He can sure lay it on thick.

The valiant crusader of engineering truth doing brave battle against the monied elite of Big Cycling, Chris and Jon Thornham and Tom Anhalt.

It's funny that they try to make the claim that as aerospace engineers they clearly just know so much more than everyone else and we should just shut up and take it. I'm pretty sure designing am airplane and designing a wheel are different enough problems that experience with one doesn't really have any relevance to the other.

Spin. The "other engineers and scientists are too stupid to understand what I did, therefore I don't need to explain it" defense is getting old. Is this as good as it's going to get? I was hoping something real would come out eventually. But I do tend to believe in miracles.

I searched but did not find the expression "rotational drag" in this thread: is there a search function which looks for words just in one thread?

Anyway, this thread seems to be about credibility of hambini, but to my poor state of knowledge, "wheels" is the only topic for which a wind tunnel is the wrong analyzing tool because of that subject of rotational drag. Wonders me that the planet x disk tests so good nevertheless.

I can't even be bothered to go read the latest claims. Maybe after more coffee. I assume if there were anything close to proof of his claims about Chris and Jon that you'd have mentioned?

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The point is, ladies and gentleman, that speed, for lack of a better word, is good. Speed is right, Speed works. Speed clarifies, cuts through, and captures the essence of the evolutionary spirit.

Was the Zipp 808 tested a FC or NSW or are they so close it would not matter? I may grab a front Reynolds 80 aero

Note that the 454 NSW (sawtooth) sucked compared to the regular 404, which I assume was some version of FC.

Hambini states that the wheels are rotating in these tests, so rotational drag is captured.

I don't think it should be that surprising that a disc + 80 beats all combinations.

Could be, but I think he might be sincere, and just doesn't understand how to handle scrutiny or communicate with peer reviewers (which he does by claiming they're not peers). Which is strange for an aerospace engineer, as they tend to be subject to some of the most intense design reviews, as the implications of flaws in testing process can be expensive in the best case and deadly in the worst.

No.
The rotational drag of the spokes in the side quadrants which have a vertical movement is not measured by the force measurement system in a windtunnel. Only that of the upper quadrant which is moving horizontally. That's why in windtunnels generally spokewheels do not test so bad against disks, compared to tests on a track.
To my point of view the outcome of tests of wheels in a windtunnel have no meaning.

Somehow I missed where he says he captured rotational drag simply by having the wheel rotating... does he also claim to have had a dynomometer on the wheel? Because that is the only way to really get it. The only test I'm aware of that actually did this was Specialized's tests of the Roval CLX50.

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Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
Instagram • Facebook

You know what’s wild? His blog posts on bearings are actually very well written and informative. It’s almost as if they are written by a different person. Not sure why the train went off the tracks with regards to the wheel testing and why he holds such enmity toward Flo (the “letter” excepted). If he was as explanatory about the airflow around a wheel as he is about bearings I’d say we would have all probably learned something.

"1. Flo is stupid and doesn't even know now to use tools and oh yeah they sent a letter that I still refuse to release or verify
2. everyone else is stupid
3. only I am able understand these things don't ask me how to explain that
4. everyone else is paid if they say a product is good
5. experience is irrelevant"

or something like that.
this guy is too much

All deflection and ad hominem. No data. Thoroughly unconvincing.

Another perspective on that:

Excerpt from page 7: https://zerofrictioncycling.com.au/...arings-Article-2.pdf

"So this data is obviously Hambini’s own data, test or “calculation”. How he has derived / arrived at this data is simply critical. It is probably THE KEY piece of information presented in the video to back up his entire main sales point that hybrid ceramics quickly become higher friction than quality steel bearings due to the harder ceramic balls damaging the comparatively softer steel races. This is at 10:25 in the video.

When questioned on this Hambini initially advised he does not discuss testing protocols. I obviously found this extremely concerning. How / where he has obtained the most crucial data of the presentation is secret?!

So not discussing how this testing was done raises a very large red flag with me, of which I advised Hambini (to which he seemed a bit put out advising he didn’t care what colour my flag was). When I fully explained (as above) why I found this so concerning – he did reply back further stating that the tests were conducted as per JIS and DIN protocols which I could find on pages “X” on a very big engineering document, but the maths is pretty heavy etc…and recommended two other engineering books I should read……

I do not understand this type of reply. Watchers of his video should be able to simply find out what equipment and protocol was used to simulate 10,000km of cycling and how was the friction losses measured / calculated. To me his answers on this point were purely deflection and nothing more. He is clearly not going to disclose how the data that sits behind his most key graph was obtained – and I really have to wonder why."

They have meaning, you just have to understand the constraints. There is no perfect test.

Point taken about translational drag from rotation vs. pure rotational drag. My understanding is that translational drag dominated, though.

For what it’s worth, years ago I asked a friend of mine who’s a mechanical engineer in the power industry what he thought of hybrid ceramic bearings and his comments were very similar to Hambini’s. Also, the old Friction Facts newsletters showed very similar findings to Hambini regarding bearing friction though they never tested longevity in my recollection.

I’m not defending the guy, I’m just saying that not everything he says is incorrect or inflammatory.

Rotational drag is smaller but definitely not insignificant. Think of it as how drag force varies around the wheel and the torque this applies around the hub. The bottom of the wheel isn't moving translationally at all, while the top is at 2x bike speed. You get a substantial retarding torque.

The issue for me is lack of data or corroborating evidence that the test was actually done.

I think if he posted some pics and some protocol etc, and clarified this whole “flo letter” thing then...

This *might* turn back into an interesting and productive discussion, not that it hasn’t turned around somewhat, there just isn’t enough clarity on his part to move the discussion in a positive way forward.

Maurice

When the hype around ceramic bearings came out, I was quick to call BS on it. Not because I'm a bearing expert, but because it's easy to calculate that any gain would be tiny. Hambini goes a bit further in claiming steel is actually (always) better on bikes. He lacks evidence to support that claim, or more precisely he makes up evidence that he can't or won't support when asked.

I'm also *very* sympathetic to the idea of unsteady flow influencing the aero performance of bike parts. But again, the supporting information is missing. Like the test protocol and data for field testing wind fluctuations, and how this led to the WT test protocol, which was supposedly modeling the "real world". This is basic stuff. Anyone who has ever done scientific research and then presented it should know how this works.

If anyone would like to send me new hybrid bearing race and /or a steel bearing race - for a before and after comparison - I would be happy to measure the surface roughness averages using our Homel profilometer and send them back to you. Then ride your wheels for x miles and send them back and I'll measure again and share the results.

Maybe run a steel bearing in one wheel and a hybrid in the other so they get the same weather, road surface and vibration and at least have that comparative information.

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Dan Kennison

facebook: @triPremierBike
http://www.PremierBike.com
http://www.PositionOneSports.com

Wouldn't the rear wheel see greater forces? I like the idea of a real world test to see how the bearing races devolve.

IMO it all depends on the initial production finish of the steel races.

I don't need to have in-put on how someone wants to set up a test. I do know that the races can be measured before and after.

If the new race Ra is down below 3.5 micro inches and they are Rockwell hardened to anything near 60 - based on my work with these materials and at these surface conditions - I don't think you will see much change.

If the initial surface roughness is higher or the Rmax is crazy and/or it is case hardened lower than 45 you will see wear with either ball material.

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Dan Kennison

facebook: @triPremierBike
http://www.PremierBike.com
http://www.PositionOneSports.com

That bearing wear test could be run with steel on one side of the front hub and ceramic on the other...

That's a good idea for the front wheel! I like it.