Crankset
It is connected to the rider by the pedals, to the bicycle frame by the bottom bracket, and to the rear sprocket, cassette or freewheel via the chain.
Historically, bicycle riders have typically chosen proportionally shorter cranks for higher cadence cycling such as criterium and track racing, while riders have chosen proportionally longer cranks for lower cadence cycling such as time trial racing and mountain biking.
However, the evolution of very low rider torso positions to reduce aerodynamic drag for time trial racing and triathlon cycling can also affect crank selection for such events.
As almost all unicycles are ungeared, crank length is a major factor in determining how much force is transmitted to the wheel.
Larger wheel diameters, such as 660 to 910 mm (26 to 36 in), require longer cranks, as do disciplines such as Mountain Unicycling, Trials, Street, and Flatland.
Cold forging gives the metal additional strength, and the cranks can therefore be made lighter without increasing the risk of breakage.
Shimano "Hollowtech" aluminum cranks are made by forging the main arms around a hard steel insert which is then withdrawn, leaving an internal void to save weight.
[disputed – discuss][citation needed] There are a variety of methods used to attach the cranks to the bottom bracket spindle (or axle).
Composed of assorted mixtures of aluminum, copper, graphite and nickel powders in a grease base, such lubrication allows repeated assembly and disassembly without wear and the elimination of fretting corrosion during use.
A solution, suggested by Jobst Brandt, is to use a 45 degree taper at the surface where crank and pedal meet, as this would eliminate precession-induced fretting and loosening (it is already done for most automobile lug nuts for the latter reason).
The solution[dubious – discuss] to the issue of fretting is to use a metal based anti-seize lubricant; being composed of assorted mixtures of aluminium, copper, graphite and nickel powders in a grease base – that allows repeated assembly and disassembly without wear and the elimination of fretting corrosion during use.
The holes on the spider arms used for attaching a chainring can have a variety of spacings, referred to as the bolt circle diameter, commonly abbreviated as BCD.
More expensive sets have the chainrings bolted on so that they can be replaced if worn or damaged, or to provide different gearing.
A chainguide is a metal or plastic housing that keeps the chain on the chainrings over rough terrain and during technical riding.
Exceptions including the E.thirteen LG-1 and the MRP G2 (and now the G2 SL) do exist which use integrated skid plates, removing impact forces from the crank's spider and transferring them to the frame.
Because the lock ring prevents the sprocket from unscrewing, it can be used for left-side drive without requiring special left hand threaded parts.
Note that if a normal right-side-drive crankset is installed backwards to create a left-side-drive bicycle, the threaded pedal holes at the end of the crank arms would be reversed.
After a first product commercialized in the late 1970s by Edmond Polchlopek, several manufacturers have tried non-round chainrings, such as Shimano's Biopace, Rotor's Q-Rings, Ridea's PowerRing and Osymetric's Harmonic ring.
However, one hold-out has been Team CSC Saxo Bank veteran Bobby Julich, and there are still a couple of pro riders using them as late as 2011.
[19][20] Bradley Wiggins has used an elliptical chainring from Osymetric since at least 2009,[21] including in his victory of the 2012 Tour de France.
Several Pro-Tour teams were using Osymetric and Q-Rings elliptical chainrings for road racing and time trialing.
As of 2006, all of the major component manufacturers such as Shimano and Campagnolo offer compact cranks in their midrange and high-end product lines.
Both Shimano and Campagnolo recommend and sell front derailleurs specifically designed for compact cranksets, claiming better shifting.
Other negative factors include higher purchase cost than other fine cranksets, and increased maintenance due to the complexity of the system.
This system originated as a cog-driven internal mechanism inside a purpose built bicycle's bottom bracket.
Unlike a standard pair of cranks that always remain at 180 degrees relative to each other, the ROTOR system varies this angle through the circle of motion.
The effect of these movements eliminates the dead spot (where little power is produced) at the top and bottom of the pedaling cycle, and reduces knee strain.
It takes a couple of weeks of regular use to become accustomed to the unusual feel of the Rotor linkage cranksets.
Many competitive cyclists, including the Cervélo TestTeam, use Rotor's Q-rings[26] which mimic the fluctuation in gear size without the added weight.
[27] However Rotor Q-rings and other non-round rings cannot duplicate the crank arm movements that allow application of power through the dead spots of the pedaling cycle.
