Forked Up

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Looks like a nice Reynolds 531 fork, doesn’t it?  Not!  While recently test riding one of my projects, I noted a lot of lateral flex in the front end of this 1976 Raleigh Gran Sport:

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I immediately thought that the giant bars, which are already flexible in and of themselves, were exerting forces over the front wheel, and combined with the long reach stem, gave the bike a very strange wobbly feel – somewhat akin to the handling characteristics of a mixte frame.  Certainly, this was not caused by the frame geometry itself, I was sure.

So, I installed some regular, narrower bars, but the same strange flex continued to occur.  Then, I rebuilt the headset, thinking that it was out of adjustment, and I adjusted the front hub again, even though it was also just fine.  Still, the flexible feeling continued.  Then, I disassembled the fork yet again (grrrr…) and examined it carefully.  Usually, you think of impact damage when looking at a fork.   But the blades and steerer tube were perfect.  There were no cracks or bends, and the paint and chrome showed no signs of any kind of damage.  I squeezed the fork legs together at the dropouts and found that they flexed quite a bit.  Fortunately, I had lots of other steel forks around to compare this fork to.  While all steel forks will flex when squeezed, this one REALLY flexed quite a bit more – several millimeters more by the naked eye.  I didn’t think the variation was caused by different tubing material, because I compared this fork to not only another Reynolds fork, but also to an ALAN fork, which is known to have a lot of flex.

I had previously checked the brazing at the fork crown, but now thought that I had better get my pick out and go over the brazing carefully.  Sure enough, on one fork leg, what I had thought was brazing, covered in a bit of road grime, turned out to be just…road grime.

fork braze

Brazing material is missing, tiny pinholes visible.

I prodded the area, got out my tiny flashlight and could see that this fork leg, while not on the verge of imminent failure, was not properly brazed into the fork crown.  It looks like the lug and/or fork leg were over-filed and too loose when inserted, and there was too large a gap to fill with brazing material.  Or, possibly the gap was too tight when brazed, and the leg loosened up over time, revealing the complete lack of any silver in the gap.  Below is a comparison of the two legs, the first one showing the normal looking braze.

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Brazing okay on this leg.

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Gaps in brazing on this leg.

I am thankful that I discovered this now, and thankful for my rigorous test riding standards.  And, fortunately, steel does a good job of warning the rider of a potential failure.  It’s another reminder of how important it is to not blow off any odd or unusual feel that your bike gives you.  Be careful out there!

My 1973 Jack Taylor Tourist

1973 Jack Taylor

I seem to be on a 70’s Brit-bike craze!  But it has lasted a while, as I have had this Jack Taylor Tourist Mixte for about 8 years.  At the time I purchased it from Hilary Stone, he thought it was a 1960s model.  After the bike safely made its crossing over the Atlantic, I disassembled it for cleaning and was able to read the matching serial numbers at both the rear dropout and the steerer tube more clearly, and have now dated this bike to 1973.

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The build quality of this bike is classic Taylor brothers, with incredibly smooth brazing at all the joints.  It is made, of course, with Reynolds 531 double butted tubing, and features Campagnolo dropouts, hand-hammered fenders, through-the-frame dynamo wiring, and those beautiful and colorful Jack Taylor logos.  The Taylor brothers followed the practice of building their mixte frames with a single sloping standard diameter top tube fillet brazed at the seat tube with the two extra mixte stays of fairly narrow diameter.  Having ridden all kinds of mixte frames, I have to say that this method is likely not the most ideal in terms of adequate frame stiffness.  On this bike, the head tube feels somewhat independent from the rest of the bike.  Mixte frames are best, in my opinion, when built with twin lateral sloping down tubes that extend to the rear dropouts, or if a single tube is used, extending the mixte stays beyond the seat tube also helps keep the frame adequately stiff, such as this design by Peter Weigle.

Stronglight 38T drilled

Sachs Orbit hubStronglight crankset

This is one of the few bikes I have ever ridden that was geared too low for me.  It was set up with a Stronglight 99 crankset carrying a single drilled 36 tooth ring (pictured first), mated to a Sachs-Fitchel Orbit 2 speed hybrid hub with a 6 speed cassette ranging from 14 to 28 teeth.  The hybrid internal hub is meant to take the place of the front derailleur (or add to it, if you are Sheldon Brown and want 63 gears), and it provides a direct drive, and one lower gear that is about 25% lower than the direct drive.  So, with this set-up, the lowest gear was around 24 gear inches – wow!  Unfortunately, the gearing topped out at 65 gear inches, and that meant that I didn’t have much in the way of a comfortable cruising gear, much less any way to power up to speed on a sprint.  Since I didn’t want to change out the Stronglight 99 crank, I replaced the 36 tooth ring with a 38, (pictured second), and that helped a bit.  Even so, I rarely engage the lower internal hub gear, as I really don’t need it, so I ride this bike as a 6 speed, for the most part.

1972 Jack Taylor

The photo above shows its original configuration as shipped, but it is very likely that the Sachs Orbit hub set up was not part of the original build, but was added later.  I don’t think these hubs were made until the 1980’s, and the 27 inch (yes, not 700c) rims do not match, with the rear being a Weinmann and the front rim remaining unbranded and probably the original wheel built by Ken Taylor.

This is one big mixte!  The seat tube measures 54cm and the effective top tube length is a whopping 55cm.  With its large wheels and big frame, it cuts an imposing  shadow.  The bike came equipped with no-rise French-sized mustache bars shimmed into a Milremo stem.

1973 Jack Taylor Tourist

So, I changed out the bars and stem to bring them closer to me using a tall no name stem with very little reach and some Soma Mustache bars.  I also swapped out the Madison leather saddle, which was pretty worn, with the Ideale Model 75 saddle pictured above.  Unfortunately, while looking very pretty, this leather saddle, though vintage, is still hard as a rock and needs some breaking in.  Here are photos of the rest of the components:

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Suntour V-GT rear derailleur

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Mafac cantilevers, of course.

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Milremo front hub with very stylish wingnuts.

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Soubitez dynamo

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Constructeur racks front and rear, mounted only to the fenders.

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Seat stay brazing, nice and simple. The paint now looks great after weeks and weeks of cleaning and polishing.

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This photo was taken before cleaning and polishing.

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Original French mustache bars. SunTour Stem mounted shifters.

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Another broken reflector

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She’s a beauty!  I commuted on this bike for a few years, but haven’t ridden it much lately, as I still have not made ergonomic peace with it.  With spring coming, I think I will dust if off and see if I can’t make this ride a bit more comfortable for me.

Book review – Lugged Bicycle Frame Construction

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I have recently been considering getting some brazing equipment so that I could make repairs to frames that have minor failures, rather than sending out to a frame builder for this service.  Having taken UBI’s lugged frame building class a few years back, I had a general idea of what I might need, but didn’t want to go any further until I re-familiarized myself with the topic of brazing.

I found Marc-Andre Chimonas’ book, Lugged Bicycle Frame Construction, on the evil empire (Amazon) website, with what appeared to be some favorable and thoughtful reviews by actual readers.  When the book arrived, I immediately delved into it and have now read if not studied much of the book.

It is written with a dry, understated wit, with an emphasis on the science of frame building.  There are numerous zingers in the text, hidden amongst the tables and formulas.  Consequently, I thoroughly enjoyed reading it.  The author is a physician (which he describes as his “day job”), a writer (of both technical manuals and fiction), and a frame builder.

After reading just the first few chapters, I began to seriously question the idea that anyone can take a frame building class that lasts only two weeks, and from which an actual frame is produced.  Whether that frame is safe to ride may be another thing altogether.  My own frame has several flaws that can probably be corrected, but more on that later.

The book is logically organized and takes the reader through introductory concepts such as nomenclature, frame geometry, measurement and sizing protocols and includes helpful tables for determining angles and lengths for different sized riders.  He naturally recommends smaller wheels for smaller frames, and there is a good discussion of toe overlap and bottom bracket height.  He states his opinions about frame geometry as if they were facts, and that may irritate some readers, but I found it refreshing.  For instance, recommended BB height is 25 cm for pretty much all types of normal road riding.  This is a lot lower than you will find in production bikes.

Another interesting concept that I found both helpful and puzzling was the idea of controlling the variables in frame building.  He differentiates between “operator controlled” variables and “outcome” variables.  Outcome variables are the result of the frame builders operator controlled variables.  But, he describes outcome variables to include BB drop and toe overlap, which in my mind are operator controlled.  At any rate, what is clear is that frame design is a highly complex  undertaking, and one that is aided by software.  He recommends using excel and offers a link to a useful frame design spreadsheet, which is available on the author’s website.

There is a quick trigonometry and metallurgy review (which the author calls optional), and then the theory turns into fabrication as the author goes through chapters on frame parts, tools, mitering, torches, brazing technique, and lug modification.  Again, the author doesn’t hesitate to state his recommendations, even down to a specific brand or manufacturer of a particular tool.  For me, someone who didn’t take shop class in high school, the specific advice is extremely helpful.

After digesting many of the chapters, I decided to drag out the frame I completed 2 years ago but never finished filing or painting.

My frame with front-center at 59 cm - a little shorter than I wanted.

My frame with front-center at 59 cm – a little shorter than I wanted.

I built this frame for myself, designed around a 650b wheel size.  I wanted enough front-center distance to allow for fenders and decent sized tires.  The book uses a formula to determine an ideal length.  I plugged my numbers into his formula and found that I won’t have toe overlap with this frame, so that is a relief.  I did have to use a longer than usual (for me) top tube length to get this much front center distance (combined of course with all the other measurements).  That means I’ll use a short reach stem when I eventually build the bike up.

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One of the things that troubles me about my frame is that it was built so hastily and with so little actual knowledge.  Well, after reading the brazing chapter I think I have reason to be concerned.  I remember having a lot of trouble sanding enough material off the top of my fork blades, and off the inside of the fork crown so that the legs could be inserted without a lot of force.  After hours of filing, I still wasn’t happy, but ran out of time so just brazed the fork legs into the crown even though the fit was tight.  This is definitely a no-n0 – there needs to be enough room for the silver to flow into the joint.

Here are some other details of the frame I built.  Using this book as a resource, I will be able to correct the other two (known) mistakes on the frame.  I may decide, however to build a new fork.  And, I now know what kind of equipment to purchase and how to use it safely, so I am looking forward to being able to do my own small repairs.

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Nice looking BB

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Mistake on the seat stays – they are out of alignment

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Drive size DO not yet cleaned up and filed – you can see I got the tubes a bit hot.

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Aaack! Seriously out of whack shifter bosses – the jig probably got bumped when I turned away to get more silver.