Talk:Rohloff Speedhub

Weight

To make a meaningful comparison we must take into account more than just the gear mechanisms themselves, although the contribution of the chain and spokes is small. Due to the symmetrical shape of the spoke flanges, the spoke tension is evenly distributed and is less than that of derailleur bike wheels, allowing fewer spokes with a smaller diameter to be used. The chain is shorter, the derailleur cassette is omitted and the spokes are shorter.

The weight can be compared with a high quality derailleur system (Shimano XT):

The Speedhub weighs about 0.5 kg more, although this does not include the weight for traditional shifters and cables.

A new version (currently in development, with testing due to begin in 2009) will weigh in at 1400g, be 20% smaller and have a larger overall ratio of 580%.^[1]

Advantages

This section does not cite any sources. (August 2009)

• There is less wear on all parts, resulting in an almost entirely maintenance-free hub. Although regular replacement of the lubricating oil is essential, this maintenance is both easily done and entirely predictable. (Routine hub-gear maintenance consists merely of oil changes, rather than the frequent cleanings, surface oilings, and rather frequent parts replacements typical with derailleur-based systems.)
• The hub is engineered for routine oil changes, a feature crucial to longevity that many other hub-gear manufacturers have neglected.
• The fully enclosed design is well suited to harsh conditions, including dry-and-dusty environments. This brings a level of durability and reliability unattainable with derailleur-type geartrains.
• The chain may be enclosed, thus protecting it against the abrasive effects of dirt. It is possible to encase the chain in an oil bath for even longer chain life. Furthermore, larger and wider chains can be used in order to bring even longer chain life. Toothed drive belts can be employed too.
• The design saves time for the user, since the user does not have to clean the drivetrain after a ride through a dirty or dusty area.
• Because the gears are enclosed, and especially if the hub gear is combined with an enclosed chain, there is no need to use solvents to clean dirt-encrusted gears. This avoids the health, safety, and environmental concerns associated with solvent use and disposal. Not having to clean dirt-encrusted gears also avoids the corrosion-related concerns of using waterbased detergents.
• The compact, closed design requires only a single chain wheel.
• Since no derailleur is involved, the chain is always in the optimal position regardless of the chosen gear. And, all 14 gears are fully usable. (In derailleur-based systems, even though the advertised number of gears is simply the number of front and rear sprockets multiplied together, many of those combinations are suboptimal because of the angle at which they cause the chain to run. That means that, for a derailleur-type bicycle advertised as having 27 speeds, only about half of those combinations are truly suitable for use. Therefore, in terms of the number of gear ratios available to the user, the Speedhub's fully usable 14 gears compare very favourably to derailleur-type systems.)
• The absence of derailleurs avoids the hassles of chain jumping, chain jamming, chain slapping, chain-suck, and other frustrations.
• The reliable and quick shifting maximizes safety for the user. (Derailleur-based systems place the user at risk if the chain jams at the same time the cyclist needs to escape from a dangerous situation.)
• Shifting is predictably quick and consistently precise. There is no waiting for a chain to move from one sprocket to another, nor is there waiting for the chain to wrap itself around the destination sprocket.
• The absence of the derailleur avoids the concern of derailleur damage due to the bicycle falling over or impacting an object. Also, there is no derailleur hanger to bend.
• The use of roller bearings in this hub makes for higher mechanical efficiency than hubs made with simple sleeve bearings.
• Because the hub is sealed from the elements, dirt, water, deicing salts, mud, and grit do not interfere with its operation. For this reason, mechanical efficiency of hub-gear systems remains more consistent over time, as compared to derailleur-based drivetrains.
• Very long life expectancy, especially if the oil is changed regularly. (Just as with any automotive transmission, regular oil changes are key to long life.)
• As the hub "wears in", mechanical efficiency improves (especially if more-frequent oil changes are done in order to remove these initial wear particles).
• The Speedhub permits symmetrical lacing of the spokes, which leads to less spoke strain and fewer breakages.
• Gears can be changed while the bicycle is stationary.
• Gears progress in constant steps.
• There is only one shifting lever, and so there is no need to co-ordinate two shifting levers. Nor is there any need to fine-tune one derailleur as the other one progresses through its gears.
• The absence of derailleurs also means there is never any worry of the chain running off its sprockets due to a maladjusted derailleur or other reasons.
• Shift indexing is done inside the hub and a two-cable system is used, thus completely avoiding the worry of gears not being correctly in place. This avoids the concern of severe mechanical wear that can arise from single-cable-operated hub-gear systems, where a stretched cable can be disastrous if left unaddressed for long periods of time.
• The design of the Speedhub's shifting mechanism also averts the concern of disturbing the shift-indexing adjustment each time the wheel is moved (in the case of slotted dropouts).
• The two-cable shifting system also avoids another bane of derailleur systems: the need to constantly adjust a shifting cable to compensate for cable stretch. The Speedhub's two-cable system completely avoids the worries inherent to single-cable systems: stretching, sticking, and return-spring failure.
• The two-cable system also means that if a cable were to break in the field, the user can manually select (at the hub) the desired gear and continue on his/her travels using that one single gear (or he/she can stop, select another gear, and then carry on again). This is a major advantage over single-cable-based shifting systems, which usually shift into the highest gear when a cable breaks. Prolonged pedalling in an abnormally high gear will result in knee strain and patellofemoral problems. For the same biomechanical reasons, the two-cable shifting system is also advantageous if the shifter itself were to fail.

Disadvantages

This section does not cite any sources. (August 2009)

• High initial price, albeit this is amortized over the very long service life.
• High price makes this hub an attractive theft target.
• Some gears require the use of all three planetary stages in series. The efficiency of a single stage planetary gear in any engineering application is approximately 97%, so the overall efficiency in some gears can be as low as 90%. This corresponds to the measurements made by Berto and Kyle for the Speedhub and other epicyclic hubs^[2].
• The very wide range of drive ratios is necessary only when riding in steep terrain. On a bicycle used in flatlands or in most urban settings, the lower gears go unused.
• Cyclists who do not ride frequently may not obtain the full value from this expensive item.
• The hub, like other current internally-geared hubs, is intended for loading imposed by a single cyclist. Use on a cargo tricycle or on a multiple-rider machine may overstress it.
• On a bicycle with rear suspension, the torque applied to the frame by an internally-geared hub results in "pogo-sticking" or bounce. This is especially so in the very low ratios which the Rohloff hub affords.
• When changing from the 7th to the 8th gear or vice-versa under very high pedalling pressure (torque), the hub may change to the 14th gear. However, this drawback is easily avoided simply by not applying high pedalling pressures when shifting.
• For the first few hundred kilometers, the friction of the hub seals may cause a forward movement of the pedals when the bike is pushed. The effect lessens over time.
• For riders accustomed to derailleur-type gearing with finer steps in the higher gears, the regularity of the Speedhub's 13 gear steps (i.e. the proportional increase between each of the consecutive 14 gear ratios is the same) can be uncomfortable.
• Although the chainring and sprocket can be changed, the individual gear ratios are fixed and cannot be changed. With derailleur-type systems, it is easy to swap out chainrings or the rear cassette (and with some rear cassettes, individual gears can be swapped out), thus enabling the cyclist to fine-tune the gear ratios and steps as much and as often as desired.
• The absence of a rear derailleur means that a non-round front chainring (such as the Shimano Biopace) should not be used. However, at some minor cost in efficiency, this problem can be solved by using a spring-loaded chain tensioner (which is also needed if the bicycle is a full-suspension model).
• Storing the bicycle in a horizontal position for a long period of time may cause the seals to leak oil. Significant oil leakage can occur if the bicycle is exposed to rapid pressure changes, as in the cargo hold of an airplane, unless the bicycle is kept vertical at all times.
• The twist shifter is not compatible with all handlebars. While there are some assembled handlebars available for racing bicycles, there is not much variety.
• In the event of failure, repair can be more complex and expensive than with a derailleur-equipped bicycle, and field repairs may be difficult. However, in an emergency situation, it is usually possible to engage at least one of the 14 gears, thus enabling the unit to be used temporarily as a single-speed hub.
• There is some risk of the user's forgetting to maintain the hub (i.e. regular oil changes), just as many people forget to change the oil in automotive gear boxes and differentials.
• Many bicycle retailers avoid stocking hub-gear systems because they fear that customers who neglect regular oil changes will be upset when the retailer must send out a neglected hub for repair.
• For users who take their bicycles to shops for routine maintenance, the local bicycle mechanic might not be familiar with the need for regular oil changes with the Speedhub. The fact that nearly all other hub gears are marketed as "lubed for life" makes it likely that an unfamiliar mechanic will completely overlook the routine oil changes that the Speedhub needs in order to last for a long time.

Les woodland (talk) 20:47, 9 February 2010 (UTC)les woodland