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Glitch
| | Posted on Tuesday, August 16, 2005 - 08:46 pm: | 
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GentlemanJon, way cool!
One of the cool things about that idea, is you made it, and it works! Didn't bitch about it, did sumthin'!
I wouldn't worry about fatigue so much, it's right there in front of you to keep an eye on first thing in the morning. |
Henrik
| | Posted on Tuesday, August 16, 2005 - 09:03 pm: |
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Great idea Jon - thanks for the idea and design. Looks a bit like the ideas behind vibration dampers used in archery. Good thinking.
Sorbothane is pretty soft/spongy feeling. It's used in some insoles for impact reduction. Not sure it would give you enough feel through the bars if used for grips.
Henrik |
Blake
| | Posted on Tuesday, August 16, 2005 - 09:10 pm: |
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Cool!
Smitty,
No worries. |
Gentleman_jon
| | Posted on Tuesday, August 16, 2005 - 09:17 pm: |
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Thanks guys:-)
Form following function:-)
The sorbothane and lead rod are not too hard to find.
The sorbothane is sold in 4x4 or 12x12" sheets for many uses that require vibration absorbtion.
The lead rod comes in 36" lengths.
I bought both of them from an industrial supplier, and I am afraid I can't put my finger on their URL, but I will post if I can remember it.
Making the handle bar grips out of Sorbothane would be a good idea. I would mold in a recess under the carpal tunnel to relieve stress in that part of the hand if I were going to design some.
Smitty- by adding mass, the lead lowers the resonant frequency of the bars, so that they do not vibrate as much. The sorbothane absorbs much of the remaining vibration. The result is that vibration is very much reduced, and the fatigue that you are worrying about is even less likely to occur - ok?
I might be concerned about using more lead than I did, ( I note you have 4 pounds of it on hand:-), because that could turn the handle bars into a sort of pendulum that once excited by a speed wobble, could make it harder to control the wobble. In addition to get that much lead into the handlebars, a lot of it would be near the center of the bars where it would not do anything to reduce the resonant frequency of the bars, and would not leave much room for the silicone caulk. Incidently, the silicone caulk, while it will absorb some vibration, will not do so as well as Sorbothane which is formulated to absorb vibration, while the caulk is designed as a sealant.
Henrik-
Sorbothane is available in a variety of stiffnesses, so that one could probably be found for the grips that would differ from the formulation used for your insoles, ( a very popular use for the material). |
Whodom
| | Posted on Tuesday, August 16, 2005 - 09:28 pm: |
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Jon-
Thanks for the additional info. I suppose the stuff could be found at McMaster-Carr or Grainger.
I'd really like to know which approach is best: mass in the bars surrounding by damping material, or mass in the bars attached as rigidly as possible. The "manic salamander" B.A. bar end weights use the latter approach. Jon's approach attempts to damp out some of the resonance, while the manic salamander approach attempts to move the resonance to as high a frequency as possible. I can see advantages to each.
Hey, since more mass is better, maybe we can get Southern Marine or one of our other BadWebbers in uniform to get us a few depleted uranium 50 cal slugs to use for bar inserts. IRRC, depleted uranium is signficantly more dense than lead.  |
Henrik
| | Posted on Tuesday, August 16, 2005 - 09:39 pm: |
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I would mold in a recess under the carpal tunnel
A recess could unload the area, but might in turn "flatten" the natural curve of the palm, thus pushing the carpal tunnel down towards the grip - at the risk of increasing pressure on the nerve.
The other way often suggested is to help support the curve of the palm by using a barrel shaped grip. Molding a patch or ring of sorbothane into a barrel shaped grip in the area of the carpal tunnel might be a good way to go??
Sorbothane is available in a variety of stiffnesses
I figured that might be the case 
Henrik |
Gentleman_jon
| | Posted on Tuesday, August 16, 2005 - 09:58 pm: |
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Exactly:-)
McMaster Carr - now I remember!!
Thanks Hugh!
When I designed this device, I did think of rigidly attaching the lead to bars at first.
However, I was influenced by several devices that were designed by myself and others to reduce perceived recoil in shotguns, (which is actually a vibration problem). This problem has been much more thoroughly studied than the handle bar vibration problem. While the impact of the recoil can be reduced by simply adding mass to the weapon, the most successful systems allow the weight to move independantly of the stock. This doesn't reduce the total amount of recoil, but it spreads it out over time, thus it is perceived as being less severe.
This led me to think that by allowing the lead to move, it would not only reduce the amount of vibration by lowering the resonant frequency of the bars, but also to spread the energy over different frequencies as the Sorobothane absorbed energy, and caused the lead and the handle bars to vibrate at slightly different times, thus lowering the amplitude of the vibrations.
Another idea I had that I did not test was to make the lead into a flexible snake by cutting it into smaller lengths, and then putting them into shrink tube, so that the lead itself would be flexible. My thinking was that this would reduce the resonant frequency of the lead bar itself.
Uranium is a splendid idea, and of course if that turns out to be a bit difficult to acquire, I can assure you that there will be no problems at all using 22 Karat gold: it too is rather heavier than lead:-)
Henrik-
I have a pair of gel palm gloves,( don't use them any more), and they were relieved under the carpal tunnel, and they didn't seem to cause any problems. Unfortunately, they didn't solve the problem either:-). However, I do believe that this approach is patented and commonly used in heavy duty industrial gloves to reduce "carpal tunnel syndrome", which is part of the numb hand problem, but I do not think it is the total problem. |
Tramp
| | Posted on Tuesday, August 16, 2005 - 10:02 pm: |
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you can avoid carpal tunnel syndrome by finding ars which keep your wrist in a natural position. this state varies for all of us, so all bars don't work for all people.
this is why i got rid of my s2 bars and changed fromtends for using bars from other makers. |
Johnnylunchbox
| | Posted on Tuesday, August 16, 2005 - 10:58 pm: |
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You guys are making my head hurt.
Whodom - if you attach the mass in the bars as rigidly as possible, wouldn't that negate the damping effect of the sorbothane surrounding the lead rod?
i need some of you engineers on my staff. |
Whodom
| | Posted on Wednesday, August 17, 2005 - 06:24 am: |
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Whodom - if you attach the mass in the bars as rigidly as possible, wouldn't that negate the damping effect of the sorbothane surrounding the lead rod?
Absolutely, that's why I'm intrigued with Jon's setup. OTOH, I can where the "manic salamander" explanation makes sense too:
Q. How do bar-end weights change the resonant frequency and reduce vibration?
A. Resonant frequency is the frequency at which an object "rings" if it is moved. When you hit a tube with a hammer, and listen at the end of the tube, you are hearing the audible portion of its resonant frequency spectrum. The "fundamental" is the lowest note. In handlebars, this is the frequency made by the bars "flapping." By flapping I mean that the bar clamps stay put, while the tips move most. This fundamental frequency is typically the strongest frequency, thus the first one to attack.
Weights on the tips of the bars reduce vibration by moving the resonant frequency lower, away from the frequencies generated by the engine. This happens for the same reason that a heavier guitar string sounds lower, under the same tension, than a lighter one.
Because the effectiveness of a weight in reducing vibration this way reduces to zero as the weight approaches the bar clamp, I was careful to keep as much weight outboard of the bar ends as possible. All the weight is concentrated where it is most effective- right near the bar-ends. All the weight is within 2.5" of the bar ends. There's no dead weight as with solutions that go all the way through the bars. By moving the resonance lower, it typically moves further from the frequency of the engine, which reduces the build-up of vibration in the bars dramatically.
The other way to look at it is in terms of inertia. By solidly mounting the weights to the ends of the bars, the bar-ends gain a great deal of inertia, which means that they are much more reluctant to change speed. Since the flapping motion involves the bar ends accelerating this way and that in rapid succession, any weight on the ends reduces this motion.
When you are trying to contain vibration by changing the resonant frequency, solid-mounting is the way to go. Any flexibility to the mounting muddies the effect of the extra weight, hurting the cause.
This is why I'd like to see someone do some sort of instrumented test of the effect of these different vibration reduction strategies. I am sure someone's perception of vibration is pretty subjective, and there's probably also something of a placebo effect- if you spend ~$50 to put something in your bars to reduce vibration, you're gonna convince yourself, at least for a while, that the vibration is reduced. I think it would be helpful to be able to have objective measurements of these different gizmos to see what appears to work best, coupled with riders' perceptions of what works best.
Hmmm, maybe we can convince Blake to include test handlebar vibration reduction gizmos as part of his upcoming XB exhaust test? |
Gentleman_jon
| | Posted on Wednesday, August 17, 2005 - 08:29 am: |
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When you are trying to contain vibration by changing the resonant frequency, solid-mounting is the way to go. Any flexibility to the mounting muddies the effect of the extra weight, hurting the cause.
You are correct when you say that flexible mounting "muddies the effect of the extra weight".
That is the idea:-)
The flexible mounting does not reduce the mass of the weight, so it is effective in lowering the resonant frequency of the handlebars. What the Sorbothane does, is to move the vibrations around in the time domain,so that one large vibration is changed to several smaller ones, as well as converting some of the energy into heating the Sorbothane, thus lowering the amplitude, and giving the perception of less vibration overall.
I do agree that testing would be a good idea. However, like many such tests, correlating the test results with perceived reduction of vibration is easier said than done, not the least because in real life, the riders hands are not only part of the vibrating mass, but they are also the sensors:-)
Curiously enough, Sorbothane was designed to mimic the hysterisis of human skin, a particularly "dead" material from the vibration transmission point of view. That means that the riders hands are themselves rather effective vibration damping devices, depending on the mass of the hand, and the way the handlebar is gripped: the lighter the better as every one knows:-)
Is that all clear now?
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Henrik
| | Posted on Wednesday, August 17, 2005 - 08:30 am: |
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Jon; I think part of the reason for the relief in the palm of gloves is our opposing thumb If you put our thumb and little finger together, you'll see flexion is necessary right in that spot. The build up of padding to both sides of the relief, granted, will take pressure off the Median nerve as it branches out in the hand.
For us motorcyclists however, I think there may be at least 2 parts to the problem:
1) if the clutch and front brake controls are not adjusted properly, you'll end up with your wrist in either flexion or extension. I think most improperly adjusted controls are too high, putting the wrist into extension. That in turn puts a strain on all structures running through the carpal tunnel, which may cause inflammation and swelling leading to pressure on the Median nerve = pain & numbness
2) Direct pressure: putting too much of your body weight on your hands instead of using back and abdominal muscles to support your upper body (difficult with slippery tanks and foot pegs set back, I know). Or, as I mentioned previously, flattening the natural curve of the hand, bringing the branching of the Median nerve forward and under pressure between the grip and the bones in the base of your hand.
But "numb hands" in general is a much more complex problem. For example; I was doing a bunch of demolition, and thought I was developing Carpal Tunnel Syndrome. Turned out the muscles in my foreams were swelling/growing due to more manual labor than I'm used to. As a result, the nerve was being compressed where it passed between forearm muscle bundles and not in the Carpal Tunnel.
I guess what I'm trying to say is, that numb hands can be cause by many different factors, and no one particular preventive measure is guaranteed to be effective for all sufferers.
Henrik |
Johnnylunchbox
| | Posted on Wednesday, August 17, 2005 - 12:59 pm: |
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"When you are trying to contain vibration by changing the resonant frequency, solid-mounting is the way to go. Any flexibility to the mounting muddies the effect of the extra weight, hurting the cause."
It is my opinion that the effect of the non-solid mounting of the bar end weight is negligible in affecting the ability of the bar end to change the resonant frequency of the handlebars. In other words, mounting with rubber is not really going to compromise the change of resonant frequency and should function almost as well as a solid mounting.
Steve
(Message edited by johnnylunchbox on August 17, 2005) |
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