guadzilla

Can you explain why? Not as a layperson using common sense argument, but with actual science/structural engineering arguments to show how voids affect structural integrity and reliability.

I would assume voids are bad too. But i would also assume there is some threshold below which it doesnt matter, And most importantly, I always keep in mind the old adage - a little knowledge is a dangerous thing. Eg, did you know that every time someone goes scuba diving, they end up with microscopic bubbles in their bloodstream? It is the same thing as a Type II DCS hit (the neurological kind). If I were to tell you that accumulated exposure to these micro bubbles can cause long term health impact, wouldnt that sound plausible? Makes sense, right. Yet it isnt true. No proven long-term damage from this.

The idea of believing anything that clown says without verification is laughable. "Hundreds of frames". Yeah right.

Bah Humbug

Oh I’m sure he’s seen hundreds of frames. So have I, and so have you - walk into a few bike shops early in the season and you’re done. Now, the notion that he’s cut up and inspected hundreds of frames, and even more so that he’s enough of an expert to understand what he’d see if he had...

Seattle Forrest

If so, that's a frightening indictment of the bike, car, sailing, and flight industries. I mean most of Boeing's planes can stay in the air ... they probably realized that the wind blows sideways sometimes. I know we're talking specifically about bike wheels, but the idea that Zipp, Enve, HED, and the rest all ignored common and obvious knowledge while making a crazy expensive racing product and testing it in the wind tunnel, until Hambini pointed it out ... seems unlikely.

DangerousDanR

I have been watching this thread and I thought I would add a couple oc comments. Take them for what ever.

1) Herr Doktor Sachin Hambini is as opinionated as many of the posters to this forum, and thus he will be controversial. He does have credentials to back up his claims about airflow which I doubt many of his detractors can match. That said, some of his opinions, like the idea that Campagnolo cranks have great bearings and then ruin the system with a horrid seal design, contradict my experience, but since I only have two Campagnolo CULT bearing crank sets (a Record and a Chorus), what do I know. I mean, mine don't seem to have the problem he was talking about. I also have the GXP cranks he hates, but mine are on threaded BBs which were not made by SRAM, so maybe I have missed the issues related to bearing size which he rightly criticizes, and I have used shims to set the bearing preload so I also avoid that issue.

2) Hambini knows a lot about air flow. He has worked designing control surfaces for high performance aircraft (AKA "fighter planes" AKA "targets" to some of us). He has also spent a fair amount of time doing wind tunnel testing of bicycle wheels and has published some of the results. This is a service to the bicycling world. If you don't like what he says about your favorite wheel brand, take a number and get in line. If I was willing to spend the money I would probably go get a set of the Swiss Side wheels he seems to like, but they are not worth the price to me. He has also made it plain that the biggest aerodynamic gains can be had by changing rider position or clothing or what ever. He also notes that for riders like himself, the gains from bicycle modifications are not going to be very great.

3) He has pointed out that there are frames which are making it through the quality control of some major manufacturers which do not meet their own specifications for BB concentricity and bore diameter. The diameter being out of spec is completely inexcusable. A set of "go/no-go" test fixtures should eliminate 100% of the bore size errors. The fact that he is seeing any of these raises a big concern.

The concentricity should be easily measured in a manufacturing setting, and if it is out of spec the frame should be reworked or scrapped. The fact that any frames as bad as the ones he gets make it out the door raises an issue about the quality control of those manufacturers. Any process that heats materials can result in deformation. The big problem may be that high volume manufacturers are testing straight from the mold or welding fixture without stress relief. Maybe Pole Bicycles has the right idea and aluminum frames should be carved from a billet

I once left a small company I worked for because the owner decided to ship an electronic product from a batch with a 25% initial turn on failure rate... that and the fact that I called him stupid made it impossible to continue working there. My current employer would scrap the whole batch and launch an investigation to find the source of the defective products, but we are a well known and highly respected brand in our field. The poor quality he has highlighted does indicate a problem with those brands.

Also, if you want to know how many catastrophic failures of bicycles happen, look at the Consumer Products Safety Commission web site for product recalls (https://www.cpsc.gov/Recalls/). I didn't see any Lynskey or Campagnolo. If you have a Specialized or SRAM you should take a look. Shimano did pretty well, except the little recall of a million cranks back in the 1990s. There is also the issue of the Hollowtech failures, but that is a different story.

4) He is correct that in theory all external bearing BBs are press fit, except maybe the Campagnolo which, since is an interference fit on the shaft and a looser fit in the cups might be classified as other.. All of my bicycles have threaded BBs. He is correct that the precision of the threaded BB is not going to be as good as a properly manufactured press fit. But they all can be good enough for the relatively low speeds involved in a bicycle BB if they are properly manufactured.

5) Dr. Hambini has made it very clear that the inspection of frames for voids is done by an outside test house and that he is stating their opinion about the serviceability of the frames. Also, on a very minor point, but they are inspected using ultrasound, not x-ray. These people are in the USA so I doubt that they are the firm he uses, but Ruckus Composites ( https://ruckuscomp.com/ ) claim to have inspected over 13,000 frames. I would expect that similar services exist in Europe who have also done thousands of frame inspections. One note on this: I have had a carbon seat post fail catastrophically and it was not fun. If I suspect any carbon fiber component it will get an ultrasound inspection, or be replaced without inspection based on cost.

6) Dr. Hambini tends to be a bit on the crude side. He claims that engineers are like that. That has not been my experience. We do, however tend to be very blunt.

Bah Humbug

He claims all that, yes. He really likes it when people trust him implicitly, and becomes hostile when asked for any documentation or evidence. He's also not "a bit on the crude side"; he is quick to personal attacks and quicker to claim racism over criticism. There's a critical difference between that and dropping the occasional FCC-disapproved word.

asgelle

Claims need to be backed up by verifiable data or analysis. The credentials of the person presenting them are irrelevant. Someone might not have finished high school, but if they present a hypothesis and then show credible results to support it, that is enough. Similarly, I don't care what credentials a person might have. If they show fabricated data or try to justify their conclusions through hand waving, ad hominem attacks, or appeals to authority, I won't believe them and just move on (though I might warn others to stay away as well).

guadzilla

^^^ This.

Guy's credentials have not been proven. What HAS been proven is that he lies and gets vindictive when challenged. Since most of his claims require you to believe in his credibility, you can see the issue there.

I dont really care too much about Hambini per se - he's a clown show. The reason i keep participating on these threads is that it offends me that this clown gets away with slandering companies and individuals by making unsubstantiated/unverified claims.

bikeforum142

As for aerodynamics ALONE it does seems he has the best aerodynamic wheel evaluation protocol and likely test bed. It is an Independent analysis but it seems he accepted the wheelset after previously criticizing independence of reviews of those that accept free products. Short of returning a product with some "rental" for use I don't know way for anyone to claim bias free product reports. Even a multiple funded testing concern such as Consumer Reviews can't achieve real independence.

noodle soup

The guy makes many claims, and can't back them up.

asgelle

It's always easy to construct imaginary experiments.

bikeforum142

Did they test under real conditions? and if they did would they want to tell us any negative results? of course not! They don't seem to follow thru on legalthreats to Hambini. He SAYS bring it on so at least if not more so reliable for me.

vespasianus

And with all of that, I am more likely to believe him than random people on these forums!

asgelle

At least that's better than the worst possible alternative, i.e., investigating and deciding for yourself.

noodle soup

They don't have much to gain from lawsuits. The guy has no money, and very few people see his "tests".

guadzilla

So you feel "saying 'bring it on'" gives him more credibility than providing ANY evidence that he actually conducted a test that would take up tens of hours of wind tunnel time and cost a LOT of money - something that even most magazines, with the exception of Tour, cannot do? Ok.

Second - the only person who claims Hambini has gotten lawsuit threats is Hambini. And that was the most laughably fake attempt at writing a legal letter. So you see why the guy has a credibility issue. And when challenged to provide info, he resorts to personal attacks. It amazes me that people actually think he has a shred of credibility.

Interesting - Hambini is not his real name. It is easy enough to find his real name and figure out that he is NOT an aerodyanmics expert nor is he employed by any aerospace company.

drewtk

A broken clock is right twice a day. Maybe Hambini has some good analysis, but I'm not going to sift through all of his crap to figure that out.

vespasianus

He is in the UK. Libel laws are very different. If they feel he has libeled them, that might be worth it.

noodle soup

all they can really do is shut him up. He has no money.

vespasianus

As I said, if they feel he has libeled them, that might be worth it.

Bah Humbug

Then the trufans would feel he was a martyr shut up by big bicycle for speaking the truth and keep repeating the nonsense.

noodle soup

few educated cyclists listen to him, so it’s not worth the legal costs to go through the court.