> Cinelli Bivalent hubs to me look like a development of the French
> "moyeu a broche," a hub that left the freewheel on the frame when you
> took out the wheel. The basic design of the hubs was the same as the
> Bivalents, including the screwed-in skewer, but they were used on
> rear wheels only. They appear to have become available in the late
> 1930s, and definitely were found on some high end cyclotouring bikes
> in 1947.
The Italian Taurus brand made roadsters that also used this type of hub in the early 30's (maybe already in the 20's). I would however never claim that the Italians 'invented' this. I guess that this idea would actually date from about the teens. In my eyes, the real advantage of such a set-up is not for replacement of spokes in cyclotouring, but for replacement or repair of tubes and tires on bikes with full chaincases. Both of these activities were undertaken far more frequently than spoke repair. Taurus was truly a leader in many aspects. They were among the very first to use special lightweight heavy strength metal alloys for frames. They also made a number of roadster bike models that had fully internal brakes (check out the Taurus page on the CR site: http://www.classicrendezvous.com/Italy/Taurus_roadsters.htm ) In the one photographed, the brake levers are visible but neither the front (built into the fork blades) nor the rear (built into the chainstays) brake calipers are visible.
> Later, chainrests brazed onto the frame and Maxi-Car hubs with
> keyhole spokeholes more or less made them obsolete, as they offered
> the same advantages (no need to touch chain when removing wheel, plus
> being able to replace driveside spokes without tools). But some bikes
> in 1950 still featured the "moyeu a broche."
I feel that the fact of being able to replace spokes while on the road has always been 95% marketing and 5% necessity. It simply doesn't count for much. On a brevet ride in the 80's, I fixed a fellow rider's rear wheel with a spoke with double bend inserted into the flange and screwed in regularly into the nipple. I then trued up the wheel and he was able to finish the ride without any problems. With all the very real advantages of Maxicar hubs, this is the one feature that I have always questioned.
> One French maker was RAS, there was at least one other. The Italians
> seem to have modified the same design with spacers and such to make
> front and rear wheels interchangeable.
As the name implies, the interchangeability of the hubs is the sole 'raison d'être' of the Bivalent hub. No other features or 'advantages' were ever highlighted or espoused.
> I never understood the advantage of being able to exchange front and
> rear wheels. Cyclists don't carry even one spare wheel (in which case
> it would make sense to make it fit in both positions). And a support
> car in a race carries 10 or more wheels, so carrying several fronts
> and rears isn't a problem (I'd carry 6 rears and 4 front, considering
> the preponderance for rear flats). Maybe others didn't see the point
> either, and that is why these hubs never caught on.
To properly understand the advantage of one single interchangeable wheel for either front or rear, you should ride in a team car when you see your rider signalling a flat tire. A mechanic can get out of the car with one free hand and a clear mind because he does not have to grab the 'correct' or multiple wheels. The mechanic's free hand is already sufficiently important to make the design worthwhile. You can get out of the car more quickly. The clear mind also allows the mechanic to concentrate solely on the repair at hand. For every second spent waiting on the side of the road, the rider must spend twice as long on the road riding with higher energy expenditure. It should also be pointed out that for any riders in a break that has less than 45 seconds of clearance from the peloton, as well as those riders in 'chase' groups caught between the lead group and peloton, they are generally only served by a motorcycle support vehicle that cannot carry 10 wheels. The major problems with the Bivalent hubs were: considerable extra costs of the hubs, extra weight, reliability problems and no widespread desire to try something unproven. Cino apparently got the Italian national team to ride on them but it was apparently not a resounding success.