Showing posts with label cottered cranks. Show all posts
Showing posts with label cottered cranks. Show all posts

01 June 2017

Without Cotters, But Not Cotterless?

The French firm Specialites TA is probably best-known for its Pro Vis 5 crankset, often called the "Cyclotouriste" (though TA itself never used that name). Even if you've never ridden one, you've almost surely seen it:




It may well be the most versatile crank ever made:  The outer chainring, which bolts on to the inner bolt circle (the one closest to the center of the crank), were available in  sizes from 40 to 64 teeth.  The middle and inner rings, which bolted to the outer ring, were available in sizes from 26 to 50.  You could bolt one or two rings to the outer ring--or ride just the outer ring as a single.  So it may well be the only crankset that ever was truly designed to be used as a single, double or triple.  (On Vera, my Mercian mixte, I use a Shimano Deore MT-60 triple crank by substituting a BBG bashguard for the outer chainring.)  

Also, it may be the only crank that spawned as many imitations as the classic Campagnolo Record:  Sugino made a crankset that looked like a TA with a satin rather than a polished finish, and an early Shimano Deore crankset had the same bolt pattern, if a different look--as did the Stronglight 49D, the crank I'd probably choose if I wanted one with the 50.4 mm bolt circle and the option of single, double or triple.

Anyway, from the time it was introduced in 1963, the TA Pro 5 Vis became the crankset most commonly used on custom and other high-end touring bikes, particularly tandems, for about a quarter of a century.  Even early mountain bikes sported these cranks because they offered such a wide range of gearing--and, in spite of their appearance, were actually all but unbreakable.

Before Specialites TA introduced the Pro 5 Vis (five-bolt professional), the company produced chainrings used on cranks by other manufacturers.  Founder Georges Navet--who started out with ill-fated front-wheel drive experiments (hence the name:  TA stands for traction avant) wanted to produce a crankset to rival the best ones made by Campagnolo and Stronglight.  




Although Stronglight had been making cotterless cranks--fitted to the familiar square-taper  bottom bracket axle, which they originated--since the 1930s, some were still skeptical about the design.  Track racers were still using cottered cranks into the 1960s and some tourists still feared being stranded somewhere because the local garage or machine shop didn't have the right tools.  Other cyclists simply didn't want to change.




So, Monsieur Navet came up with a crankset that has the same arm and chainring bolt pattern we see on the Pro 5 Vis.  Unlike the Pro 5 Vis, this crankset--called the Criterium--was not cotterless.  So, in following the logic of cycle componentry from that time, you might say it was a "cottered" crank.  And you would be right--sort of.





If you didn't look closely, you might mistake them for cotterless cranks--which they are, sort of.


Specialites TA Criterium cranks with Spence Wolf-modified Campagnolo Nuovo Record rear derailleur, 1969.  From Velo Vecchio.


OK, you ask...What are they?  Well, the cranks were held to the axle by a bolt with an allen key head on one end, and a nut that threaded on to the other end.  That made the "cotters"--and the cranks easier to remove than those of traditional cottered cranks, and didn't require a special extractor, as cotterless cranks require.

An engineer once told me that the bolt holding the Criterium crank to its axle is technically not a "cotter", but rather a "pinch bolt."  The reason, he said, is that the traditional cotter has a wedge cut-out that is force-fit (usually by hammering) onto an axle with a flat spot.  The force--or stress, if you will--is what holds the crank to the axle.  On the other hand, the bolt in the Competition bore no such stress, and it merely holds the arm in place on the nearly pear-shaped axle end. 

The "not-cottered-but-not-cotterless" design had its advantages, in addition to not requiring special tools.  For one, the bolts were less prone to breaking or stripping than traditional cotter pins.  For another, it allowed 4mm of lateral movement in either direction on the axle.  That allowed the crank to be positioned for the best possible chainline.


One further advantage was that the design allowed the cranks to be made from aluminum.  A few companies made aluminum cottered cranks, but nearly all of them broke outright or ended up so gouged that the cotter pins could no longer hold them on to the bottom bracket axle.  But, because the Criterium's pinch bolt did not need hammer-blow forces to attach them, and because the shape of the axle and the way the bolts fitted into the crank provided an inherently more secure attachment, there was little to no danger of breaking or gouging the cranks.

What that meant was that the Criterium was, at the time it was introduced, the lightest crankset on the market.  It weighed even less than the alloy cranksets from Stronglight and Campagnolo because the Criterium's design allowed it to be made with skinny arms, like cottered cranks, and thinner around the axle interface.  it almost goes without saying that the Criterium was lighter, by far, than any other crankset because most--besides the aluminum cotterless sets made by Campy, Stronglight and a few other companies--were made of steel.


Cinelli Super Corsa with the drivetrain shown in the above photograph.  Also from Velo Vecchio.


The Criteriums were, like most Specialites TA products, meticulously made and beautifully finished.  Spence Wolf, the owner of Cupertino Bike Shop (one of the first in the US to devote itself to high-end bikes), equipped a few of the Cinellis and some of the Alex Singer bikes he sold with these cranks when the customer wanted wide-range gearing.  He would pair the Criteriums with a Campagnolo Record rear derailleur he modified with a long pulley cage he made for it.




But Specialites TA didn't make Criteriums for very long.  They introduced the Pro 5 Vis only a couple of years after the Criterium and, by that time, most dedicated, high-mileage cyclists--even track racers and tourists venturing into remote areas--were convinced that cotterless cranks were indeed a superior design.  To use a cliche, the rest is history.

Note:  I have seen only one of these cranks in person, on a bike I tuned up when I was working at the Highland Park Cyclery.  The bike had no markings on it, but the customer said it was "built in France".  I don't think it was a constructeur bike, but it looked fairly high-end.

18 January 2013

Another Forerunner To A Shimano "Innovation"

For today's post, I'm going to engage in a bit of bike geekery, as I did in yesterday's post.  Fear not:  This will not be a regular feature of Midlife Cycling.  At least, I don't intend it to be.

As I did in yesterday's post, I'm going to write about a long-forgotten component that featured a design used in later, more successful (at least commercially) bike parts.

From the 1920's until the 1970's, many British bikes featured Williams cranks, chanrings and bottom brackets.  That is not surprising when you consider that those parts were, like the bikes, made in England.  

As Steve Griffiths notes in "Classic Lightweights," Williams has been unfairly judged on the basis of its lowest-quality--and, unfortunately, most commonly-used--model, the C34.  It was a cottered steel crankset, and the arms (or spider) onto which the chainrings mounted was swaged (forced).  Willliams also make much nicer models,including some of those thin,elegant cranks you see on British bikes from the 1960's and earlier.  

But their best crankset--and the only cotterless crankset made in any significant quantity in England--was the AB 77. I have seen one of them in my entire life: on a Claud Butler that came into the first shop in which I worked.  

The AB77 was actually quite nice:  the quality of the materials, machining and finish were high.  It had the same chainring design as the TA Cyclotouriste, Stronglight 49D and the Nervar crank that aped them.  That meant the AB77, like those other cranks, could be set up as a road double with a 42 tooth small chainring  or as a triple with a 26-tooth inner ring.  



But the most interesting part of the AB77 was its bottom bracket.  Presaging a trend by two decades, its axle had a splined rather than square end.  In other words, it was a proto-Octalink or ISIS bottom bracket.  

Unfortunately, that bottom bracket was its fatal flaw.  During the period when the AB77 was produced (1962-mid 1970's), only one other crank had such a design.  It was made by Gnutti in Italy and its splines were of a different pattern from Williams', so the two could not be interchanged.  That was especially unfortunate for Williams, because the bottom bracket, which was made by T.D.C. (once a major manufacturer or headsets and freewheels), didn't last very long. 

When Shimano decided to resurrect this long-forgotten idea during the 1990's, it made the splines broader, which was supposed to increase the stiffness as well as the lifespan of the bottom bracket.  However, they, like their TDC/Williams predecessor, wore out quickly.  The problem with the Shimano splined brackets--and the similar, though not interchangeable, ISIS-pattern bottom brackets made by other companies--had narrower axles and smaller bearings than their square-ended counterparts.  Interestingly, Shimano's Octalink and other companies' ISIS bottom brackets had an even shorter run--not much more than half a decade--than the ones from TDC/Williams.  

A few years after Williams ceased production of the AB77, they were taken over by Nicklin,one of their former competitors, which offered only the C34 and a couple of other low-priced models that were fitted to mass-market bikes from Raleigh, Dawes and other manufacturers.  As production of such bikes ended, so did most of the British cycle-component industry, including Nicklin/Williams.  


09 December 2010

Eccentric Rings

Tonight, on my way home, I stopped in Flushing for a bite to eat.  Now, I've never been to Hong Kong, but Flushing is what I imagine Hong Kong would be like if it were transported to Queens.  Or, perhaps, with its ubiquitous neon, it could be seen as an Asian version of Times Square.




I wonder whether the makers of this Rudge-Whitworth ever imagined it in magenta neon light.  In some odd way, bike and light are not incongruous, at least to me.  


One particularly interesting feature of this bike is its chainring cutout pattern:




Is the hand halting or waving? Whatever it's doing, it looks good doing it on this bike.  


I'm guessing that the bike is from the 1940's or 1950's.  At that time there were dozens, if not hundreds, of bicycle manufacturers who made what we now think of as classic English 3-speeds.  (Many of those companies, including Rudge, were bought by Raleigh during the 1950's.) While, at first glance, they seemed almost the same, each model had its own particular set of details that set it apart. An example is in the chainwheel you saw in the above photo. Many other British makers used chainwheels with interesting and sometimes whimsical patterns cut into them.  The Raliegh three-speed I rode last year had a heron--Raleigh, which of course was Raleigh's corporate symbol. 


I've seen other chainrings cut out in interesting patterns. Here's one of my favorites:



It's on an AJ Warrant bike from Austria.  Although there's no earthly reason to use a cottered crankset today, I wouldn't mind having the one in the photo.