facial

I've always wondered why fiberglass bicycle frames were not made. I'm cautious with saying "never," as there might be the occasional rare one out there. Yet I am close to using the word "never" with regards to seeing a fiberglass bicycle because I have never seen one marketed or in real life.

Fiberglass is a lot cheaper to make than carbon fiber, and it has good strength to weight ratio. Furthermore, it is more shock-resistant than carbon fiber because of its lack of stiffness, which I think may also act as a drawback. Is adequate stiffness really that important?

flatlander_48

Good but not good enough. Strength to weight and stiffness to weight is far superior for carbon fiber. I'm not sure if fiberglass would be that much cheaper to make. The raw materials would be cheaper, but I think the manufacturing costs would be fairly similar.

Stiffness is important because the bike would tend to act like a big spring. You want your energy to go into moving the bike and not to be absorbed in the frame. Stiffness also makes the handling more predictable.

rokudan

I used to work for Ski Nautique, building boats.. And hence worked with fiberglass a bit... My guess... Falls in line with what you assume, as well one other thing... First, fiberglass cloth, pound for pound, does not have the strength near that of carbon fiber... And two, the cost difference between high weight, quality fiberglass, and a stronger/stiffer carbon fiber counterpart of the same weight/quality, is very little...

So, from a manufacturing standpoint, they spend 10% more to use CF, and get 30% more strength... (Note: my numbers are completely arbitrary guesses, but probably close)

nahh

aren't most good surf boards now epoxy and not fiberglass? Isn't this because fiberglass is more fragile?

I might not know my stuff about that, I only surf occasionally when i get somewhere w/ some good waves.

StephenH

https://en.wikipedia.org/wiki/Itera_plastic_bicycle

I'm not sure if this was fiberglass, but of interest none-the-less.

Doug5150

The reason there's no fiberglass bicycle frames now is because most of the expense of building a composite frame is the labor, which is the same no matter what fiber you use.

For a fairly-small increase in price (-and the same amount of labor-) you can use carbon instead of glass fiber and get a much-better product in the end.
~

tatfiend 

Current surfboards use Epoxy or Polyester resin over a foam core I believe. Cheaper & a bit lighter than a foam core + fiberglass and resin outer shell but not as strong IMO as the older construction method.

Remember that fiberglass and CF are very similar technologies. Both use a resin impregnated into the cloth material to turn it into something other than a limp cloth. CF is a lot lighter and requires less material for a given rigidity and strength so for equal strength and rigidity characteristics a fiberglass frame would be a lot heavier from what I have read.

facial

The stiffness to weight can be around the ballpark of magnesium alloys, but with much greater strength.

So if magnesium frames exist (in minority), why don't fiberglass frames exist?

There is a large disparity between the prices of the two types of fibers. Epoxy is cheap, so that's discounted in the price difference. In the manufacture of carbon, you have to spend a lot of energy in the carbonization/graphitization processes, whereas in glass you have just a one-step melt spinning at roughly carbonization temperatures. The graphitization temperature is much higher, but those are never needed for glass.

facial

There is some good discussion here.

This might be the first one I have ever read of. Not bad.

If you use E-glass, it (the glass) is somewhat inferior. If you use S-glass, it is slightly inferior, but that also hinges on the cost of the S-glass, I suppose. Now quartz fiber would be more interesting, with strengths in excess of 10 GPa.

Ah yes, I forgot to bring this up. If people tried plastic bicycles, which have relatively low stiffness-to-weight ratios, then of course fiberglass should've been tried from this era as well. I imagine sometime around the 1980's, but I haven't seen anything other than the 1960's example above.

Jeff Wills

From far-left field comes part of an answer: several velomobiles are built from fiberglass with bonded-in subframes to locate the drivetrain. A velomobile is a fully-enclosed human-powered machine, designed for aerodynamic efficiency and weather protection. In some designs the shell is a monocoque, with mounting points for the front wheels. One such design is the Quest:

https://www.bluevelo.com/quest_velomobile.html


I led a ride here in Portland for the Left Coast Velomobile Gathering last weekend. Tremendous fun:
https://www.flickr.com/photos/wmbates...7618744819975/

bbattle

crackerdog

Have you ever picked up a fiberglas ladder and then an aluminum ladder? Fiberglas would be better for shells and such but as a structural agent, way too heavy.

127.0.0.1

this.

fiberglas for strength means extremely heavy. your bike would weigh like a concrete huffy

facial

I have - keep in mind that this type of fiberglass contains calcium carbonate and pultruded w/ volume fraction of fiber at around 50%. Shells seem to be the preferred application of fiberglass.

60-70% volume fraction is seen in experimental aerospace applications, alongside carbon. I know this because my university department does this stuff all the time.

facial

It would be more accurate to say stiffness. The strength of fiberglass is adequate, just there's too much flex so inevitably the wall thicknesses are larger.

I would also add that the stiffness of a frame should be pretty small compared to the rubber stiffness on a tire, even when the latter is inflated to high psi. The flex in the frame can damp out unwanted rigid motions.

Booger1

Too heavy,after getting the strenght needed.

100bikes

Check out the Bowden Spacelander.
I believe it was a fiberglass or composite.

I own an Itera - plastic bicycle. All bearings and bearing surfaces are metal.
Plastic with an engineered structure.

facial

I would totally get one of these. edit: too bad they're only made in Canada.

wahoonc

And NL among other places (I so want one of these!) I think we may be seeing more of them in the future. Here is a link to a blog from NL showing them in action.

Aaron

Jeff Wills

It's still a very limited market, but if you're really interested in looking one over Dana Leiberman at Bent Up Cycles in Van Nuys has a couple.

hotbike

Here's an interesting How-To article;
https://www.nordicskiracer.com/news.asp?NewsID=2940

You know, I didn't see this thread when it first appeared, in 2009. Now, looking back, I realize that June '09 was when I got my new DVD Burner, and software to convert DVD's to MP4's, and I was very busy, uploading over 700 videos to YouTube. I want to thank bbattle for posting the photo of the NFA Vehicles Type 9 , otherwise known as the Fiberglass Ladies Bicycle by Mellisa Manning.

I'm thinking of a Do-Over, wherein I build another bike like this , but 50% Fiberglass, and 10% Carbon Fiber. That only adds up to 60%, you think? Wrong, that is the Weight Savings of 40%. The Fiberglass will remain where there is compression, and the Carbon will take up the slack where there is tension.

Anyway, this bike is a mule, part velomobile and part cargo/utility bike. There is no other, that I know of.

Another link , to an article about plastic bikes:

https://www.treehugger.com/bikes/why-...practical.html

hotbike

Never say Never...

cafzali

On this, you can pretty much say never. Fiberglass has been around for ages, but it's application has been relatively limited. There's no reason to reinvent the wheel to make another bike frame material when carbon and aluminum provide all that the vast majority of people need, for the most part. Aluminum is making a resurgence as it's getting easier to work with and shape, much like carbon fiber. The most recent Bicycling magazine has a good article on this issue.

flatlander_48

If the Green Lantern was looking for a bike...

wphamilton

How does that handle at around 20-24 mph? I experimented with a fiberglass front this year more highly concave and pointed at the front, but for me it was highly sensitive to wind shifts so I reverted back to my older more rounded front (corrugated HDPE). I was wondering if your design had similar characteristics.

(ps, I have a new appreciation for your craft skills since it took me months to make one piece that still wasn't right. It's harderer than it looks)