Two Speeds, Two Chains

 Most of you, I suspect, ride or have ridden a bike with two chainrings.  I would imagine, however, that none of you have ridden a bicycle with two chains that isn’t a tandem.

Some folks are about to have that experience. They’re not Grand Tour riders or triathletes; none (as far as I know, anyway) plan on embarking upon a cross-country or round-the-world tour.

Rather, they are folks who use their bicycles as taxis, pickup trucks and cargo vans. I encountered such riders in Cambodia and Laos and even rode bicycles like the ones they use.  Those bikes, however, didn’t have the unique feature I mentioned at the beginning of this post.

So why, you ask, are some people about to ride a bike with two chains? And, where are they?

I’ll answer the second question first:  Africa.  I’ve never been there, but I imagine that parts of it are like the Southeast Asian countryside I saw:  unpaved roads and paths with few, if any bike shops.  And the shops that exist can’t order a part you need for your SRAM Red 13 speed shifter and have it delivered by Fed Ex the next day.

In such an environment, a bike that would need such a part would be all but useless.  And it would be worse than impractical for hauling a 15 liter metal jug of milk from farm to village.

World Bicycle Relief has been working to address people’s needs in rural Africa and other parts of the world.  It developed the Buffalo bicycle: a “tank” with wide tires, steel rims and a coaster brake. This was believed to be the bike with lowest possible maintenance. Also, because the bike has a coaster brake, it can be ridden with wheels that are significantly out-of true.  Oh, and it has a rear rack that can support up to 200 pounds.

As you can imagine, the bike is heavy. But its users didn’t mind:  Reliability is more important to them. That weight, however, combined with its coaster brake hub—which has only one gear—meant that most people couldn’t ride it up a hill, especially if it was loaded.

A new version of the Buffalo bike is designed to deal with that problem.  So why two chains?, you might ask.

Well, each chain runs on one of the two chainwheels—and one of the two sprockets on the rear.  Those sprockets are part of a freewheel that looks like a wider version of the ones found on BMX bikes. One chain wraps around the smaller sprocket and chainwheel while the other winds around the larger sprocket and chainring.

This arrangement results in a two-speed bike without a derailleur, internally-geared hub or coaster brake. So how does the bike “shift?”

Well, the freewheel contains a mechanism that disengages one gear while the other is being used. So, if you are pedaling in one gear, the chain still spins on the other.  And the “shift” is made by pedaling backwards, just as you would on a coaster brake.

Achieving that, of course, meant giving up that coaster brake.  Instead, a pair of dual pivot brakes binds on robust alloy rims to stop or slow down. As the developers explain, some strength may be sacrificed but, apparently, there’s still enough to support a 200 pound load in addition to the rider. And it’s also easier to true an alloy rim.

Oh, and everything on the bike—including the freewheel mechanism—can be fixed with a tool that looks like an oversized version of the old Raleigh spanner—or an adjustable wrench.

I, for one, would be interested to try such a bike, if for no other reason than to experience the two-speed, two-chain system.  And I am always happy when a practical bike—whatever that means for a particular place or kind of user—is designed.

OTEC Will Keep You Going In Circles, But Not In The Way You Expected

Back when I was racing--and even when I wanted to stay in (or pretend that I was) in the same kind of shape I was when I was racing--one of the goals of training could be summed up in three letters:  RPM.

In other words, we believed that spinning at the highest cadences possible would make us go our fastest.  That meant riding, at least at first, in a lower gear and working up to higher gears.  The one who could spin the highest gear would win the race.

Now, of course, nobody is going to turn cranks with a 54X11 gear (which I actually had on my road bike for a time) at the same rate as, say, a 42X15.  But all of the trainers and training manuals told us that it was better to do 120 rpms on the latter (or a higher gear later in the season) than to mash the former.  If nothing else, it gives you a better cardio workout and is easier on your knees.

Apparently, there are some folks who don't agree.  Ever since the invention of the "safety" bicycle (two wheels of more or less equal size driven by sprockets and a chain), someone or another has tried to "improve" on circular pedaling motion.  Examples of such endeavors include the oval and elliptical chainrings that seem to reappear in one form or another every generation or so. Shimano's Biopace is probably the most famous example; currently Osymetric rings have a following among some members of the peloton.  There have been all sorts of other ways to make pedaling more efficient by eliminating the "dead" spots so that power is transferred all through the arc of pedaling.

Just recently, I came across something I saw in the bike magazines some years ago but never actually saw in person.  It seemed like one of the most bizarre, Rube Goldberg-ian contraptions I'd ever seen on a bicycle.  But, apparently, the idea has stuck around:  The organization that patented it in 2007 was founded in 1998.

At the risk of offending anyone with any sense of political correctness, I will say that the idea is so high-tech and so complex (complicated?) that it could have come from one of only two countries:  France or Japan.   

If you chose the Land of the Rising Sun, enjoy your sake.  OTEC, the company that patented and produces the SDV system, says "The direction of a motion of a pedal in its power phase is designed to coincide with the direction in which the rider can most easily apply force on the pedal while stretching his or her legs."  The result is that its geometry  "makes riders use larger muscles, resulting in lower cadences than expected".  

That is exactly the opposite of what we were all trying to achieve all of those years!  But, in looking at it in motion, I can see how it would make sense for, say, someone like a climber or, perhaps, an individual time trialist.  It also seems to me that it also might be better suited to a recumbent bike, on which the rider pedals from behind, than on a diamond frame, on which the cyclist pedals from above.

I am curious enough to try an OTEC if given the opportunity.  What differences, if any, would I notice in my pedal stroke or my ride?