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Expandable front chainring

Last Post 04/08/2014 12:26 PM by Mike Shea. 11 Replies.

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Posts:537

04/06/2014 02:40 PM
With electronic shifting taking hold. Even wireless. How long before we see a single front chain ring that can expand and collapse by a driven motor ? There as some patents out there on chain rings that can do that now. It seems like just a matter of making them work without adding a ton of weight, Would help chain lines and give you more steps. I just think it would be a cool project to work on, being a mechanical engineer.

Posts:2881

04/06/2014 04:48 PM
Would it be circular? With teeth?

Posts:537

04/06/2014 04:53 PM
http://www.google.com/patents/US4952196

Posts:537

04/06/2014 04:55 PM
http://www.core77.com/blog/object_culture/id_student_chris_holloways_invention_one-ups_bicycle_engineers_16962.asp

Posts:3180

04/06/2014 08:07 PM
Do the same for rear cogs and we can have variable speed fix gears and a happy Ben. Guess who

Posts:4499

04/06/2014 09:07 PM
the concept has been around quite some time; i wonder how it would ride; it must be a stange feeling (at least at first) having your gears adapt automatically to pressure you put on pedals. Kinda like a CVT car; anyone drive one of those?

Posts:93

04/07/2014 01:02 PM
Always wanted to race a CVT car backwards - CVTs (at least the early versions in DAFs) allow the same ratios in reverse as in forward i.e., you can go as fast backwards as forwards. In the Netherlands, from where OC and I hail, we had races where where DAFs were raced in reverse - very entertaining!

Posts:4499

04/07/2014 01:43 PM
Posted By Joop Zoetemelk (as if..) on 04/07/2014 01:02 PM Always wanted to race a CVT car backwards - CVTs (at least the early versions in DAFs) allow the same ratios in reverse as in forward i.e., you can go as fast backwards as forwards. In the Netherlands, from where OC and I hail, we had races where where DAFs were raced in reverse - very entertaining! Good memories...I had forgotton about that

Posts:511

04/07/2014 04:06 PM
I have snowmobiles a bit and they have a form of CVT using v belts and pulleys that widen or narrow to let the belt ride a larger or smaller circumference I think. Pretty simple to ride. The thumb accelerator makes it go. That's it.

Posts:340

04/07/2014 07:47 PM
I recall a browning transmission (different than this one) and another type that did expand the chainring. It looked very heavy and unrefined but I would guess it had a very broad gear range.

Posts:511

04/07/2014 08:30 PM
Wasn't the browning the one where the chain rings were hinged? A quarter of the ring swung in or out to shift. Electronically operated if I remember. Heavy and never went far. There's also that two speed Truvatiiv Hammerscmidt. I think they just quit making them recently.

Posts:340

04/08/2014 12:26 PM
Posted By Andy Eunson on 04/07/2014 08:30 PM Wasn't the browning the one where the chain rings were hinged? A quarter of the ring swung in or out to shift. Electronically operated if I remember. Heavy and never went far. There's also that two speed Truvatiiv Hammerscmidt. I think they just quit making them recently. Yes a hinged system that you could shift under load. there were a few of these odd configurations and like you said heavy. While some of these ideas work well mechanically they are generally much heavier than derrallieurs.

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