General-Remarks-How-It-Works-Lubrication-Chain-Adj110

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General-Remarks-How-It-Works-Lubrication-Chain-Adj110

  1. 1. General remarks How it works LubricationChain adjustment Anti-rotation Setting gearrange with: 3 speeds 5 through 8 speeds 9 or more speeds Hybrid gearingInformation on specific brands and modelsRohloff SRAM/Sachs Shimano Sturmey-Archer14-speed All, but alsoseelinks below 3-speed 3-speed4-speed 4 and 5-speed7-speed 7-speed9-speed 8-speed 8-speed12-speed 11-speed hybridGeneral remarksfixed gear bikes
  2. 2. Since the first decade of the 20th century, internal-gear hubs, usually3-speeds, have offered a practical, reliable gear-shifting option to thecyclist With the popularity of derailer gears taking off in the early 1970sbike boom, internal-gear hubs went out of style in most US markets Thisis unfortunate, because many casual or utilitarian cyclists are best servedby this type of gearing tn pas cherInternal-gear hubs are more reliablethan derailer systems, and require much less maintenance The step-upratios of their top gears make oversize chainrings unnecessary onsmall-wheel folding bicycles Unlike derailers, internal hubs can shift at astop, very nice in stop-and-go urban traffic Internal-gear hubs tend to beheavier than derailer systems, and are slightly less efficient in somegears The direct-drive middle gear can be more efficient than in aderailer system, as there is no drag from derailer pulleys Mostinternal-gear hubs cannot have a quick-release axle If you are interestedin old bikes, or the history of this sort of gearing, refer to my page onEnglish Three Speeds How an internal-gear hub worksInternal-gear hubswork on the principle of "planetary gearing
  3. 3. "The basic 3-speed hubs have a single "sun" gear solidly attached to themiddle of the axle 3 or 4 identical "planet" gears mesh with and revolvearound the "sun" gear The "planet" gears are surrounded by (and meshwith) a"gear ring" with its teeth on the inside (an inside-out gear) As theplanet gears, attached to a part called a "planet cage", revolve, the gearring revolves 4 times for every 3 times the planet cage goes around(Some models have different ratios )Low Gear has the sprocket drivingthe gear ring, while the planet cage drives the hub Thus, the wheel turns3 times for every 4 revolutions of the sprocket, lowering the gear by 25%Middle Gear has the sprocket still driving the gear ring, but has the gear
  4. 4. ring drive the hub Thus, the drive is direct Although the internal gearsare always rotating when the sprocket is in motion, they dont have anyeffect on the drive in middle gear High Gear shifts the sprockets drive tothe planet cage, while the gear ring continues to drive the hub shell
  5. 5. Thus, the hub turns around 4 times for every 3 sprocket revolutions,giving a 33% gear increase There is a more detailed explanation of thison the Sturmey-Archer Web site, from which I lifted the image aboveHubs with more than three speeds use two or three planetary stages,and/or compound (stepped) planet gears with two or more sets of teethside by side -- see John Allens article describing these in more detail tnpas cherIn the late 1990s, internal gears underwent something of arenaissance, with the development of wide-range 7-speed hubsProgress has continued since Four different brands are currentlyavailable, with as many as 14 speeds Three-speeds and five-speeds arestill currently in production, and they offer an economical, practicalalternative [Next three sections are by John Allen ]LubricationOlderinternal-gear hubs have an oil fitting on the shell Oil lubrication generatesless drag than grease and washes wear particles, dirt and water out ofthe mechanism
  6. 6. Use machine oil, not a spray lube or other thin oil Unless a hub hassealed bearings, also use grease, to form a seal at the bearings and helpkeep the oil in The Rohloff Speedhub and the Shimano 11-speed areoil-lubricated Other current internal-gear hubs are suppliedgrease-lubricated As sold, they require periodic cleaning andreplenishment of a special grease that does not make the pawls stickShimano sells a relubrication kit for grease-lubricated hubs Still, manyhubs are inadequately lubricated as sold, and frequent failures ofgrease-lubricated hubs due to water contamination have been reported inwet climates --see photos here Better lubrication sidesteps this problemIt is best to add oil to the lubricant regimen when rebuilding a hub, so itgets a clean start and you also can regrease it This is desirable evenwith a new hub
  7. 7. Follow the example shown in the photos from Aarons Bike Repair (nearthe bottom of the page, after you get past the horror-show photos ofrusted parts at the top) Use plenty of waterproof marine grease (as usedin boat-trailer wheel bearings) for the bearing assemblies -- this keepswater out and oil in; use lightweight white lithium grease for the gears,especially with modern wide-mouth hubs that hold oil poorly; Phil WoodTenacious Oil on the pawls and in the shell to slop around and get towhere the grease didnt reach An internal-gear hub with a hollow axlemay be re-oiled by removing the pushrod or indicator spindle andsquirting oil into the end of the axle The SRAM i-Motion 9-speed, diskbrake model, can be oiled through a disk brake rotor hole Plug all theholes with machine screws between oilings On a hub which doesnt allowone of these tricks, you could install a Sturmey-Archer oil cap Tools: #3(or 5 5 mm) drill and a 1/4 inch 28 TPI tap A simpler but less convenientapproach is to unscrew the left bearing cone and squirt oil in past the leftend of the axle Oil can accumulate on the hub shell, and can become abit messy, but, big deal
  8. 8. On the other hand, if used to excess, oil can run down the spokes ontothe rim, soften the brake shoe rubber and make a rim brake squeal andgrab This is hazardous in a front wheel, but the internal-gear hub is inthe rear wheel Cleaning the oil and brake-shoe rubber deposits off therim restores brake function Also, it is best to store your bicycle in anunheated (but dry) area When you take it out from a heated area in cool,moist -- or wet -- weather, the air inside the hub contracts, pulling inmoisture If you must store your bike in a heated area, be especiallycareful about keeping the hub oiled Old Sturmey-Archer coaster-brake3-speeds have an oil fitting, but other hubs with a coaster brake require aspecial high-temperature grease for the brake shoes Some hubs use adifferent grease for the rest of the mechanism, so the pawls dont stick Acoaster brake in an internal-gear hub is, all in all, a poor idea because ofthe wear particles it generates, and because you cant use oil lubricationOil lubrication may cause problems with a drum brake, by seeping outpast the bearing and contaminating the brake shoes
  9. 9. Phil Wood Tenacious Oil stays in place better than most other oilsUnlike with derailleur bicycle, if you must store or transport the bikehorizontally, lay it on its right side This will prevent oil from leaking intothe drum Place something under the rear wheel to catch the drip,especially if you have just oiled the hub Shimano roller brakes aresometimes referred to as drum brakes, but are actually similar to coasterbrakes They use steel brake shoes inside a steel drum and requireperiodic lubrication with high temperature grease Adjusting thechainInternal-gear hubs typically use a single sprocket and singlechainwheel The chain is held in place by moving the hubs axle forwardor backward in the dropout slots until the chain is just barely slackDetails of how to do this are in another article on this site A bicycle withvertical dropouts must have an eccentric bottom bracket, or a chaintensioner must be installed
  10. 10. As the chain wears, it lengthens, and it is more likely to fall off It must bereadjusted periodically Technique for chain adjustment is described inthe article on fixed-gear bicycles Anti-rotationThe axle is part of the geartrain of an internal-gear hub You can check this out for yourself If youhold the hub shell or rim when the hub is not installed on the bicycle andturn the sprocket, the axle also turns -- backwards if the hubs drive ratiois lower than 1:1, forwards if higher Special anti-rotation washers keepthe axle from turning when the wheel is installed on the bicycle Thesewashers engage flat surfaces on the axle, and have tabs that fit into thedropout slots Different washers fit different models of hubs and dropoutslot widths Many newer hubs attach the shifter cable to a pulley thatrotates around the hubs axle, between the right dropout and the sprocket
  11. 11. Depending on whether a bicycle has horizontal, vertical or reversed(track) dropouts, different washers are needed so the shift cable canapproach from the front of the bicycle Follow the instructions for eachhub Anti-rotation washers for Shimano Nexus internal-gear hubsA hubbrake of any kind also must resist rotation Brakes on internal-gear hubsuse a reaction arm for this purpose, separate from the anti-rotationwasher(s) for the gearing You must install them too The Rohloff hub hassuch a wide gear fixed gear bikes range that some models use a reactionarm instead of anti-rotation washers On a bicycle with rear suspension,the suspensions pivot is usually ahead of the rear hub Because it tries torotate the hubs axle, an internal-gear hub lifts the rear end of the bicycle,reducing "pogo sticking" in gears below 1:1; the opposite in gears above1:1 Pogo-sticking reduces pedaling efficiency, to a degree which dependson the design of the suspension click here
  12. 12. fixed gear bikes

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