Thursday, September 30, 2010

A pic to make you happy

Catching Up

The 'day' job has been getting in the way of real work.  Then I discovered I was a bit short on some supplies, which are now on order. Consequently, there hasn't been much work done on the carbon frame, nor posts associated with same.

Perhaps now would be a good time talk some theory, to fill in the time-gap and maybe make you better informed consumers.

There is a lot of misinformation out there about frame-building, frame materials, and frame design.  I'm not going to try to address all of that here.  But all of these topics will be touched on, at least a little.

Carbon fiber is a great material for building frames because it can be formed into light strong structures that fit (literally size-wise) into the requirements for a bicycle frame. Of course, Aluminum, Steel, and Titanium all fit this brief too.  As far as I'm concerned, there is no hierarchy of good, better, best among these materials.  They all work.

I don't work with Aluminum or Titanium because I don't know how to Tig weld, and don't have a Tig welder (quite an expensive setup).   If the facts were otherwise, I'd consider working with both of these materials.  However, they're not, and I don't have time to change the facts, so I stick to Steel and Carbon Fiber.

Carbon builds up to a low-weight frame easily.  A very-low-weight frame takes a bit more work.  But a simple question, that is worth asking, is: How low a weight do we need?  It might be fun to build yourself a bike that is too light to race (legally).  But how practical is that?  The simple answer is: Not very.  Very light is expensive, less durable, and at some point loses functionality.  A well made and designed bike, that falls between 15 and 17 pounds, is capable of winning in the Pro Tour.  And we can pretty easily build to this weight at a price that many riders are willing to pay.

Nonetheless, some riders want to be nearer to 15 (or less) than 17 pounds.  And they don't want to achieve their goal by using $6000 wheel-sets.  Carbon can help us meet that requirement more easily than does steel.  While I enjoy the aesthetic of steel frames, I've come to also appreciate the aesthetic of carbon frames.  It's a different flavor, not necessarily better or worse.  And as a builder, I'm learning how to leverage it to create a beautiful bike.

In the press, you will find all sorts of claims about special forms of carbon fiber and uniquely shaped tubes.  Also there is discussion of tube to tube (T2T) versus monocoque versus lugged, and frankly it gets tedious to read after a while.  As a rider, it doesn't really matter if your bike is T2T, monocoque or lugged.  Each method works well, and produces competitive frames.  The palmares of each of these frame types is extensive and up to date.

As a side note, the term monocoque is probably misused in this application.  Arguably, any tubular bike frame is a monocoque structure.  In the case of carbon frames, the term is generally used to indicate that a frame is laid up and cured as one piece.  Generally this isn't how carbon frames are made.  Instead, most of the so-called monocoque frames are build a triangle at a time.

Further, there frames, such as Trek, that look otherwise, but are essentially lugged frames.  Individual parts are made, with male/female joints on the end, and the parts are then glued together.  Careful paintwork and decaling helps to hide the joints.

But what about the types of carbon fiber?  Here too, it's hard to decipher the importance of this information for a rider.  Everyone claims that they use 'high-modulus' carbon fiber. Via that term, they are implying that they have selected  form of carbon fiber that is particularly stiff.  And we all know that stiff bikes are good, right?

Actually, its not clear how stiff a bike needs to be to efficiently transmit your power to the rear wheel.  It's also not entirely clear where the stiffness is needed (except in so far as it protects the frame from fatigue failure).  Many will quarrel about this point, but after researching the issue, I'm convinced that there is a material divergence of opinion in the scientific and engineering communities regarding this point.  So I'm not willing to say that 'stiffer is better'.

But lets say we don't want a noodle (while remembering that Alan bikes were noodles that also won all sorts of championships).  All else being equal, a bike made of fiber with a higher modulus of elasticity will be stiffer.

Unfortunately, terms such as 'high modulus' aren't very precise descriptors.  From what I can tell, most carbon fiber used in bicycle frames varies between what could loosely be called the high end of low modulus (LM) and the middle range of intermediate modulus (IM).  I hope that folks don't find that to be too disturbing an observation - it doesn't change how CF bikes perform.

You may wonder why builders aren't all using very high modulus CF?  After all, we want to make our bikes stiff, don't we?  Generally, the answer is 'yes' the manufacturers are trying to make their bikes stiff.  They are also trying to make them strong.  And for many families of carbon fiber there is nearly an inverse relationship between strength and stiffness.  If the fiber is too stiff, it is less strong and may also be more brittle (so it doesn't hold up well to shocks).  A bike frame needs to be made of a material that is strong and can handle shocks, so a number of HM carbons just aren't appropriate.

This is the first way in which manufacturer claims, should be taken with a grain of salt, regarding HM carbon fiber.

Consider also, these claims almost never specify how much of the CF in a frame is HM.  And now we have two ways by which the term High Modulus carbon fiber is misleading in various marketing and editorial material.

There are a couple of ways that a material can be made to act more stiff, regardless of it's Young's Modulus.  First of all we can use more material.  The wall thickness can be increased, making the tube stiffer and stronger.  When we're trying to reduce weight, this may not seem desirable.  But consider that we need enough material to provide the required strength for a job, and this volume of material may prove to offer sufficient stiffness for the job at hand.

In the case of bicycle tubes, we can also increase their diameter, further leveraging the stiffness imparted from their being a monocoque.  Naturally, this approach has limits determined by the physical space available. Probably the biggest limit, for tubing diameter, however, is that a certain minimum wall-thickness is necessary to maintain the integrity of the tube.  This is true regardless of the material which we use.  And in my experience, light frames, of any material, explore the limits of wall thickness of that material.  In other words, we may not be able to get enough strength, in a tubular form, with an amount of material that merely offers sufficient stiffness for our goals.

I remember a reading a review where the manufacturer proudly described how his tubes could be squeezed by hand, suggesting that this was proof of how they would absorb shock.  My personal reaction was that there was minimal wall strength causing me concerns about the durability of such a frame.  BTW, I haven't heard that manufacturer continue to make such claims, leading me to believe that they may have backed away from this approach.

If you do a search online for carbon fiber, there are a number of sources from which to purchase small quantities of CF.  Heck, there are a number of sellers on ebae alone.  Rarely, however, do these sources reveal much about the characteristics of the materials that they are selling.  Sometimes claims are offered regarding commercial or aerospace grades.  Often there is a description of the weave, which is merely a matter of style.  Generally the the weight per square yard and dimensions are provided.  The weight is interesting because it speaks directly to how much of this stuff there is - which leads right into the question of strength.  But, even sources supplying experimental aircraft builders don't provide the modulus of elasticity, the modulus of strength, much less the manufacturer and model code of the actual carbon fiber.

When you go to any lumber yard, its possible to specify your materials by a number of variables that indicate its suitability/strength for your use.  But most of the CF sources, selling in lots of less than 100s of yards, don't offer this basic service.  Leaving their users to either overbuild for safety, or limit their use of CF to cosmetic purposes.

After a long period of time, I've found some sources which allow me to spec CF materials properly.  They either provide the technical specs, or provide manufacturer and model info so I can confirm these myself.  This is important, and anyone who wants to experiment with CF building needs to have this information if they want to achieve repeatable results.

Back in the archives are posts about some of the fabrics I use.  I'm going to repeat some of that here, because traffic is up and many folks may never search back that far through the archives.

Uni, uni, uni, uni, uni-directional carbon fiber.  Many we hear the term a lot.  Everyone reading this probably knows that the strength of CF is along the length of the individual threads.  Moreover, that it is very much stronger in tension than compression.  And that the proper orientation of the fiber is necessary to give strength in the direction of forces in any one area of a bike frame.

If things were a simple as this, CF bike frames wouldn't work.   The frame and its tubes are made of layers of CF.  Generally a layer is made of uni-directional CF, that is, CF where the fibers run in parallel.  But the main part of a tube may only have 5-6 layers of CF, with the majority running either + or - 45 degrees from the axis of the tube, and a little running parallel to the axis.  I can guarantee that the forces faced by the tube don't all align with these three directions.

Think of a sailboat tacking into the wind.  A force pushing in one direction can move an object to ultimately move in the opposite direction.  Similarly, the various directions (vectors) of force encountered by the tube can be channeled into the fibers going in multiple directions, and successfully resisted - allowing for the creation of tubes with a very limited set of alignments of CF.  If we had to have fibers arranged for all the forces experience, we would need many more layers of CF, and therefore much more weight.

Within joints, things get a little more complicated, but one of the complications is that the physical shape of the joint can interfere with placing fibers in the desired orientation.  For example: It might be nice to run a fiber across the top of the BB, and then up either the seat tube or down tube.  But this generally leads the CF around a sharp corner, even if a fillet has been built up in that corner.   CF doesn't like sharp corners, and doesn't provide good strength around them.  Much better is to run the CF at an angle across the BB, and then wrap the respective tube in a spiral.  This reduces the bend in the fibers, and essentially requires another layer in the reverse direction.  Then the two together resist the forces that led us to want the fiber to go straight up the tube.  And, these spiraled layers also resist torque or twisting movements in the tube and joint.  Cool, huh?

Next time someone talks about their proprietary layups, or trade secrets, take it with a grain of salt. It isn't all rocket-science.

In a similar vein, how about those seat/down tubes that flare out to the full width of the BB?  Having never cut one of those apart (other riders are very sensitive, it seems, about my experiments), I can only guess.  But my guess is that the cup or cylinder in which the BB is affixed, has an internal fillet which allows the fibers to shift directions to parallel the axis of the BB axle.

Now the extra width is supposed to make this junction stronger and stiffer.  Does it?  Again, I can only speculate, but suspect that the impact is this design is minimal.  For any form of bending, there is a question as to where the bending occurs.  If the bottom bracket is made sufficiently rigid, it is likely that bending forces move up the respective tubes to a less rigid location.  A chain is only as strong as it's weakest link, eh?  And without further reinforcing the tubes away from the joint, reinforcing the joint is apt to offer minimal gains.

This is shaping up into a pretty good rant, and there's more ground to cover, including some discussion of the materials that I use.  Given the length of the post, combined with the fact that Comcast is acting up today and the inter-tubes aren't acting happy for me, we're going to stop here and finish in another post soon.

Until next time.


As long as I'm outing builders today, check out Argonaut Cycles - they're part of the strong and growing Portland community of frame-builders. 

It's Phantastic!

There's a new builder thread at Smoked OutIt's Phantasm Cycle Works.  Check it out!

Thursday, September 23, 2010

Villin Cycles


Check out Villin Cycles, the latest in Smoked Out.  Now I'm going to fix the side bar so you can also click from there.

Saw this on my ride today

Road down to the city, turned around at Edgebrook.  Spotted a traditional coffee shop, and this was what they had in the window.

Click the pic to enlarge, and read the sign.

Wednesday, September 22, 2010

Just Grooving Along

Did you know that there are two (2) frame-builders with "groove" in their name?  Peacock Groove Cycles and Groovy Cycleworks are two very cool builders - but very distinct from each other.  Please don't confuse one with the other.  What's the best way to avoid confusion?  Learn more about each of them.  Where do you do that?  At Smoked Out, naturally.  So head over to the bar on the right on click on each of their links.  That way you can be a more informed cyclist and a more discerning connoisseur of custom bicycles.

Ciao and tell 'em Rick sent ya!

Tuesday, September 21, 2010

Dirt Bikes

If I was looking for a dirt bike, whether an mt. bike, cruiser, or expedition style, my goto builder would be Steve Garro at Coconino Cycles.  Check him out now, click on his entry in the Smoked Out list on the right.

Sunday, September 19, 2010


Yipsan is a framebuilder with a nice sense of aesthetic.  Click on his link near the bottom of the Smoked Out list on the right!

A few more pictures

Progress continues with reinforcing and faring joints.  It seems like a few more pix might be in order, as getting this done right tends to make the vacuum bagging process go more quickly.

This is a good example of shaping a joint.  In this case, the initial reinforcing goes under the faring.

This is an example of a joint that is nearly ready.  A little additional sanding is left, especially to ensure that the head-tube shape is round, not a series of random planes.

Here is an example of how nicely this knit fabric drapes.  Without much excess epoxy, the fabric hugs the shape of the joint.  Now it will be wrapped with tape to compress it down and squeeze the excess epoxy out through little holes.

Also note how the pattern of the knit looks very different from the pattern of the woven cosmetic layer on the tube.

Here's is a wrapped joint, and you can see the beads of epoxy oozing through the holes in the tape.

And here's what the joint above looks like after unwrapping.

See you later...

Friday, September 17, 2010

New Frame Builder in Town

Actually, a new Builder is listed in Smoked Out, by the name of Huckleberry Cycles.

Check it out!

Thursday, September 16, 2010

Filling Joints

The current step of the carbon bike build is probably the ugliest.  It involves glopping a special epoxy mixture onto the joints, trying to form it to a shape, waiting for it to harden, then filing and sanding it smooth.  It doesn't usually go down in one fell swoop, and involves lots of clean up between efforts.

There aren't pictures for each step in the process, but here are some mid-stream:

The joint above has been filled, filed, and sanded.  Now a lighter layer of filler is applied.  When dry, it will be sanded down to a smooth transition between the tubes.

Here's the lower head-joint at about the same point.  As the epoxy tacks up, a rag with acetone is used to clean the excess from the tubes away from the joint itself - which saves on sanding later.

The bottom of the BB is done, and a woven reinforcement has been applied.  The upper between the tubes is almost finished, and filler still needs to be built up between the seat-tube and chain-stay.

More soon....

The Dean of Custom Carbon Bikes

Have you checked out the Dean of Custom Carbon Fiber Bikes?  That would be Nick Crumpton, just click on Crumpton Cycles in the Smoked Out list on the right.

Wednesday, September 15, 2010

Carbon Builders


If you're interested in custom carbon frames, you ought to check out Kevin at Polytube Cycles.  Just click on Polytube Cycles in the Smoked Out list on the right.

Tell him Rick sent ya,


Monday, September 13, 2010

Wade Patton

Hey gang, it's Wade Patton's turn to get Smoked Out over at the VelocipedeSalon.  He's a very interesting new builder with a fascinating story.  So take a peek.

Just go over to the Smoked Out alumni list on the right and click on Wade Patton!



Saturday, September 11, 2010

Getting Ready for Wrapping

As pictured below, the frame now holds together as a unit, even out of the jig.

Therefore it's time for an alignment check, and it all looks good.  Here's a picture of the rear alignment test.

The height gauge is a nice antique Starrett that I picked up on e-bay for less than $50.  It has decimal inches on one side and mm/cm on the other.  Even came in a nice leather covered case:

All of this led to the largest task of the evening; marking joints and masking the rest of the frame.  It's the voice of experience talking when I say you should always mask the frame before wrapping joints.

Stay tuned....

Thursday, September 09, 2010

Glue it up!

My 6061 Alu tubing arrived this week.  I cut off a piece and turned it down in the lathe to fit the inside of hte steering tube.  It's hard to read the scale in this picture, but it reads 5 grams, so the pre-joining weight of this frame comes out to 995 grams.

It's also hard to see that I turned this offset, so the wall that will be tapped is thicker than the one opposite.

Here you can see the reinforcement through the mounting hole for the front derailer hanger, and a shot mid-way through tapping the hole.

I'm pleased with how this detail is working out.

Next is putting everything together in the jig and checking alignments one more time, then cleaning and gluing the joints.  You can see the high-tech methods used to hold the top-tube in position during the curing of the glue.  The bike will cure in the jig at least 24 hours before moving on to other steps.  In this case, it will probably sit until Sunday.

Then came a detour to service a few bikes that have been waiting.  Mostly just cleaning, and changing an inner-tube.

The later is interesting.  I did a 45 mile ride Sunday, most of which was off-road.  So I took my rough-rider with the Cross tires.  UCI legal, BTW, with a 32mm width.  Getting home from the day-job on Monday, it's clear that the front tire is flat.  After pulling the tire tonight, and inspecting the inside, there is no evidence of a hole.  Looking at the tube reveals a different story with a 1.5" long split in a seam.  I'm guessing it let go with a bang when no one was around to pay any attention.

It's import to work to a sequence and schedule when building frames.  By this I mean that there is no room for impatience - which could lead to shortcuts (never work), or expecting materials to be ready before they are. 

Besides the service work above, there's another important task prior working further on this frame: I need a place to vacuum bag!  If you've been paying attention, my shop is very small, and very full.  To wrap the joints requires space to mix epoxy and wet out the carbon fiber, as well as a big flat space for the bag itself.  Fortunately, there's a table in the shop dedicated to this function.  But when not wrapping and vacuuming, it gets re-purposed.  Consequently, the last task for the evening was cleaning up this space.

Tasks still remaining include building and shaping the fillets around the joints, and laying down a special reinforcing layer of knit CF that will be applied and cured  before doing the main laminating of the joints.

More soon.

Tuesday, September 07, 2010

Couldn't weight.

Still need to install the reinforcing for the front derailer, but I was curious about the pre-wrap weight of this frame.

Monday, September 06, 2010

Working on Details Cont'd

Got a to work on a few more details today - including the first round of polishing for some bits that go on two frames, one steel and the other carbon.

To begin with, I'm installing a 'braze-on' front derailer mount on the carbon bike.  Because we can't braze carbon fiber, a different method of mounting is required.  This mount will be bonded with epoxy, but that's not enough for the stresses on the front derailer.  Moreover, I'd like to have the option to use band style derailers.  The seat-tube should be plenty strong, but it makes sense to add a little reinforcement for a long-term bike.  My supplier ran a day behind schedule, before a 3 day weekend.  So the inner aluminum sleeve is still at UPS, it'll get bonded in Thursday (check-in then for pix).  The sleeve will also provide a threaded base for a mounting M5 screw that will fix the derailer mount.  For now, the screw is threaded into the carbon tube.

More pictures later, once I've finished polishing the mount.

The brake cable stops are now installed on the top tube.
These are bonded and riveted in place, and then the backsides of the rivets are bonded.  The holes are drilled for the derailer cable stops, but problems with the rivet tool have delayed their installation.  Should be done by Thursday.  So at this point, things are ready to clean up and start wrapping joints.  Which means that its time for me to start cleaning and organizing the space for wrapping and vacuum bagging - which will probably occur next week.

On Nick's bike (steel), we have a pump mounted to the left seat-stay.  At the bottom (drop-out), feet on the pump head sit on the chain and seat stays.  To prevent the feet from wearing out the paint, I've brazed on stainless plates.  There's a little filing left to do around the edges of the plates, and a little more polishing to be done on the plates, but they're coming along and beginning to look nice.
The curve of the pump handle necessitates a long plate on the seat-stay.

The small plate

The big plate.

And that's about it for now.

Saturday, September 04, 2010


If you haven't heard of Gaulzetti bikes, and there is a good chance that you haven't, then you probably ought to check in at Smoked Out and get up to speed.

Thursday, September 02, 2010

Putting Together More Details

This is getting close to ready for wrapping joints, just a few details left.  Here's an overall shot:

There's lots of work getting to here.  You can see a bit of white on the front of the chain stays.  That's paint so my marks will better show up for mitering.  There's also which on the seat tube under where the seat stays join, again to show off marks and measures.

The head tube fit up is good:

The top tube is sitting a little low from it's final spot, but the fit is fine.

Water bottle mounts go in before bonding things together.  This allows me to coat the backsides (inside the tubes) with a heavy epoxy to better reinforce the hole and mount.  I'll also be mounting front derailer hanger, but haven't got that done today.

The rear triangle seems to be fitting nicely too!  As always, a bit needs to be trimmed from the backside of the seat tube miter to clear the box section of the chainstays.

It I get any more done tonight, I'll update this post.

Sorry, nothing more to show.  Decided to use stainless front derailer hanger, and I spent time sanding on it.   hope to get it polished.  I'm afraid it will be quite the little time sink.


Check out Drew and Engin Cycles