Hi All!
A new/old cainring shifting method has come to my attention, and you may find it interesting. It is the Vyro, developed since 1993 by Austrian Gregor Schuster. He has run out of funds and is requesting a buy-in to meet his production costs for an initial run in Spring 2013. I have no financial or other interest in the product, but do find it intriguing.
On his YouTube video, Gregor says the unit is much simpler than derailleur systems and much lighter than hub-gear (IGH) units such as those offered by Shimano and Rohloff. He indicates someday he would like to expand the system to the rear of the bike, but for now his efforts center on the front changer/chainring selection, which appears to be limited to a double setup at present (aiming for the downhill/freeride market).
In my memory, the basic principles are not new, but the execution may be; he is pretty tight-lipped about the actuator details. Basically, his design uses a segmented large outer chainring and what appears to be an intact small inner. The segments in the large ring are hinged and "fold" over the small ring to pick up the chain. It appears the chain is engaged at two points until it seamlessly makes the transfer completely from one to another.
It is certainly an intriguing idea, but there have been many expanding-segment and hinged/folding segment chainrings and rear-drive systems over the years, including the ill-fated Browning B.E.A.S.T. unit that SunTour poured a lot of money into before it um, folded (
http://www2.bsn.de/cycling/articles/browning.html ). Yankee Bicycles*/NordicTrack (
http://www.youtube.com/watch?v=ZsZJhPGcByQ ) marketed an expanding/contracting segmented-chainring bicycle in the very early 1990s. In turn, its drive system was much like the Tokheim (
http://www.parktool.com/blog/calvins-corner/tokheim-shifting-system ).
The Vyro video is here:
http://www.youtube.com/watch?v=toym0NTle5QThe Vyro company (at present, only Gregor) website is here:
http://www.vyro.com/index.php?p=aboutA nice overview and summary of available information about the Vyro appears here:
http://www.bikerumor.com/2012/08/06/german-approach-to-a-practical-revolution-in-gearbox-tech/#more-47070While the Vyro shows promise, the version we are shown is clearly a proof-of-concept/advanced prototype with some refinement needed. For example, the exposed springs of the shifting mechanism will have to be shielded or they will soon clog with mud and dirt. While the chain is guided, the entire mechanism is exposed, and that can't bode too well over time. I can't help but think a Hammerschmidt or Schlumpf (especially) semi-sealed or fully-sealed planetary 2-speed crank-based gearbox would be more reliable, but without a 58Euro minimum buy-in, there is really no way to fully and fairly evaluate what Gregor has. I wish him well; there's always room for innovation, and I like the apparent transparency of grass-roots approach to raising funds.
Anyway, fun to see another stab taken at a shifting alternative.
Best,
Dan.
*(Side note: The Yankee bicyce had one of the most interesting braking systems I have ever seen, and it was amazingly effective in the sample I tested back in the day. It depended on an extruded side channel in the rear Araya rim, with a contracting-band brake consisting of an extra-long braided stainless-steel brake cable [not a "steel band" as the YouTube video claims], whose end was anchored to the frame with a bolt that allowed it to loosely graze the extruded channel. There were no brake blocks of any kind; the sole friction material was a woven tube of Kevlar that rode with almost no friction in the alu rim channel. The beauty of the system -- besides its utter simplicity -- was the inventor's discovery that a) braided Kevlar makes a great dry friction material against aluminum in contracting-band applications, and b) the friction coefficient actually increases when the lot gets wet. I was lukewarm on the expanding "gearing" but was really hot on the braking system. Here's a tip for budding marketeers: Make brake blocks using folded Kevar weave. These things get invented over and over again, only to be forgotten or replaced. They do work in the wet, though. Boy! Do they! Last a good long time, too, but so do Kool-Stop salmon-colored pads and they have name recognition and market penetration, so there you go).
