Monday, December 24, 2007
I originally built a low-trail replacement fork for Jay’s Rivendell Canti-Romulus, designed with a 60mm offset that produced about 44mm of trail. Soon after receiving this new fork, Jay telephoned to say that he wanted to commission a new frame, incorporating this fork, if possible. He had some fit issues which could be addressed with a made-to-measure frame. He also had a wish list of small details, including a kickstand plate, which would be easy enough to get just right on a custom frame.
No problem. Every frame that I design begins with the fork. There certainly wasn’t anything to prevent Jay’s fork from being recycled, as long as it passed my inspection for damage or misuse.
Jay planned to strip the components from his Romulus to use on this new frame, which would be built with cantilever bosses. Before those rear cantilever bosses had been brazed into place, he sent an e-mail saying that he’d unexpectedly sold the Romulus complete, and would be buying all new components. I pointed out that brake technology now was an open option, and asked if he might like to consider using extra long reach (55-73mm) dual-pivot sidepull caliper brakes. Jay already was familiar with the beautiful “Silver” model from Rivendell, and jumped at the chance to use brakes which would match so nicely with the style of bicycle he envisioned.
But wait … doesn’t the fork have cantilever bosses? It sure did, but those were removed with some very careful hand work with files and sandpaper. No additional heating on the fork blades, and no trace that the canti bosses ever were there. Spoiling the fork’s paint wasn’t a concern since the new frameset was going to be painted in a different color.
So there it is, a second life for a Frame-Neutral Replacement Fork™ and a happy customer with a new bicycle designed to fulfill a dream. That, I propose, is why I do this.
And, finally, a few details, starting with that mounting plate for a fancy Pletscher kickstand.
Friday, December 7, 2007
The customer requested separate under-crown mounting points for both a fender and the new Velo Orange randonneur front rack. This rack, intended to be used with caliper brakes, features a center tang made from a flat strip which attaches underneath the crown. With the limited space available in the open end of the steerer tube, this called for a carefully designed piece to provide two threaded sockets with enough separation to be functional, enough depth-of-thread for a solid connection, and no interference with the brake’s center bolt.
The mounting solution shown above provides a 6mm socket (front) for the rack, and a 5mm socket (rear) for attaching the fender. The spacing between the sockets is maximized, and the socket depth provides 5mm of full contact thread. The bridge that carries the sockets is about 2mm thick, and, with this crown, provides the extra bit of vertical drop required to allow the rack’s tang to pass cleanly beneath the arch of a Tektro R556 caliper brake. With the additional fork length built in to compensate for the added fork offset, all of this stuff underneath the crown won’t interfere with the clearance needed to properly position the fender over a 700Cx30 Grand Bois tire.
The customer will use a generator hub, running the light wire all of the way up the right fork arm, then down the left arm to a low-mounted light. To eliminate that whole unsightly zip-tie and p-clamp scene, this fork received a full set of brazed-on lighting wire guides, along with a dedicated light mount low on the left arm.
Small details like these really clean up the appearance of a bicycle. In doing so, the details themselves tend to disappear from the casual observer. But they’ll always be there, providing a perfect foundation upon which to carry your load, keep you dry and light your way.
Saturday, November 3, 2007
By the time that this Low-Trail All-Rounder frame returned from the painter, the light here in northern New Hampshire had undergone the seasonal shift from green to golden. When I carried the frame outside to view it in natural light, I was stunned by how elegant the color appeared in the Fall colors.
Standing there, staring at that lustrous Maroon, I was conflicted …. Should I build it up as promised for the next day’s inaugural ride, or should I just keep it as a centerpiece for the Thanksgiving table? Better judgement always seems to prevail, and I realized that our dining table isn’t large enough to hold both frame and food. What a shame.
The next morning dawned clear and cold, and Jackie arrived early for the first ride on her new dream bike. We picked a route to exercise this bike's great versatility, starting with mixed-surface backroads, then later heading for Crawford Notch as the day warmed. Watching her spinning along in the Fall colors made me realize that Meteor Maroon is one of those colors which looks so much better in real life.
Monday, September 24, 2007
So, why does this concern someone like me, who builds and uses only steel forks? It provides a perfect counterpoint for telling you a little about my approach to building – and aligning – custom steel forks.
Building an aligned fork is more difficult than building an aligned frame. On a fork, there are seven independent dimension and location variables, which must be satisfied simultaneously, in three dimensions. My work process for building a steel fork is based on subassemblies, similar to my approach to building a frame. The crown is brazed to the steerer, and the crown race seat is machined to specification on a lathe. The dropouts are brazed into the raked fork blades. The fork’s alignment variables all come together when these subassemblies meet in the fork jig, where I cut the fork blades to a precise final length, and pin the blades into the crown sockets. The securely pinned fork is removed from the jig and free-brazed in a specially designed rotating fixture, producing a finished fork which is free of residual stresses and very close to its final alignment standard.
Any brazed steel fork will benefit from a final alignment, simply to remove the small displacements which are a consequence of the heating cycle. This is an area where my clock-be-damned approach to framebuilding allows me to be exceptionally picky. Like most builders, I align off of a granite surface plate, using machinist’s v-blocks and gauges. But, by the time that all of the fork alignment tools are out – including custom tooling that I’ve created just for this task - I feel a little like the crazed dentist that Steve Martin played in that movie.
The Calfee article notes that “A diligent steel frame builder can align the fork blades to within a millimeter of symmetry. Certain well known builders align them to within 0.5 mm.“
I routinely confirm the alignment of my forks to within 0.5mm of specification, on each measured variable. Apparently, I devote more attention to fork alignment than many other builders. That’s OK by me. As I see it, your fork is too important for anything but the best in craftsmanship.
Friday, March 2, 2007
I have developed the Frame-Neutral Replacement Fork™ as an intelligent solution to retrofitting existing frames with a longer-rake fork. This fork is custom designed to provide the new low-trail steering that you seek, while preserving your frame’s original orientation. More than a simple fork fabrication, this is a comprehensive design service, working with you and your existing bike, and advising about workable options.
Let’s look at the interaction between the fork and frame. To help with this, the diagram below defines the key elements of a bicycle’s front-end geometry. The data listed for the original fork (black) and the Frame-Neutral Replacement Fork™ (red) is from a completed retrofit project.
A bicycle frame is supported by its fork, and the design of a frame begins with the fork’s length and rake. In this discussion, the fork length is measured along the steering axis, from the crown race seat to the point where a perpendicular line intersects the axle center, as shown by the FL dimension in the diagram. Fork rake is measured on a line perpendicular to the steering axis.
From the designer’s perspective, the front end of a bicycle frame is located in space by the distance along the steering axis from the lower end of the head tube (point A) to a baseline drawn through the axles (point B). As shown in the diagram, this distance along the steering axis is the sum of the fork's length-on-axis (FLA) plus the headset’s lower stack height. When the headset is a constant, this leaves us with an evaluation where the key variable, fork length-on-axis (FLA), is calculated directly as a function of the fork length (FL), the fork rake (RA), and the head angle.
In order to preserve the frame’s original orientation (head tube and seat tube angles), a longer-rake replacement fork must produce the same length-on-axis (FLA). As seen in this diagram, this requires the longer-rake replacement fork to also have a longer axle-to-crown length (FL). In the case illustrated here, increasing the rake by 22.5 mm required that the replacement fork’s axle-to-crown length be 7 mm longer than on the original fork. This may seem like an insignificant number, but leaving off those 7 mm would have made the head angle steeper by nearly 0.4 degrees. From the perspective of this bicycle’s owner, that much change in head angle would have been unacceptable.
There’s a bit more to this than simply making a longer fork. If you’re using caliper brakes, we’ll have to take a look at the longer brake reach, and how to deal with it by using various crown designs and/or an alternate front caliper. There really are a lot of neat ways to make this work. If you’re using cantilever brakes, you’re good to go with your existing components.
I have my own numerical design model, designed to solve on this specific problem. Using this model, along with a few key pieces of design data from your existing frameset, I can quickly, and precisely, define the Frame-Neutral Replacement Fork™ which best meets your needs.
Saturday, February 10, 2007
I design and build a frame with the goal that it will become your favorite bicycle. The one that you’ll ride hard, rely upon, and lovingly maintain. The one that you won’t worry about taking everywhere, because each scratch in the beautiful paint just reminds you of a great adventure. The one that you’ll outfit with different components as your cycling interests change over the years. The one which you want to last as long as you do.
I work in a single traditional medium, silver-brazed lugged steel. As an engineer, I understand that this is a superior method for joining the high quality steel tubes that are available today. As an artist, I find that this method allows for a level of creative expression not available with other, more industrial, fabrication techniques.
I build frames designed for the types of cycling that I know the best, and love the most … all-day social rides, long distance touring, and exploratory rambles on mixed-surface back roads. For all of these uses, my frames are designed along the traditions of classic road cycles. They build into the type of comfortable, versatile and durable bicycle that you’d want if you could have only one. Sure, you can set them up stripped down to ride fast. But, when you’ve outgrown that and find yourself ready for pure fun or serious adventure, these frames readily accommodate wider tires, higher handlebars, racks and fenders.
My framesets include a custom steel fork, designed to provide the desired handling characteristics. Building a fork is a time-consuming task, but it provides a level of design flexibility that simply is not available with the ubiquitous, but narrowly defined, aftermarket forks. A custom steel fork also allows the use, if desired, of a traditional quill stem, with its inherent advantages for easily adjusting the handlebar height.
Every frame designer should have a bias, and mine is for rider comfort. I believe that comfort is paramount to performance, as well as to the overall enjoyment of the sport. If you’re not comfortable, you can’t pedal efficiently. I rarely ride with skinny young racers, but I’ve cycled on long cross-country tours for years in the company of “mature” men and women, many of whom simply can not achieve a comfortable posture atop the style of race-inspired bicycles currently crowding the showrooms. Over and over, I have observed how simple measures, such as raising the handlebars to near saddle height, can ease the common complaints of neck, shoulder, lower back, and crotch pain. The custom frame which I design for you will consider not just your body measurements, but also your flexibility, your weight and where you carry it, your issues with old injuries and the way that you relate to your current bicycle. Above all, I won’t build anything that I’m not convinced will allow you to ride moderate distances in relative comfort.
For each frameset, I select tubes which will be appropriate for your weight, strength and riding style. Tube selections also correlate to the overall theme of the frame, such as light road/sport or fully loaded touring. My goal in selecting tubes is to present steel’s legendary silky feel, while maintaining strength and durability. My frames are light enough, but never intended to be contenders in today’s frame-weight wars. I’ll mix tube sources to get the right combination, and your frame may contain tubes from Reynolds, Dedacciai, True Temper or Columbus, all of whom make excellent products.
This is a wonderful time to be building lugged steel frames. Modern investment casting technology is available to produce high quality lugs, and the masters are stepping forward to design new lugs and sponsor their production for the framebuilding community. I've worked with modern lugs from Henry James, and the great new lugs from Kirk Pacenti and Richard Sachs. Richard's are designed with classic profiles, intended to be used without modification. For creating something special, I turn to Kirk's artisan lugs, which contain a generous amount of extra material that may be carved as desired. Even though it requires an additional 12-15 hours per frame, I like to use these artisan lugs to express my own style, and make a frame truly unique.
I believe that there’s no point in building a frame which inherently limits the owner to only one style of cycling. It is such a simple mater to provide ample clearance for wider tires, secure attachment points for racks, clearance for fenders, and the easy ability to change the handlebar height. These features greatly increase the versatility of a bicycle, without significant performance penalties for the recreational rider. Once you have achieved a comfortable rider posture, a smartly designed frame can, within reason, be used for a variety of types of cycling by simply swapping a few components.
I have an interest in the bicycle designs, perfected fifty years ago in France, which combined wide, supple 650B tires and a low-trail steering geometry. Largely forgotten by the American market, the 650B tire, and low-trail steering in general, is enjoying something of a revival among riders interested in comfort and versatility. Using my own 650B-based prototype and a set of frame-neutral test forks, I have tested a range of low-trail geometry options over thousands of riding miles. I understand the nuances of this design option and how it may be applied to benefit various cycling styles. The photo below shows a detail of my low-trail All-Rounder frameset, designed around wide 650B tires, extra-long reach caliper brakes, and a long-rake fork.
I also offer a design/build service for bicycle owners wishing to convert their existing high-trail bicycles into a low-trail configuration. Using a special purpose numerical model, I can evaluate the specifics of the retrofit application and design a Frame-Neutral Replacement Fork™ which provides the larger rake and preserves the frame’s original orientation.
When it comes to visual effects, I prefer elegant simplicity. A bicycle’s overall appearance should be like that of a graceful bird, not a rolling advertisement. Paint should be simple and beautiful, but simple doesn’t mean dull. Bright, rich frame colors can appear quite simple, as long as they’re not competing with assorted panels, stripes or logos. No matter what the color, your frameset will receive a gorgeous multi-coat paint finish from one of the masters of the trade. I also feel that the traditional style for frame decals is mostly just cheap advertising, and tends to spoil the innate elegance of a finely crafted, lugged bicycle frame. The only decal on your frame will be my small “signature” graphic near the seat cluster. Such styling is unusual, I know, but this is no ordinary bike.