The Efneo design is a three-speed front gearbox to replace the front derailleur system on standard bicycle frames

Bicycle gearbox project shifts to top speed with CNC prototyping

A Polish family company has developed a three-speed front gearbox to replace the front derailleur system on standard bicycle frames and launched an online Indiegogo campaign aiming to attract $30,000 of funding for its initial production run.

The Efneo gearbox packs a three-speed planetary design into the same volume as the triple-chainring it replaces. Two-speed front gearboxes already exist, but the Efneo team argue that two is not enough for urban cycling, not least because the typical 66 percent difference in ratio on a two-speed box means a huge change in resistance when you change gear. Three speeds gives you a middling one for most needs, plus first gear for climbing hills and third for downhills, open roads and tailwinds.

The requirements on a bike gearbox are considerable. It faces huge working loads so it must be robust and reliable, yet at the same time it needs to be light and slim. It must also be well sealed against dust, water, mud and other airborne particles and it has to meet the bicycle industry’s construction standards.

Any cyclist who rides a bike with more than half a dozen gears will probably be aware of the difficulties presented by a front derailleur gear-shift. It readily goes out of alignment, cannot change gear while stationary, and skews the chain sideways so you might only be able to use a handful of the nominal 21 or 24 gears.

“Making a two-speed gearbox is a lot easier!” said Wiktor Migaszewski, Efneo's product development specialist and son of the gearbox's inventor, Stefan Migaszewski. He said that other companies have tried to develop three-speed gearboxes but cancelled their projects early on, most probably because the design was either too fat or they could not get the gear ratios right.

“We have seen various designs of three-speed front with gear ratios like 100-120-220 or 100-180-200 or similar – completely dysfunctional for a cyclist,” added Franek Migaszewski, elder brother of Wiktor and the person handling Efneo's marketing. “Our ratios are 100-143-179 per cent, which is almost the same as a three chain-ring crank.”

Efneo's next challenge was professional prototyping for its super-slim design. Eventually two of the three Migaszewski brothers learnt SolidWorks CAD so that parts could be prototyped for them in steel and aluminium on CNC machines. To protect their intellectual property Efneo has made several submissions, including two for international patents.

While other innovators have used the likes of Indiegogo and Kickstarter to finance entire projects, Efneo's ambitions in using it are more modest: it wants to pre-sell some discounted gearboxes before production starts. “$30k is far too little to finance product development and manufacturing – we have already invested almost $500,000 in this project,” Franek Migaszewski said. “This is for making the first order to the factory bigger.”

Production is due to begin in summer 2015 in conjunction with an established bike parts manufacturer. A complete kit of gearbox, left crank, shifter, cable and bottom bracket (the axle for the pedal cranks) is expected to list for approximately £160.

Further information

Efneo gearbox

Efneo Indiegogo campaign page

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