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#11
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Bike Weight and Climbing Speed.
On Tue, 05 Jan 2021 08:22:35 +0700, John B.
wrote: Thus simply looking at the inside of the tubes with a "bore scope" really is not really a conclusive check as defects can actually be inside the body of the structure. But if a borescope reveals a fatal flaw, there is no need for the more-expensive test. -- Joy Beeson joy beeson at centurylink dot net http://wlweather.net/PAGEJOY/ |
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#12
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Bike Weight and Climbing Speed.
On Tue, 05 Jan 2021 01:32:46 -0500, Joy Beeson
wrote: On Tue, 05 Jan 2021 08:22:35 +0700, John B. wrote: Thus simply looking at the inside of the tubes with a "bore scope" really is not really a conclusive check as defects can actually be inside the body of the structure. But if a borescope reveals a fatal flaw, there is no need for the more-expensive test. True. But equally true that just because one couldn't see a defect doesn't mean that there isn't one. -- Cheers, John B. |
#13
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Bike Weight and Climbing Speed.
On Mon, 04 Jan 2021 21:55:58 -0800, Jeff Liebermann
wrote: On Tue, 05 Jan 2021 08:22:35 +0700, John B. wrote: One of the problems is that weak points in composite structures are frequently a matter of various layers of the fabric not being completely saturated with the adhesive and thus not adhering to the adjacent layers completely. To completely check the structure you will require something that can check the entire thickness of the structure and check it completely with no spots missed as even a tiny point with lower strength can result in a stress concentration point. Yep. However, I never suggested that a bore scope should be used as the sole method of inspection. It just happens to be a cheap and easy way to inspect the inside of the tube for damage. The choice between a zero dollar "tap test", a $10 borescope, or a $250 ultrasound inspection, is limited by the resources of the owner. If the bicycle has been in a crash, then the $250 test is probably the right choice. You have but one life to give for your bicycle ride. However, if it's just paranoia, suspicion, or preventive maintenance, the borescope is cheap and easy. And, I wasn't accusing you of anything. I was only trying to point out that simple checks might not find all defects. And, $250 seems like a lot of money, but if you compare it to the cost of the frame breaking and one breaking a hip as happened to me (although I fell off the bike didn't break) it could seem a mere pittance. Thus simply looking at the inside of the tubes with a "bore scope" really is not really a conclusive check as defects can actually be inside the body of the structure. Oh, you want conclusive. We'll, there's nothing more conclusive than a destructive test. Plug up all the holes in the bicycle frame and apply air pressure. Carbon fiber is very good in compression, but not so great in tension. I have no idea how much pressure it can survive, but a number should be available from the manufacturer. Apply something less that what is required for a catastrophic failure and look for cracks and bulges in the paint. If there are any internal imperfections, one should see a "blow out". If air pressure is insufficient, maybe fill the frame with water or oil and perform a hydro test. (Hydroforming is how aluminum frames are shaped.) If the destructive pressure test blows out a tube or a glue joint, thus precipitating an expensive repair job, the owner should thank the bicycle gods that he wasn't riding the bicycle when it failed. Yes, you could "pressure test" the frame but it wouldn't be a valid test of the entire frame as some sections of the frame will be of thinner material than others and thus a pressure low enough to NOT fracture the thin sections may not be sufficient to adequately test the thicker. If you are actually interested in Non Destructive Inspection, NDI, (sometimes's called to as Non Destructive Testing NDT-) of composites read https://www.aviationpros.com/home/ar...ection-methods for some basics. Apparently it is a very hot subject in the latest aircraft designs as if the composite fitting breaks you will likely end up with more then a broken hip :-) -- Cheers, John B. |
#14
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Bike Weight and Climbing Speed.
On 1/5/2021 12:32 AM, Joy Beeson wrote:
On Tue, 05 Jan 2021 08:22:35 +0700, John B. wrote: Thus simply looking at the inside of the tubes with a "bore scope" really is not really a conclusive check as defects can actually be inside the body of the structure. But if a borescope reveals a fatal flaw, there is no need for the more-expensive test. +1 -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 |
#15
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Bike Weight and Climbing Speed.
On Monday, January 4, 2021 at 5:22:42 PM UTC-8, John B. wrote:
On Mon, 04 Jan 2021 10:47:14 -0800, Jeff Liebermann wrote: On Mon, 4 Jan 2021 10:07:25 -0800 (PST), Tom Kunich wrote: `Wrinkles may or may not be a problem. The real problems are voids and you have to have a lot of experience with the position and placement of voids to be able to know whether they are a threat or not. Buying the improper tool - a scope instead of an ultrasonic scanner, makes little sense. From 2016: "Why isn’t the bike industry scanning composites for flaws?" https://www.bikebiz.com/why-isnt-the-bike-industry-scanning-composites-for-flaws/ CT scanning is faster while ultrasound is cheaper. Only £400,000 for a CT scanner. No clue on the price of an ultrasound scanner. A $10 borescope or endoscope certainly has its limitations, but methinks sufficient for finding really gross problems. I don't do CF so I don't know what's involved, but the borescope was rather handy for inspecting welds and repairs on steel and aluminum frames. From 2020: "Ruckus Composites Inspects Thousands of Bikes with One Ultrasonic Thickness Gage" https://www.olympus-ims.com/en/insight/ruckus-composites-inspects-thousands-of-bikes-with-one-ultrasonic-thickness-gage/ https://www.olympus-ims.com/en/45mg/ Only $2,400 ea: https://www.ebay.com/itm/Olympus-Panametrics-45MG-Ultrasonic-Thickness-Gage-w-D7906-SM-Transducer-Gauge-/353320469558 Maybe you can take up a collection among the local CF riders and share the expense? One of the problems is that weak points in composite structures are frequently a matter of various layers of the fabric not being completely saturated with the adhesive and thus not adhering to the adjacent layers completely. To completely check the structure you will require something that can check the entire thickness of the structure and check it completely with no spots missed as even a tiny point with lower strength can result in a stress concentration point. Thus simply looking at the inside of the tubes with a "bore scope" really is not really a conclusive check as defects can actually be inside the body of the structure. -- Cheers, John B. Perhaps you should cease showing your vast unknowledge of carbon fiber construction methods? They use "prepreg" which is all uniformly coated with the resin. |
#16
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Bike Weight and Climbing Speed.
On Tuesday, January 5, 2021 at 5:28:20 AM UTC-8, AMuzi wrote:
On 1/5/2021 12:32 AM, Joy Beeson wrote: On Tue, 05 Jan 2021 08:22:35 +0700, John B. wrote: Thus simply looking at the inside of the tubes with a "bore scope" really is not really a conclusive check as defects can actually be inside the body of the structure. But if a borescope reveals a fatal flaw, there is no need for the more-expensive test. +1 Do you expect Joe Bike Rider to be able to tell a fatal wrinkle flaw simply by it being there as opposed to it being in a critical area which most people wouldn't even be aware of? |
#17
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Bike Weight and Climbing Speed.
On 1/5/2021 11:01 AM, Tom Kunich wrote:
On Monday, January 4, 2021 at 5:22:42 PM UTC-8, John B. wrote: On Mon, 04 Jan 2021 10:47:14 -0800, Jeff Liebermann wrote: On Mon, 4 Jan 2021 10:07:25 -0800 (PST), Tom Kunich wrote: `Wrinkles may or may not be a problem. The real problems are voids and you have to have a lot of experience with the position and placement of voids to be able to know whether they are a threat or not. Buying the improper tool - a scope instead of an ultrasonic scanner, makes little sense. From 2016: "Why isn’t the bike industry scanning composites for flaws?" https://www.bikebiz.com/why-isnt-the-bike-industry-scanning-composites-for-flaws/ CT scanning is faster while ultrasound is cheaper. Only £400,000 for a CT scanner. No clue on the price of an ultrasound scanner. A $10 borescope or endoscope certainly has its limitations, but methinks sufficient for finding really gross problems. I don't do CF so I don't know what's involved, but the borescope was rather handy for inspecting welds and repairs on steel and aluminum frames. From 2020: "Ruckus Composites Inspects Thousands of Bikes with One Ultrasonic Thickness Gage" https://www.olympus-ims.com/en/insight/ruckus-composites-inspects-thousands-of-bikes-with-one-ultrasonic-thickness-gage/ https://www.olympus-ims.com/en/45mg/ Only $2,400 ea: https://www.ebay.com/itm/Olympus-Panametrics-45MG-Ultrasonic-Thickness-Gage-w-D7906-SM-Transducer-Gauge-/353320469558 Maybe you can take up a collection among the local CF riders and share the expense? One of the problems is that weak points in composite structures are frequently a matter of various layers of the fabric not being completely saturated with the adhesive and thus not adhering to the adjacent layers completely. To completely check the structure you will require something that can check the entire thickness of the structure and check it completely with no spots missed as even a tiny point with lower strength can result in a stress concentration point. Thus simply looking at the inside of the tubes with a "bore scope" really is not really a conclusive check as defects can actually be inside the body of the structure. -- Cheers, John B. Perhaps you should cease showing your vast unknowledge of carbon fiber construction methods? They use "prepreg" which is all uniformly coated with the resin. In theory. But just as aluminum sand castings can have serious structural voids, fiberglas or carbon layups can be done both well and badly. Trek even owns a trademark on the acronym 'OCLV': http://tmsearch.uspto.gov/bin/showfi...805:68wqot.2.1 Which stands for Optimum Compaction Low Void. Hmm. Not zero voids, just fewer or smaller... -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 |
#18
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Bike Weight and Climbing Speed.
On Tue, 05 Jan 2021 01:32:46 -0500, Joy Beeson
wrote: On Tue, 05 Jan 2021 08:22:35 +0700, John B. wrote: Thus simply looking at the inside of the tubes with a "bore scope" really is not really a conclusive check as defects can actually be inside the body of the structure. But if a borescope reveals a fatal flaw, there is no need for the more-expensive test. If a flaw is found, and the owner decides to have the CF frame repaired, there's no guarantee that there are no additional defects in the frame. The problem with visual inspection is that it's effectiveness is highly dependent on the abilities of the inspector. In the distant past, I designed marine radios. I could see production defects with little more than a quick glance. Then, a real inspector arrived and showed me what I had missed. With a machine inspection, most of the limitations of the inspector are removed. There is still some interpretation of the results needed, but it's much less than what a visual inspection would require. It's like a doctors diagnosis. Much can be learned by a superficial inspection or probing with a stethoscope. However, if you want detail and a higher confidence level, an X-ray, CT scan, blood test, etc is needed. The problem with any form of testing is that it's really easy to demonstrate that something is unsafe. All it takes is one minor defect or potential problem and the bicycle is instantly declared to be unsafe to ride. However, it's also impossible to demonstrate that something is 100.0% safe to ride. One can run every test and perform every manner of inspection, and still not be certain that bicycle is rideable. Nothing is prefect. In QA (quality assurance), the standard measurement of that uncertainty is the AQL (acceptable quality limit): https://insight-quality.com/what-is-aql-and-what-do-you-need-to-know-about-it/ Basically, it's how many defects a manufacturer is willing to tolerate, how much inspection is necessary to achieve it, and what manner of sample size is necessary to obtain a valid AQL percentage. Ignoring the inevitable debate over what is an acceptable AQL for your bicycle, I should point out that few production bicycles are inspected 100%. Therefore, besides crash damage, the bicycle owner runs the risk of riding a shiny new bicycle with built in defects. Want to lower the risk? Just add $250 to the cost of a new bicycle, buy from a custom frame builder, or do your own $10 inspection. A borescope inspection will probably only catch major defects, but it's better than ignoring the problem or blindly trusting the manufacturer. Pressurizing the frame and looking for air leaks might be amusing. It's not a replacement for a proper ultrasound inspection, but it's a good start. One idea that I posted to RBT in the distant past was to mold conductive wires between the CF layers and measure the resistance (electrical conductivity) between the wires and between the ends of the tubes. If measured and recorded when the frame is new, any changes in resistance will indicate cracking or delamination. For an extreme case, the thin wires should break before the tube collapses. With a sufficient number of wires, the general location of the defect could be found. It wouldn't take much to make a measurement. Some electrical contacts on the surface of the various tubes, a digital ohmmeter (about $50), an a chart of the resisances when the bicycle was new. -- Jeff Liebermann PO Box 272 http://www.LearnByDestroying.com Ben Lomond CA 95005-0272 Skype: JeffLiebermann AE6KS 831-336-2558 |
#19
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Bike Weight and Climbing Speed.
On 1/5/2021 1:52 PM, Jeff Liebermann wrote:
Ignoring the inevitable debate over what is an acceptable AQL for your bicycle, I should point out that few production bicycles are inspected 100%. Therefore, besides crash damage, the bicycle owner runs the risk of riding a shiny new bicycle with built in defects. Want to lower the risk? Just add $250 to the cost of a new bicycle, buy from a custom frame builder, or do your own $10 inspection. Um... buy from a custom frame builder? I'm the guy who bought a tandem from a custom frame builder, Jim Bradford. Instead of tandem gauge fork blades, he used fork blades designed for track racing, with 1/3 the wall thickness. Granted, they lasted for over 25 years, but I was still hugely disappointed when they suddenly fractured. Perhaps "buy from a custom frame builder who is honest and who is not rushing to complete the bike before his honeymoon." -- - Frank Krygowski |
#20
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Bike Weight and Climbing Speed.
On Tue, 05 Jan 2021 12:12:54 -0600, AMuzi wrote:
On 1/5/2021 11:01 AM, Tom Kunich wrote: On Monday, January 4, 2021 at 5:22:42 PM UTC-8, John B. wrote: On Mon, 04 Jan 2021 10:47:14 -0800, Jeff Liebermann wrote: On Mon, 4 Jan 2021 10:07:25 -0800 (PST), Tom Kunich wrote: `Wrinkles may or may not be a problem. The real problems are voids and you have to have a lot of experience with the position and placement of voids to be able to know whether they are a threat or not. Buying the improper tool - a scope instead of an ultrasonic scanner, makes little sense. From 2016: "Why isn’t the bike industry scanning composites for flaws?" https://www.bikebiz.com/why-isnt-the-bike-industry-scanning-composites-for-flaws/ CT scanning is faster while ultrasound is cheaper. Only £400,000 for a CT scanner. No clue on the price of an ultrasound scanner. A $10 borescope or endoscope certainly has its limitations, but methinks sufficient for finding really gross problems. I don't do CF so I don't know what's involved, but the borescope was rather handy for inspecting welds and repairs on steel and aluminum frames. From 2020: "Ruckus Composites Inspects Thousands of Bikes with One Ultrasonic Thickness Gage" https://www.olympus-ims.com/en/insight/ruckus-composites-inspects-thousands-of-bikes-with-one-ultrasonic-thickness-gage/ https://www.olympus-ims.com/en/45mg/ Only $2,400 ea: https://www.ebay.com/itm/Olympus-Panametrics-45MG-Ultrasonic-Thickness-Gage-w-D7906-SM-Transducer-Gauge-/353320469558 Maybe you can take up a collection among the local CF riders and share the expense? One of the problems is that weak points in composite structures are frequently a matter of various layers of the fabric not being completely saturated with the adhesive and thus not adhering to the adjacent layers completely. To completely check the structure you will require something that can check the entire thickness of the structure and check it completely with no spots missed as even a tiny point with lower strength can result in a stress concentration point. Thus simply looking at the inside of the tubes with a "bore scope" really is not really a conclusive check as defects can actually be inside the body of the structure. -- Cheers, John B. Perhaps you should cease showing your vast unknowledge of carbon fiber construction methods? They use "prepreg" which is all uniformly coated with the resin. In theory. But just as aluminum sand castings can have serious structural voids, fiberglas or carbon layups can be done both well and badly. Trek even owns a trademark on the acronym 'OCLV': http://tmsearch.uspto.gov/bin/showfi...805:68wqot.2.1 Which stands for Optimum Compaction Low Void. Hmm. Not zero voids, just fewer or smaller... Yes they trademarked a term, not a process. The actual process comprising "optimum compaction" and "low voids" probably dates back to the Cooper race cars of the 1960's. -- Cheers, John B. |
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