A gearbox bicycle is a bicycle that uses a gearbox to convert torque and rotational speed from the power source, usually the rider's legs, to what is desired at the drive wheel. The gearbox is usually incorporated into the frame near the crank, and it may be used in addition to or instead of derailleur gears or a hub gear. Cited advantages include improved shifting performance, protecting the gearing from damage and exposure to dirt and moisture, as with hub gears, plus locating the additional mass between the two wheels and on the frame where it may be suspended, unlike with hub gears.
Patents for built-in systems to change gear ratios appeared as early as 1890. Adler offered a three-speed gearbox bicycle in the 1930s. Several attempts to develop gearbox bicycles during the 2000s for downhill racing, such as the Honda RN-01 G-cross, incorporated complete derailleur gear drive trains in an enclosure. Around the same time Schlumpf Innovations and Hammerschmidt offered cranksets with two different gear ratios and just one chainring. Pinion launched their spur-gear system in the 2010s.
At least three different gearing techniques have been employed.
- Epicyclic gears, as in hub gears.
- Spur gears, as in most automobile transmissions.
- Derailleur gears, as on many bicycles, but fully enclosed.
- Dylan H. Brown (June 3, 2014). "Preview: Nicolai Bikes Available in the U.S." Bike. Retrieved 2015-03-22.
Nicolai's gearbox bikes have also been popular.
- Sven Martin (February 17, 2014). "Zerode's Prototype Full Carbon 27.5 Gearbox Trail Bike". VitalMTB. Retrieved 2015-03-22.
Zerode founder, Rob Metz, built this incredible prototype carbon gearbox trail bike in his garage.
- Bryan Betts (February 18, 2015). "Bicycle gearbox project shifts to top speed with CNC prototyping". The Institute of Engineering and Technology. Retrieved 2015-03-22.
The Efneo gearbox packs a three-speed planetary design into the same volume as the triple-chainring it replaces.
- Ben Coxworth (October 7, 2014). "Efneo gearbox is made to replace a bike's front derailleur". GizMag. Retrieved 2015-03-22.
- Ben Coxworth (July 10, 2014). "Nuseti mountain bike features a sealed drivetrain". GizMag. Retrieved 2015-03-22.
Both the gearbox and the chain are sealed against water and outside contaminants, plus they're kept lubricated by separate sealed-in oil baths. This means that riders won't be exposed to greasy crud, and won't need to frequently clean or lube the drivetrain.
- Robert Annis (March 16, 2014). "German Gearbox Makes An NAHBS Splash On Reeb Mountain Bike". Bike. Retrieved 2015-03-22.
They toyed with the idea of an internal rear hub, but didn't like the idea of adding additional weight to the rear of the bike.
- Ben Coxworth (March 13, 2013). "Pinion sealed gearbox offers an alternative to those darn derailleurs". GizMag. Retrieved 2015-03-22.
[Hub gears] add revolving weight, and that weight is added in the back of the bike – not low and in the middle, where you want it.
- Berto, Frank J. (2008) . The Dancing Chain: History and Development of the Derailleur Bicycle (3rd ed.). Cycle Publishing/Van der Plas Publications. pp. 39–47. ISBN 978-1-892495-59-4.
- Berto, Frank J. (2016) . The Dancing Chain: History and Development of the Derailleur Bicycle (5th ed.). Cycle Publishing/Van der Plas Publications. ISBN 978-1-892495-77-8. Retrieved May 30, 2017.
"1936 Adler Drei-Gang Typ 155". The Online Bicycle Museum. Retrieved 2015-03-22.
With its automobile-style gear-stick, the Adler Drie-Gang (it means '3-Speed') has a most distinctive appearance. It was Germany's best-selling bottom-bracket-geared bicycle.
Richard Cunningham (October 5, 2004). "Hayes to Market Chain-Driven Gearbox System". Mountain Bike Action. Retrieved 2015-03-22.
The PeteSpeed patented gearbox is actually a small derailleur that is packed into machined-aluminum housing, mounted in the frame near the bottom bracket area.
Jez Loftus (October 23, 2007). "Honda gearbox revealed". BikeRadar. Retrieved 2015-03-22.
The system basically comprises of a drive crank, chained through what looks to be a reworked derailleur running onto a regular cassette.
- Davis, Alan (August 13, 2008). "Previewed: Unveiling Truvativ's Hammerschmidt". bikemagazine. Retrieved 2009-12-08.
- "Schlumpf Innovations". Retrieved 2010-05-05.