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In 25 years of passion in the worship of the bicycle and its benefits to mankind and the world, one common theme seems to be the fear of gears and shifting on your bicycle. I first thought about naming this "Understanding Bicycle Gears and Shifting", but if you are reading this you probably want some basic information. In 25 years of selling, fixing and racing bicycles, gears are a blessing and a pain in the behind. They allow you to go faster and farther with less effort and up steeper hills than if you just had a single speed. But there is some complexity for its added benefits.

You need to make the shifts while you are moving forward and pedaling. Pedaling should be a medium or soft pedaling effort when making shifts, this helps the chain up and down the shift ramps on the chainrings and sprockets.

Sprockets are in the rear, and chainrings are connected to the cranks and are in the front. The rear shifter (rear derailleur) is controlled by the right shift controller on the handlebars. The front shifter (front derailleur) is controlled by the left shift controller on the handlebars. Remember right =rear. Don't be afraid to shift, as long as you are pedaling you will be OK, shift to your heart's delight.

Most bikes have 3 chainrings in the front and 5 to 10 sprockets in the rear. The number of gears on your bike is figured by multiplying the number of chainrings by the number of sprockets. Just because you have a "21 speed" doesn't mean you have 21 different gears, but rather you may only have 12 or 13 as many gears are near duplications.

The biggest chainring on your cranks will make you go fast. The smallest sprocket in the rear will make you go fast. So the gear ratio for the most amount of speed will be big in the front and small in the rear. This will be hard to pedal.

The smallest chainring in the front will make you go slow but give more leverage for going up hills. The large sprocket in the rear will make you go slow but give you more leverage for going up hills. So the gear ratio for going slow, but going up a really steep hill will be small chainring and large sprocket. Beginners may like the idea of putting the chain on the middle chainring and just forget that you have a left shift lever. The middle will be just fine until you get to the steepest hill in town or the opposite, the wind is behind you and you want to go a decline at 30 mph.

So ride along in the middle chainring, pick any gear in the rear and start pedaling, a good cadence ( the number of times your pedal goes around in a minute) is at least 60 rpms, This means when you are riding your right knee should come up at least once every second. If you are slower that that, you need to "upshift" or get into a larger rear sprocket. If you are pedaling a lot faster than 60 rpms, and if you feel not in control, or a bouncing on the saddle, you need to downshift, or get into smaller sprocket.

Just decide which way you need to go in your future shift, keep pedaling, and make the shift. If it seems worse just shift the other direction. Try not to look down at the chain for more than a second, as this is when a nasty accident tends to happen. Eyes on the road, until you get good, just shift until it feels good. If you hear or feel scraping or grinding, you may need to pick another gear.

There are 2 combinations of gears you need to try to avoid. They are called "crossover" gears. They are the combination of Big Chainring and big sprocket or small chainring and small sprocket. This causes extra wear and tear on the gearing system. Not life or death, but a good habit, and will make you look less like a rookie.

Still making noise? Go to a repair shop for their expert opinion, it should be for free, we want you to be safe and happy.

Go ride,get some exercise and fresh air, shift often, enjoy technology, wear a helmet.

Tim Lutz runs a bike repair shop out of his garage, putting to use 25-plus years of bicycling experience. His website can be found at http://www.affordablebikerepair.com.

Chain Drive

History

Polybolos (reconstruction) described by the Hellenistic writer Philo of Byzantium (3rd century BC). The semi-automated arrow thrower features the earliest known chain drive.

Oldest known illustration of an endless power-transmitting chain drive, from Su Song's book of 1092 describing his clock tower of Kaifeng

The oldest known application of a chain drive appears in the Polybolos, a repeating crossbow described by the Greek engineer Philon of Byzantium (3rd century BC). Two flat-linked chains were connected to a windlass, which by winding back and forth would automatically fire the machine's arrows until its magazine was empty. Although the device did not transmit power continuously since the chains "did not transmit power from shaft to shaft", the Greek design marks the beginning of the history of the chain drive since "no earlier instance of such a cam is known, and none as complex is known until the 16th century. It is here that the flat-link chain, often attributed to Leonardo da Vinci, actually made its first appearance."

The first continuous power-transmitting chain drive was depicted in the written horological treatise of the Song Dynasty (9601279) Chinese engineer Su Song (1020-1101 AD), who used it to operate the armillary sphere of his astronomical clock tower as well as the clock jack figurines presenting the time of day by mechanically banging gongs and drums. The chain drive itself was given power via the hydraulic works of Su's water clock tank and waterwheel, the latter which acted as a large gear.

The endless power-transmitting chain drive was invented separately in Europe by Jacques de Vaucanson in 1770 for a silk reeling and throwing mill. J. F. Tretz was the first to apply the chain drive to the bicycle in 1869.

Chains versus belts

Drive chains are most often made of metal, while belts are often rubber, plastic, or other substances. Although well-made chains may prove stronger than belts, their greater mass increases drive train inertia.

Drive belts can often slip (unless they have teeth) which means that the output side may not rotate at a precise speed, and some work gets lost to the friction of the belt against its rollers. Teeth on toothed drive belts generally wear faster than links on chains, but wear on rubber or plastic belts and their teeth is often easier to observe; you can often tell a belt is wearing out and about to break more easily than a chain.

Chains are often narrower than belts, and this can make it easier to shift them to larger or smaller gears in order to vary the gear ratio. Multi-speed bicycles with derailleurs make use of this. Also, the more positive meshing of a chain can make it easier to build gears that can increase or shrink in diameter, again altering the gear ratio.

Both can be used to move objects by attaching pockets, buckets, or frames to them; chains are often used to move things vertically by holding them in frames, as in industrial toasters, while belts are good at moving things horizontally in the form of conveyor belts. It is not unusual for the systems to be used in combination; for example the rollers that drive conveyor belts are themselves often driven by drive chains.

Drive shafts are another common method used to move mechanical power around that is sometimes evaluated in comparison to chain drive; in particular shaft drive versus chain drive is a key design decision for most motorcycles. Drive shafts tend to be even tougher and more reliable than chain drive, but weigh even more (robbing more power), and impart rotational torque.

Use in vehicles

Bicycles

Main article: Bicycle chain

Chain drive was the main feature which differentiated the safety bicycle introduced in 1885, with its two equal-sized wheels, from the direct-drive penny-farthing or "high wheeler" type of bicycle. The popularity of the chain-driven safety bicycle brought about the demise of the penny-farthing, and is still a basic feature of bicycle design today.

Automobiles

Transmitting power to the wheels

Chain final drive, 1912 illustration

Chain drive was a popular power transmission system from the earliest days of the automobile. It gained prominence as an alternative to the Systme Panhard with its rigid Hotchkiss driveshaft and universal joints.

A chain drive system uses one or more roller chains to transmit power from a differential to the rear axle. This system allowed for a great deal of vertical axle movement (for example, over bumps), and was simpler to design and build than a rigid driveshaft in a workable suspension. Also, it had less unsprung weight at the rear wheels than the Hotchkiss drive, which would have had the weight of the driveshaft to carry as well, which in turn meant that the tires would last longer.

Frazer Nash were strong proponents of this system using one chain per gear selected by dog clutches. The Frazer Nash chain drive system, (designed for the GN Cyclecar Company by Archibald Frazer-Nash and Henry Ronald Godfrey) was very effective, allowing extremely fast gear selections. The Frazer Nash (or GN) transmission system provided the basis for many "special" racing cars of the 1920s and 1930s, the most famous being Basil Davenport's Spider which held the outright record at the Shelsley Walsh Speed Hill Climb in the 1920s. Frazer Nash cars are still raced in the UK.

Parry-Thomas was killed during a land speed record attempt in his car 'Babs' when the chain final-drive broke, decapitating him.

The last popular chain drive automobile was the Honda S600 of the 1960s.

Inside motors

Internal combustion engines often use chain drive to power the timing chain used to drive overhead camshaft valvetrains. This is an area in which chain drives frequently compete directly with belt drive systems, and an excellent example of some of the differences and similarities between the two approaches. For this application, chains last longer, but are often harder to replace. Being heavier, the chain robs more power, but is also less likely to fail. The camshaft of a four stroke engine must rotate at half crankshaft speed, so some form of reduction gearing is needed and a direct drive from the crankshaft isn't possible. Alternatives to chain drives include gear trains, bevel gear and shaft drives, or toothed flexible belt drives.

Transfer cases

'Silent chain' drives inside a 1912 gearbox

Today, inverted tooth drive chains are commonly used in passenger car and light truck transfer cases.

Motorcycles

Chain drive versus belt drive or use of a driveshaft is a fundamental design decision in motorcycle design; nearly all motorcycles use one of these three designs. See Motorcycle construction for more details.

See also

Bicycle chain

Chain pump

References

^ Green 1996, pp. 2337-2361

^ Cross & Morse in Birmingham, http://www.crossmorse.com

^ a b Werner Soedel, Vernard Foley: Ancient Catapults, Scientific American, Vol. 240, No. 3 (March 1979), p.124-125

^ Needham, Joseph (1986). Science and Civilization in China: Volume 4, Part 2, Mechanical Engineering. Cave Books, Ltd. Page 109.

^ Needham, Joseph (1986). Science and Civilization in China: Volume 4, Part 2, Mechanical Engineering. Cave Books, Ltd. Page 111, 165, 456457.

^ a b c Temple, Robert. (1986). The Genius of China: 3,000 Years of Science, Discovery, and Invention. With a forward by Joseph Needham. New York: Simon and Schuster, Inc. ISBN 0671620282. Page 72.

Bibliography

Green, Robert E. et al. (eds) (1996), Machinery's Handbook (25 ed.), New York: Industrial Press, ISBN 978-0-8311-2575-2 .

External links

Wikimedia Commons has media related to: Drive chains

The Complete Guide to Chain

Motorcycle primary and drive chains explained

Categories: Mechanics | Automotive transmission technologies | Mechanical power transmission | Mechanical power control
About the Author

I am an expert from China Bags Wholesale, usually analyzes all kind of industries situation, such as tial sport , clearance puma shoes.

Going from 6sp to 8sp cassette. Will I need a new Front Derailleur?

I'm upgrading my rear cassette soon and noticed while looking at front-derailleurs on the net, that they mention what size they're suited for. I currently have a 6 sp freewheel on my bike at the moment, and want to upgrade with a new wheel (and freehub) and an 8 speed cassette. Do I need to worry about the front derailleur in the case?

Thanks a lot.

The reason you might need a front derailleur is because the old cage might be too wide to actuate the chain over the chainrings properly.

What you WILL need is the cassette, a new freehub, a new chain, a new axle, new chainrings, new front (probably) and rear derailleurs, and new shifters. Don't forget to have the rear wheel redished and the frame reset for the wider wheel (which is next to impossible if the frame is aluminum).

EDIT: OOPS. You can't retrofit a cassette onto a freewheel hub. This means new wheel time (or relace your old one).

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