Bike to Work Conflict

Last week, during “Bike to Work” week, I received the email shown above from the North Central Texas Council of Governments.

I’ve received a number of such items from time to time, but this time, I pondered the matter a little, and THAT caused me to wonder about things. For example, what is the cutoff between “regular” and “older” adults? Are “older” adults that ride their bikes to work supposed to stop, heeding the direction to limit outside activity or are they supposed to ride their bikes in order to cut air pollution? Or are they only supposed to do that until they pick up one of the lung disorders cited? Will Fort Worth have a “moment of silence” for the cyclists that aren’t at the “Bike to Work” event because they followed the advice to limit their outside activity? What about people that have to WORK outside? Are they simply supposed to take vacation? Actually, I asked the“tryparkingit” lady at the event, and she was well aware of the conflicting advice. She took my queries in stride, and I found that air pollution alerts come in “watch” and “warning” levels just as tornado alerts do. A “warning” is much more serious. Their email advice in future omits the encouragement to bike or walk on “warning” days. To my mind, this seems like a negative feedback loop. When it pollutes, you have to pollute when you wouldn't normally. Seems sort of topsy turvy to me. How about - when it is polluted, everyone takes the day off without pay. Maybe motorists would appreciate cyclists more when they get to go back to work. Nah, call me a dreamer!

Bottom line – This is a classic governmental conflict between a short-term event and long-term advice. After all, I think few of us would volunteer to simply stop breathing during the duration of one of these events. Probably fewer of us will consider that the items advised do not affect many major sources of local air pollution. Certainly cars make a lot of smog, but the same government that wants us to “drive less” encourages more driving by building more freeways and other highways that encourage people to drive more and further. Few politicians will make useful suggestions about what local governments can or should do to avoid such events in the future. Instead, we’re told to “limit outdoor activity.” And campaign promises promise cheaper gas. So the cycle continues.

On a more positive note, I got some "Air Quality Index Crayons." Read the description on each.

Carbon Lacks Luscious Lugs

In the Olden Days, a Quality Bicycle Had a Lugged Frame and Reynolds "531" Tubing

In past “Carbon” articles, indexed here, characteristics of carbon, such as its low density and ability to be tailored, were highlighted along with many elements that present challenges to the designers and users of carbon bikes. If you weren’t reading carefully, you might have concluded that people should just stick with steel and avoid all those ways things can go wrong. You’d be wrong.

There remain many people devoted to steel bikes. Locally, in the DFW Metroplex, Southwest Frameworks will build you a custom steel frame made to the highest workmanship standards (they have a lot of good photos showing the process at their website). Indeed, I grew up under the influence of Eugene Sloane; believing that any good bike was lugged, while one with Reynolds “531” double butted steel tubing was a bicycle aristocrat. When Sloane’s book was published, my 1967 Jaguar XKE came without air conditioning or power steering, the windows went up and down via a winder, and side mirrors were an extra cost option. Nobody had heard of cassette tapes, much less MP3 or satellite navigation. Unlike less sporting cars, Jaguar had special mounting points for anyone wanting to install shoulder belts.

Reynolds Had it all. Even the Russians Used it in Their Track Bikes. Note How Sloane Spells "Columbus"

That was then. Things have changed.

Nowadays, steel remains an excellent material to make heavy bicycles from, particularly when the manufacturer wishes to avoid investing in facilities capable of competitively building high performance machines. That fact is the main reason why cheap bikes, like the Chinese Flying Pigeon, universally use steel frames. A traditional steel frame will weigh four pounds or more (sometimes MUCH more), compared to three pounds for aluminum, while a high end carbon frame weighs in closer to 2.5 pounds, and a few weigh even less. With modern analytical methods, the ride of steel can be closely matched, or improved on, with either aluminum or carbon. Certainly, if identical components are used, the steel bike will only weigh 2 pounds more than its carbon counterpart, but that is a world of difference for a performance bike, and particularly for a lightweight, high end bike, since most of the cost is in the components.

On the other hand, if you are looking for a utility bike, and plan to load it with accessories, 2 pounds is a minor consideration. In such a bike, esthetic considerations, such as lugs, may or may not be important to you, along with such creature comforts (all of which add even more weight) as double legged kick stands, chain cases, and internal gears. In these cases, the steel frame becomes more than just a material, it becomes part of the total bike experience, and those lugs on steel frames ARE luscious.

I still ride steel framed bikes where speed performance is secondary. Frankenbike was partly chosen for its combination of Reynolds tubing and lugwork, combined with its low cost. As I said, I like steel bikes, but remember I also like vintage Jaguars. I will probably always keep a steel bike around, just as I keep the Jaguar E type. Aluminum and carbon are the real present and future of fine bicycles, and designers are still learning how to exploit the full potential of each of these materials that have passed steel by. Nowadays, bikes such as the Gary Fisher Simple City and Civia Hyland are made of aluminum.

By the way, the 1967 Jaguar E type also used Reynolds “531” steel tubing, unlike new Jags which use aluminum. Aristocrats may be fading relics of the past, but they’re still proud.

The Front Subframe of Jaguar E types Used Reynolds "531" Tubing, Just Like Raleigh and the Schwinn Paramount

Carbon Bike Proof Testing – Part 2

Cervelo Carbon Fork, After Failing Impact Test - from Wikimedia Commons, here

The Impact in this Case Was With a Garage While Being Carried on the Roof of a Car

REAL WORLD EXAMPLE –CARBON NON SUSPENSION FORK

Picking a component at random, the carbon fork seems like a good subject as an example case study. It is expensive enough to be worth a little effort to save if its integrity is in question. It is critical enough that you could be hurt badly if it unexpectedly failed at an awkward moment (inconveniently, that is the time it is most likely TO fail). It is comparatively simple to test, since the only places loads get applied are at the dropouts and at any bosses where brakes or racks are attached. The dropouts are the critical load application point unless those bosses are badly damaged to the point that a proof test is not needed anyway.

At this point, I’ll refer to EN 14781 because it seems more cyclist oriented to me than its CPSC counterparts. I would not infer from that statement anything at all, either in favor or against either standard. Anyway, EN 14781 defines the following conditions for bike forks:

Impact Test – Paragraph 4.8.2 – This paragraph is intended for a complete bike/fork assembly, so you wouldn’t normally use it just to test a fork. It is also a difficult test to perform at home without collateral damage.

Fork Clearance Test – Paragraph 4.9.3.2 – This paragraph is more applicable to suspension forks, but it will assure that your carbon fork won’t collapse as you ride along without heavy braking being involved. The standard requires an ultimate load of 2,800N (630lb). An appropriate proof load for this would be 420lb. If you were to apply the load to the single leg of the fork that has the damage, this would be 210lb. Be careful to align the load and stabilize the fork so it doesn’t go flying across your shop.

Fork Tension Test – Paragraph 4.9.3 – This paragraph is one that I’d dispense with. In the real world, you are NOT going to be pulling on your fork unless some gremlin has nailed your front wheel to the ground!

Fork Bending Test Schematic from EN Standard

Fork Bending – Paragraph 4.9.4 – This paragraph is one that is VERY relevant to you. Your fork must be able to withstand the bending imposed by braking and potholes, not to mention when those are combined with stuff like potholes. Here, the ultimate load recommended by the standard is 1200N (270 lb). 2/3 of this load would give you a proof load of 180lb. I imagine most of you know someone of about this weight. To actually apply the load, the thing I would be most concerned with would be to avoid damaging the steerer or the head bearings. Carefully support the upper end and then apply the load. I would recommend having the load tester bounce several times on the dropouts to verify that the fork is sound (don’t have them actually jump up and down). When you are done, make sure that the fork is not bent due to the load. If there IS any set, it is probably due to something in the upper end and you must take care of that, but your carbon is OK. For those that are engineers (or architects), please note that the “bending” test in the standard is not a pure bending test. It is actually a combination of shear (the 1200N) and bending, which is dependent on the length of the fork. In this case, the actual bending is the shear times the length measured from the dropouts. If you REALLY wanted to do a fancy schmancy (is that spelled right?) test, you could change the angle of the load to get a combined compression and braking with bending, but the standards people didn’t think of that!

Fork Impact Test from EN Standard

Fork Impact – Paragraph 4.9.5 – Another one that is VERY relevant to you. I haven’t rigorously compared this to the fork bending test, but basically it involves dropping a 50lb weight from a height of 28 inches. Paradoxically, if the fork were metal, the drop height would be only 16 inches. I have a strong suspicion that this test is more severe than the static bending test since the standard allows a greater permanent set than for that test. If I were doing this test, I’d brace the fork upper end and “known to be good leg” firmly against movement and twisting, and then drop 25lb from a height of 16 inches onto the dropout of the fork leg with suspected damage. Actually, I’d do it a bit differently. I’d tie weight to the dropout with wire of the right length, and drop it from the fork. That would avoid the possibility of damaging the dropout.

Fork Bending Fatigue – Paragraph 4.9.6 – This is basically the same test as the static bending except the load is only 620N (130 lb) which is basically half of the load noted above. I’d suggest that a 130 lb load would also be a sensible and standards-based alternate to the 180 lb load derived from the static bending test. Actually, I’d go simpler yet, and suggest that you just get someone that weighs somewhere between 130 and 180. Have them bounce several times just to make sure. If you feel more daring, get someone a bit heavier. DO NOT PERFORM THIS TEST WITH THE FRONT FORK HANGING OVER A PIT OF BOILING OIL! If it breaks, the tester getting injured would show “bad form.”

CASE STUDY WRAPUP
Basically, all this translates into two fairly simple tests. Have someone bounce on the dropouts with the upper end securely supported, and drop a weight with things securely supported. If you want to be extra cautious, take the wheels off and find the heaviest person you know to weight the front fork in compression. IMHO, this is something entirely practical for a cyclist to do in order to confirm his/her front fork is not about to do something really ugly.

Carbon Bike Proof Testing – Part 1

Cycler has a VERY Apropos Sense of Humor!

Presuming that you have decided that the damage to a carbon bike component is enough that you don’t want to just take the chance that everything will be OK (Choice #1 or Doohickie’s Choice #5), but it doesn’t warrant spending $300 for a repair, you now face “Choice #3.” At this point, my own past aircraft carbon experience is irrelevant. Fortunately, the path to validation by test is very similar whether one is talking bikes, planes, trains, or automobiles. The following information is not especially complex, but there is a LOT of information and so you may want to print this off and absorb things slowly.

This Article Came out Around February, Raving Over a New Carbon Bike, Using a Truss

That article didn't mention the race experience. For that, go HERE

No need to proof test THAT bike! PS: The rider wasn't seriously hurt

STRENGTH

You are not entirely on your own. While bike manufacturers do not make strength specifications readily available for their products, basic information can be obtained, and used as a basis for validating that the component is reasonably safe. This information is publicly available. Two major sources are the US Consumer Products Safety Commission and the European Committee for Standardization. Any bike sold in the US must meet the first set of requirements, and it’s likely that anything sold by a major manufacturer will meet both sets.

CPSC Bike Regulations (These are Code of Federal Regulations, Title 16, Part 1512)

ASTM Bike Standards (these cost money to get copies)

EN 14781 (for Racing bikes. EN 14764 is the equivalent for city and trekking bikes)

COMPONENT TEST APPROACHES

Frame – Normally, unless it is a “low end” carbon frame, I suggest repair. Properly done, a carbon repair can completely restore the strength of the frame, and you may have difficulty even being able to tell the difference from an undamaged frame. If you are doing a home repair, I suggest a proof load to validate the strength. The specifications give methods of accomplishing this proof load.

Front Fork – If damage has actually thrown your front fork out of alignment, perhaps by bending of a metal steerer, that should be corrected before testing. If you can’t get the fork straight, get a new one. I also suggest that this test is best conducted with the fork removed from the bike, and the loads reacted by blocking up the steerer, so that you do not damage bearings, the steerer, or the frame during the test. Because carbon front forks are ubiquitous nowadays, I have picked the front fork as a proof test case study  and it will be part 2 of this post.

Seat Post – I suggest this test be performed using a seat tube that you do not require for riding afterwards. It need not be a high quality seat tube, just the right diameter.

Handlebars – I suggest this test be performed using a stem you do not require for riding afterwards. It should be noted that stem choice can affect handlebar test results.

COMPONENT TEST GENERAL PROCEDURE
Obtain a helper of sufficient weight to obtain the desired proof load. You may achieve this artificially by clever addition of free weight such as provided by barbells, pulleys, or other means of load amplification. In almost all cases, the “human scale” of a bike means the loads are also “human scale.”

Apply proof load. Note any “popping sound,” or any sharp “crack.” The first is an indication that you have loaded the part more than it has been loaded during riding, or during manufacturer actions. This is not necessarily bad. That is part of the point of the test. The “pop” likely is due to resin cracking that is not structural. A “crack” may or may not be serious. Regardless of any noise, or of no noise, the next step is identical.

Remove proof load. Check to ensure that the part is back at the starting position and that it is visibly unchanged.

Reapply proof load. If all is well, you will not hear noises the second time around. If the sounds are worse than the first time, that is not a good sign.

Repeat the cycle for a total of at least a half dozen load applications. Carefully reinspect, and if it passed, reinstall and know that your carbon component meets reasonable strength levels. Just to be safe, I’d also get some wet layup resin, or even a bit of clear fingernail polish, if the damage is small, to touch up and stick down any exposed fibers. While this isn’t really structural, it does help stabilize everything and makes it look a little prettier.

DESIGN VERUS FATIGUE VERSUS ULTIMATE LOAD AND YOUR PROOF LOAD

ULTIMATE LOAD – BANG!
The CPSC and European standards are loads below which stuff is not allowed to actually break or get bent beyond limits they pick somewhat arbitrarily. The tested component need not be fully usable afterwards. This should be considered as “ultimate” load for the standard in question, though the standard doesn’t really match up with the traditional definition of “ultimate” as the breaking load. Clearly, there is no point testing your bike component if you cannot use it afterwards. This quandary is part of what differentiates “design” loads from “ultimate” loads. The first is the maximum load the component should see in normal service and normal service shouldn’t permanently bend things. The second is the minimum acceptable failure load.

DESIGN LOAD
While the standards do not directly provide information on the design loads, aircraft use a 1.5 factor between “design” and “ultimate.” This means the “design” load is 2/3 the “ultimate” load. Conveniently enough, for metal structure, this is enough of a factor to ensure that permanent set is minimal for “design,” while avoiding excessive weight to achieve the “ultimate” strength.

FATIGUE LOAD
The bike standards also provide fatigue loads for some components. In the standards, they’ll typically specify that the fatigue load will be applied several thousand times. Fortunately, since we’re talking about carbon, the failure load will be pretty much the same whether you apply the load once or a few hundred thousand times.

YOUR PROOF LOAD
You definitely do NOT want to load your bike up to the “ultimate” load since you’d run the risk of just breaking the thing even if nothing was wrong. I suggest you consider using a convenient load in between the specified fatigue load (if available), and 2/3 of the specified failure loads as a proof load. This minimizes the chances of destroying a “good” part while providing confidence in the part’s capability. It also ensures that the proof load is at or above the expectation for normal use of the part. This difference also points out one of the fundamental differences between metal and carbon. The metal gets permanently bent before it breaks. The fork gets bent and you don’t use it. The carbon does NOT usually get permanently bent, unless associated metal bits are what got bent. The GOOD news is that a proof test gives a high level of assurance that the carbon has at least a reasonable capability. One cannot know if a metal component is about to crack. A proof load should be applied at least a half dozen times to provide confidence that the loading was not on the verge of failure. The BAD news is that if your carbon gets hit five minutes after the proof test, it might no longer be good.

ONE OTHER CONSIDERATION
Cycler inquired about static versus dynamic loading. She also wondered about combined loads. Fortunately (or not), carbon behaves quite differently under dynamic conditions than metal. Metal is very sensitive to the rate at which load is applied. Carbon is not. If a hunk of carbon is going to break under a thousand pound load, it’ll break at a thousand pounds no matter how quickly or slowly the load is applied. A metal hunk may withstand a rapidly applied load that would break it if the load were applied slowly. This phenomenon makes things simpler for the cyclist determined to check if a damaged carbon component remains safe. Combined loads are a little stickier, but are mostly ignored by the testing standards. This makes things simpler for the cyclist, but raises a possibly awkward question about the true safety of that brand new, undamaged carbon bike you just bought. That question, however, is the subject of another post.

Damaged Carbon Bike

Snagged from "Cycling, London, and Life" - Ham's Fork. Hmm...

If you have damaged, or suspect you have damaged your bike frame, fork, or seat post, you have four choices. Regardless of your choice, I suggest you start by taking the damaged item to your local mechanic. While few local mechanics have training or equipment to effect a carbon repair, they MIGHT be able to help you get consideration from the manufacturer on a warranty action or manufacturer goodwill gesture. Yes, it may be a long shot, but an inquiry is always a good start. In rare cases, a local mechanic may know a place to go for composite repair. If nothing else, you’ll feel a better about whatever course you may take afterwards. I also suggest that you take GOOD, dated photos of the damage and the damaged area for future reference.

#1 – You can ignore the damage and hope for the best.

#2 – You can send it to a specialist.

#3 – You can proof load it to verify it is safe to keep in service.

#4 – You can scrap the thing.

Depending on the component, any of the four choices may be best.

IF the damaged item is unlikely to cause serious bodily harm upon failure, I suggest using approach #1, #3, or #4. Components I would take this approach with include seat posts, drivetrain components, and items such as the carbon water bottle holder. Actually, I’d ONLY take approach #4 once the offending part either broke or was clearly falling apart. Obviously, if your carbon water bottle holder snaps, it’s time for #4.

IF the damaged item is so expensive that #4 is unacceptable, and the damage is severe and readily apparent, I suggest considering approach #2. In truth, if you have enough money, almost any carbon damage CAN be repaired and made as good as new. If you are the sort who enthusiastically has learned how to build his/her OWN carbon bike, as outlined here, you can repair it yourself, and then apply approach #3. I would usually restrict this approach to structural damage to the frame itself.

IF the damaged item’s failure might inflict serious bodily harm, but isn’t the frame itself, I suggest you consider approach #3. The advantage of approach #3 is that if it fails in proof load, #4 becomes a “no brainer.” Items that fall into this category include the front fork, wheels (especially the front), and handlebars.

Notes on #2

Assuming you come up short locally, there ARE outfits that perform structural repairs on composites. One example is here. Another is here. They’re not cheap, but neither is a new carbon frame.

Notes on #3
This merits a separate post of its own. IMHO, this is the only reliable and economical way you can ensure that your damaged carbon bike item is safe. Keep in mind that if it FAILS, it WILL be broken. At that point, unless you have complete and thorough documentation of the actions you have taken, the manufacturer will probably take the position that you have voided any warranty by your actions. "Do ya feel lucky, punk? Well, do ya?"

Don’t Try This Carbon Stuff at Home

Actually, you CAN. Better yet, you can do it in your garage without any serious danger of explosions or other bad things happening. I’m not sure I’d try to do it in a dirt-floored shed. All it takes is the determination to do it, and the money to support that determination. Despite the mystery and exotic cachet of composites, it is entirely practical for you to manufacture carbon bike frames or components AT HOME! I don’t imagine that most people are going to want to make their own carbon parts, but you could, if you were so inclined. Far fewer of us would have the capability or expertise to fabricate our own aluminum or even steel components. Hardly any of us would have the expertise to do work in titanium. Titanium frames SHOULD cost a lot of money. The rules for fabricating carbon parts are not dramatically different than making stuff from fiberglass, and people have been making fiberglass stuff - in garages, for a LONG time. You could be the very first bike commuter with a CARBON tub!

How it works:
Basically, all it takes to make a carbon part is the right amount of heat, pressure, and time applied to the carbon “prepreg” that have been placed in a mold. If you have access to an oven, you have the heat source. Carbon parts can also be made with a “wet layup” approach in which dry tape or cloth is cured after the fabricator adds resin. “Prepreg” will usually achieve superior results compared to “wet layup” because the amount of resin is better controlled. Most composite “thermoset” (see definitions below) materials you might want to use for a bike, cure somewhere between room temperature and 350F. Carbon can also be made from “thermoplastic,” but that is tougher for the home fabricator, so we’ll not cover them unless someone requests it. A vacuum pump and bag can get you the pressure for many of these materials (think of a “seal a meal” bag). Any number of mold materials can withstand the combined heat and pressure for a small production quantity. The choice of mold material depends on how many parts you want to build. If the part is small enough, you could even use a toaster oven. On the other hand, if you want to compete with Trek, you’d buy large autoclaves and install stuff for mass production, with mold cost being secondary to mold longevity.

More than just theory:
You really CAN do this. In fact, people HAVE built carbon bikes at home. Go visit here, here, or here for their experiences. Arundel, a supplier of high end carbon items, and now, non carbon ones, started out this way.

Safety:
Remember, if you are working with heat and pressure, you have the potential for some bad things to happen if any of this stuff gets carried away. Do NOT just plan on turning on your toaster oven out in the garage and come back the next morning to see your wonderful new carbon water bottle holder. You just might want to also read the MSDS on the raw materials. While they aren't going to be toxic, some people are sensistive and it's better to find out this stuff ahead of time.

Lots of Details I’m Not Telling You:
In truth, your garage is probably not currently suited to build composite parts, because the layup of these parts is completed in a “clean room” environment. Certainly, you can produce a “clean room” area in your garage, but it takes a bit of effort. It’s the same general idea as keeping dust off of a part that’s getting painted. Also, carbon “prepreg” is a bit spendy, so you don’t want to do a whole lot of trial and error. Fortunately, you can do some of the learning from books, and with fiberglass. If you’ve built a fiberglass boat, you understand many basic concepts. In addition, there are a lot of different places that sell this stuff. I haven’t purchased carbon composites from ANY of those below (at work, somehow the stuff just shows up after our purchasing experts do their magic), but there are hundreds more. What’s more, much of this stuff requires refrigerated storage until you are ready to use it, but freezers aren’t rocket science, either. Finally, there are lots of things you need besides the carbon prepreg itself – vacuum pumps, bagging materials, damming materials, mold release agents, and so on. None of this stuff is particularly expensive individually, but if you have to buy 100 yards of bagging material, it can be pretty expensive unless you have a plan to build more than a single bike frame. Let’s just say if you want to build the world’s most exotic carbon bike items, it’ll cost you more than if you were to take up embroidery as a hobby, but it IS within financial reach.

eBay
West Marine
Carbon Sales
Surplus Composites
Fiberglass Supply
RC Forums
 
Definitions:
Clean Room – A location with active dust control and controlled environment so that a composite part may be fabricated without environmental contamination.

MSDS – Material Safety Data Sheet. You should read this whenever you are working with chemicals and stuff. It tells you all sorts of handy stuff, like if the material will kill you.

Prepreg – Prepreg is the combination of carbon (or fiberglass) fiber and resin that make up an individual layer (ply). Prepreg comes with the fiber and resin already to lay up. Prepreg is the preferred raw material for structural parts in which low weight is an objective.

Thermoset – A material that changes permanently when you cook it. Biscuits, for example, are a thermoset. You cook them and the dough changes to a biscuit. You cook them again and they just burn.

Thermoplastic – A material that changes when you cook it, but if you mess up, you can cook it again. Within reason, chocolate is a thermoplastic.

Wet Layup – Wet layup is a more traditional way of making mostly fiberglass parts, in which dry fiber has resin added to it at the time of layup. Typically, wet layup produces a heavier part than layup with prepreg since the resin content is not as well controlled. Wet layup is preferred when minimizing equipment and consumable materials is more important than low weight.

Request:
Any of y'all build your own "homebrew" carbon bike, I want to see photos!!!!!!!!!!!

Carbon Update

Over in the sidebar, you'll now see an item called "Carbon Bike Stuff." It leads you to the index on the continuing "Carbon" series. As you may see, we're about halfway through...

So, You Got a Carbon Bike?

Point 4 Illustrated

It happens to a lot of people nowadays. Even Wally World sells carbon bikes, so they are definitely mainstream. Now your objective is to get the best value out of it. Most of this is evident from past posts in this series. For my reader that has read all of this series, this is review - except for #4.

#1 – DON’T put the bike in situations where stuff gets banged. Make sure your front derailleur won’t throw the chain into the chainstay and damage it. When you lock the bike, avoid throwing a heavy, uncoated, metal locking chain against the frame. Be doubly careful if you are one of those people that carry your bike around on a car. I have noticed that my bikes are MOST likely to get damaged when either loaded into or unloaded from a motor vehicle. Your first line of defense is to avoid impacts that might cause substantial weakening of the carbon – weakening that may not be readily visible. This approach has the side benefit of keeping your bike’s paint nice, and looking much better than a bike you just toss around. If you are going to bang a bike up, steel is the best material choice.

#2 – KEEP the bike clean and dry. A clean and dry bike gives galvanic action little opportunity to eat up the metal bits. The simple act of cleaning causes you to look at things more frequently and closely, noticing possible problems before something collapses on you. I’m not suggesting you avoid riding such a bike in the rain, and through mud, but avoid the old horse problem of “ridden hard and put up wet.” It is LONG TERM wet and dirt that is the killer. You have a large investment in that carbon bike. Wipe it down when you put it away, and don’t store it in a humid swimming pool maintenance shed.

#3 – PROTECT the bike from UV. Store it somewhere where it won’t experience the daily sun damage that causes paint on old cars to fail. If you want to go even a bit further, wax the bike occasionally. Wax has UV resistant agents so it’ll help keep that carbon like new, as well as making the bike easier to keep clean and dry.

#4 – SHOW SELF RESTRAINT*. The whole point of having a carbon bike in the first place is to enjoy an unusually spirited, lightweight ride. Your carbon bike should be kept that way as much as possible. Racks and fenders, and all the other paraphernalia you might want to load a utility bike down with should be kept AWAY from your carbon bike. There is a REASON that Dutch bikes are not made from Carbon. More often than not, utility bikes even dispense with things like carbon forks. Keep your carbon bike pure, and light, and fun.

* This is one item in which I’m not really following my own advice when it comes to Buddy. Buddy’s frame is mostly aluminum, but Buddy has a carbon fork, seat stays, seatpost, a carbon crank, and a carbon front wheel hub. Buddy also (for the moment) has a rear rack and trunk, and fenders. I’d have been better off with a low end Tricross with none of the add-ons. HOWEVER, it’s now getting to the warm season and all that stuff will be coming OFF of Buddy soon. It COULD have been worse, however. I notice the 2010 Tricross S-Works all-carbon frame has now got rear rack mounts, so you’ll have the opportunity to load up your $6000 racing bike until it’s heavier than the $1000 version if you so desire.

ANOTHER Carbon Digression

Campagnolo - 0.67oz to carry water that weighs 24 oz
What Would Tullio Say About This?

For THIS one, you can blame a possibly innocent observation by Lizzylou. Said she, "I find it interesting that when placing a solitary bottle cage you chose the seat tube instead of the down tube."
This set off a chain of events. My loyal reader may recall that I have posted on the danger aspects of water bottles, here. Many more will recall that I have an ongoing "carbon" series. In reality, what Lizzylou SHOULD have asked was "I find it interesting that when placing a solitary bottle cage, you chose the seat tube instead of the down tube, and your cage isn't made out of CARBON!" Opportunity missed!

Bontrager Plastic Cage on a Cannondale
Just over an oz and all-plastic With Places
I Could Remove Weight
Bontrager and Cannondale - Does
that Combo Corrode?
Well, she's got a point. It is more or less traditional that solitary water bottle cages are mounted on the down tube. What's more, I actually mounted my own ones that way at one time, but they just seem to work better for me when mounted on the seat tube. What's more, I only mount one, because that is enough water to go between Starbucks stops under any conceivable weather conditions (for those NOT experienced in such things, Starbucks offers free cups of ice water. Those cups are triple filtered, and the Venti size is PERFECT to fill up a 24 oz water bottle, and will last at LEAST until the next Starbucks - what's more, Starbucks do NOT usually have bike racks so you need not feel guilty walking your bike in with you - I've checked! You should, however, check at your own local Starbucks ahead of time since we ALL know what "assume" stands for). The only time I will mount TWO water bottle holders when I next run in the "Hotter 'n Hell 100" and even then I'll only carry one water bottle. The second holder will be reserved for picking up a sweet bottle that has been discarded along the way by some rider. Last year, I was AMAZED at the variety of bottles along the way, but didn't want to carry one a long way in my jersey pocket. One interesting aside - my Tricross has also got mounting points on the BOTTOM side of the down tube. I haven't, to this date come up with anything I'd really want to have to clean off from the escaped mud and dust that collects down there, despite my protestations about keeping everything clean and dry.

Anyway, back to carbon. Carbon water bottle holders definitely fit into the "style" area of carbon on bikes. Perhaps, some might claim I should say otherwise since Arundel is local and a big player in the area of carbon bottle cages. But they didn't bribe me to say otherwise. While one might CLAIM weight savings with carbon bottle cages, even one of the lightest carbon holders, shown above, is really designed to carry stuff that weighs darn near TWO pounds. What's more, if you go to "weight weenies" listings, you'll find that many carbon cages weigh more than their plastic or aluminum counterparts. When you get back to things, carbon has lots of stiffness - which has marginal utility for carrying over a pound of water. Myself, for the road bike, I use a plastic holder that weighs 1 1/3 oz, and whose red color goes well with the bike. It was also on sale and didn't cost much more than the ugly steel ones. On Buddy, I use a plastic "Rib Cage Pro Road" plastic cage that also matches the bike well, and it weighs just about the same. Conveniently, it was also on sale. In both cases, there's weight that could be carved off the holder, if I felt ambitious, and this weren't "get the taxes done or else" weekend...

The Specialized Cage at 1.3 oz, Looks GREAT on Buddy and it was on Sale, too!

Carbon in the Sun

Shuttle Atlantis, with Carbon Damage Underneath and on Leading Edges, From Wikipedia

So far, these articles have tended to either be background, or to make people a bit nervous. One recurring theme that has been raised by commenters was whether exposure to the sun, as in exposure when out riding, or while the bike is stored, might fatally weaken it. Adding to those fears, one might read articles such as this. Crimeny, 1000 hours of exposure? A well ridden bike could see that in a year or two? Does that mean a carbon bike will die due to the sun after such a short time?

Well, actually, there's some good news here. Most carbon bikes are also painted, at least in some areas. The paint suffers due to UV. The tires suffer due to UV. The brake cable housings suffer due to UV. YOU suffer due to UV. In reality, UV is one of the things you really do NOT need to worry about when it comes to your carbon bike. If the paint is fresh looking and you don't have skin cancer, and you aren't storing that really expensive bike out in the sun, it WILL probably survive UV longer than you will, and probably your children as well. The shiny finish probably has UV-resistant chemicals in it, and even if not, the shiny surface will go before those strong fibers even notice.

OTOH, if you want to use your bike as a replacement for the Space Shuttle, and subject your bike to reentry while exposed to high moisture, you ought to be very careful about UV, and rapid oxidation generally. Likewise if you have a wooden bike that you leave out in the sun. If the shellac/varnish disappears, the fibers are getting attacked and termites may follow.

Consider this article a "whew, I'm glad Steve made me feel a little better" day. For the sun, the paint will go before you have to worry about the carbon. Next the epoxy will go, but even then the carbon fibers will be as good as the day they were cured into the epoxy. Just you worry about impact!

If it makes you feel any better, my road bike is now 12 years old, and I have absolute confidence in its carbon front fork. Of course, the frame itself IS aluminum, but pay no attention to that man behind the curtain...

Carbon Corrosion

Corroded Statue of Liberty - from Wikipedia

Y'all know what corrosion is. In regular steel, it's referred to as "rust." Aluminum tends to turn to a whitish powder. Zinc is used as an anode to keep boat components from corroding.

Corrosion is not necessarily a BAD thing. It is galvanic corrosion that makes a battery work. Still, you do not want to try to use your expensive bike components to power your headlight.

Enough of that, what about corrosion and composites, you might ask? I'd respond it is a reasonable question, given the title of this post. Well, there's good news and bad news. The first, is that your new carbon bike will NOT corrode away any time soon. In point of fact, it is THE most "noble" material used in bicycle construction. It is even more stable than gold. You see, materials are susceptible to galvanic corrosion in the presence of a conductor and a more noble material. If you look at the figure below, you'll see that carbon is at the very top (I did not include materials such as gold which are only slightly worse than carbon). The "steel is real" crowd will be relieved to see that their bike material of choice IS, in fact, better than aluminium. Bringing up the bottom are things like zinc and magnesium. As I recall, a couple of years ago, Colnago built a bike with a Magnesium frame. Just because you CAN do something does NOT mean it is a good idea.

The Further Down the Scale, the Easier Carbon Will Make it Rot!

The BAD news is that your carbon won't rot away in front of your eyes, but those expensive aluminum and magnesium components ARE at risk. If, for example, you have an aluminum frame and a carbon seat post, for example, the potential exists for corrosion of the frame due to that contact. You have risk for corrosion to those cool dropouts that hold your wheel to your carbon fork.

Lest you think this is overdramatic, back when the F/A-18 fighter went into service, one went into the drink. They fished it out a couple of weeks later and the aluminum was basically GONE.

There are a couple of approaches to avoid trouble. First, avoid "intimate" contact between the carbon and metal that is more reactive than stainless steel. A rubber pad would suffice, or a swatch of fiberglass. Undamaged (no scratches or rock chips) paint and primer. Even WAX. Yay, WAX! Just keep the two apart so they can't pretend to be a battery cell. Hopefully, your bike manufacturer took this precaution in things like gluing the fork ends into the carbon. If not, you're still left with the second strategy.

The second strategy is to KEEP THINGS CLEAN AND DRY. Dirt and moisture in combination really get the galvanic action going. If it's dry, there is no medium for the electrons to zip around in. On the other hand, if you leave it out in a damp garage next to the pool chlorine tablets, you will have interesting things happening before you know it. Especially, if you have a cyclocross bike such as I do, do not wait a week before cleaning after a race.

Anyway, I don't think I have to tell you how to look for corrosion in the metal. You'll detect IT pretty easily. Clean it away until you get down to sound metal. Reprime and repaint. When you are out of sound metal, it's time for a visit to your LBS. Remember, keep that puppy clean and dry - and ESPECIALLY watch that carbon seatpost in that aluminum frame! Ham should be happy with THIS post. His carbon frame may outlast his grandchildren's grandchildren if he's lucky. They'll just have to replace the metal bits as they rot away.

I don't know if y'all can take a log of comfort in it, but I've now had Buddy for over a year and there is still sound aluminum in the frame, though I haven't attempted to remove the seatpost recently. Hmm...

A Carbon Seatpost In an Aluminum Frame is Not the Best Galvanic Combination

The Ti Rails are Not a Likely Problem

Damage to Composites

In practice, as long as you don't do something dumb like take a torch to the composite, there are two main types of damage that the owner of a composite bike component needs to worry about. The first of these is impact damage and the second is delamination. I'll discuss each separately, though an impact may well cause delamination along with the more obvious symptoms of the impact.

Schematic of how Impact Can Propagate and Spread as it Travels through a Laminate

The Wiggly Lines are Broken Fibers (I don't CLAIM to be an Artist)

Think of the Damage to a Window from a BB Pellet

Impact Damage
100 foot pounds. It's an energy measurement. It's the energy that a 100 pound object the size of a 4 foot by 8 foot piece of wood would impart to whatever it hits if dropped from one foot in the air. It is also roughly the energy of a 22 caliber bullet as it leaves the muzzle of a gun. Clearly, not all impact energy is created equal. If you are going to get something on your carbon bike smacked, if it gets hit by something very small in diameter, you'll be able to see it long before it becomes a cause for concern. On the other hand, it it gets hit by something blunt, you may not be able to see the damage until after it has fatally compromised the structural integrity of the bike. That damage consists of broken fibers, and in delaminations (plies get unstuck from each other).

If you have ever seen the Zapruder film of the John Kennedy assasination and how the bullet takes half his head off on its exit, you can clearly see the problem with impact damage to composites - things are often MUCH worse on the back side. A minor pip on the front side may represent major broken fibers and extensive delamination on the back side - the side you cannot see if you are looking at a damaged fork or frame. Amazingly, a Google search on carbon impact damage doesn't show this very clearly. There's one, halfway decent photo of a fiberglass part, from this page, here, but even the better photos, here, really don't show how the impact spreads through the composite as it propagates through the material. In a nutshell, the damage may be small on the front and extensive on the back.

Photo from Wikipedia

This is NOT a Photo of a Simple Delamination, but Rather

of What Happens When the Part Takes Too Much Load

AFTER a Delamination

Delamination Damage
Delamination occurs when, often in response to an impact, the composite layers come "unstuck" from each other. Imagine, if you would, a half dozen 2X4's screwed together with screws every couple of inches. You could put one heck of a compression load on them. Now, imagine that all the screws are removed. The load capacity would be much less. Well, carbon is exactly the same way. If a delamination occurs, the part has a reduced compressive capability. The bigger the delamination, the more the reduction. The more layers that are delaminated, the more the reduction. Fortunately, delaminations usually have to be fairly big before a large compression strength reduction occurs.

Other Damage
There ARE other damages that occur to composites. I've already mentioned burning. Most composites used on bikes are like cookies rather than chocolate. If overheated, they burn rather than melt. In addition, the epoxy resin can be subject to deterioration by extended exposure to UV, leading to failure to support the strength giving fibers. Another potential problem is softening of the resin or dissolving of it via solvents or acids. Fortunately, most of these other forms of damage are readlily apparent from a casual visual inspection and they LOOK horrible long before they make the bike dangerous. Corrosion can also be a problem, but THAT will be another article, because it probably WON'T be the carbon in your carbon bike that rots away.

Carbon Comedy

If you believe that Carbon is all about lightweight performance, look at the lid of the scanner above. It's not REALLY made out of carbon composite, just a molded impression of it. Still, I imagine that HP figured they'd sell a few extra scanners with that black "carbon" scanner lid, though we didn't realize it had pretend carbon until after we unpacked the thing.

Composite Inspection

THIS is the question that prompted this whole series. CITIZEN RIDER was frustrated at a lack of solid information he can use. I suspect he’ll remain somewhat frustrated reading this, but he’ll be smarter and frustrated, which I hope will represent an improvement.


Basically, there are five major ways in which carbon composites are widely inspected today. Only three of them are likely to help a bike mechanic or owner wondering if that carbon rim is still OK after the curb hit.

These are:
Visual Inspection, Ultrasonic Inspection, Radiographic Inspection, Tap Test, and Load Test.

Visual Inspection
The first inspection technique has the major advantage that no special equipment is needed. Purchase price of the equipment is zero. Unfortunately, in many cases, you get what you pay for. Visual inspection is widely used as a part of the inspection process by the OEM manufacturers and it helps them immensely. I’ve often relied on photomicrographs to determine laminate quality and ply orientation of composites, and excessive porosity or resin pooling in the laminate is often evident to even a casual inspection. A bike mechanic or owner, on the other hand, is trying to determine if an impact is something to worry about. In the case of solid laminates, such as brake handles and such, a visual inspection may be very helpful. Carefully look for broken or loose fibers. Use a good magnifying glass in the area of the impact, and even more, on the back side of where the impact occurred. Damage is often more severe on the back side of a laminate. Still, even if you see damage, all it will really tell you is that you have cause to worry. In the case of hollow laminates, such as frame tubes, you are even in worse shape. The back side of the laminate will not be inspectible. If you are relying on visual inspection, the OEM advice to throw it away if you see something disturbing is about all that can be done. Still, looking is free and it can do no harm. Look hard, look REAL hard. Get a good magnifying glass. Inspect both sides of the composite.

Ultrasonic Inspection
Ultrasonic inspection is the inspection method of choice to detect and characterize delaminations and impact damage in composites. What’s more, it is the workhorse method for OEM manufacturers, at least in the aircraft industry. Equipment can range widely in price. On eBay, for example, an ultrasonic hand inspection unit can be obtained for somewhere in the $4000 range. Ultrasonic thickness units can be had on occasion for more like $200. I do not know if such could be used An aircraft manufacturer would use a more sophisticated automated unit that will be more sensitive. Such would be beyond even a very upscale bike shop, though some manufacturers might use such units if they were volume producers. An ultrasonic inspection works by detecting how far the ultrasound travels into the composite before being reflected by an air gap or other discontinuities that reflect the ultrasound. Essentially, it can “see” if the plies are separated internally or if there’s a busted up inside surface on that tube. You’d actually have a GOOD chance of finding it if you were a trained ultrasonic technician and had comparison standards to use. Some of those guys are wonders – equivalent to the Navy sonar operators that can tell whales apart from each other from miles away. Maybe there’s a business opportunity here for a savvy guy that wants to sell inspection services to bike shops. Still, even with the best ultrasonic operator, my engineers and I constantly puzzle over what the strength effects really ARE of that “indication” that was detected. Still, if nothing else, you’d have more than just a hunch before deciding to throw that $3000 frame in the trash. You could tell the customer that your ultrasonic inspection service got an indication of a half inch defect on the chain stay and that isn’t covered by warrantee. He could even frame the inspection report if he were so inclined.

There are a lot of places that can do ultrasonic inspection. A FEW are listed below. I've used none of them and cannot recommend any of them, either as being wonderful or useless.

PTL Testing
NDT Specialists
191 others at ThomasNet
One problem ANY of these places will have trying to inspect your bike is that none of them will have usable STANDARDS. A STANDARD is a reference part that shows what a GOOD part and a BAD part look like. All they will be able to tell you is there may be something odd inside that fork.


Radiographic Inspection
Radiographic inspections are widely used by OEM manufacturers. They are helpful in determining where internal porosity is in a laminate and if the fibers have bunched up during a cure. Besides being impractical for an end user, nothing an end user is likely to do will change anything a radiograph will find. The one time you might want to have a bike component radiographed is to establish evidence in a product liability lawsuit. The owner did NOT cause the composite to be porous or the fibers to shift to one side of a tube that failed. The bike was built that way. I presume most that are reading this post are not lawyers looking to sue Trek. Still, Radiograph is one way you can build a case that it wasn't abuse, but OEM failure to take due care.

Tap Test

Tapping is something I sneer at whenever someone tries to tell me it’s a valid inspection technique. Tapping, whether with a quarter or an official tap hammer has been repeatedly found to be somewhere between unreliable and equivalent to consulting a magic eight ball. The theory is that you carefully tap the laminate and listen for “dead” sounds. If inspecting a fork, you have the advantage that you can try tapping one fork leg, and then tap the other to see how they sound the same or different. If it’s starting to sound like dowsing, you’re not real far off. On the other hand, if I’m in the field and there’s a suspect carbon laminate, I’ll get my calibrated quarter out and carefully tap away. It’s SOMETHING you can do. As in the case of visual inspection, it won’t harm anything unless you rely on it. I prefer to use a new, shiny quarter. American ones have more “heft” than their Canadian counterparts. If nothing else, tapping the laminate will make you feel a little better.

Load Test
Load tests are, in my view, the superior method of establishing that a composite part remains safe after experiencing an impact or other post-manufacture damage. Ski binding settings are validated by a simple load test. You WANT a ski binding to release AT the intended load, neither coming loose during normal skiing, nor failing to release when needed. What’s more, load tests do not require specialized equipment or training for the operators. What’s best of all, if you load a damaged part to the proper test load and it splinters into a million pieces, there is no doubt about the proper course of action. You can tell that guy his $3000 bike was unsafe and the proof is in the bag of splinters you give back to him. What’s more, you can explain to him what the test is about and he can even watch. Because composites are not fatigue sensitive, if it passes, as long as it is a good load, you know the part is good to go. Myself, if I was running a load test, I’d cycle it a half dozen times, just to be safe.

If we were talking about an aircraft, conducting a load test on a wing would be a difficult undertaking. It is much simpler for a bike, where the loads are simpler and more “human sized.” In an ideal world, the bike and component manufacturers would provide directions on how a load test could be carried out and what the recommended test load should be. Even better, this would be provided by an industry group, since a safe fork test load on a road bike is not likely to be very different for, say Trek versus Schwinn. Ditto for that zinged chain stay. What’s more, conveniently enough, since there are industry and government standards, these could be made readily available for someone trying to decide to do with a possibly damaged component. Even in the complete absence of useful data from the OEMs, an owner need not be completely helpless. Even without me outlining it, I imagine most of you could devise a reasonable way to test a suspect crank arm. In the case of a front fork, it can’t do much more than throw you over the handle bars.

For reference, THREE locations I found that have at least superficial credibility are all by Sheldon Brown and Damon Rinard, namely here, here, and here. More on testing later...

Closure
I quizzed my engineers about all those inspection methods that CITIZEN RIDER identified. Mostly, I got quizzical looks back. The consensus was, however, that squid magnetometers sound really cool, even if they do nothing useful whatsoever. In the final analysis, however, the old truth still holds. “A test is worth a thousand expert opinions.”

Composite Questions Answered

Y'all are certainly a curious lot. Rather that attempt to comment back at all the questions, I'll do this post where I deal with them all at once. Some of them will be treated further in future posts. One prompts an addition to the agenda. Anyway, here goes, from newest to oldest, grouped by post.

In "Aero Diversion," Rantwick opines "experts in complex topics" meaning someone other than himself.

REPLY: This from the only known human to capture a half-breed Yeti on video in the wild. It's like Tex Johnston passing himself off as an ol' country boy.

In the same post, Whareagle speculates that "Yeah, but if Kelly Johnson had had access to the composites that are now available, don't you think he would've made the thing 'Leak-Proof' by using composites throughout the infrastructure?"

REPLY: Whareagle, I don't think you are advocating that we make bike frames 'leak-proof' so that we can use them to go to the gas station in order to fill our frames up with gasoline for the lawn mower. Seriously, carbon is an attractive material not because it is inherently more "aero." A lead casting can be aero. It is not attractive because it has low density. Magnesium has low density. It is not attractive because it is strong, or stiff. There are alternates that provide either of these more than carbon. It is attractive because of the combination of ALL of these. If it was simple, all bikes would be the same!

In the same post, Anonymous wonders "Perhaps the real question is not Aero or anything else 'speed related' but longevity."

REPLY: I will treat this at more length in the "corrosion" and "sun" that are three and four posts away in the series. However, I will note that properly cared for, there is no reason that carbon composites cannot outlast your grandchildren if you are old enough to read this post. There are a LOT of 1953 Corvettes in prime condition around and carbon is much more durable than the fiberglass cloth used in those. Likewise, today's resins are better as well.

Anonymous also wonders in the same comment "do composites really represent the best value for the typical (non racing) cyclist?"

REPLY: This will also be explored in more detail in "Carbon Weight Myths, Legends, and the Truth." My personal opinion, however, in a nutshell, is "no." Bikes, however, are not entirely about the "best value." There is cachet to having carbon on a bike that goes beyond pure value. What's more, non racing cyclists represent a huge spectrum, and some carbon items represent much better values than others, and not always for the obvious reasons. My SRAM Rival brake levers are, for example, carbon. I am very glad they are carbon and not aluminum when I first touch the levers when it is 107F outside or below freezing. THAT has little to do with weight or raw performance. Plus they look REALLY cool!

Finally, polishing off the comments in THAT post, Big Oak looks forward "As carbon technology continues to develop, it'd be interesting to have a glimpse...into the future."

REPLY: Good Point, add "Today's Technologies on Bikes Your Kids Will Ride" after the Lance post. In truth, there are many existing composite technologies that have not yet found their way onto bikes, but they will. I will leave pure speculation to others, but bike designers have many untapped elements in composite technology still to explore.

In "How Composites Work," Ron inquires "Its interesting you state that that the hole will decrease strength by half but in what mode of loading? Was this stated in literature somewhere or you have this knowledge from experience? Is it any different from the behavior of metals? For example, the stress concentration of a .125" transverse hole in a 1" OD .5" ID tube for bending is about 3.11, so factor of safety decreases approx. 33%."

REPLY: Tension, Yes, Yes, Yes (profoundly so- look again at the last table in the post), Factor of Safety does not decrease. Factor of Safety is a design criterion. MARGIN OF SAFETY would decrease. I may need to add another post for techie types reading this, though some elements will be in the experimental stress and loads posts. That "techie candy" post will be an addendum after the last of the main series and ought to include some references for future study. Besides, Ron, why didn't you ask about "compression after impact?" THAT is the big bugaboo.

In "Carbon for the Rest of Us," Ron notes "So bike manufacturers could do a lot more to help bike mechanics in this area? Meaning they don't? Ha. I wouldn't be surprised. Check my blog out for failures from time to time."

REPLY: Yes, No, OF COURSE you aren't surprised. What's more, we're just getting to the parts of this series where bike mechanics and owners start to see stuff that they can potentially put to practical use. The history and "how they work" posts really are just setting the stage to address the CITIZEN RIDER challenge. I hope I'm not giving too much away to state that "squid magnetometers" are NOT going to make life wonderful for mechanics OR owners. But they really DO sound cool, eh?

HOMEWORK PROBLEM FOR RON
Calculate how many fatigue cycles a chain experiences in 1000 miles assuming you are in your favorite gear and are a spinner instead of a pure "big gear" guy. Ignore the minor cycles where the links change direction as they go around the rear derailleur pulleys. Hint, I would guess it's upward of 250,000 cycles. Now consider what happens to even a minor chain defect after those numbers of cycles. Mainly, why are you still messing with Shimano when there are at least two better choices around, one of them based in the USA? You get used to SRAM and Shimano will never be the same again. Even if you keep the levers and cassettes, SRAM makes chain that works well until you can spring for REAL drivetrain equipment.