Tuesday, December 18, 2007

Story - Ti BB axle

One of the first things I ever learned about bicycles was that Campagnolo (aka Campy) was the end all for all components, Super Record (aka SR) was the end all for all Campy parts, and that the SR pedals and bottom brackets were the end all to all SR parts. This is because they had titanium axles.

Titanium.

At the time, titanium was used on Eddy Merckx's Hour Record bike, F-15s, space ships, the SR-71, super secret Soviet subs, and, well, the lightest pedal and bottom bracket axles out there.

There was one small problem with those axles.

They broke.

In fact, they broke at the most inopportune times. Laurent Fignon, in some race early in his career, was on some solo break (or perhaps a TT) when, pedaling hard over the top of a slight rise, his crank arm and part of the bottom bracket axle separated from the rest of the bike. He ended up on the ground, his director Cyril Guimard pleading with him to get up. This shot was captured in magnificent form in a photograph I can't find and by a photographer whose name I don't recall. After this happened both Fignon and Guimard swore off the unreliable titanium axles. To win a race you must first finish, and sitting on the ground with only the crankarm attached to your shoe doesn't help you finish.

"Wimps!" I thought. Victory requires sacrifice! A racer at that level must be willing to risk everything to win!

This was my introduction to titanium axles.

To be fair, the SR generation of titanium was not a strong alloy. Contrary to what some may think, titanium on its own is not incredibly strong. Only when alloyed with other metals does it gain the strength that gave it the miracle metal status in the bike industry. Pure titanium is most useful as a fuel to burn - the resultant pure white ash is used as white paint pigment, replacing the lead based pigment used until then.

So for a long time, the titanium equipped SR groups were exotically expensive and terribly unreliable. Retailers would repackage Campy SR groups as "SR Pro" groups, where the lightweight SR pedals and bottom brackets were replaced with similar looking but more reliable steel-axled Nuovo Record (NR) counterparts.

Back then weight was everything. Aero meant wearing your cap backwards. Everyone's obsession was with lightening the bike.

Since weight was a big deal, racers would sacrifice a bit of reliability to lose a few grams. In this power-measuring era it's apparent that such gram counting did not save any significant amount of energy, but the psychological effects must have been tremendous. Racers would trim cable housing down as much as possible, drill out all sorts of components (even head set cups!), and saw off the outer part of a NR pedal cage (made of aluminum). These Swiss cheese bikes looked really cool but their functionality was, at best, suspect.

I was no different from the drill-wielding pros from the 70s, albeit I was 10 years down the road. I drilled out and filed down shifters, a bunch of chainrings, and even went as far as filing down stress-raising ridges from the back of some of my crankarms.

Proper design, though, reduces weight much better than drilling out overweight bike components.

One of the things I did was to use Aerolite pedals. They were awkward off the bike, took forever to set up, had a one shot deal with your shoes since you had to drill out the sole for the exact cleat placement, but once set up they were a dream. They weighed about 168 grams for a pair (including cleats and hardware!) for the steel version, less than half that for the titanium version. The pedals are light enough that virtually every single "super light bike" built in the last few years used these pedals.

Drilled out of course.

Anyway, since the pedals were so light, I tended to use the steel ones as my budget didn't cover the price difference to the titanium ones ($70 versus $140 for a set).

A significant problem was that they were made in the US using standard measure fittings so the 5 mm allen wrench didn't fit - you had to use a 3/16 inch. So the shop would buy a couple sets of standard allen wrenches just for the Aerolite folks.

In addition, the pedal threads were actually standard threads, not metric. Although similar in size, the 9/16" threads would bind in the metric cranks. Tightening and loosening the pedals required a vice, a steady supply of 3/16" allen wrenches, and a lot of time and patience. Once done you'd be left with a pile of twisted 3/16" allen wrenches, a hot pedal (from friction unscrewing it), and a crankarm suited for only Aerolites from then on.

Another problem is that the pedal sometimes broke apart, the body sliding off the axle, leaving you with half the pedal in your shoe, the other half still on the bike, and the two halves far enough apart to cause all sorts of problems. You could tell when this happened because you'd look down at the pedal on the crank and it looked like it went on a serious diet, losing half its diameter.

Approaching the finish of one race, my team lined up in perfect formation, I accelerated to stay with their leadout when suddenly my foot slammed the ground, my thigh slammed on the top tube, and my rhythm went to pieces. After I picked myself up off the top tube, I looked at my foot. The pedal axle was still there so no spontaneous pedal disassembly. But there was a lot of blood on my ankle, blood that wasn't there a second ago. I tried to pedal but my foot plummeted to the road again.

I looked at my crank.

No pedal axle.

My pedal had come unscrewed and had fallen out of the crank.

Obviously I didn't do very well in that sprint. At least I learned that if my foot suddenly dropped onto the ground, the first thing I'd check was to see if my pedal was still connected to the crank.

When SRP started coming out with titanium bolts for replacing the steel ones in brakes, cranks, seatposts, stems, and other parts of the bike, I immediately thought of poor Fignon, sitting on the pavement, a crankarm strapped to his shoe, the rest of his bike on the road a few feet away. I let the "beta testers" buy and try the light bolts. SRP and other manufacturers were careful to point out that this titanium was a strong alloyed version of the primitive titanium from 10 years prior.

When the beta test riders returned from their rides, intact and breathing, I decided to try a few parts. The structural ones were titanium, like brake bolt replacement kits (replacing every bolt and nut on a caliper brake), crank arm bolts, stem bolts, seatpost bolts, etc. The best value pieces were the axles - big pieces, they were heavy in steel and seemed oddly light in titanium. The less loaded pieces were aluminum - chainring bolts, the stem binder bolt, a derailleur pivot bolt, maybe the water bottle bolts. All told a bolt kit costing half as much as a group might save you, on a good day, 100 grams.

But it was fun swapping out the parts and so we did it.

Some more adventurous companies came out with, you guessed it, titanium pedal and bottom bracket axles. Mind you, these were pedal and bottom bracket companies, not aftermarket tuners selling stuff aimed at the big companies' stuff.

One such company was Sampson, and although their foray into pedals was simply disastrous (unusable, hard to get in, too easy to get out, impossible to walk on), their cranks and bottom brackets gained some favor.

In fact, I couldn't help but buy a bottom bracket for my bike.

With aluminum cups and a titanium axle, this bottom bracket was as light as could be, and it cost just more than a pair of ti axles for my hubs. This was about the time I came up with my 45 gram increment method of calculating weight on a bike, and according to my excited calculations, the titanium bottom bracket was worth almost three 45 gram counts - in other words, about a third of a pound. I installed it carefully, rode it a bit, and it seemed okay.

At that time I had quite the noisy bike. The replaceable dropout always loosened up so the bike was always creaking. My bar and stem never liked each other so that creaked too. And some other miscellaneous parts creaked in sympathy. In this cacophony of creaks, I never noticed when a new creak popped up.

I was doing Gimbles, went long, and was looking to get a good workout. We'd gone over the initial steps (when the ride splits long and short) and somehow I ended up chasing down the guys attacking the group by the time we were down to this one light a mile or two after the downhill right turn (the biggie at the bottom of the short descent). Feeling good, I was scampering after everything that moved. I felt a good ride in my legs and I wanted to use my ride currency 100%.

We eased a bit before a right turn which brought us to the short climb unique to the "regular" long loop and I found myself at the front of the group. An ambulance, lights flashing, came flying at us from the other side. Like a good boy I eased, moved right, and surprisingly the whole group sort of followed. Once the ambulance passed I went to crank up the big gear again, anxious to get back up to speed.

My chain skipped and a rock or something bounced off my ankle at the same time, causing a sharp pain. The ankle pain made me think of a pedal axle unscrewing, but by then I had moved to SPD-Rs so it seemed wrong that the pedal would unscrew. I looked down to see if the pedal axle was missing from beneath my shoe, or, as I learned the hard way in that one sprint, if the pedal has come out of the crank.

Pedal axle under shoe?

Check.

Pedal axle attached to crank?

Check.

So why was my foot dragging on the ground?

Then, the woman behind me shrieked.

"Oh my God your chainring is broken!"

I looked down again. The reason why my foot was dragging on the ground but my pedal checks came back okay was that although my pedal was in once piece, as was the crank, the crankarm itself had done a "Fignon" - the whole right crankarm was dangling from my shoe, bouncing along the road.

I thought of correcting the woman's shrieking but technically inaccurate call (the chainring was not broken, not even the crank) but I figured since her shrieking got me to figure out what it was, the spirit of her shriek was accurate. So I let it go.

I pulled over, letting the chainring bounce along the road. I didn't know if lifting my foot would cause it to unclip from the pedal, and the last thing I wanted to do was to inadvertently fling a right crankarm into the Gimbles ride.

Talk about a way to get banned for life.

An ex-girlfriend, the only one I really stayed in touch with after the fact the fact, slowed and asked if I was okay. I hollered I was fine but I was a bit stranded because I couldn't ride. She turned around, examined my predicament, and concurred. Although I insisted she complete the ride and then get the car, she went back on the route instead to get her car.

I walked slowly to the little four way intersection we had just passed. I never paid attention to the stores there but now I hoped one would be a deli or convenience store. Then I remembered I had no money.

At the corner I found a warm piece of curb in the sun and sat down. My ankle had an angry blotch on it from smacking the big ring, and I'd ground the top of about four teeth on said ring down a bit. I could see the piece of bottom bracket axle sticking out from the crank, but when I touched it I cut myself. I left it alone.

I examined the sharp piece of axle. It was about as sharp as could be. The titanium inside appeared fresh for half the axle, but the other half looked dusty and old. I realized that when the axle finally gave way, it had already been cracked halfway through. The axle had a poorly designed profile with an enormous stress raiser between the thin bit that went into the crank and held the bearings and the thick middle bit that made the axle so stiff. Mechanical engineering dictates stress raisers fail first and my axle followed the rule to the letter.

I thought of the big efforts I had just made - pushing the big gears over the initial steps (a couple miles of step climbs), sprinting after that really strong rider, then attacking after a short pause. I realized how lucky I'd been - even the ambulance going by had helped save me because if I'd been sprinting out of the saddle out of the turn, the axle snapping could have thrown me off the bike.

Instead, I had been coasting along at about 18 mph, pushed down on the pedal once, and that was that.

I had a long time to think before the familiar green car pulled up and brought me out of my post-ride daze.

Wimp or not, I have never ridden a titanium bottom bracket since that day, and I even passed up on buying my Keos with titanium axles.

After all, to finish first, you must first finish.

4 comments:

Anonymous said...

Great story, Aki.

Any photos of your drilled-out bikes?

I can remember when Ti bolts were not enough. We had to have bright neon anodized bolts (and other parts).

Aki said...

thanks :)

No pics unfortunately. A couple things here and there, like a shift lever, but many of the bikes have since been disassembled. I have one chainring on my track bike. I even tossed the ti BB recently since I was always afraid of cutting my hand on it again (it sat in my tool box for the longest time).

Ron said...

Neat story. I'm not sure if you're familiar with M2 Racer at all, but there's a story on those pedals in my blog, second latest entry. I can relate the threading issues of the pedal spindle with your story. The ORBs had somewhat a lesser threaded spindle than others in the market and it always seemed as if the pedal would crack any moment.

I would have loved to see a picture of that unfortunate crank axle to mentioned there.

Sharp edges can be stress risers, so can cracks. Are you sure there weren't cracks somewhere in the axle? That can be a manufacturing defect as well. I'm choosing to believe these things are either cold forged or stamped out. Not sure how they did it back in the days. Now its probably all CNC to save costs.

Aki said...

The M2Racer seemed to be an evolution of the Aerolite, borrowing part of the idea and trying to improve on it. Personally I never tried them so I couldn't tell you much about them.

The Sampson BB was thin (square taper diameter) until just past the bearing, then it immediately went to a large diamter, perhaps an inch, with machined grooves for reducing weight. It all looked machined (CNC?), but the step from the thin bit to the thick bit seemed excessive. The initial crack was quite deep, 1/2 the thin bit's diameter. I'll have to see if I have the little piece since I am pretty sure I tossed the big one.

I never checked to see if there were cracks in the axle, not in any methodical way (flouro dye and UV light would have been a good way to check).