This is a golden comment. Glad Chung got to immortalize it. Are you actually a Hambini shadow account?

I have a hard time believing that a supposed aerospace engineer refers to the phases of flight as “takeoff mode” and “landing mode” when talking about drag changes on that Boing 747.

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MS: Exercise Science
Your speed matters a lot, sometimes you need to be very fast, where sometimes you need to breakdown your speed.

Neither one is selling wheels. One of them is selling clicks on their youtube page.

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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

He keeps popping up on my YouTube feed. I don’t think I’ve ever watched any of his videos, because, quite frankly, I don’t give a shit about whatever he happens to be talking about. I click on the “not interested” but they keep showing up in my “recommended” feed. Totally aggravating.

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I thought is was interesting that a supposed aerospace engineer referred Boeing as (Boing)

His 2.5% error overlaps performance of rims he calls $hit vs good. I smell grudge. Only the worst, and best performers are not overlapping as per the data and error ranges. But at least he gave error numbers.

Deeper rims are faster in non laminar airflow is what i get out of it. I think he is on to something, but then deeper rims are also faster in laminar flow. 🧐

If the argument is that laminar data is not (less) valid, i want to see by what degree, and in what conditions, before i support a change in protocol. I have proposed a test of wheels in both conditions to compare differences, but his reply was that he would not drop to that level. fair enough if your are selling the concept and not sharing data in public... but i hope he has lots of access to the aerospace wind tunnel for his side project.

Personality aside, I'm a fan of his mechanical solutions for various bike problems (designing and machining one-off solves). I've enjoyed his videos on these.

On the aero side; he understands basic fluid dynamics, but uses overly simplistic modelling and assumptions (about at the level we were doing in the early 90's). In looking at the Zipp wheels he only looks at the flow at 3:00 (looking at the bike from drive side). The dimples are on the leading edge at 9:00, and of course the profile is totally different at 12:00 (where the wheel is encountering the fastest flow [2x ground speed]).
I watched his diatribe on aero profile downtubes; he did all his CFD modelling assuming the flow was perpendicular to the downtube (doh!). The shapes are designed based on the downtube being angled into the wind (the path from the BB to the headtube is not a vertical line).

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ECMGN Therapy Silicon Valley:
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I'm somewhat skeptical of this. The only evidence I can find that it's true are his own statements. Google only points us at his cycling-related efforts (though other people clearly did the search because "Sachin Hambini Airbus" and "Sachin Hambini Rolls-Royce", etc, are suggested search terms).

I also work for an aerospace lab. And I'm also not supposed to announce it publicly. But when I search myself, it's very clear what professional industry I'm in. Papers in college, conferences I've spoken at, book chapters, patent applications, etc.

So either his professional work is *very* clandestine. Or maybe he goes by another name in his other industry or something.

Shhhhh. Come on now.

But that being said, in my mind, the issue with the dimples at 9 oclock is that the spokes have already done a pretty good job of chopping that air up. Hard to say how much of a trip strip is really needed at that point. Reynolds did the same thing, just in a different way. My view is that benefits would only be marginal at best, but then i only have a self declared armchair phd in aerodynamics. Marketing and or engineering at Reynolds and zipp apparently disagree with me.

I think if hambini is guilty of being overly simplistic, it is because he criticizes designs based on aerodynamics only (but that is his thing, and he gives some disclaimers on that level). Saying everything should be naca shaped with hidden spoke nipples is easy to say, but an aero wheel is also engineered for things like compliance, durability, lateral stiffness, stiffness to weight, manufacturing cost/limitations, price considerations, balancing side forces etc. Basically, it is hard (simplistic?) to criticize a design for it’s aero properties when more than just aero was factored into the final design.

Hambini is the engineering equivalent of GameChangers

Basically all shout and no actual science to back it up.

´

The "durianrider" of aero testing.

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What's your CdA?

He had a Linkedin profile that included his role at Airbus (unfortunately, I never archived it). IIRC, he also worked at Rolls Royce on the engine side, supposedly was seconded to the Skunkworks, and had a PhD from a German university (I think Hamburg).

Profile has completely disappeared after the start of the Wind Tunnel Shootout incident. I don't know if it was because it was fake, or because he was actually taking heat at work for bring disrepute or unnecessary attention to Airbus or his projects. Maybe someone with Linkedin Recruiter can dig up the profile again.

A 32 minute video about race wheel dimples?


OUT

He's not wrong about the dimples. Zipp themselves plastered logos all over them rendering them ineffective. So, it couldn't be THAT much a thing. I don't think it was marketing so much as "guess and check and sell anyway". It doesn't hurt anything and they tried something. It's the profile itself that makes the Zipps, not the dimples. Even then, if you're at a smaller yaw, the newer profile probably doesn't get you much anyway.

IMO, from the older posts, I've never been able to look at some brands of fairing wheels the same. The big spoke gap on some of them (the Flo's) just looks really bad compared to other ones. Maybe it doesn't matter, but it looks lazy compared to even my 2012-ish Giant wheels. The spoke hole in the fairing on those is just enough for the spokes to pass. I'm guessing Flo, and others, made the spoke hole symmetrical in the left/right plane to make install or design/fab easier. It's gotta be harder to have all those holes in the perfect spots alternating back and forth.

The attitude generates clicks.

exactly

anyone can sit there and pick on one word taking it out of context but when I said 'sell' I knew Josh didnt work for Zipp any more but thats not to say he doesn't have a vested interest emotionally or financially in Zipp. If he has been compromised by the marketing department he certainly wont be the first highly talented engineer to have that happen to him.

The guy throws up Reynolds number and other equations a first year engineering student would know and calls himself an expert. He’s an embarrassment to the engineering field.

If I was his current employer, his attitude and blatant unprofessional behaviour would cause me to disassociate from him in every manner. His statements against others in the industry (I.e Damon Rinard) Id argue border on slander, for no apparent reason than to get YouTube clicks on the videos he makes in his parents basement

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the world's still turning? >>>>>>> the world's still turning

IOW, that wasn't at all taken out of context.

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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

disagree with him yes.... effect is worklife ... ahhh that gets a big no from me. it's not worthy of a twitch hunt.

Hello HAMBINI FANS!!!

You may not like the analysis or the way it is delivered and it may be short of the level of detail that the majority of you well heeled aero specialists require but the aero is valid. I am not the only one who has found this, SwissSide and DT swiss (one and the same) came to the same conclusion.

The turbulent boundary layer needs to build up on the HP side. As others have said, if it worked, they would not have pasted their stickers over it. Some have asked about the differing profile across the wheel - that is totally correct and I didn't discuss it because it's Youtube and not M.Eng Aerospace. Towards the top of the wheel (especially a deep wheel) the aerodynamics would tend towards discontinuity rather than turbulent trip.

As for the broken record about the faked testing and or transient testing... Wheel companies send their wheels in to be tested so that is "fake news".

SwissSide and Princeton Cycleworks test or design for unsteadiness so you can clearly see that it's not me who is using modern practices.

There is a lot of love for Damon Rinard on here because he imparts his knowledge in a much more polite and professional way than me. However, He specs things that even NTN and SKF would not warranty and does not respond to any questions about that - that is unacceptable for all of those people who have problems with his bikes.

Lots of people will dislike me, and I can accept that but unlike others, I won't sit on the fence and get splinters in my backside and not call out the poor engineering practices when I see them.

Unsurprisingly, my linkedin was removed at my employer's request but you can see a bang on character reference from one my colleague's brother here, Scroll down to Bristolpete

https://forum.bikeradar.com/.../13099885/aero-tests



Thanks.


Hambini

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HELLO HAMBINI FANS!!!

Well one fan, and a whole lot of people pointing our serious issues with your video, which you of course didn't address. But, thanks for playing.

Also:

No pictures of his test rig
No pictures of any testing
No original of the "Flo Letter"

But hey, seems to do a good version of the BBinfinite BB though.

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Heath Dotson
HD Coaching:Website |Twitter: 140 Characters or Less|Facebook:Follow us on Facebook

Sorry, I would rather keep my job than post that to satisfy you.

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HELLO HAMBINI FANS!!!

Not to be that guy but could someone give me cliff notes?

I have some Zipp wheels but my purchasing process went like this:

1). Need wheels, building bike from frameset
2). Kona count - lots of Zipp wheels
3). Friends say - Zipp wheels were good, didn’t fall apart, no quality issues
4). LBS could get them quickly.
5). Read reviews that said they were good

Is this guy saying I bought crappy wheels or they just aren’t significantly better because of the dimples.

The short of it is that benefits may be debatable. But they won’t slow you down. And they may help. Likely they marginally help in some situations, marginally hurt in others, nothing in others still. How is that for an answer? I have not wind tunnel tested them. All i have are questionable armchair aerodynamics (Like everyone else). But the dt swiss guy felt they would not help. Fwiw. He seems legit, but is zipp competition.

To oversimplify, but josh (ex zipp) once said that aerodynamic shapes are better being smooth, and non-aerodynamic shapes are better to have a texture. Or something to that effect. He might have addressed the question on the marginal gains podcast. Ask him privately and he may answer. He is good that way.

At the end of the day, i think you will find that elevated prices do not guarantee better performance. Aerodynamically. There are lots of cheaper copies that are decent, if largely untested. And as time passes, i note those eastern copies are increasing in price, and quality. Just as oem are dropping prices and outsourcing out east to compete. How the unbranded eastern stuff holds up to big hits, hot brake temps, etc are the issue. So there is always a risk... and i guess looking at warrantees is key. I suspect there are many copycat wheels out there that likely have minimal testing beyond visual flaws. Yikes. who knows?

But you can expect that quality control will be good with zipp. Same for things like brake track quality/performance/durability. And zipp wheels hold their value. So at resale, you will get back more of your original investment. Some would argue hubs are questionable at times. I can not comment. Many cheaper oem hubs are rebranded cheap stuff put there to hit a price point.

When it comes to wheels, i have a “tires first approach”, as optimal tire size/compound/durability/pressures will be big for performance. I chose a tire, width and pressure that meets my needs, and then i select rims to back it up (width, depth, weight, spokes, hubs). Get as deep a wheel as you can handle. Keep valve stems short, and spokes cxray. And i like my carbon ti hubs for lightness, stiffness, and quality bearings. The downside is that the wide spoke Bracing angles generate a laterally stiff wheel, but expose more spoke to the clean air. So they are not my tri/tt choice, but are good all rounders for road bikes.

There is more to be gained lost with optimal tire compound, size, pressures than with dimples. So get that big stuff right first.