surface for the moving fluid to work against. so it is not just a top and bottom flat cap on a tube. they have much more working area than just the top and bottom.

also one of the real benefits of mercury in this application is that we need weight/fluid that moves in an essentially frictionless manner this allows the mass to start moving quicker with smaller displacements. Mercury is about perfect in this way, it has such a high surface tension that it is essentially frictionless in the steel cylinder. It also follows the shape of the surface it impacts and this "instant" deformation absorbs more energy at a quicker rate than say lead shot, lead shot actually impacts the working surface in many small spots rather than the entire surface, it also has the disadvantage that with every impact it deforms and becomes less round, this leads to it moving even slower and being less effective over time (more friction), the liquid does not have this problem. The ideal damping media is frictionless, totally deformable, and dense. (for an inertial damper) We are looking here for a material that does not bounce when it hits something it just goes splat.

When you go with say a lead block in a cylinder you have to introduce a lubricant into the equation, and you also have to carefully seal the system (lead oxidizes readily, and when it does the friction goes way up) add that lubricant and all of a sudden performance will change over time. And if the lead oxidizes in the system that will mix with the lube and then we have sand and oil mixed into a part that is supposed to be moving very quickly and freely. not to mention the lubricant changing with temp.
even bagged lead shot is lubricated with graphite to help it keep from oxidizing and to allow it to pour smoothly, without it it clumps and locks together in a solid plug. It is a plug flow fluid like ketchup as far as its flowing qualities are concerned.

The addition of rubber inner tube strips between the spreader bar and the side bars helps as well, I have had this in place for years already it just doesn't help nearly as much.

plain weights of the right amount in the right places work quite well, if you have dozens of hours to fiddle with them. (they however will only work for some resonant frequencies (and they are different for every bike), I was just looking for a thing that works, that is basically self adjusting (it helps across the whole rev range(I found that out this afternoon), and is a quick and easy install.
 

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When I got my Givi crash bars for my '07 Wee, I'd read about how they vibrate and buzz at certain rpm's, so I got to thinking how I could eliminate or reduce that. I was also under the impression that the vibes originated in the area where the two halves bolted together at the front of the bike. What I came up with was the idea of eliminating or insulating any play where they join together. So what I did was smear on a good coat of silicone sealer, both inside the female side and the male side. This accomplished two things: 1.) The slippery silicon sealer made it easier to slip the two halves together, and 2.) It actually appeard to eliminate vibrations generated by the crash bars, as I didn't feel anything after mounting them. I used clear silicone sealer/adhesive and it was easy to wipe off the excess that oozed out, and you couldn't tell I'd done anything at all there. The grips, footpegs and seat were vibration-free as far as I could tell, except for the passenger portion of the seat which had a lot of vibes before the crash bar installation. AND IT WAS CHEAP!!
 

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Worth a go, I thought...

I was lucky enough to come across this thread right when I was finally getting a Wee. Preferring the extra coverage of the Givi bars, thought I'd see how they do.

First off, I put a zip tie on the connecting piece between the bars, and liberally filled the female ends with silicone before assembly. So the connecting piece is firmly held and doesn't rattle around.

I noticed additional vibration at around 5,500-6,500 RPM during freeway cruise. Not immediately intrusive, but I could see how it might come to grate over time. And I'm a geek, so was interested in this idea. So C&H recoil suppressors; ordered a couple in the size suggested in this thread. Have fitted only one so far.

Since I was mounting on Givi bars rather than H&B I couldn't exactly follow the suggested mounting position. I tried a couple, settling so far on the "B" option below on the idea of mounting as far from the anchor points as possible, guessing that's where the deflection would be greatest when the things buzz.

Location A




Location B




Finally found a use for the stock grips in the mounting process, cutting a 1/4" strip out to sit between the recoil suppressor and the Givi guard and using hose clamps to hold them together. I zipped tied the remainder of the grip over the top for some sort of (mumble) protection against road debris, or something.

Haven't road tested "B" yet, but even in "A" I noticed a subjective improvement as described by the OP. So results to follow.

I don't think this will seriously compromise the function of the bars, but made sure I faced the lumpy bits outward in case the bars are pushed in toward the faring in a lay down. Not sure how the suppressor itself will fair when that happens, but it feels pretty solid so I'll guess it's not at huge risk of rupturing.
 

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Okay. Thanks. Now go test B, damnit, and report back. Inquiring minds...
 

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I have H&B crash bars and a skid plate. I have never ridden the bike without the bars, so have nothing to compare to. Can someone describe where the vibrations occur and what they sound/feel like?
 
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I have H&B crash bars and a skid plate. I have never ridden the bike without the bars, so have nothing to compare to. Can someone describe where the vibrations occur and what they sound/feel like?
I've got the same set-up as you do on my 2005 DL 1000...and my bike doesn't make any funky vibrations...so I'd not worry about it.

BTD.
 
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