THE DEVELOPMENT, DRIVES AND GEARS
The distance covered by one crank rotation is called the development. The more meters we want to travel, the harder we have to push on the pedals. (In England they use the gearratio in inches). Most important parameters are rearwheel diameter, and the sprockets and chainrings used on the bike. Riders often talk about the gear ratio on their racing bike: "I rode the Cauberg with 42-18 ". Because the rear wheels of roadracing bikes have a standard size, you can instantly compare the gear ratios. On the mountain bike this is more difficult nowadays. In the eighties and nineties we rode a standard size, a rim diameter of 559mm ; 26 inch as mountain bikers usually say. The current range of ATB's has also got extra large tyre sizes of 27.5 and 29 inch. Especially if you want to compare different gear systems or wheel sizes, a conversion to the distance travelled, is the best way to make that comparison.
An old-fashioned city bike travels about 4 or 5 meters, for every revolution of the crank. Riders in a sprint or descent, use about 10 meters development. An ATB with the smallest chainring of 24 and largest sprocket of 32 teeth at the rear (often the lowest gear), travels around 1, 5 m. The speed drops to 5 km/h and it's more difficult to keep balance. Even with the same rim diameter, differences can occur, because there is a large variation in tire size. By choosing wider tires, or just using a higher pressure , the distance travelled per revolution of the wheel is longer. On the page "downloads" you can find an Excel file for calculations.
From 1865 to around 1884 all bicycles had a fixed drive (single speed). The efficiency of the drive was high because there were no additional friction losses; the crankset was directly connected with the hub. If the wheel diameter is 1 meter, the distance travelled is 3,14 m. That is actually a light gearratio and to ride faster, they choose for an increasingly larger front wheel. Cyclists were looking for a way to change that distance while riding. The variation possibilities of the development are called gears. The first gear system on the bike, was in the hub of the front wheel, an Internal Gear Hub (IGH) or planetary gear system: the Crypto-hub from 1878. As soon as we are going to use gears, we must accept additional losses by the friction of gears and/ or chains. The introduction of the Rover Safety with chain drive in 1885, made it the possible to fit the rear wheel with a sprocket left and right. The rider had to get off bike and turn the wheel around though. The differences in gears were never really large, because the chain length had to fit; that was done by sliding in the dropouts. This was used during the first decades of cycle racing ( in the Tour de France until 1935 !).
The efficiency of the chain on a track bike (fixed drive) is up to 98%. A regular road bike with freewheel is up to 96-97%. In the non-pulling part of the chain we can find the derailleur (see FIG. 1 for B). Here is a 2 to 5 percent loss, on a dirty or rusty chain even up to 10%. The use of small cogs (11-12) can lead to 3-4% extra losses and extra wear of chain and sprockets. The twist of the chain around the jockey wheels is actually too large ( the jockey wheels are too small; CeramicSpeed has adressed that problem). This is certainly true in the high gear, this makes the chain wear faster. With optimal lubrication, the light gear (40-24) has a 97% efficiency; The high gear only has a 92% effiency using 50-11. Recumbents often use tube-like protection systems and rollers to guide the chain. Especially in the pulling part of the chain (in FIG1.a/b at A) this waists up to three percent efficiency; in part B about half of that.
Every drive has losses; an average derailleur about 5%. That percentage is often higher in geared hubs. This is a downside to planetary systems: all gears that are interlocking, rotating and transmitting forces. lose energy by friction. Usually the bearings of the planet wheels are plain bearings. The losses of friction by bearings and sprockets can add up to 10-20%. In some gears there will be many planetwheels enabled and in others less. The efficiency of the geared hub will therefore depend on the gear selection and the type of hub. An expensive hub like Rohloff, does use bearings; the efficiency is similar to a derailleur. The efficiency of Shimano Nexus 7-speed was very moderate, averaging 85%; the current 8-speed has been improved by using some bearings and another shifting pattern.
THE EARLY DAYS OF DERAILLEURS
Around 1895 in England a system is marketed with an expanding chain wheel. This "Protean 4 speed" had chain tensioner to take up the difference in chain length; an arm with an auxiliary wheel and pressure spring, which was supported on the rearfork. In that same year a Frenchman designed a system with such a chain tensioner, but it also had a swing arm with a fork, which could lay the chain from one sprocket to another: a real derailleur. Probably this was never produced, but the idea existed already.
In fig. 2a, 2b and 2 c we see designs from the 1930s. Until 1950 these are the most common types of gear changing in the sport of cycling. In Italy before the war, they used the Vittoria Margherita, see fig. 2 c. This is a similar construction, but it had the shifting fork reversed above the chainstay ; the rider had to pedal backwards to shift. This was also the case in the first Campagnolo systems (see fig. 5a). At first the rear hub was disconnected. The rearaxle was dented, just like the dropouts (see fig. 5b), it could move to take up the difference in chain length, see the YouTube video.
But even before the war, there were more advanced models, like the Super Champion of fig. 3 and the vulnerable Simplex of fig. 4.
The front derailleur of fig. 3 was not used by racers, but by tourists and commuters.
Racers had three sprockets on the rearhub; that used to be enough for a real man in those days.
Just after the war, Simplex and Campagnolo front derailleurs were operated by a lever on top (see fig. 5b) ; it meant that the rider had to bend over deeply, what could lead to crashes, hence the nickname "suicide levers". From 1949 Campagnolo experimented with a rear derailleur on basis of a deformable parallelogram. In 1953 the final version came on the market. The shifters of the front and rear derailleur moved to the down tube. The Campagnolo Gran Sport is the most imitated derailleur ever ( Fig. 6).
It was not until 1964 that a new improvement was made by the manufacturer Suntour. They placed the parallelogram at an angle ("slant parallelogram"); see the right image in fig. 7a. The upper Jockey wheel remains closer to the gears and the derailleur is more accurate. The patent expired after 20 years and all the manufacturers like Shimano, Campagnolo, Sachs etc. design new series, according to this principle.
In the mid-1970s the shifters from Suntour don't use friction but a ratchet system (micro-ratchet fig. 7b,); this was also copied by many other manufacturers.
The next big leap forward is index-shifting. Note that the Super Champion of FIG.2a already had such a system. There were many experiments, before a good solution to the problem was found. At the end of the 1970s Bridgestone introduced Synchro Memory Shift and Shimano the "Positive Pre Select" derailleur. The last one did not use a braided cable, but a rigid wire; you could not only pull, but also push. A spring operated pin moved over a series of notches on the derailleur. It shifted fairly rough and was especially popular with people who had little experience riding a bicycle.
For the illustrious aerodynamic AX-groups , Shimano was also attempting to get indexed. Here they ran a catch on a series of small steps on the rear derailleur; very vague and vulnarable.
In 1984 came SIS! Shimano Index System, a system that actually worked! Something for old women, they said at Campagnolo. This arrogance has almost become fatal for them. Campagnolo's shifting system was no longer up to date! Instead of a trend-setter the company became a trend-follower within a year.
Although I had been riding a Suntour rear derailleur and bar-end shifters for years on my touring bike, it took until 1986 before I changed the Campagnolo Nuovo Record on my racer for a Shimano 600 SIS derailleur. The quality of all the parts was great, and it shfted fantastic.
Most derailleurs and Shimano shifters are interchangeable. An exception are the first 3 series of Dura-ace. The rear derailleurs from 1984 to 1993 can only be used with Dura-ace shifters.
It doesn't matter if it shifts 6, 7, or 8 speeds; the rear derailleur is interchangeable. Shimano did a masterpiece in marketing policy: the derailleurs, gears and chains, all had to be from Shimano to get the best possible SIS action. Not only in road bikes, but also at the new fashion: the All Terrain Bikes. With the top groupsets like XT and Dura-ace they spoiled the cyclists, and after a testride, they did not want anything else.
The standard was set! Each competitor had to be at least almost as good as the Shimano group in its price range, in order to remain on the market. Each renewal, like STI and Rapidfire (the switch levers), was introduced in the top group and then trickeled down in the cheaper groups. Suntour is gone, Huret and Sachs are bought by SRAM. In the roadracing market, Campagnolo is still playing a role, but the whole ATB-market was lost after 1 attempt. Shimano rules!
Is the derailleur fully developed now? Eh, no; there are always improvements made by various manufacturers. The cablerouting on the rear derailleur is very inefficient. SRAM, M5 (U-turn-away) and Suntour, have made better desings. The framebuilders had to design frames with other dropouts for the Suntour S1 derailleur; that was just a step too far. Actually the Suntour S1 was a redesign of the Nivex and Altenburger from 1938 and the 50's.
There have been prototypes, with a moving cassette; the derailleur is nothing more than a fixed chain tensioner. So you avoid the out-of-line chain, but the construction is more complicated and more expensive (simplicity obliges).
Another possibility to shift gears is the planetary system (= epicyclic system), usually in the hub. The basis of this design comes from clocks and was already applied as a gear system in the 1800 steam engines. The Crypto crankshaft for high Bi (1878) was the first planetary system in the cycling technique; It had two modes: a direct drive and a high gear (acceleration). With the invention of the Safety bike, the driving force moves to the rear hub. Around 1900 the first internally geared rearhubs are marketed; in England by the manufacturer Sturmey-Archer and in Germany by Fichtel & Sachs.
Epicyclic systems are based on the roller principle (see fig. 8a); If we have a shelf (black) moving on two rollers (blue) over the bottom (yellow), the rollers will cover a distance after a rotation equal to the circumference 2 * π * r . The pivot point of the shelf on the surface goes around the beam d, and explains the distance covered 2 * π * d , wich is twice as much. That might seem a little odd at first glance, but otherwise you would be able to roll a cupboard through the house on just two loose rollers.
We provide everything with teeth, roll the bottom and the shelf to a circle, and we get fig. 8b.
A planetary system consists of: a sun wheel (yellow), planet wheels (blue) the planet carrier (red) and a gear ring (black).
Note: the planet carrier runs slower than the gear ring.
The planetary system in total is in a hub; the hub includes an axle, a hub shell where the spokes are attached and a driver with the chainwheel attached. The axle is fixed in the frame; the sun wheel is fixed on the axle.
We're going to connect the hub shell and the driver, to the planet carrier and gear ring. If we connect the driver with the planet carrier (slow) and the gear ring (fast) with the hub shell, we have an acceleration. If we connect the driver with the gear ring (fast), and the planet carrier (slow) with the hub shell, we have a reduction. The chain wheel turns more often than the hub shell. Our three speed gearbox has not only got the ability to speed up or slow down: the driver can also be linked directly to the hub shell. This happens in second gear. Our three speed gearbox now has: 1. A reduction 2. A direct drive 3. An acceleration .
By the planet wheel double ("stepped" see FIG. 9 ), it may be for example a second power ring gear. This extends the capabilities. There is a big downside to planetary systems: all gears interlocking, rotate and forces pass, lose energy by friction. Usually the bearings of the planet wheels are simple plain bearings. The sprockets are made via sintering of metal powder (pressed and baked). The surface is somewhat rougher (more friction). One advantage is that the lubricants better stick and attach in the cavities. The losses by friction of bearings and sprockets can really add up to 10-20%. In some gears there will be many wheels enabled and others less so. The efficiency of the gear hub will therefore depend on the gear selection. Only Rohloff used anywhere real bearings in the sprockets. Those wheels make them also through machining (only the SRAM Spectro P5 Cargo has also machined wheels). Usually there is one circuit in which the chain wheel to the hub home linked; the return is then maximum (96%).
The number of teeth on the ring gear is equal to the number of teeth on the Sun wheel, + 2 times the number of teeth of the planetary gear.
The relationship between the gears determine the steps between the accelerations and decelerations. It depends or the ring gear or the planet wheels powered, or we an acceleration (> 1) or delayed (< 1). If the slight acceleration 3/4 of the hard drive, then the 4/3 of the heavy gear fixed drive. This is for example the case for the classic Sturmey-Archer AW and copie hubs, such as Hercules, Steyr, Suntour, Brampton, etc.
At drive through the planetary carrier applies: the gear number = (teeth ring gear teeth + Sun wheel)/ teeth ring gear (> 1) in drive via the ring gear: the acceleration-number = teeth ring gear/(teeth ring gear teeth + Sun wheel) (< 1).
When the derailleur is still in its infancy, was the circuit with planetary systems all adult. Before the second world war, there was also made by drivers do use; especially in England. If option had the hubs wing nuts to quickly Exchange wheels at flat tires; there were smaller steps between gears ("close ratio"). A topper was the Sturmey-Archer 3-speed type AR from the thirties ( FIG. 10); in 1939 they even released a 4-speed type FM .
If we make the Sun wheel very small, we make the steps between gears smaller. Unfortunately, the forces submitted, remain the same. The strength of the small wheels is not enough and the construction is unreliable. The steps in a single planetary system are therefore large (at a 3-bake gives a great gear without saying a big delay). The consequence of a real "close ratio" box, if the AR, is a compound planetary system (tiered planet wheels and an additional ring gear) and thus what additional losses.
The way you approach your planetary system (s) want to switch, is one of the problems with the design. The Fichtel & Sachs 4-bak from 1912 (fig. 11) even had all three planetary systems; This construction was complicated, to switching of simplicity.
At the shift system of the Sturmey-Archer 3-speed (fig. 12) serves a chain control pen. The cross bar goes through the slot in the shaft. The threads of the control pin in the cross bar is turned. During switching takes the cross bar, and the sterclutch (link) brings so the connections. The spring loaded causes the sterclutch comes back. If the control pin, disables the hub by the spring loaded to the heavy gear. If we combine a 3-bake with a coaster brake, the braking performance in first gear, sometimes noticeably better than in the third (depending on the construction).
In a planetary system the fixed sun wheel will transmit the torque, through the axle to the frame. The axile of SA in fig. 12 is flattened, so it can not rotate. Many manufacturers add a special rings with a cam. At Rohloff (fig. 13b), a hub which is used by many strong riders, and where many light gears in it, they choose even for very rigorous solutions. There is a strong lever coupled to axle, which is supported by the chainstay. This lever can be omitted if one uses the special Rohloff dropouts. These are even can be equiped with chain tensioners.
The Rohloff is the absolute top of the IGH. This is a very thoughtful design; There is no compromise: Everything must be top quality and super reliable; it runs in an oilbath. The yield is similar to a derailleur, about 95%. At low power like 70W , the efficiency is much lower (10% loss) than with 300W (4% loss). The teeth of the gears are of high quality machine steel; to save weight, the center of the larger gears is resin with carbon reinforcement. The total weight is about 1.7 kg. The price of the hub is about 900 euro. The ratio of this hub is very large, 526%; the 11th gear is the direct drive. The hub can be shifted stationary, and under load. Especially the latter is important, because Shimano hubs can be wrecked that way. Both the Shimano and Rohloff hubs use a cartridge-gearbox system that can be removed from the hub in one piece for replacement or repair, leaving the wheel intact.
On the pictures below we see the inside of a SRAM Spectro P5 with 2 switchable Sun wheels, 3 stepped planet wheels in a carrier, and 1 ring gear.
In fig. 14a we see the cams on the axle at B; These are engaged by the control pin pushing the sun wheels (the small sun wheel A or the big one C) . Both sun wheels are continuously connected with stepped planet wheels. There are two sets of pawls; on the right side on the ring gear (see fig. 14 c + e) and to the left side in the hub are the pawls of the planetary carrier (see top fig. 14f ). In fig. 14 d we can see the two rows of ratched cams in the hub, where the pawls connect.
The functioning of the 7-speed of SRAM is the same. The only difference is, that there are 3 switchable sun wheels and that the planet wheels have 3 steps.
The construction of the 7-speed from SA, is somewhat similar to the SRAM (both three Sun wheels).
The construction of the Shimano 7-gearbox is totally different; with 4 Sun wheels, two ring wheels and two planetary carriers. Because there is no direct drive and the forces sometimes go through both systems, the yield in some gears is lower than 80%, and the average about 85%.
The 8-speed by SA works quite different. The first gear is the direct drive here. This means that all other transmissions are real up-gears. So choose a very low set up, like a 32 chainwheel and 24 sprocket on the hub.
In the early 1990s Sachs worked on a 12 speed gearhub; This would be the great leap forward. There was a lot invested in development and automation, but the result was a relatively expensive and heavy hub. There were some technical and financial problems. This made Sachs vulnarable for the takeover by SRAM. After a year SRAM stopped the production, development and support for this product.
The Nexus 8-gearhub is a design with 4 down-gears, the fifth gear is a direct drive, and there are three up-gears. By the planet wheels with needle roller bearings, and the fact that there is a direct drive, the average yield of this gearhub above the 90% off. The range (the difference between the highest and lowest acceleration) of the 8-speed is in addition, risen to 307%, instead of the 244% of the 7-gearhub.
In 2010, the Shimano Alfine 11 gearhub entered the market. The weight is about 2 kg; the lubrication is done by an oil bath, the range is 409% and the price approximately 390 euro; This makes it a formidable competitor for Rohloff, which however scores better, on all points, except the price .
In old (folding) bicycles we sometimes find 2-speed hubs made by Sachs; see the page Duomatic. Here you change gears by pedaling backward; a later variation of this hub was self-shifting: the Automatic, which recently has been revived by SRAM as Automatix. Sturmey Archer also had such a 2-speed: the S2 (1966). In 2010 Sturmey Archer even introduced a whole new range of these hubs; for convenience, these are called S-2 Duomatic.
COMBINATION DERAILLEUR AND PLANETARY SYSTEM
It is of course possible to combine a derailleur and a planetary system. In particular Sachs has applied this combination. The "Torpedo 2 x 3" was a three speed hub with coaster brake, combined with a derailleur and two sprockets. If you use the brake at first the derailleur is tensioned; this means an extra time delay before the brake works.
The Sachs Orbit was a two gear hub, but equiped with a freewheel for up to 7 sprockets. This is supposed to replace the second chain wheel and the front derailleur. This construction was more successful. Later a 3-speed combined with a 7 or 8 cassette (the Dual Drive) was interduced by Sachs and, after the acquisition, of SRAM. Unfortunately you combine not only the benefits of both gear systems, but also the disadvantages. Only in certain cases, such as an Alleweder recumbent, I have chosen for this solution.
The Efneo GTRO Gearbox is a 3 speed internally geared crankset. It will give you an effective gear range identical to having a 28/40/50 Triple Crankset up front, without having to use a front derailleur. You can always shift the Efneo, riding or standing still! The Efneo GTRO Gearbox comes in 3 different configurations : Twist Shifter, Trigger Shifter, or Bar End Shifter.
THE CONTINUOUS VARIABLE TRANSMISSION
Since 2007 there is an infinitely adjustable gear hub: the Nuvinci, this is not an epicyclic system but a traction-drive. This CVT ' turns off ' with rotating balls instead of gears, such as that in the conventional geared hubs. The special traction-oil in the hub plays an important role in the transmission. Depending on the distance of the point of tangency of the input drive (connected to the sprocket, right) and the output drive (connected to the hub, left) relative to the axis of the gear lighter bullets (gear fast, small RADIUS) or heavier (gear slowly, large RADIUS). The touch point is continuously adjustable by means of a simple rotary switch that has been processed in the handle of the bike. A slight movement is enough to adjust the transfer and in any desired. This allows for an almost infinite variety in the number of ' gears '.
The return of the hub is in the middle (85%); in the lowest or highest gears are the losses even pretty, especially at high power. Since 2011 is a new version of the hub, which weighs just 2.5 kg and has a range of 360%. The technical capabilities of this hub also take, such as disc brake application and loss-as. In terms of data to get than in a real competitiveness with for example a Shimano Alfine 8 or 11 FRY.
A new development is the Harmony-gear, which at a certain adjustable pedal pressure, automatically adjusts the gear. This Harmony is especially intended for mounting in E-bikes and it is potentially very promising. Especially the application of a mid motor makes the Harmony a good solution, because the hub will also shift good under load. In this case Shimano is vulnerable. Just make sure the batteries are full ; when empty this combination will have a low yield: very inefficient.
There are tests done with some of the internal gear hubs, which are described here (on the left), in a chart made by the German engineer Andreas Oehler; here we can see the yields . Some knowledge of the German language is useful when reading that website, but the graph gives a good idea. The thick lines are for a (sports) power of 200 watts. At very low power (50W) the yields decline (thin lines).
GEAR SYSTEMS IN THE BOTTOM BRACKET
A gearbox that we see hardly in Netherlands, is the 2-speed of Schlumpf . This is not in the hub, but at the bottombracket. While in a hub the torque is more than halved by the drivetrain, the Schlumpf transmits it fully. You shift this 2-speed, by moving the crankshaft to the left or to the right. The steps between the gears are large; it is used in folding bikes (including Brompton) or recumbents (extra light or extra heavy gears).
Schlumpf also offers a 2-speed (150%) front wheel hub and a crankshaft, type FSU, for unicycle or imitation high-wheeler; if the tyre choice is 60-787, you get a development of 4,27m.
There are other bottombracket gears in use. The Dutch bicycle manufacturer Phoenix has used a real 3-speed gearbox (no planetary system) type Mutaped (Swiss), for which a special large bracket was needed . Several German manufacturers had that before the war. Bismarck, Wanderer and Brennabor were 2-speeds, Adler a 3-speed, and Rappa a 4-speed. All were beautiful examples of German engineering (see figure 17a/b), sturdy but heavy.
In 2013, this modern gear bottom bracket (see FIG 17 c/d) went into production; the German Pinion has 18 gears and a range of 636%! The weight is 2.7 kg. You must built frames with a special bracket. The yield is around 91%; somewhat less than Rohloff, but certainly as good as other IGH and with greater range. Meanwhile they also produce a 12-speed and two 9-speeds: wide ratio (XR), and close ratio (CR).
This gearbox is often combined with belt drive: http://www.gatescarbondrive.com/ ; a trend that we also see for hubgears like Rohloff and Shimano Alfine. The rear triangle of the bicycle must be divisible, because the belt does not split. Compared to a well lubricated chain, you have some extra losses.
A totally new concept for a drive comes from Denmark. The crankset drives a dynamo and the current that you generate, drives the electric motor in the rear wheel. The chain and gears are not necessary; the combination with a battery or accumulator, is becoming very easy. Maintenance is also much simpler. For a biker on an E-bike for commuting, this can be a very interesting product, but it is only recently marketed. I doubt if yield is sufficient to replace a chain transmission.
FIG. 18b CeramicSpeed shaftdrive with 13 gearpositions
Shaftdrives have been around since the end of the 19th century, see FIG.18a. The efficiency of the drive is usually less than 90%.
In FIG.18b we see the Ceramicspeed Driven shaftdrive ; 13 speeds on a sprocket with horizontal (!) teeth. The efficiency is claimed to be 98%. You will need a special frame and a lot of money.
More www. knowledge?
ALMOST ANY OLD BRAKE HUB AND GEAR HUB CAN BE FOUND HERE! http://sheldonbrown.com/sutherland.html
Calculation sheets: http://john-s-allen.com/gearing/hubratios.htm
VIRTUALLY EVERY OLD DERAILLEUR CAN BE FOUND HERE! http://www.disraeligears.co.uk/Site/Home.htm
Lots of archive material from Campagnolo: http://www.campyonly.com/history/catalogs.html
The modern stuff of Campagnolo: http://www.campagnolo.com/jsp/en/index/index.jsp
Information by Shimano for mechanics: http://si.shimano.com/
On "rijwiel.net" you will find this interesting page: http://www.rijwiel.net/4versnln.htm
The official history of SA: http://www.sturmey-archerheritage.com/index.php
An infinitely adjustable gear hub: www.nuvinci.com
A 2-speed in the bottom bracket: www.schlumpf.ch
Rohloff, when quality is the only thing that counts: www.rohloff.de
Lovers of Internal Gear Hubs have their own place on the internet: http://hubstripping.wordpress.com/