Luis G.

Steerer tubes have the compression ring inside which is why they're not crushed easily. The OP Video mentioned he sees crushed steerer tubes where slamming usually happens (several spacers on top) thus the stem is putting all the stress on the steerer tube instead of the compression ring.

If it's purely cosmetic, that's good to know.

WalksOn2Wheels

I keep meaning to watch this video at home, but haven't yet had a chance. But I have a feeling from the comments that this is a case of a very smart individual applying a very high standard from the aerospace industry to carbon bicycle frames. One point to consider is that aircraft are built to a VERY specific maximum load case as well as a life-cycle expectancy for both inspection and service intervals. There is pretty much zero room for error in aircraft manufacturing.

Bicycles are a different animal. They are often well overbuilt to receive stress under all normal riding situations for a vast array of riders. I think you could put a 300 pound guy on a mid level frame and just not even worry about it. most of the cycling population is going to range from 150 pounds to 250 pounds on the high end. Lots of high end manufacturers have been doing this carbon thing for a while and have a preferred method of layup to reduce any voids in the material. While they make a very good carbon bicycle frame, these processes would never pass muster under the eye of the FAA, but remember that aircraft maintenance shops can't even use regular bolts. They need to be approved for use in aircraft and they cost a LOT more than perfectly good bolts available at any hardware store. But we don't see videos of guys who used to work in the aerospace industry telling you that your cars are about to fall apart because they aren't using aerospace quality hardware.

TL;DR: Bicycles are not planes.

Luis G.

This reminds me of the servicing done on some fuel tanks. From what an old client explained the area where the sensors are requires a mandatory maintenance, and this means replacing bolts for the most part and checking of sensors.
These few bolts cost the company about $25~ however the maintenance time takes several days since the fuel tank has to be dismantled, recoated, and rebuilt.
There were more details but I forgot. Overall the service runs 70k, but almost none of the technicians ever want to do it since it requires working non-stop.

WalksOn2Wheels

Exactly. One of my co-workers was an aircraft mechanic and he often got the assignment of "tank rat" because he is a small guy. He hated it though. Told me one story where a guy ended up suffocating due to the odorless chemicals and they had to cut the wing open to pull his body.

And speaking of fuel tanks: An airplane is a vehicle that is built to such specific loads that it cannot land with a full fuel load because it will snap the wings off. So if a plane needs to do an emergency landing, it has to dump fuel before it is safe to land. Gee, I wonder why bicycle industry standards aren't held to these extremely high standards.

Luis G.

Yeah the client I had was pretty good to their team. They refused to do high risk jobs or botchy jobs, no matter the pay. So there had been incident free since they started.
At $800+ an hour for labor, many clients want rush jobs that involved high risks or skimping.

noodle soup

in many cases it is cosmetic, but not all cases.

He spoke of crushed steerers like it was very common, and in my experience it isn't very common at all.

jlax2485

He mentions in the video that the service life of the carbon parts on the aircraft are 25 years I believe. Imagine having a carbon bike frame for 25 years.

Bah Humbug

Aren't there 25-year-old carbon bikes?

noodle soup

I don't find that hard to believe at all with modern carbon frames.

Nearly all of the repairs we do are for damage from wrecks. Very few repairs are from manufacturing flaws. Part of that is because manufacturing flaws are usually handled by the manufacturer(but sadly not always). When someone brings us a broken frame, and we hear the JRA story, we recommend they contact the manufacturer. Usually the manufacturer handles the situation.

FTR very few of the frames we see are manufacturing flaws, and I can't remember one that was a catastrophic failure from JRA.

jlax2485

I don't doubt that there are carbon frames kicking around from 1991 and older, but those seem more like the exception than the rule, compared with how many vintage steel and aluminum frames are still being ridden.

Bah Humbug

Well that's not really a fair comparison, given how many steel, aluminum, and carbon frames were made 25 years ago. Total count doesn't matter.

jlax2485

Without some sort of statistics we will never know the proportion of actual carbon bikes made from that era which failed, compared to the proportion of steel/aluminum bikes. I take the guy in the video at his word, that older carbon bike frames, even from a few years ago are not nearly as well made as ones today. I have nothing against carbon at all...I ride a 16 year old CAAD frame and my next bike will most likely be built around a nice carbon frame.

Bah Humbug

The point is that the material lasts just fine, and a bike made out of anything is likeliest to be killed by a crash, not by degradation of the material.

noodle soup

that is a huge assumption.

noodle soup

Correct. Even the problems that old CF lugged frames had can be avoided now. There's no reason to build frames with aluminum lugs today, because there are better ways to accomplish the same thing.

Fiery

I guess what you wrote was not what you meant, but these are your exact words:

T700 and T800 are not the greatest quality carbon fiber and they're cheap.

The ultra high modulus carbon fiber he's talking about is the nutty expensive kind. I've seen it CNC'ed for airplane industry, it destroys steel router bits... You are talking about fiber strands, I was talking about the finished product.

The implication being that lower modulus carbon and the products made from it are intrinsically lower quality than higher modulus carbon and the products made from it.

And there's this exchange:

Me: Why talk about high modulus then, and why even bring T700 and T800 into the discussion at all, if you are not talking about fiber but about the finished product? By the way, saying that T700 and T800 are intrinsically "not the greatest quality carbon fiber" is still completely wrong.

You: Already mentioned I was referring to the sheets or finished product.

The only thing I can parse from this is that you are either saying that "high modulus" refers to sheets or finished product, or "T700 and T800" refer to sheets or finished product. Sorry if I'm misunderstanding, but I can only see what you write, not what you think.

jlax2485

I wouldn't call accepting the advice of a carbon fiber expert who at one point worked in the aerospace field a huge assumption. At the same time I'm not here to bash carbon fiber....if anything it's going to push me in the direction of buying a new carbon frame of bicycle instead of a used one.

Maelochs

It makes sense, as bicycle companies gained experience with the design, materials, and methods, the quality of the finished products improved---in fact it wouldn't make sense any other way.

Still the stresses on bike frames are so much lower than on airframes the kind of quality issues he mentions might not turn out to be problems for most riders---most riders probably don't stress their frames enough for voids to cause delaminations, etc. Seems CF frames fail either through hard crashes, or people overtorquing fasteners or not aligning the compression plug with the stem and crushing the steerer. Some of the old bonded frames separated but again ... brand new technology to those manufacturers at that time.

Older CF bikes were good enough, but the designs weren't as well suited to the materials, and the production techniques weren't worked out (he talks about the humidity of the layup room has to be controlled, for instance ...) Current CF bikes are a lot better (I would certainly hope) because of 25 years of experience. Future CF bikes are going to be amazing.

redfooj

Depends on how you perceive the magnitude of a "full fuel load".

Keep in mind for something like a 767, the fuel capacity is nearly equivalent to its operating weight.
Assuming heavy passengers, about 1000 additional passengersr.

Put another way, if a passenger sedan carried 20x more fuel than it normally does. Enough to drive half way around the Earth.

redfooj

Wings do not simply snap off if landed overweight. Damage could be to things like the landing gear. Or no damage at all (but for certain will require inspection).

They build high margins into load limits for good and obvious reasons. Youve probably seen the popular Boeing test videos - their wings surviving at 150% of designed limits. Most weights are conservatively established to err on the safe side during operations, but of course the tolerance has to be critical during manufacturing otherwise you can throw all these safety measures out the window.

BikingGrad80

One of the people I ride with has a very early Trek carbon with quill stem (obviously metal steerer) and 6500 group probably late 90's. It rode pretty nice though I think it spent most of that time unused in an attic.