PDA

View Full Version : curious on the science behind hub noise?


jasonification
03-23-2016, 01:15 PM
Was riding around yesterday when my mind began drifting to the quietness of my Shimano hubs. I started to think about how Chris King hubs are akin to angry bees and wondered about the science behind it?

From my elementary understanding of science, noise is a form of energy dissipation. Does that mean that there is energy lost with louder hubs? Furthermore, I wonder what makes the noise, and whether this results in a quicker wearing out of the hub (the longevity of CK hubs would prove otherwise).

Would love to hear some thoughts and insights into this! Thanks forumites!

Mark McM
03-23-2016, 01:41 PM
Louder hubs don't necessarily mean more energy loss. On some hubs, the ratcheting mechanism is buried more deeply inside the hub, and the vibrations are absorbed before they can escape. On other freehubs, the ratcheting mechanism is closer to the outside of the hub, and noise can escape more easily. Other factors are whether the parts that move/vibrate resonate more on some hubs than others.

On most shimano freehubs the pawls are deep inside the freehub body, underneath the splined body (and the cassette that is mounted on the freehub). In addition to the thick mass of these parts, any air vibrations inside the freehub has to escape through 2 sets of bearings.

On Chris King (and Campagnolo and several other hubs), the ratcheting mechanism is at the junction between the freehub and the hubshell. Any vibrations generated have a shorter path through hub to the outside world (less metal and typically only a single seal). Plus, a thin-walled hubshell may vibrate more easily than a steel freehub body mounted with a cassette.

In other words, the audible sound that reaches your ear may not be a good indication of the actual vibration losses occurring inside the hub.

MattTuck
03-23-2016, 02:04 PM
If I am not mistaken, there are also few pawls on the Shimano hubs than others. So there are fewer clicks per rotation. Don't quote me on that, but I think I read it here a long time ago.

chiasticon
03-23-2016, 02:35 PM
If I am not mistaken, there are also few pawls on the Shimano hubs than others. So there are fewer clicks per rotation. Don't quote me on that, but I think I read it here a long time ago.this is true. certainly less than DT or CK. I think OP is questioning more the loudness of the sound rather than why they're different (buzzing from dozens of clicks per rotation versus around 4-6 on most wheels).

Mark McM
03-23-2016, 02:54 PM
If I am not mistaken, there are also few pawls on the Shimano hubs than others. So there are fewer clicks per rotation. Don't quote me on that, but I think I read it here a long time ago.

It's not the number of pawls, its the number of teeth on the ratchet ring.

Freehubs are designed so that all pawls engage simultaneously. Therefore they click simultaneously (so close together that it should sound like a single click). So, with a 32 tooth ratchet ring, you'll hear 32 clicks per revolution, regardless of whether there are 2 pawls, 3 pawls, or a complete set matching face teeth (like the DT star ratchet).

JStonebarger
03-23-2016, 03:24 PM
What about the type or amount of grease? Any difference?

steamer
03-23-2016, 03:51 PM
What about the type or amount of grease? Any difference?

Sure. I quieted a fairly noisy Velocity hub by putting a ton of grease in the area around the hub ratchets and the freehub pawls. Not as quiet as a Shimano, but pretty close.

Tickdoc
03-23-2016, 03:58 PM
I hate loud hubs.

My American classics were fairly quiet, my campys are acceptable, but my Dt Swiss are the best...nice and quiet.

The newest ones, old cane creeks, are uneven. I mean the clicks don't sound consistent. I cleaned and greased and they were quieter, but then I had terrible chain lag. Cleaned again and greased with light oil and they are loud again but with less chain lag.

Dt Swiss has it down, IMO.

I want to hear some of the new magnetic ones.

OtayBW
03-23-2016, 03:59 PM
My HED Ardennes are dead quiet. I could sneak up behind someone and it's like I've got a cloaking device....

Ralph
03-23-2016, 04:03 PM
You have to be careful about getting too much grease in and on the pawls. I know on my campy hubs, with the ring spring, too muchgrease and pawls don't work.

oldpotatoe
03-23-2016, 04:37 PM
Sure. I quieted a fairly noisy Velocity hub by putting a ton of grease in the area around the hub ratchets and the freehub pawls. Not as quiet as a Shimano, but pretty close.

Be careful, lots of grease and the pawl(s) can stick down...bad.

HillDancer
03-23-2016, 04:39 PM
An exception, Onyx Racing hubs. No pawls, ring gear, star ratchet, or pinion mechanism; no noise.

steamer
03-23-2016, 05:29 PM
Be careful, lots of grease and the pawl(s) can stick down...bad.

Yah, it's true guys. Can definitely be too much of a good thing.

I used a very thin grease but filled up most of the space. It has worked for the last 400 miles or so, but I suppose the spring could lose it's spring over time and have engagement problems down the road?

Interestingly, I added the grease because the first (original) spring broke (manufacturing issue) and Velocity kindly sent me a replacement spring and pawl set, presumably made out of a better material. I noticed that the mechanism was almost dry inside. And the broken spring seemed to be corroded at the site of the breakage.

I discovered the problem with the spring when I rode a 200K with my hub creaking and clacking the whole way. After that ride I took the freehub off and found the problem. I got pretty lucky because at best I had two pawls doing all the work, maybe only one. It's a good thing I am a weakling.

kramnnim
03-23-2016, 05:34 PM
American Classic hubs are quiet because the drive pawls are not spring loaded...they are pushed into position by the cam plate. Only the tiny spring attached to the freehub body is dragging/slipping/sliding/clicking.

bicycletricycle
03-23-2016, 05:48 PM
this is true. certainly less than DT or CK. I think OP is questioning more the loudness of the sound rather than why they're different (buzzing from dozens of clicks per rotation versus around 4-6 on most wheels).

Dt and ck hubs don't have pawls

parallelfish
03-23-2016, 06:00 PM
On Chris King (and Campagnolo and several other hubs), the ratcheting mechanism is at the junction between the freehub and the hubshell.

The Chris King drive rings are actually inboard of the hub bearings.

Peter P.
03-23-2016, 06:32 PM
I think the reason grease tamps down the audible ratcheting is because is slows the return of the spring loaded pawl.

I believe the level of the ratchet is in part due to the strength of the pawl return spring and the velocity the pawl reaches when it engages the teeth-higher velocity = louder sound.

Of course, pawl and tooth profile play a role as well.

Mark McM
03-24-2016, 10:14 AM
In any case ...

The energy that creates the sound of pawls hitting the ratchet teeth is from the energy stored in the pawl springs (which in comes from the energy of rotation). How loud the sound is depends on both the spring energy, plus mechanical/acoustic factors in the hub. Regardless of how loud it is or isn't, the pawl spring energy is lost, and is not returned to forward motion. But this energy is very small compared to other energy losses in the system, so it is relatively inconsequential.

HillDancer
03-24-2016, 09:43 PM
...Does that mean that there is energy lost with louder hubs?...
This bit of research shows the level of velocity decay between a group of hubs https://www.dropbox.com/s/cs2g251nz9faz14/dev-wheel-spindown.pdf?dl=0 It is from an ongoing test conducted by Duke University, the graphs only show the top five of hubs tested.

Note the loudest hub (my subjective opinion) in the group, Profile, has the greatest decay. The quietest hub of the top five group, Onyx, is the most efficient.

jasonification
03-25-2016, 12:42 AM
This bit of research shows the level of velocity decay between a group of hubs https://www.dropbox.com/s/cs2g251nz9faz14/dev-wheel-spindown.pdf?dl=0 It is from an ongoing test conducted by Duke University, the graphs only show the top five of hubs tested.

Note the loudest hub (my subjective opinion) in the group, Profile, has the greatest decay. The quietest hub of the top five group, Onyx, is the most efficient.
Super interesting! It's also cool to read how the different ways hubs are constructed also contribute to loudness!

Sent from my D6653 using Tapatalk

Ralph
03-25-2016, 06:50 AM
I have never worn out a hub ratchet ring in all my years of cycling. But tend to over grease them sometimes.

Recently put on rear wheel with a Black Campy hub that hadn't seen use in about 6 months, and the pawls were stuck. Maybe one working. Took it apart, and the pawl ring was kinda messed up....so put in a new ring spring. Followed OP's advice, and greased the ratchet ring only, and liberally used motor oil on the pawls themselves. Now hub is very loud.

I don't care if it's loud or quiet.....but is it wearing fast now? Does noise level equate with wear? Or does design of free hub and how it spins, reduce wear, whether heavily greased, or just oiled? This question make sense to you mechanics who tear apart a lot of hubs?

oldpotatoe
03-25-2016, 07:04 AM
I have never worn out a hub ratchet ring in all my years of cycling. But tend to over grease them sometimes.

Recently put on rear wheel with a Black Campy hub that hadn't seen use in about 6 months, and the pawls were stuck. Maybe one working. Took it apart, and the pawl ring was kinda messed up....so put in a new ring spring. Followed OP's advice, and greased the ratchet ring only, and liberally used motor oil on the pawls themselves. Now hub is very loud.

I don't care if it's loud or quiet.....but is it wearing fast now? Does noise level equate with wear? Or does design of free hub and how it spins, reduce wear, whether heavily greased, or just oiled? This question make sense to you mechanics who tear apart a lot of hubs?

Considering the amount of time you coast on most rides, the pawls making noise isn't really wearing much of anything. I use oil because if you get a sticky pawl, engage it partially, it slips and you crash into the next one..it may break the pawl. Break one and you may break the next also..

But pawls or ratchet rings or whatever..wear when you are coasting really isn't an issue. Bearing wear or contamination is the 'issue' with any hub.

chiasticon
03-25-2016, 07:32 AM
Dt and ck hubs don't have pawlsyes I know. when I said "this is true" I was referring to the number of engagement points per rotation bit.

oldpotatoe
03-25-2016, 07:40 AM
yes I know. when I said "this is true" I was referring to the number of engagement points per rotation bit.

And some DT hubs do have pawls. DT370 hub.