calstar 

Dawes-man has this on his flicker in his thread on the Japan handbuilt show.

https://www.flickr.com/photos/2298367...n/photostream/

I've never seen one operating before and now that I have wtf! Does the rider loosen the quick release lever, shift with the chain derailuer lever, and then tighten the qr lever again? Any explanation will be appreciated.
BTW, thats renowned Japanese frambuilder Mr. Nagasawa doing the shifting.

thanks, Brian

Chombi

I don't know either, but do I see the axle moving forward and backwareds on the rear dropout slots when he shifted the chain up and down the FW gears?? If so, what keeps the rear wheel axle from falling out of the dropouts all together?? There seems to be a rod clamped on to the drive side seat stay and attached to the end of the drive side axle that seems to retain the wheel on the DO slot, but is that enough??

Chombi

Bianchigirll 

It is cycling magic!

The way I understand it... one lever opend the QR so the axle (fixed gear) can move back and forth on the teeth/gears on the dropout. The other lever moves the 'fork' controlling the chain from gear to gear. I guess a quick pedal backwards would allow the chain to move to smaller cogs while move in a normal motion moves it to the bigger cogs. I think!

rhm

The video is deceptive. Normally when you're riding a bike, the wheels would be turning.

I've never seen one in person but have gleaned the following from the internet. No doubt an expert will correct me:

In the video the guy is playing with the shift lever. It moves the chain side to side. The other lever locks the wheel into place. So before you shift, you must release the QR on the axle, then shift. Shifting to a smaller cog reduces chain tension, so the wheel automatically rolls back in the dropouts until correct chain tension is realized. Shifting to a larger cog does the opposite, so the chain pulls the wheel forward in the dropouts. Either way, when you're done shifting, you lock the QR again.

Doohickie

The tensioning is achieved by sliding the the hub in the dropout. Note that the quick release for the rear wheel is operated on a rod that goes up the seat stay. Looks like you'd have to loosen the quick release, shift gears, adjust the spacing (not sure if you could do that while rolling), then tighten the quick release.

Holy wtf, Batman.

Bianchigirll 

These




The hub w/ QR rod and shifter. The axle has teeth/gears too



Lots of pics.

https://www.bing.com/images/search?q=...orsa&FORM=IGRE#

David Newton

Nobody is fooling me.
Way up on the mountain, when Emilio needed gears, he hopped off and slipped the chain to a bigger sprocket, and jumped back on. Either that or crashed.

Bianchigirll 

Actually at one time they did just that, actually flipping the wheel!

You guys really need to curl up by the workbench with a big mug of coffee and skim/read through the dancing chain. I learned so much about older bikes just from it.

rhm

The dropout is angled; it is higher at the back than at the front. The rider's weight pushes the wheel back.

Which means, incidentally, that changing gears changes the frame geometry slightly. In lower gears you have steeper frame angles and shorter wheelbase. Probably not enough to notice.

Chombi

Holy cow Batman!, The system actually releases and locks the QR on the axle when shifting?? Kinda sounds scary....I don't think I'd be willing to bother trying that system out any time soon...

Chombi

calstar 

Ok, thanks for the link, the pics help a lot. Brian

20grit

My experience with axle slippings in in semi-horizontal drop outs tends to make me doubt this. Any force at all caused my wheel to engage the left stays and then 20grit made contact with the ground.

bikingshearer 

To clarify: (1) while coasting or pedaling backwards, flip upper lever to open the hub quick-release; (2) while pedaling backwards, use the lower lever to move the chain to the desired gear; if shifting to a larger cog, the increased tension will pull the wheel further forward in the dropout; if shifting to a smaller cog, the lack of forward pressure from pedaling will allow the hub to move further back in the droput; (3) flip the upper lever back to close the hub quick-release; (4) unless you are Gino Bartali, who was reported to be the master of the Cambio Corsa, sprint to close the gap that developed while you were futzing with your gears.

The toothed dropouts and matched teeth on the axle make the hub move forward or backward uniformly, meaning without the wheel pulling to one side or the other.

The one I don't get is the Paris-Roubaix, the next iteration of the Cambio Corsa that had both the quick-release and the shifter operated from a single lever. The basic action was the same, I'm sure, but how it worked mechanically I have no clue. Since it lasted about 15 minutes (the Gran Sport came out very soon after the Paris-Roubaix was introduced), we may never know . . . .

puchfinnland

there is a vid on youtube....anyone remember where?

ThermionicScott 

Were you 10grit before?

azgreg

I can just see my hand going into the spokes. No thank you.

Italuminium

very cool video, and amazing that mr. Nagasawa build a bike like that for himself. just a shame that the really cool campagnolo dork disc (somehow crafty Tullio even made those things look good) with a plastic one.

iab

Flying Merkel

Up until a few minutes ago, I felt macho for using downtube shifters

bbattle

Fausto Coppi was very good at shifting the Cambio Corsa. His rival Bartali used the Margherita.

Way back, it was felt important to keep the chain tension high so the derailleur principles of today would be anathema to the old timers. Though there was that one guy in "Dancing Chain" that was quite the opposite and had a loose chain even on a singlespeed bike.


I cannot recommend enough Berto's "The Dancing Chain". it should be required reading for anyone entering the C & V.

iab

Actually, Bartali used the Cervino derailleur. Cervino was an independent company that was co-owned by Bartali and Tommaso Gnieddu.

jjvw

Both dropouts are toothed and both sides of the axel are toothed. This keeps the wheel "square" in the frame as the axel rolls back and forth in the dropouts. What causes our loose wheels to twist usually into the left chainstay (beyond the lack of toothy drops) is the the chain pulling on the right side of the wheel. This would be most pronounced on a single speed.

The key to the Cambio Corsa system appears to be chain tension resulting from the weight of the rider.

The weight of the rider on the slanted drop outs acts the same way the spring loaded derailer acts as a chain tensioner. When shifting by forcing the tensioned chain back and forth on the gear cluster while pedaling, the chain switches gears. this action is what causes the wheel to roll back and forth in the dropouts as a means of naturally compensating for the increase or decrease in chain tension. If I am understanding this correctly, the rider does not manipulate the wheel position because, when the wheel is released and the chain moves to a bigger/smaller cog, this wheel movement occurs automatically. Its really quite elegant and makes the rider very aware of the forces at play on the rear wheel. For better or worse, that physical connectivity and awareness is lost on modern derailers.

Oddly enough, it seems like the actual chain tension is determined by the weight of the rider. A skinny rider would have a loose chain, while a fat rider would have a tight chain.

Bianchigirll 

Oh right DUH! it can't be a fixed gear right?

jjvw

I'm not sure why it couldn't be a fixed gear. The axle spins independently of the hub. If I recall correctly, the main reason a modern derailer can't be used on a fixed gear is because the derailer can't handle the the back-pedaling forces. Putting tension on the lower run of chain during the back-pedal crushes the derailer. I would think with careful pedaling it would be possible to shift a cambio corsa with a fixed gear. Because the chain tension is always tight because of the movable wheel, the system wouldn't care if it was fixed or free wheel.

Someone explain why this wouldn't work?

Michael Angelo