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Damping Fork Vibrations

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Damping Fork Vibrations

Old 04-17-19, 01:19 PM
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TiHabanero
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Damping Fork Vibrations

Was sitting around thinking about bikes and had this thought that a rubber plug stuffed in the steerer tube might absorb some high rate frequencies. Any thoughts on this?
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Old 04-17-19, 01:58 PM
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Try it out then report back. Andy
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Old 04-17-19, 02:40 PM
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Fill the fork legs with lead shot...

[Sorry, the day job has my snark on high output today.]
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Old 04-17-19, 02:54 PM
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Only from added mass. I don't think that a rubber plug in isolation would do much as it is not an intermediary between 2 different structures of differing rates..

As long as we are fantasizing: Between the drop outs & the axle would have an effect.

But in reality land: So would between the rim & the road, between the headset & the stem or the stem and the handlebars.

Or as added mass on the bar ends. Effectivly minimizing the distance x force moves the lever.
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Old 04-17-19, 04:10 PM
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I don't think people find the small amplitude vibrations that could be damped out to be objectionable. You need more compliance to reduce the shock of hitting bumps. Don't see how this would make the fork more compliant.
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Old 04-17-19, 05:14 PM
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I think one of the reasons people like the ride of carbon is because it damps out high frequency vibs, but I think compliance in a fork does more for overall comfort.

Last edited by Nessism; 04-17-19 at 06:53 PM.
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Old 04-17-19, 05:18 PM
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Wider tires are lower air pressure.

Redshift Stopshock stem.
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Old 04-17-19, 08:38 PM
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Originally Posted by Nessism View Post
I think one of the reasons people like the ride of carbon is because it damps out high frequency vibs, but I think compliance in a fork does more for overall comfort.
It's a very complex subject and I know too much about it to make any statements about it without seeing some decent literature or experimental data. So this is conjecture. I suspect the damping properties of carbon relative to comfort are mostly marketing. Note that Spesh used to have elastomer elements in their carbon frames and have moved towards suspension without ever admitting the old way was mostly just marketing. This suggests to me that the thing people find bothersome is hitting bumps, including small ones like chip seal that are experienced at high frequency.
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Old 04-18-19, 09:39 AM
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Originally Posted by unterhausen View Post
I suspect the damping properties of carbon relative to comfort are mostly marketing.
I don't know about the "mostly" part, but maybe "some" part. What I do know is that there is a distinct reduction in impact harshness when using a carbon golf shaft compared to a similar stiffness steel shaft. Guys with hand/elbow/shoulder pain issues almost to a man report some relief when switching from steel shafts to graphite. Chuck this one in the "for what it's worth" file and disposition as appropriate...

Last edited by Nessism; 04-18-19 at 12:10 PM.
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Old 04-18-19, 10:28 AM
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Front load .. Panniers with stuff in them..


build a 4 tube fork? 2 per blade?

2 can run to the top of the headtube over the headset back to the fork steerer, ..

more triangulation .. https://www.jonesbikes.com/fork-truss-steel-black/


...

Last edited by fietsbob; 04-21-19 at 02:31 PM.
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Old 04-19-19, 05:35 AM
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Originally Posted by Nessism View Post
there is a distinct reduction in impact harshness when using a carbon golf shaft compared to a similar stiffness steel shaft.
I'm sure carbon has more damping than steel. Golf shafts are a different application, because they have resonances in the range of the typical excitation input. Hitting a golf ball is almost a perfect impulse, which excites a significant frequency band. And due to the length of the shaft, the transient vibrations last for a measurable length of time. I'll bet someone filled golf club shafts with a damping elastomer. Okay, I asked google https://www.google.com/search?q=goll...hrome&ie=UTF-8

Seems like most people put the damping in the head of the club
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Old 04-19-19, 06:53 AM
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This is basically the idea behind the Specialized Zertz that you saw on pre-future shock Roubaix and Diverges. Not sure it was all that successful since they dropped them completely.
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Old 04-19-19, 09:17 AM
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those zertz were not fully constrained though. Rubber is incompressible so it needs room to squish.
And most rubber compounds don't offer much damping.
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Old 04-19-19, 09:25 PM
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I could imagine the rubber plug damping vibrations on something like a guitar string.

Although, perhaps one would be better off filling the space between the head tube and steer tube with something like synthetic quilt batting.

But, I have to agree with @unterhausen that the high frequency low amplitude vibrations carried through the tubes likely isn't a big problem.

It is quite possible that material selection would also affect those high frequency vibrations with higher strength steels carrying the vibrations, and softer metals simply dissipating the vibrations.

A couple of summers ago I got to ride my bike on a road that had been ground for repaving. Whew, the whole thing wiggled and jiggled. I had no idea I had so much frame flex!!!
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Old 04-20-19, 11:06 AM
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Originally Posted by base2 View Post
Or as added mass on the bar ends. Effectivly minimizing the distance x force moves the lever.
In practice (sample=1), I remember my Trek Madone from like 2006 or so came with these little rubber bar plugs that suspended a small (maybe 5/16 dia x 3/4" length?) rod in rubber webbing. I was using 44cm alum bars and 23mm tubulars on that bike and I couldn't tell a difference with them in or out. They were Bontrager branded and looked pretty cool so, I guess that's something.
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Old 04-20-19, 11:12 AM
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Originally Posted by base2 View Post
Only from added mass. I don't think that a rubber plug in isolation would do much as it is not an intermediary between 2 different structures of differing rates..

As long as we are fantasizing: Between the drop outs & the axle would have an effect.

But in reality land: So would between the rim & the road, between the headset & the stem or the stem and the handlebars.

Or as added mass on the bar ends. Effectivly minimizing the distance x force moves the lever.
Originally Posted by duanedr View Post
In practice (sample=1), I remember my Trek Madone from like 2006 or so came with these little rubber bar plugs that suspended a small (maybe 5/16 dia x 3/4" length?) rod in rubber webbing. I was using 44cm alum bars and 23mm tubulars on that bike and I couldn't tell a difference with them in or out. They were Bontrager branded and looked pretty cool so, I guess that's something.






I remember the short lived Bontrager "Buzzkill" bar plugs. Emphasis short lived, least I thought they stopped making them.

https://www.ebay.com/sch/i.html?LH_CAds=&_ex_kw=&_fpos=&_fspt=1&_mPrRngCbx=1&_nkw=NEW+BONTRAGER+BUZZ+KILL+BUZZKILL+BAR+END+PL UGS+DAMPER&_sacat=&_sadis=&_sop=12&_udhi=&_udlo=&_fosrp=1
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Old 04-20-19, 01:47 PM
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Squirt a bit of expanding foam in every spot you can.
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Old 04-20-19, 01:51 PM
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I've heard that expanding foam will cause rust. It's also really weak, I don't think anyone uses it for damping. There are sprays that work to reduce vibration on sheet metal, but they are heavy.
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Old 04-20-19, 07:03 PM
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[QUOTE=Marcus_Ti;20893006]I remember the short lived Bontrager "Buzzkill" bar plugs. Emphasis short lived, least I thought they stopped making them.
Yep, those are the ones I was talking about.
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Old 04-23-19, 06:00 PM
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This weekend I rammed a rubber plug into the steerer tube opening under the crown and went for a spin. Noticed no change in vibration damping. Gel under the bar tape will be more effective, or lower pressure in the tire.
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Old 04-24-19, 09:54 AM
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Use Thicker tube wall fork blades .. (yes Heavier) ....

(drum brake hubs?)

vibrating as sub audible brake squealing?







.....
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