Planetary drive systems and bicycle transmissions: Why internally-geared hubs on electric bikes are having their moment
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Outside of some specific cycling niches, the mainstream bike world largely viewed internally geared hubs as the oddball cousin of more traditional drivetrains.
Bicycle commuters who trudged through snow and rain liked them because all the important bits were sealed inside the hub shell, protected from the elements. And they had a cult following in the long-distance bike touring crowd who loved the fact that they require virtually no maintenance and you could get them to shift even when the drivetrain was under extraordinary load, perfect for pedaling fully-loaded touring rigs over mountain passes.
The inside of an internally geared hub&#;s oversized shell is a complex mess of gears that would make a Swiss watchmaker blush. How this all works is difficult to explain, and you don&#;t really need to know it in detail, so here&#;s the CliffsNotes version: That complex interlocking gear system inside the hub is made up of &#;planetary gears&#; that orbit a &#;sun gear,&#; which is fixed to the axle. As a rider pedals, power is transferred to the rear hub via a drive system that is effectively the same as a single speed drivetrain, with a sprocket at that cranks and a primary cog mounted on the rear wheel. But once the power gets to that rear cog, it passes through a complex transmission-like system of gears inside the hub before being translated to the rear wheel. As a rider shifts, different combinations of gears inside the hub engage to make for different gear ratios. These gears either amplify the force applied at the pedals to turn the wheel faster, or reduce it to turn the wheel slower.
Few in the mainstream cycling world, myself included, paid much attention to internally-geared hubs. That is, until e-bikes came along and shattered the definition of mainstream.
Suddenly, the market was flooded with cycling neophytes on the hunt for e-bikes they didn&#;t need to be experts to ride. They wanted something to ride to the store or work that requires little maintenance; little prior knowledge of good shifting technique (which is absolutely a thing); and something that would last a long time.
The e-bike also presented a new mechanical problem for traditional drivetrains: They produce a TON of force. Not only did the torquey motors threaten to stretch chains and wear out cassettes quicker, the lateral forces of shifting multiple gears at a time and &#;cross-chaining&#; became a much greater concern.
Internally geared hubs are a readymade solution to those two mechanical problems, as they wear slowly and shift under load exceptionally well. They&#;re also friendly to newbie cyclists, as you can easily shift while pedaling uphill, shift while stopped and there&#;s not much to mess up once they&#;re installed and properly tuned.
Consumers still don&#;t have a ton of brand options, as there&#;s only a few internally-geared hubs on the market today, but there&#;s still good choices for entry-level cyclists and experts alike.
Shimano makes the affordable and reliable Alfine and Nexus hubs, which we see come stock on a whole host of commuter, cruiser and cargo e-bikes. There&#;s also the English-made Sturmey Archer hubs, which are less common (at least in the U.S.). And for those with a more refined taste in internal hubs, German manufacturer Rohloff makes the 14 gear SPEEDHUB, a favorite for high-end e-bikes and long-distance tourers.
Enviolo (formerly known as Nuvinci) has its own unique take on the internally-geared hub with its stepless drive system. Instead of packing the hub full of gears, Enviolo uses a unique system that uses an interface of rotating balls and rings to create a continuously variable bicycle transmission. In effect, it&#;s the same idea as the geared systems above with the notable difference that there are no set gears to choose from &#; you just twist the shifter and the gear ratio adjusts accordingly.
But while internally-geared hubs are certainly having a moment of relevance in the cycling world thanks to e-bikes, the traditional drivetrain still reigns king.
E-cycles are classed&#;as regular non-assisted cycles in Great Britain. However, if they supply electrical assistance when travelling at more than 25kph (15.5mph), have a motor which generates more than 250 Watts of power or motor assistance can be provided without the bike's pedals being in motion, they will be legally treated as a moped or motorcycle. These powered two-wheelers are subject to a different regulatory framework.
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As long as your electric bike complies with the restriction listed above, that is right. You can ride on roads, cycle paths and other places where bicycles are allowed under GB law. You don&#;t need to register the bike as you would a motor vehicle, including mopeds and motorbikes, or have insurance or wear a helmet.
One more thing, the law states you must be 14 years of age or over to ride an e-bike on public roads. However, someone under 14 can ride an e-bike off road. Sixteen years is the minimum age to ride a moped in the UK, but this was reduced to 14 years for e-bikes, taking into account their lower levels of power.
If you want to use it on a public highway, you will need to register the e-bike with the DVLA, plus you&#;ll need a driving licence, insurance and to wear a helmet like you would on a motorbike or moped. More information on the regulations are explained in Is your e-bike legal? Electrically assisted pedal cycles regulations.
It&#;s not illegal to own an e-bike with a power output exceeding 250 Watts, or where the electrical assistance doesn&#;t cut off at 25kph. However, it is illegal to ride it as you would a standard bike (without it being registered and insured like a moped), on a public highway &#; this includes both roads and off-road rights of way such as bridleways and byways.
Unregistered and uninsured e-bikes that do not conform to regulations can only be ridden on private land where the public doesn&#;t have access, with the permission of the landowner.
The legal position is the same in Northern Ireland as the rest of the UK. In May, the Northern Ireland Assembly passed the Electrically Assisted Pedal Cycles (Construction and Use) Regulations (Northern Ireland) which updated an outdated law. While the Assembly had not been sitting an opportunity to bring the law into line with other nations had been missed.
Some e-bikes&#;don&#;t need to have their pedals in motion for the motor to be engaged. Some manufacturers produce bikes controlled by a throttle, which can be twisted to start, without pedalling, hence the name &#;twist-and-go&#; machines.
New models of this kind are now&#;classified under EU law under the L1e-A &#;powered cycles&#; category which allows power up to 1,000 Watts. This means that they are not classed and regulated as conventional cycles, but the exact requirement for registering them in the UK remain unclear.
The legal position is further complicated because &#;twist-and-go&#;&#;e-bikes bought before the introduction of the new laws and limited to a 250 Watt motor remain effectively legal and can be bought second hand.
In practice most new e-bikes in the UK are built for the European market and so comply with European standard; look for the CE conformity mark to confirm the product has passed the relevant tests.
Looking at the shape and size of a bike won&#;t tell a purchaser all its specifications, but Construction and Use regulations define the legal safety criteria for bikes.
The most relevant of these for electric bikes is that they should be fitted with a sticker or plate showing the manufacturer&#;s name and the power output must default to the off setting so there is no power assistance without pedalling.
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