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Hub Engineering – Machining tollerences and real-world effects
From:
caleb May 25, 2006, 4:54 PM
Question:
How good are Zipp hubs, really? Zipp often brags about their hubs, and most people seem to agree that they're pretty good.
Also, Zipp claims to send off-the-shelf wheels to sponsored teams.
So, I was kind of surprised to see Phonak riding Zipp 404 rims laced to DT 240 hubs in the Giro today.
Josh:
Good eye on spotting the hubs. For the record, it was Tyler Hamilton who wanted us to work with Phonak when he went there from CSC, but our company is rather small and family owned, so we just couldn't afford the sponsorship of two teams, plus we make what is probably the most expensive to produce hub available right now, so DT and cyclops came on to supply hubs for the team and we became Phonak’s rim sponsor. However, for all critical stages, you will see the team on Z series wheels with our ceramic bearings and hubs.
Index Categories:
Hub Engineering – Machining tollerences and real-world effects
Hub Engineering – Hub noise and bearing play
From:
clyde rock May 10, 2006, 12:48 PM
Question:
Am I the only one who dislikes the Zipp hubs?I have a set of 2006 Zipp 404 Clydesdales, and it feels like they take forever to engage. Am I the only one who's noticed this? Anybody else changed the hubs out? I saw some recommendations for Shimano DA, Wood, and King. I love the King hubs on my MTB. Any thoughts on pros/cons? Also, why are the Zipp hubs so loud?
Josh:
First the noise issue. Our previous generation of 202 hubs had a heavier pawl spring than what we are using now, we have since replaced this in the new design with a Phynox watch spring, this is the same stuff they use in high end automatic watches as well as avionics equipment, and allows for the use of a spring that is roughly half the thickness and therefore less stiff. However, the reason the hubs seem loud is because the spoke tension telegraphs the hub noise out to a hollow rim which acts like a drum head.
The king hub is is actually slightly louder than ours unless you continually pack it with grease, and sounds more like a swarm of bees chasing you when laced into one of our wheels. Any hub will quiet down if you lube it, we recommend 10W-40 Mobil1 synthetic motor oil, this is the base oil of most every high end lubricant on the market, is quite cheap by comparison, and is compatible with the barium-hydrocarbon grease in the bearings.
I've said it here before, but hubs are a very difficult product to make as everybody has a perception of what a hub should be and should do. We have chosen to go for the lightest weight and most efficient spinning hubs on the market, and that leaves us with a rear hub weighing 182 grams and spinning with roughly 1-1.5 watts less resistance than anything else currently available. Our Grade1 ceramic bearings save another 0.75-1 watt. Now to get there, we are using Alcoa 7XXX series aluminum and making all parts in the US on Swiss type machines with the tightest machining tolerances ever used in this industry (even including King) and perform 100% dimensional inspection of all bearing bores and axial tolerances in order to match parts for the tightest possible final assembly. But you have to understand that these are ultra high end racing parts, sort of like the formula1 car of hubs, they can't be everything to everybody. The main complaint we get is that there is no bearing adjustment, but every hub is set from the factory with bearings aligned axially within 0.0005", which is tighter than most CNC machines can hold bearing bore tolerances (we hold those to 0.0002").
This gives the ultimate in low friction and precision, but is a number so small that no human could possibly adjust the hub within that tolerance band using adjustable cones, so we have to match hubshells at assembly and fix this dimension with machined parts. The new hubs have a higher tooth count on the ratchet (up to 30, same as Campagnolo and tighter than most everybody but King who has 72, industry standard is 24) and engage faster than old designs, but still require 12 degrees between engagement teeth compared to King's 5, although the reduced tooth count increases coasting efficiency as internal frictions are severely reduced in our design over theirs.
For those who haven't like our hubs in the past, you should really look at the 2006 models, they are significantly different from anything we've previously done, are extremely user friendly and have thus far proven to be unbelievably solid considering their weight (CSC has been racing and training on prototype and production models of this hub for nearly 2 years and found it to be nearly bulletproof)
Here’s a little more information on the desing and production of our hubs:
A Note on Hubs
SHIFT (Spoke Hole Impact Forming Technology)
http://www.zipp.com/Technology/HubTechnologies/SHIFTSpokeHoleImpactFormingTechnology/tabid/105/Default.aspx
Re: Hubs on a disc Pt. 2
Index Categories:
Hub Engineering – Machining tollerences and real-world effects
From:
randall t Sep 21, 2005, 12:23 PM
Question:
Machining tolerances? As a working machinist I have a real hard time beliving a millionth here or there matters in a hub bearing at those tolorances heat,from your hand or a disc sitting with the sun hitting only one side has blown your millionth of a inch, But then I will try to remember only to ride inside in carefully controled conditions.
Josh:
The reason that the millionths matter so much on the balls is that ball tolerances cover both sphericity and diameter. If you think of having balls in the race at the high and low end of the tolerance, you end up with the smaller balls not even making contact, thus concentrating the load on the larger balls. Since the sphericity of the balls is also covered in this number, you start to realize that the roundness of a 40millionths ball vs. a 10 millionths ball is dramatic, this is why Campy always had such a good reputation, they were the first to use true 25 millionth toleranced balls back when they were very expensive and hard to get (and everybody else was using 40-50 millionths balls), but as a result their hubs were always butter smooth.
There's a million other things to consider as well, like we were the first in the bike industry to use thermoplastic ball retainers instead of brass, this saves like 1gram per cartridge and can nearly double bearing life, and now numerous companies have gone in this direction. Grease is another huge factor, we work with a German company and we spent 4 months in testing to determine the optimal type and amount of grease in the cartridge. The stuff we ended up with costs something like $100 per kilogram, but as a result the bearings run with lower torque values and last longer than anything else we can find. After about 6 months of CSC being on the stuff we started getting calls from some of the other teams as the mechanics were hearing that CSC never replaced bearings, so we now sell our bearings to a number of other teams and their suppliers, so in our opinion those millionths of an inch are in fact a very big deal.
As a machinist you will appreciate why we feel that our American made hubs will never be supplanted by Asian made hubs, mainly air-conditioning. We temperature control our manufacturing facility and our cutting fluids within a 2 degree F window. This guarantess that parts made today are identical to those made tomorrow and so on. At the tolerances we work with a 10degF shift in temperature will take a part out of the tolerance band, but if all parts are made identically at the same temp, then they will all grow and shrink identically once they are assembled and out in the real world.
I often joke with our Taiwanese agent who is always trying to sell us hubs that they will never get there until they air condition their factories (this is mostly a joke as the super volume oriented Asian machine shops also shy away from ultra tolerance equipment for the sake of equipment that can produce larger volumes, whereas for us volume will never be an issue as we will never make enough to fill the machines we have, so we concentrate on making them perfectly).