billridesbikes

But we do know what a bottom bracket spec itself should be, it is well published. It is 41.960mm- 0.025mm. Manufactures need to be within this range to be in spec.

If we look at Hambinis own data from why is our bottom bracket creaking he shows a plot at 2.10 of his BB shell measurements from a bunch of different frames. First, from a data analysis stand point, Excel is not a good platform for this type of data. If you can’t afford a good statistics package any engineer can create one using R or Python with open source platforms. Second, he has the so called ideal at 41.96 to 41.98mm which would make the shell spec tighter than the BB spec itself, but where this ideal range comes from isn’t explained well. Is it a proprietary thing Hambini discovered for optimal operation of his BB. We don’t know.

Third, Because no statistical results are supplied (it’s a PITA in Excel) it appears the BB shells here from different manufacturers are likely statistically the same, but we don’t know for sure because because no anova is shown and we don’t have the raw data. But because all manufacturers are producing BB shell with an IQR of less than 0.04mm and the body of the boxes all overlap there are probably no out of spec frames in this dataset and all manufactures are probably the same. Only looking at the IQR here because boxplot whiskers can represent different things depending on the software and method and may or may not represent any actual data, no outliers are shown on the plot.

Just because a manufactured good costs $4K only means the process is designed to make a quality product at that price point. What quality means is meeting customer expectations. I think you could make at $40K frame with 10X better reliability and 10X better tolerances, but that doesn’t mean you’re manufacturing something that anyone would pay money for if the current 4K frame are meeting customer expectations. One would soon be bankrupt. In a similar manner you would not spend $10 per frame to inspect every frame if you expect only 1 out of every 10000 to be have a big enough problem to be OOS. You would be spending $100000 to fix maybe a $10000 warranty issue, frustrating for the customer yes, but likely you only sample a few frames to ensure the process is running in spec. Too many 100% inspections in the manufacturing process and you are also soon bankrupt because someone else will have a better process, sample inspect, and sell generally a better product for less than you. This is the same of all manufactured goods, even luxury car makers with 6 figure price tags have the occasional lemon.

Anyways just keep in mind Hambini is making informercials that help his company, duh, so view his channel from that angle. It is presented to help sell his products.

tyrion

I must say I disagree with Hambini's proposal that bad engineering be punished with castration. I think that's too severe.

u235

A car has probably 10000+ parts. A bike frame is exactly 1 part. We are not talking about a bike frame from a bike at Walmart where the whole bike is 1/20th of just these frames or an Alibaba frame for $120. You set the bar at $40K or 300x times the cost of others before you'd expect someone does QA for something so basic? I refuse to make excuses for a company because that is the way it is.

asgelle

You really have no sense of what even a monocoque carbon fiber frame comprises. I assure you there’s more than one part as even a cursory look will show.

u235

Wow, in the big scheme of things, some people really think a bike frame is some marvel of engineering and manufacturing. Regardless of our opinions on that... My point is it would take 30-60 seconds to verify the entire thing it is built to tolerances in the bearing areas and aligned correctly before it went out the door and something that should be done on something marketed as it is to the professional and sold at that price level. Do it at the outsourced facility where they are made or when they arrive at their facility.

AnkleWork

You sure do know a lot about modern QA/QC science. And you sure do know a lot about the history and condition of the props that guy uses in his hype (and about his honesty).

u235

When did I claim anything about either of those? A lot of 2+2=5. Thinking a company should do some QA on a very expensive part that costs that much is what I claimed. Nothing more. Apparently a few basic measurement would cost a hundred or a few thousand dollars more per frame according to some people here. Talk about hyperbole.

asgelle

Perhaps here where you expressed a detailed knowledge of how much time it takes to verify requirements.
Or here where you express an expert opinion on the cost of QC.

Racing Dan

Funny how ppl that have no real knowledge thinks its rocket science verifying basic tolerances. It is what goes on in every machinist shop every day and it doesnt take long or cost a fortune*. I used to be one, i should and do know and Hambini is absolutely right calling them out for the hacks they are.

*The real cost is discarding the out of spec products that someone just spend an hour or more manufacturing.


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WizardOfBoz

When you think of it, if you make a bike with a bad fork, and it breaks in the wrong (i.e. worst) way, you are punishing the customer with castration.

Chris Titus is a comedian who talks about the lay people of the RC church getting fed up with lack of apparent action or accountability with respect to child molestation. His imaginary solution was pedophile crucifixions. So in the announcements: "The pedophile crucifixions will take place this Friday. We'd like to thank the DeNunzio Brothers construction company for the loan of the industrial nail guns". The point it, its easy to write pretty hyperbolically vengeful stuff on a forum (or, manifestly, if you're a professional comedian).

u235

You interpret those as me claiming to be an expert? Ad Hominem.

asgelle

I took you at your word when you claimed you knew what you were talking about (implied by posting); I'll take you at your word now when you say you don't have a clue.

u235

I must have missed the posts in this thread where someone gave insight into why or how it takes a lot longer and checking a bearing surface and alignment is an extremely difficult task on a bike frame compared to anything else with bearings and alignments. There is a grand total of two, the headset and the BB. Even for a company that specializes in making high end bike frames. Is that just common knowledge?

WizardOfBoz

Aside from the flame wars (cheese and crackers, guys, give it up. No one's attacking you. The argument you are pouring passion into DOESN'T MATTER. Go for a ride!), I had one other observation.

The point pertains to the question Who is Hambini's target audience? Some adult bikies will tolerate 29 minutes of crude language for the one minute of useful stuff. I suspect that Hambini's target audience is the young male bikes who want to be part of the group of "Cool Kids". That is, in their mind, the group of people that know the deep knowledge, along with the secret handshake. To them, the 29 minutes of crude language is not a turn-off, its part of the appeal. Perhaps the heart of the appeal.

When I think about the videos, I think that those of us who are mature and are watching them for the bike info tolerate the crudity and logorrhea, and will think Hambini a bit of an immature jerk. But if Hambini's goal is to attract 12-17 YO bikie zealots, then his videos make sense. I mean, the bike he fixed was a kid's bike (they actually sawed down the crank arms to give a crank length that would allow the kid to ride). Maybe that demographic is his target market, and we ... ahem.. "mature" folks are just collateral damage?

davidad

Yes.

Duragrouch

What matters is that the BB is aligned in angle fore/aft and up/down, and position laterally, so the crank axis is not off. Also, the threads want to be aligned square so that the bearings are the same tightness all the way around. However, a cartridge bottom bracket eliminates the latter concern, as along as it is able to screw in.

Tight tolerances are good, but sometimes unnecessary. A conversation I had years ago with a technician at work:

Me: I'd like closer tolerances.
Him: It meets spec. If spec wasn't good enough, it wouldn't be spec.
Me: You're right.

AnkleWork

And you have excellent reading comprehension and critical thinking skills.

u235

You're going down the list of the common fallacies in your quest.

WizardOfBoz

If the bearings go directly into the frame then the lateral misalignment would cause higher friction, premature bearing wear, and possible premature frame damage from the increased stress. If you shoved a BB in their that was aligned, then the only issue is that the chainring is't parallel to the chainline and cogs. I think Hambini's fix was appropriate in getting the crank lined up right (but, as I say, why would you fix a defective bike?).

Regarding specs, your point is excellent. Novice engineers often spec things out to +/- 0.001" (or 0.02 mm), rather than saying "Size nominal, use of shop tools with nominal sizing acceptable". One way to explain it to newbies is to tell them to replace every digit in the tolerance specification with a dollar sign: +/-0.001 is $$$, 0.01 is $$ and so forth.

smashndash

I agree with everything you said except this. He states in the video that the frame is probably not hazardous. It’s more of a performance issue - and it shouldn’t be, for the extravagant prices that these companies charge.

AnkleWork

Which fallacy would that be? (And please guess my quest -- you'll never guess.)

davidad

Bad engineering killed 15 people in an explosion in Texas City. So his punishment might not be enough.

tyrion

That's more like bad management. Castration of BP executives might be acceptable.

guy153

Two bearing surfaces but it's also worth getting the seat tube diameter right. Maybe that's why they often have those weird "aero" posts these days, to save machining the seat tube.

No expense is spared on the latest Cervelo frames however which actually come with their own built-in metal head-tube reaming tool:

CycleryNorth81

Looks like that those 2 frames passed the QC test but failed the common sense test.