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by John 'i-Motional' Allen
SRAM i-Motion 9 hub, coaster-brake version
There are also articles on this site more generally about internal-gear hubs,
and about Sachs/SRAM internal-gear hubs.
Rebuild this hub?
The SRAM i-Motion 9-speed hub, introduced around 2006, offered a wider range and more even steps than the competing Shimano Nexus 8-speed. The i-Motion 9 was offered in four versions:
- disc brake with a standard 6-bolt rotor fitting;
- brakeless -- which also could be used with a disc brake, as it is identical to the disc-brake version except for a dustcap;
- coaster brake;
- and, i-Brake (large external drum brake -- this version may also be used without the brake).
Drive ratios are:
Ratio | 0.542 | 0.621 | 0.727 | 0.853 | 1.000 | 1.172 | 1.375 | 1.611 | 1.844 | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Step | 14.6% | 17.1% | 17.3% | 17.2% | 17.2% | 17.3% | 17.1% | 14.6% |
The i-Motion 9 was rather large and heavy -- 2.4 kg (5.3 pounds) for the coaster-brake version, 1.9 kg (4.2 pounds) for the others, not counting external brake parts. A mechanic at Harris Cyclery once described this hub as a 'cannonball.' It has been discontinued as of this writing, but in the spirit of completeness, we cover it, especially as SRAM has provided meager information about it.
Some people really like this hub, and if that is you, give it extra care, and don't overstress it.
Also note: a reviewer on a German Web page says:
'Diese Nabe ist nur im Vorwärts-Betrieb nutzbar. Rückwärts schieben oder wackeln an der Ampel bringt das Getriebe in merkwürdige Zustände.'
Translating:
'This hub is usable only in forward mode. Pushing the bicycle backwards or track-standing while waiting at a traffic light puts the mechanism into unusual states.'
'This hub is usable only in forward mode. Pushing the bicycle backwards or track-standing while waiting at a traffic light puts the mechanism into unusual states.'
I think this means that rearward rotation of the wheel turns the sprocket backward and actuates the coaster brake, but I'm not sure. A plain coaster brake can freewheel backwards without turning the cranks.
Technical documentation
I have documented disassembly of the disc-brake/brakeless version of this hub (PDF file). The hub is rather complicated, but an accomplished mechanic should be able to read the instructions in reverse and reassemble the hub from individual internal parts -- unlike the earlier 12-speed Elan hub, whose axle assembly was only rebuildable with factory tooling.
There are a couple of hitches, though: SRAM doesn't supply individual replacement parts. The gear unit was only ever sold as a single part, and SRAM does not stock replacement parts for its internal-gear hubs in the USA. Also, an internal nut is destroyed in disassembly and is not available for replacement. Aaron's Bicycle Repair in Seattle, Washington, USA has had replacement nuts fabricated and sells them. Aaron is assembling a stock of spare parts and can rebuild these hubs.
The SRAM 2010 technical manual (also available in German) covers removal and replacement from the shell of all versions of the hub, and servicing the coaster brake. The instructions in the manual should be followed in connection with my PDF disassembly instructions. Note RAM's warning about damaging the right-side outer dust seal during disassembly. I'm not sure whether there is a workaround.
Parts lists for all versions of the hub are in the SRAM 2010 spare parts catalog in English and German, but again, SRAM doesn't stock spare parts in the USA.
Installation and maintenance issues
The SRAM online user's manual provides good information on installation, in English, and versions are available in several other European languages, linked here.
The hub should be removed from the shell, cleaned and re lubricated, even when new, because factory lubrication is inadequate. See the information on lubrication in the main article about internal-gear hubs on this site. Gta 5 sea monster mod. The disc-brake and brakeless versions (possibly also the i-Brake version) can be re-oiled through one of the brake mounting holes. These should be closed off with machine screws when not in use: the plastic cover supplied with the brakeless version does not seal well.
Anti-rotation washers are different from those of other SRAM internal-gear hubs except the newer G8 hub. As this is a rotary-shifting hub, different anti-rotation washers are needed depending on the angle of dropout slots, as shown in SRAM's manuals. Shimano Nexus antirotation washers can be made to fit with some filing.
The axle flats are aligned vertically to face the cable attachment forward. Except with vertical dropouts, the washers do not hold the axle flats parallel with the dropout slots, and so an older bicycle with narrow slots will need to have the slots widened. File the underside of each slot only, so as not to misalign the axle. Also, the overlocknut spacing of this hub is 135 mm, and many bicycles need to have the frame respaced -- possible, though, only with steel frames.
The axle should be secured and chain slack adjusted before securing the reaction arm of the coaster brake or i-Brake to the left chainstay -- as with any hub brake that has a reaction arm. Best house in gta v.
The chainline is 49 mm. The hub uses a non-standard sprocket, supplied only in sizes of 18 through 22 teeth. As it is a flat sprocket, it can be flipped over to double its wear life; also, its life can be greatly prolonged by replacing the chain frequently, or grinding away the hooks which a worn chain wears into sprocket teeth. The hub was available only for 32 and 36-hole spoking.
The brake lever in the i-Motion 9 IBS SL integrated brake/shifter is direct-pull brake compatible and will not work correctly with other brakes, except some disc brakes. The same is true of the matching BL 60 brake lever.
How it Works
The i-Motion 9 has an unusual planetary gear system with four concentric parts instead of the usual three. From the outside to the inside, there are:
- a ring gear;
- a cage made of two parts locked together with lugs around the outside, the larger (right) end of which has stepped planet pinions that engage the ring gear in the previous step, and the smaller (left) end of which includes another ring gear.
- a cage which carries planet gears that engage the ring gear in the previous step and also carries two sun gears, one, the other, or neither of which may engage the planet gears in the previous step;
- a single sun gear, locked to the axle, which engages the planet gears in the previous step.
These parts are shown in steps 25 through 29 of my disassembly sequence.
Power is applied at the right side of the hub, as usual, and taken off at the left side. Thanks to the two ring gears, power may go from right to left inside the hub, then to the right, and then back again to the left. The two cages and the ring gear may be engaged or disengaged at either side of the hub. In this way, the same gear train can achieve both increase and decrease ratios, including ratios using both planetary systems.
Shifting is by means of a cam which pushes shifter elements to the left along the axle. I haven't taken the time to scope out the shifting sequence, though I have managed to calculate the drive ratios based on gear tooth counts. My example hub doesn't have a coaster brake, so I'm not sure just how that is engaged either.
Sheldon's i-9
Sheldon installed a SRAM 9-speed on one of his bikes and wrote about it here,
You may look up the gear ratios in his Online Internal Gear Calculator.
Articles by Sheldon Brown and Others
Accessories | Bicycles | Parts | Specials | Tools |
---|
Copyright © 2013 John Allen
Harris Cyclery Home Page
If you would like to make a link or bookmark to this page, the URL is:http://www.sheldonbrown.com/i-motion-9.html
Last Updated: by John Allen
The SRAM i-Motion series of products is a sport, urban, and trekking oriented product series developed and manufactured by SRAM Corporation. Branded i-Motion are internally geared hubs, shift levers, and dynamo hubs. Related to the i-Motion series are also changeable free or fixed single speed hubs, hybrid epicyclic and derailleur gear hubs, and hydraulic disc brakes.[1] The i-Motion series of products were developed at SRAMs Schweinfurt R&D and manufacturing plant in Germany, formerly of Sachs.
Products[edit]
i-Motion 9 - This hub gear has nine speeds in percentage increments of 14,17,17..17,14, offering an overall range of 340%. The coaster-brake version weighs 2400 grams, while the non-brake integrated versions weigh just under 2000 grams. This product was discontinued in 2012, and replaced with the SRAM G8.
i-Motion 3 - The 3 has similar gear ratios as the Shimano Nexus three speed hubs, 36% intervals and an overall range of 186%.
References[edit]
Retrieved from 'https://en.wikipedia.org/w/index.php?title=SRAM_i-Motion&oldid=541799131'
There are also articles on this site more generally about internal-gear hubs.
We have links to technical information on most Sachs/SRAM hubs.
and articles about the Sachs Elan 12-speed hub,
the Orbit hybrid gearing system
the i-Motion 9 9-speed hub
and the G8 8-speed and G9 9-speed hubs.
We have links to technical information on most Sachs/SRAM hubs.
and articles about the Sachs Elan 12-speed hub,
the Orbit hybrid gearing system
the i-Motion 9 9-speed hub
and the G8 8-speed and G9 9-speed hubs.
History
The German company Fichtel & Sachs, often called only 'Sachs', started making internal-gear hubs in the early 20th century. In 1997, the American company SRAM acquired Fichtel & Sachs, and so recent products carry the SRAM name. SRAM quit making internal-gear hubs in February, 2017, citing a race to the bottom in the market, and the increasing popularity of e-bikes.
In the mid-20th century, Sachs specialized in products for utility cyclists -- two-speed kickback hubs, three-speed hubs and coaster brakes -- while Sturmey-Archer offered a broader product line, including many narrow-ratio hubs intended for use by avid recreational cyclists and racers.
Starting in the 1980s, Sachs expanded its line of internal-gear hubs to include hybrid gearing systems -- first the Orbit, a two-speed hub with proprietary sprockets, then the 3 x 7 followed by the 3 x 8, and 3 x 9 DualDrive 2 systems and the 3 x 10 DualDrive 3 using a three-speed internal-gear hub and Shimano-compatible cassettes. These newer hubs are especially useful on small-wheel bicycles, because the step-up top gear avoids the need for an extra-large chainwheel. Sachs also introduced 5-speed and 7-speed models and the Elan, a very large and heavy 12-speed hub which was a marketing failure. In the 2007 model year, SRAM introduced the i-Motion 9-speed hub. It was withdrawn, and as of 2014, SRAM offered an 8-speed hub, the G8, and a different 9-speed, the G9, but they also were withdrawn. In 2013, manufacture of SRAM internal-gear hubs was moved from Germany to Taiwan, though engineering was still in Schweinfurt, Germany and in 2017, as described, the line of internal-gear hubs was discontinued.
Design Strengths and Weaknesses
SRAM internal-gear hubs are notable for the fine quality of machining of their internal parts. Gear-tooth surfaces and bearing races are smooth. The SRAM 3-speed, in particular, has higher measured drive efficiency than other 3-speed hubs, possibly due to the quality of the machining.
Most Sachs/SRAM internal-gear hubs are quite rugged, like classic Sturmey-Archer hubs, with simple and conservative mechanical design. Exceptions are the i-Motion 9 and Elan, which were overcomplicated and failure-prone. Older hubs shifted with pullchains, but one weakness with recent hubs is the plastic 'clickbox' shifter mechanism which clamps onto the right end of the hub axle and is vulnerable to damage. A guard is sold, and it should always be installed. With the Elan and the 8- and 9-speed hubs, SRAM abandoned the 'clickbox' for a pulley mechanism inboard of the right dropout.
Older Sachs 3-speeds and the 3 x 7 used a trigger shifter like Sturmey-Archer's, which could be fastened to any handlebar. A Sturmey-Archer trigger also will work with these hubs. A Sachs trigger will not work with a Sturmey-Archer hub, which needs a longer cable pull between the top and middle gear. An old Shimano drop-bar front-indexing STI shifter for triple chainwheels also works with a Sachs hub -- my Bike Friday has Shimano RSX STI brake-lever shifters, and the hub shifts flawlessly. (Bike Friday adds a small return spring to the cable to take up extra slack in the top gear. You need to do that too.) The newer SRAM hubs which use a clickbox were generally available only with twist shifters that fit flat handlebars. SRAM's assumption seems to have been that performance-oriented bicyclists don't care to use internal-gear hubs -- a bit of a self-fulfilling prophecy. There are various tricks to make the SRAM shifters compatible with drop bars -- for example, attaching a mountain-bike bar end to the stem. Aftermarket shifters also are reported to be in the works.
The 5-and 7-speed models with clickboxes use a single cable and concentric pushrods, with a dual bellcrank inside the clickbox. I've considered modifying a 7-speed to use a pullchain on the left side and bellcrank on the right.
The DualDrive hubs and Spectro T3 are supposed to be used only with their proprietary shifters, but they have a pullrod, not a pushrod, suggesting that a conversion to use a pullchain might be possible. Shimano-compatible cassettes that attach to DualDrive hubs work with a wide range of derailers and shifters.
The DualDrive hubs have aluminum shells and are relatively light in weight. Other than this, SRAM has paid relatively little attention to weight reduction over most of its internal-gear hub product line. Many models have been available only with heavy steel shells. The Spectro S7, for example, was made in three versions -- with no brake, with a coaster brake and with a drum brake. They all weigh about the same. You might expect the drum brake version to weigh more, but it is the only one with an aluminum alloy shell. The steel shells of the other 7-speeds are very thick and heavy.
The i-Motion 9 9-speed hub, introduced in 2006 (and since discontinued) has been described as a 'cannonball' because of its size and weight! A version with a carbon fiber shell was marketed, but the weight of the internal parts is still substantial. The G8 8-speed hub, introduced in 2013, and G9, introduced in 2014 and since withdrawn, are larger but lighter and have a much simpler internal mechanism.
Lubrication
Many Sachs/SRAM hubs have coaster brakes, and these hubs must be lubricated with grease -- often two types of grease: one for the gear mechanism, so it doesn't make the pawls stick; another for the brake parts, to resist heat buildup.
Other recent Sachs and SRAM internal-gear hubs also use grease lubrication, and also have no oil cap. Except for the hubs with rotary (pulley) shifting, these hubs all allow addition of oil by removing the shifter parts and squirting oil into the hollow end of the axle. (The disk-brake version of the i-Motion 9 can, however, be lubricated through one of the disk-brake bolt holes at the left side. After disassembling some of the other disc brake models so metal chips can be cleaned out, drilling through one of the disc brake mounting holes allows it to be used as an oil port.). Oil is preferable for drag reduction, and because it can be replenished without disassembling the hub. Caution is in order not to use too much oil when it could seep through the bearing into a drum brake
Phil Wood Tenacious Oil is a good choice, if used in moderation and replenished once every thousand miles or so, or at least once every couple of years. Too much oil will get messy, while stale Phil oil will gum up and can make the pawls stick. The stickiness that keeps Phil Wood oil from being messy also allows it to gum up.
Also see the more general advice on this site about lubricating internal-gear hubs, and on types of oil.
My favorites
My favorite Sachs/SRAM hubs are discontinued models -- the 3 x 7 DualDrive, discontinued in 2000, and the S7 7-speed with drum brake, discontinued in 2010.
The 3 x 7, unlike the later DualDrive models, can take an 11-tooth sprocket only after modifying the cassette body or adding a spacer as described here. Bike Friday modified the cassette body on its bicycles. I prefer the 3 x 7 over the more recent DualDrive models because the 3 x 7 has pullchain shifting, no vulnerable clickbox, and compatibility with drop-bar shifters. I equipped the 3 x 7 on my Bike Friday with a 13-15-17-19-21-24-28 cassette, so the hub's high and low gears each gave me two additional nicely-spaced speeds. Then I found a 33-tooth dished sprocket in Sheldon's basement and added that, widening the range -- see details about putting 8 or 9 sprockets on a 7-speed body here.
The S7 7-speed hub can be set up for an overall range from 27 through 82 gear inches, excellent for utility riding in a hilly area. The weight of the drum-brake version is reasonable, thanks to the aluminum shell. I plan to build an S7 into a wheel for a Raleigh Twenty.
I have spares of both the S7 and 3 x 7 hubs or I wouldn't be using them.
The G8 and G9 look promising for urban use, but I don't have hands-on experience with them.
Parts Availability
Sram I-3 Coaster Brake
Aaron's Bicycle Repair in Seattle, Washington, USA specializes in repair of internal-gear hubs and stocks parts for SRAM hubs including discontinued models.
Other options? I needed two internal parts for a 3 x 9 DualDrive hub. Bike Friday has installed DualDrive hubs on many of its small-wheel bicycles, and so I contacted Bike Friday's German distributor -- writing in German, yet! I found that the parts would cost me over $200, nearly the full price of a complete internal assembly.
Then I contacted Bike Friday directly. Bingo! Bike Friday cannibalizes returned DualDrive hubs to maintain a supply of spare parts. Tim Link at Bike Friday was able to send me the needed parts for $30. Thanks Tim! If you also need parts for a DualDrive hub, you might give Bike Friday a call.
In Europe, Sachs/SRAM hubs are common and spare parts, both new and used, are more widely available. They are going to be harder to get, now that production has been discontinued.
The axle threading of most SRAM internal-gear hubs is unusual, 10.5mm x 26 TPI, but close enough to that of many Sturmey-Archer hubs (13/32 x 26 TPI) that Sturmey-Archer axle nuts are usable in a pinch. The i-Motion 9, G8 and G9 use common 10 x 1mm threaded axle nuts.
Troubleshooting, Maintenance and Rebuilding
My intention here is to provide the best information I can on rebuilding Sachs/SRAM hubs.
You do well to keep a spare hub for parts.
The first thing to check if a hub doesn't get all the gears is whether the problem is in the shifter, or the hub.
On older hubs with a pullchain, the chain should only be able to pull out a tiny bit farther in its tightest position. Having established this, the hub should shift correctly into all of the gears. If an indexed Shimano brake-shift lever is used to shift a 3 x 7 hub, as on some Bike Fridays, there needs to be an additional return spring on the cable to latch the shift lever. Bike Friday can supply this item.
The 5- and 7-speed hubs use dual, concentric pushrods. With the clickbox removed, the hub should be in its lowest gear. Pushing the outer pushrod in should shift the hub to the middle (direct drive) and highest gear. Pushing the inner pushrod in should shift the hub from low, to second, and in the 7-speed, to third gear. If the clickbox doesn't shift the hub to these gears, then it is the problem. If these gears work with the clickbox installed but the 4th gear of the 5-speed, or 5th and 6th of the 7-speed don't work, you may have to push on both rods at once to isolate the problem. You may need an assistant to help with this.
If a DualDrive or other three-speed hub with a pullrod doesn't shift properly, remove the clickbox and pull out the pullrod (which has a head with a screwdriver slot) as far as it will go, while spinning the rear wheel forward so the shifting mechanism will release. Stop the wheel, hold the rod in the outermost position with pliers, turn the crank forward and see whether the hub is in low gear (the wheel turns slower than the sprocket). Release the rod in two steps and you should get middle and high gear. If so, the problem is with the clickbox, shifter or cable, so replace those. Otherwise, the problem is internal.
Here are some information sources for rebuilds.
There are pages on this site about hubs which get little coverage elsewhere: the G8 8-speed and G9 9-speed hubs, the i-Motion 9-speed hub, the Elan, and the Orbit 2 x 6 (or 2 x 7) hybrid-gear hub.
SRAM keeps an excellent resource online. You can start with SRAM's technical page. The Product Manuals and Quick Starts listed on that page cover installation and adjustment of hubs.
If you are going to rebuild a hub, then you need to look at the Technical Manuals. The manual for each year is very similar except for the introduction of new models and deletion of discontinued ones. Some archived manuals are here but others have been moved to SRAM's Chinese site. The 1999 manual ( another source) (yet another source) (yet another) (auf Deutsch) (en français) is the only one online which covers the Elan/E12 and the 3 x 7. The 2015 spare parts manual covers the G8, G9 and DualDrive 3.
Aaron's Bicycle Repair also has technical information online about Sachs/SRAM hubs, including tips for practical assembly and disassembly.
Sutherland's Handbook of Internal-Gear and Coaster Brake Hubs, published in 1992 and now online on this site, has very complete information, including trouble charts and comparative parts lists, on Sachs two-speeds and the models 415, 515, H3102 and H3111 3-speeds. (Disclaimer: I was one of the authors!) The Third Edition of Sutherland's Handbook for Bicycle Mechanics, published in 1981, and Fourth Edition, published in 1985, cover most of these hubs. Many bicycle shops keep copies.
Karsten Stielow's site Karstilo.net covers many Sachs hubs from the 1960s onwards. The text is in German but there are many exploded drawings and photos.
A reader of this site has sent us links to a photo guide to rebuilding the S7, along with some additional useful information -- in Russian.
- SRAM S7 coaster brake overhaul, photo guide and illustrated article in Russian
Walter Jakuba, Das Zweirad -- has ample information on Sachs hubs from the 1950s through 1990s. The site is in German but the clickable links in the column at the right side lead to lists of hubs. Most of the exploded drawings and parts lists are in both German and English. They are best viewed if you right click (in Windows; or use a similar command on the Mac) and select 'Only This Frame'. Das Zweirad sells a considerable selection of spare parts for Sachs and SRAM hubs.
Jens Hansen's Scheunenfun (barn-find fun) site has information on many older Fichtel & Sachs hubs:: exploded drawings, parts lists and step-by-step rebuilding instructions, with photos. The text is in German, but the drawings should make the rebuilding process clear enough. Hansen sells replacement parts for older hubs, too.
Andree Schote's site also has information (in German) on older Fichtel & Sachs hubs.
See also: |
SRAM Corporate Site |
SRAM Internal Gear Hub page |
SRAM History Page |
SRAM Technical Page |
Sachs Elan 12-speed Hub |
Sachs Orbit |
SRAM G8 and G9 |
i-motion 9, 9-speed SRAM hub |
SRAM hubs on sale at Harris Cyclery |
Aaron's Bicycle Repair |
Karstilo.net (in German; many drawings and photos) |
Walter Jakuba, Das Zweirad |
Jens Hansen's Scheunenfun (barn-find fun) site |
Articles by Sheldon Brown and Others
Copyright © 2013, 2015 John Allen
Harris Cyclery Home Page
If you would like to make a link or bookmark to this page, the URL is:https://www.sheldonbrown.com/sachs-internal.html
Last Updated: by John Allen
The invention relates to a twist-grip shift mechanism for bicycles and in particular a twist-grip shift mechanism having a housing part formed by an injection molding process using a single half of an injection mold to eliminate undercuts.
German Patent Application DE 197 23 346.5 discloses a shift mechanism for controlling transmissions on bicycles, in particular a twist-grip shift mechanism to be fitted on the handlebars. This shift mechanism includes a fixed housing connected to the handlebars and a housing that is fixed axially with the fixed housing and can be rotated by hand. The fixed housing and the rotatable housing form a unit. The rotatable housing has an inner cylinder with outward-facing recesses and the fixed housing has an outer cylinder with bayonet hooks on its axially outer end face. The inner cylinder of the rotatable housing may be pushed onto the outer cylinder of the fixed housing to form a bearing. The two housings may be connected permanently to one another by rotating the rotatable housing relative to the fixed housing until a latching point is reached.
A problem associated with the above configuration is the proper molding of the two housing to form a satisfactory bearing. During the molding process, undercuts may form. The undercuts cause parting seams and molding inaccuracies which may cause connecting problems when the two housings are bought together to form the bearing. Therefore, there is a need for a shift mechanism that eliminates the above stated problem.
The present invention provides a twist-grip shift mechanism for bicycles with a fixed housing which has a cylindrical extension surrounding a handlebar to support a rotating part. To eliminate the above stated problems the cylindrical extension is configured in such a way that no contours that connect with the rotating part go beyond the outside diameter of the cylindrical extension. Another factor that contributes to an efficient manufacturing process is that there is a housing extension surrounding a cable bobbin on the rotating part. The housing extension is formed as part of the housing part. The contours are formed on the outside diameter of the cylindrical extension during an injection molding method using a single mold half of an injection mold. The advantage of this manufacturing method is a homogeneous cylindrical surface of the cylindrical extension, which serves as a bearing for the rotating part resulting in no parting seams or molding inaccuracies that could impair operation of the twist-grip shift mechanism during actuation.
The above-mentioned manufacturing method may also be used for molding tongues with retaining profiles onto the cylindrical extension for releasable assembly with latching profiles of a ring. The retaining profiles include apertures to prevent them from projecting beyond the limits determined by the inner and outer diameters of the cylindrical extension. The latching profiles on the ring are designed as hooks engageable with the apertures in the tongues.
The rotating part and the cable bobbin may be encapsulated with a grip part made of rubber-elastic material. Such a configuration allows a radially inward-pointing lip to be molded on the grip that extends beyond the overall length of the rotating part on the side opposite the cable bobbin. In the installed condition, the lip engages in a radially outward-facing groove arranged in the ring. This allows the bearing between the rotating part and the cylindrical extension to be kept free from penetrating dirt, thus ensuring the functioning of the lubricated bearing over a prolonged period.
It is therefore the object of the invention to provide an injected molded housing part for a twist-grip shift mechanism having a cylindrical extension that includes an outer functional surface and a housing extension that includes inner contours that is configured to allow the use of a single half of an injection mold, thereby eliminating undercuts and other molding inaccuracies.
In the drawings:
Referring to FIGS. 1 and 3 , the ring 12 may be pushed over the tongues 9 within the rotating part 3 until the latching profiles 11 of the ring 12 fit together with the retaining profiles 10 of the tongues 9 . Resulting in the tongues 9 being forced to bend radially inward during assembly. Once the latching profiles 11 are fitted together with the retaining profiles 10 of the tongues 9 , the rotating part 3 is fixed axially relative to the ring 12 by an end face 17 and, in the other direction, is fixed axially relative to the housing part 1 .
In reference to FIGS. 1 to 4 , the smallest inside diameter 7 ,7 a of the cylindrical extension 2 ,2 a with its tongue 9 ,9 a corresponds to the diameter of the handlebar tube. The bearing for the rotating part 3 ,3 a has an outside diameter 8 ,8 a which must not be exceeded by the integrally formed tongues 9 ,9 a with their retaining profiles 10 ,10 a in order to ensure that these parts can be produced with a single half of an injection mold by a material injection method. However, efficient production of the housing part 1 ,1 a is only possible if inner contours 6 ,6 a of a housing extension 5 ,5 a that is formed integrally on the housing part 1 ,1 a and forms an annular space that essentially surrounds the cable bobbin 4 ,4 a can likewise be formed by this half of the injection mold. The contours 6 ,6 a are arranged in the housing extension 5 ,5 a to guarantee the functioning of the two parts 1 ,1 a and 3 ,3 a. To ensure that the bearing on a functional surface of the cylindrical extension 2 ,2 a and the inner contours 6 ,6 a in the housing extension 5 ,5 a can be produced economically and with optimum molding accuracy, it is necessary that the retaining profiles 10 ,10 a on the tongues 9 ,9 a do not project beyond the diameters 7 ,7 a and 8 ,8 a.
The rotating part 3 ,3 a has a grip part 13 ,13 a connected to a radially outward-facing surface of the rotating part, which is made from a rubber-elastic material to allow better operation by the hand of the bicycle rider. The grip part 13 ,13 a has a lip 14 ,14 a that projects beyond the axial length of the rotating parts 3 ,3 a. The lip 14 ,14 a points radially inward and extends into a groove 15 ,15 a in the ring 12 ,12 a, thereby providing a labyrinth-type seal against contamination of the bearing from outside. The groove 15 ,15 a is formed by an outer collar 16 ,16 a at the end of the ring 12 ,12 a. The collar 16 ,16 a protects the end face of the grip part 13 ,13 a, which is sensitive to shock loading. In reference to FIGS. 3 and 4 the lip 14 ,14 a is deformed elastically during the fitting of the ring 12 ,12 a in order to enter the groove 15 ,15 a. FIGS. 3 and 4 likewise show the twist-grip shift mechanism as an assembly in the form in which it can be pushed onto the handlebar tube of the handlebars of the bicycle and fixed there by a screwed or clip-type connection (not shown).
Referring to FIGS. 2 and 4 , which show another embodiment of the twist-grip shift mechanism, the twist-grip shift mechanism includes the housing part 1 a having the cylindrical extension 2 a and the tongues 9 a plus the twisting part 3 a and with the ring 12 a. While the retaining profiles 10 of the twist-grip shift mechanism shown in FIGS. 1 and 3 are designed as apertures, the tongues 9 a shown in FIGS. 2 and 4 have T-shaped retaining profiles 10 a that can interact with correspondingly shaped latching profiles lla in the ring 12 a. The difference between the assembly of the ring 12 with the tongues 9 and the assembly of the ring 12 a with the tongues 9 a is that, after being latched in, the retaining profiles 10 a of the tongues 9 a can be disengaged from the latching profiles 11 a by turning the ring 12 a. During this process, the tongues 9 a are deflected radially inward, and the ring 12 a can be pulled off axially, although this is only possible while the shift mechanism is not mounted on the handlebar tube of the handlebars of the bicycle. It should be pointed out once again that the functional surface of the cylindrical extension 2 a with the outside diameter 8 a can be molded with a single mold half and the T-shaped retaining profiles 10 a do not exceed the outside diameter 8 a.
(Redirected from Electronic Gear-Shifting System)
Electronic front derailleur (Shimano Di2)
Electronic shifting control unit and battery pack mounted to bottom of bottom bracket and left chain stay
Electronic rear derailleur (Campagnolo Record EPS)
An electronic gear-shifting system is a method of changing gears on a bicycle, which enables riders to shift with electronic switches instead of using conventional control levers and mechanical cables. The switches are connected by wire or wirelessly to a battery pack and to a small electric motor that drives the derailleur, switching the chain from cog to cog. An electronic system can switch gears faster, and because the system does not use Bowden cables and can calibrate itself, it may require less maintenance.[1]
- 2Implementation
History[edit]
In 1990 the Japanese bike component manufacturer SunTour introduced the Browning Electronic AccuShift Transmission (SunTour BEAST) - a triple chainset system for mountain bikes in which one quarter of the circle is hinged along a radius. During shifting, this segment is pushed sideways by a relay operated mechanism like a railroad switch and picks up the chain that is currently running on the next cog.[2]
In 1992 the French manufacturer Mavic introduced their first electronically controlled gear shift mechanism called Zap at the 1992 Tour de France. It was a prototype, but it achieved neither technical success nor commercial application. A development of this was used by Chris Boardman to win the opening time trial (prologue) of the 1997 Tour de France.[3]
In 1994 Sachs introduced the Speedtronic.[4][5]
In 1999 Mavic introduced the Mektronic, its second electronic shift system, which suffered from reliability issues and was subsequently discontinued.[3]
In 2001 Shimano introduced a set of trekking components called Di2 (Digital Integrated Intelligence), which included electronic shifting and automatic adaption of front and rear suspension to riding speed.
During the 2000s both Shimano and Campagnolo (2005)[6] experimented with electronic shifting in professional cycle races.[3]
The first commercially successful electronic gear shift system for road bicycles was introduced by Shimano in 2009, the Di2.[3] Three professional teams used the Di2 in the 2009 Tour of California: Columbia High Road, Garmin Slipstream, and Rabobank;[3] and several teams and riders, including George Hincapie, used it during the 2009 Tour de France[7]
Also in 2009 Giant released a bicycle equipped with the Shimano Di2[3][8] and Trek began providing a battery mount and Di2-specific cable routing and stops on its Madone frames.[9]
Production SRAM RED eTap rear derailleur installed on bike.
In 2015 SRAM announced its wireless electronic groupset called, SRAM RED eTap. The group was released in Spring of 2016 and is available on complete bikes and through aftermarket SRAM component dealers. (See below)[10][11]
A wireless system that can be retrofitted onto any bicycle was announced in 2016.[12] The front and rear derailleurs remain place, while a wireless gear-change controller is added to the handlebar, with configuration of the system via an iOS/Android app, and customization can be added to the button controllers via the Bluetooth app.[13]
Implementation[edit]
As of 2009, one system was commercially available from a major parts manufacturer: Shimano's Di2 (Dura-Ace 7970) for road bicycles. While the traditional method of gear shifting uses mechanical control levers that pull and release Bowden cables and spring-loaded derailleurs, Di2 is controlled by electronic switches located either in the integrated shift levers and/or at the end of time trial bars. The switches send signals through a wiring harness to a battery pack, placed near the bottom bracket. The rechargeable lithium-ion battery pack supplies power to the derailleur motors, which move the derailleurs via worm gears. Shimano estimates that their 7.4-volt battery pack can last up to 1,000 kilometres (620 mi) per charge.[14] The system also has an LED light to warn when it needs a charge.[15]
The rear derailleur has shift times similar to mechanical systems and a break-away system to protect it in case of a crash.[15] The front derailleur, however, switches gears almost 30% faster than Dura-Ace’s mechanical counterpart.[1] On traditional bikes, the front derailleur is problematic because the chain can be under tension and has to make a large vertical jump between chainrings. The electronic system's controlled motion overcomes these problems. The Di2 can also trim the front derailleur to eliminate chain rub and calibrate itself to adjust for wear and tear.[16] Finally, the entire 7970 groupset weighs approximately 113 grams (4.0 oz) less than the 7800 it replaces but 68 grams (2.4 oz) more than the new 7900.[17]
In 2011 Shimano introduced the Ultegra Di2[18] electronic gear change set, a cheaper version of the electronic Dura-Ace system. This set seemed to provide an electronic option within reach of a wider audience.
Campagnolo introduced their first system of electronic shifting, EPS, in the same year.[19] By 2012 Campagnolo had three electronic shifting groupsets available.[20] Cyclists began to see a growing range of electronic alternatives to traditional mechanical shifting for derailleur gears.
Wireless shifting[edit]
A wireless system was announced by Tiso in 2012, but this did not achieve widespread use.[21]
SRAM RED eTap HRD brake lever
In August 2015 SRAM Corporation announced its wireless shifting system, eTap.[22] The system had been extensively developed and secretly tested over several years from initial design to a stage win in the 2015 Tour de France. The front and rear derailleurs use direct-mount batteries and communicate wirelessly with the shifters through a proprietary wireless protocol developed by SRAM called, Airea (pronounced: area). A set of small satellite shifter buttons, called Blips, can be connected to the shift levers or aero shift module (BlipBox) and placed anywhere along the handlebars as part of the system. A maximum of four Blips can be used per bike. The company also took the opportunity to introduce a new shifting convention with this system. The right lever shifts the rear derailleur outboard, the left lever shifts the rear derailleur inboard, and pressing both levers together shifts the front derailleur. SRAM made the groupset available for purchase on complete bikes and as aftermarket components sold through dealers from Spring 2016. Eventually, extension of the system is expected to the company's lower group sets, such as SRAM Force. In May 2016 the company announced a hydraulic disc brake version of its wireless road group called SRAM RED eTap HRD. The new brakes make use of a hydraulic lever design with both lever reach adjustment and lever contact point adjustment, a first for road disc brakes.
SRAM RED eTap HRD caliper and rotor installed on bike.
At Eurobike 2015 Held in Friedrichshafen, Germany, the FSA company displayed their working prototype of a wireless gear shifting system. The system was trialled at the 2016 Tour de France in stage 17, and at Eurobike 2016 the final form of the WE (Wireless Electron) groupset (which includes wireless shifting) was displayed. FSA plans to make this available from May 2017.
At Interbike 2016, in Las Vegas, Nevada, Paul Gallagher displayed a working prototype of his XSHIFTER universal wireless gear shifting system. It is a patent pending device that is claimed to convert any bike with mechanical derailleurs to wireless smart shifting in a few minutes. The XSHIFTER will be seeking funding for development in November 2016. If successful, this project will further extend the range of electronic gear-shifting systems.
Advantages[edit]
An electronic system can have several advantages over a comparable mechanical system:
- eliminate the need for the rider to switch hand positions in order to shift[1]
- allow for an accurate and effortless shift, even in difficult circumstances, such as if the rider has cold hands or is completely exhausted
- shifting performance is not affected by contaminated, stretched, or worn Bowden cables
- automatic trim function can eliminate chain rub[1]
- shifts can be timed to occur at a particular point in the cassette or chainring rotation, making best and smoothest use of ramps and cutouts in the sprocket teeth
- the front and rear shift pattern on a bike with multiple chainrings can be programmed to make best use of the gear progression, avoid duplicate ratios and relieve the rider of the need to decide what combination of front and rear sprockets to employ
- the smoothness of electronics can reduce the shock on drivetrain components[5]
Disadvantages[edit]
An electronic system may have some disadvantages when compared to a mechanical system:
- There is currently no option for manual override when the battery is exhausted. This could pose a problem for riders, depending on the type of terrain on which they are riding.[3] However, SRAM's RED eTap groupset's interchangeable derailleur batteries makes it possible to manually switch batteries between the two derailleurs in order to place the battery with remaining charge onto the derailleur the user intends to shift.[23]
- Reliability issues have caused previous electronic systems to be withdrawn from the market. As of recently, all electronic group sets are fully waterproof. External connectors are completely waterproof, but internal connectors (internal routing for wired systems) need to be shrink wrapped with shrink tubing to be waterproof.[16]
- Cost: The system is expensive compared to lower end mechanical derailleur systems. (The Shimano Dura Ace Di2 system costs in excess of $2500 in May, 2010).[24]
- Weight: Electronic groupsets are typically heavier than their mechanical counterparts.[25]
See also[edit]
Transmission types |
---|
Manual |
Automatic |
Bicycle gearing |
- Hub gear - another bicycle gear shifting system alternative
- NuVinci - continuously variable planetary transmission for bicycles
- Semi-automatic transmission - electronic gear shifting for automobiles and motorcycles
Gallery[edit]
- Electronic rear derailleur
- Electronic shift lever
- Electronic front derailleur (front view)
- Mavic Mektronic rear derailleur
References[edit]
- ^ abcdBest, Paul (08 04 2009). 'Shimano's Dura-Ace Di2 electronic shifting to give road racers a time advantage'. Gizmag. Retrieved 2010-02-10.Check date values in:
|date=
(help) - ^Michael Sweatman. 'Browning'. Retrieved 2012-09-10.
- ^ abcdefgIan Austen (February 13, 2009). 'Cycling Enters the Electronic Age With a New Gear-Shifting System'. The New York Times. Retrieved 2010-02-12.
- ^'SRAM History'. Archived from the original on 2009-10-06. Retrieved 2010-02-17.
- ^ abPhillips, Matt (9 Feb 2010). 'The Shift to Electric'. Bicycling Magazine. Archived from the original on April 17, 2009. Retrieved 2010-02-10.
- ^Lennard Zinn (September 15, 2009). 'Campagnolo's Magic Lives on in Vicenza'. VeloNews. Retrieved 2010-02-17.
- ^David Arthur (9 July 2009). 'Pro riders on Shimano Dura-Ace Di2'. RoadCyclingUK. Retrieved 2010-02-12.
- ^'TSR Advanced SL LTD'. Giant Manufacturing. Retrieved 2010-02-12.
- ^'Madone 6 Series'. Trek Bicycle Corporation. Retrieved 2010-02-12.
- ^https://sramroadsupport.zendesk.com/hc/en-us/articles/206573428-When-is-SRAM-RED-eTap-available-
- ^https://sramroadsupport.zendesk.com/hc/en-us/articles/206573508-Where-is-SRAM-RED-eTap-available-
- ^Ben Coxworth (December 7, 2016). 'The 10 best cycling innovations of 2016'. New Atlas. Retrieved 2017-06-04.
- ^Tyler Benedict (November 2, 2016). 'X-Shifter's universal wireless shifting kit goes live'. Bike Rumor. Retrieved 2017-06-04.
- ^Crowe, Paul. 'Electronic Shift By Wire on Bicycle'. The Kneeslider. Retrieved 2010-02-09.
- ^ abJames Huang (Aug 2009). 'Shimano Dura-Ace Di2 transmission'. BikeRadar.com. Retrieved 2010-02-13.
- ^ abHagerman, Eric (2008-07-31). 'Shimano Shuns Cables for Full Electronic Shifting'. Wired. Retrieved 2010-02-09.
- ^Cole, Matthew (01 08 2008). 'Shimano unveils Dura-Ace Di2 electronic groupset'. BikeRadar.com. Retrieved 2010-02-09.Check date values in:
|date=
(help) - ^Richard Tyler (Jun 20, 2011). 'Shimano Ultegra Di2 – First look'. BikeRadar.com. Retrieved 2012-09-10.
- ^Stephen Farrand (Oct 25, 2010). 'Campagnolo show off new electronic gear system'. BikeRadar.com. Retrieved 2012-09-10.
- ^Robin Wilmott (Jul 17, 2012). 'Campagnolo Athena EPS 11-speed launched'. BikeRadar.com. Retrieved 2012-09-10.
- ^Ben Coxworth (December 18, 2012). 'Tiso unveils wireless electronic gear-shifting for road bikes'. GizMag. Retrieved 2015-09-12.
Shift signals are transmitted from the shifters to the control unit via Bluetooth and/or another unspecified type of radio protocol – Shimano and Campagnolo’s systems, by contrast, use electrical wiring.
- ^Warren Rossiter (August 26, 2015). 'SRAM Red eTap ushers in wireless shifting era'. BikeRadar. Retrieved 2015-09-12.
- ^'SRAM Road Electronic Groupset FAQ Batteries Batteries'. SRAM Corporation. Retrieved 2015-09-12.
Are the front and rear derailleur batteries interchangeable? Yes. Additionally, shifters use one CR2032 coin type battery each.
- ^'The Competitive Cyclist'. Retrieved 2010-12-22.
- ^'SRAM Road Electronic Groupset FAQ Batteries Batteries'. SRAM Corporation. Retrieved 2015-09-12.
The complete SRAM RED eTap groupset is 137 grams heavier than SRAM RED mechanical with the same crankset, bottom bracket, and a short cage rear derailleur.
External links[edit]
- Shimano's description of their Di2 with technical specifications and exploded views
- Campagnolo's description of their EPS with technical specifications and exploded views
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