Efneo 3-Speed chainring

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steve browne
Posts: 111
Joined: 8 Oct 2009, 12:30pm

Efneo 3-Speed chainring

Postby steve browne » 29 Jan 2015, 8:51am

https://www.indiegogo.com/projects/3-sp ... rbox-efneo

This looks interesting. The lowest gear is direct drive, middle is +43% and top is +79%, giving the equivalent of a 28/40/50 chainring according to their video.
I quite like the idea of upgrading my Dutch utility bike with its three speed rear hub gear and brake. Does it matter much in practice which of the three chainring gears is direct drive?

Brucey
Posts: 41508
Joined: 4 Jan 2012, 6:25pm

Re: Efneo 3-Speed chainring

Postby Brucey » 29 Jan 2015, 9:12am

steve browne wrote: ....Does it matter much in practice which of the three chainring gears is direct drive?


usually the direct drive gear is most efficient and the ratios that are most departed from that are least efficient. It might be a 'very efficient' design, it might not. Impossible to know which without testing, but in the former case additional losses of 2% to 5% might be a reasonable estimate, but if not 10% to 15% might be more like it.

Most (middle normal) three speed hub gears are 'very efficient' and given that they have to (typically) contend with about 40% of the torque vs. the BB torque they have a fairly easy time of it. They are also cheap and easy to make, not too complicated or heavy, and the bike doesn't have to be engineered around the gear system. All these things go a long way towards explaining why a 100-year-old idea is still going strong.

cheers
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