Breaking the Chain: Exploring Chainless Electric Bike Mechanics

The technology in electric bikes has accelerated forward at an (almost) unprecedented rate. If you’ve only recently come up to speed concerning electric bikes and how their motors work, then brace yourself! Below we’re taking a look at how chainless electric bikes work.

Chainless electric bikes operate on one of several “alternative” systems, including an all-electrical system, a drive shaft system, or a hydraulic system. These alternatives differ in how they supply the rear wheel with power, how efficient they are, and are more expensive than chain-driven.

With technological improvements, chainless electric bikes are becoming more and more popular. But how do the various alternative propulsion systems work? What are some advantages and disadvantages of going chainless, and are chainless electric bikes the way of the future?

How Chainless Electric Bikes Work

While they may not seem like it, chainless electric bikes (e-bikes) still follow the same principle as chain-driven electric bikes. Namely, converting the energy generated by the person pedaling into forward motion.

However, the methods they employ to achieve this forward moment are where things start to differ.

There are several varieties of chainless e-bikes.

  • Those that replace the chain with a different mechanical system (i.e., converting power produced in the pedals to motion in the wheel). Including those that use a belt instead of a chain (which functions in the same way as a chain).
  • Those that convert mechanical power into electricity to turn the rear wheel.
  • Those that use a hydraulic system to create movement.

Below we’ll examine electrical, shaft-driven, and hydraulic chainless e-bikes.

How “Free Drive” Chainless Electric Bikes Work

The most “confusing” of the chainless motors, the all-electrical (also called digital drive, bike-by-wire, or free drive system) bikes operate by converting the power produced from pedaling into electricity.

This electricity powers a motor in the rear wheel hub (where the wheel attaches to the bike).

But how does it work? These e-bikes make use of a Schaeffler generator connected to the pedals.

As the rider pedals, the motion produces an electric charge; this electricity travels through wires to the rear hub, which powers a motor that turns the rear wheel.

Interested in the power behind e-bikes? Unmask the types of motors used.

These e-bikes work with a control unit that adjusts the generator according to the rider’s energy output (how much electricity they generate) to ensure that the rider generates electricity efficiently.

The Free Drive system, developed by Schaeffler and Heinzmann and released in 2021, differs from other e-bike systems in that the mechanical pedaling and the electricity produced to turn the wheel are directly related (without one, the other won’t work), while other e-bikes work on an “either-or” basis.

I.e., in chain-driven e-bikes, you can pedal or use the electric motor function. You don’t have to use both together.

These e-bikes are equipped with a battery (in case you are anxious about needing to pedal at the same speed without stopping), which stores excess electricity generated and sends it to the rear motor as needed.

The great news is you can charge the battery as you would a normal e-bike (via a wall outlet), which means you won’t be left stranded with a bike without a chain and no charge.

The Advantages

  • Free Drive motors (all electrical) are ideal for cargo e-bikes which require lengthy chains to reach from the pedals to the rear hub. By running on wires, the issue of chain length is removed.
  • Chainless e-bikes cannot lose their chain (slipping off), nor is there wear and tear on the chain (less maintenance).
  • In the future, Free Drive systems will work well with regenerative braking (when you’re traveling downhill and press the brakes, the motor starts turning the other way around and charges the battery).

The Disadvantages

  • The most significant drawback is the loss in efficiency. A standard bike has roughly 95% energy efficiency (when pedaling power is converted to forward motion). These e-bikes are only around 50% to 70% efficient due to the change from mechanical to electrical and back to mechanical.
  • These e-bikes are roughly 25% heavier than other bikes.
  • A limited number of manufacturers make these bikes, which pushes their prices up significantly (expensive).

How Shaft-Driven Chainless Electric Bikes Work

Much like chain-driven bikes (electric and regular), shaft-driven e-bikes use the energy created by pedaling to power the rear wheel without changing from mechanical to electrical.

These e-bikes have a shaft/rod (usually made from carbon fiber) that connects to the pedals via bevel gears (gears that fit together at an angle).

As the rider pedals, the gears connected to the pedals turn the gears on the rod. The rod then turns another set of gears in the rear hub, turning the wheel.

While this process is rider dependent, the e-bike’s electronics monitor the rider’s progress and send power from a battery to the motor on the rear hub as needed.

The Advantages

  • These e-bikes require less (some even claim they need none) maintenance than those with a chain, thanks to the protective housing.
  • Several companies manufacture this type of e-bike (including Honbike), so they are more readily available.
  • They are quieter than chain-driven e-bikes.

The Disadvantages

  • They are more expensive than most chain-driven e-bikes.
  • If the mechanism is not properly sealed and dirt gets in, it can cause extensive damage to the gears.
  • Some models require you to reach 3mph before the motor switches on.
  • Most are not designed for high speeds and may struggle on hills (not high-performance e-bikes).

How Hydraulic Chainless Electric Bikes Work

If you’ve never thought of using fluid to power a bike’s rear wheel (let alone an e-bike), you’re not alone! However, thanks to the OYO e-bike (made by BC Bikes), hydraulic-powered chainless e-bikes are a reality.

These bikes work similarly to all-electric (Free Drive) e-bikes. The pedals are connected to the rear hub by pipes that contain the hydraulic fluid.

As the rider pedals, pressure builds in the hydraulic pump, which pumps fluid through the pipe to the rear hub. At the hub, the pressurized fluid enters and turns the hydraulic motor, causing the wheel to turn (almost like how a water wheel turns to produce electricity).

The “used” fluid returns to the “reservoir” (the area close to the pedals where the fluid is stored) to start the process again. Aside from the hydraulic motor/system, these bikes also have an electric motor connected to sensors that signal it to switch on to assist with pedaling as needed.

These bikes work on “automatic gears,” which work together with sensors to determine the optimal setting. So if you’re heading up a hill, the gears will automatically shift to allow you to continue riding at ease.

The Advantages

  • Thanks to the closed system, there is very little maintenance required.
  • These e-bikes are reputed to be one of the smoothest riding bikes on the market.

The Disadvantages

  • With all the technology, these bikes are heavy (around 55.1 lbs).
  • Due to limited availability, these e-bikes are also on the expensive side.
  • If there are any issues, you’ll need to send the damaged part(s) away, as most local bike shops don’t have the correct tools to assist with hydraulic e-bikes.

Are Chainless Electric Bikes The Future?

While chainless electric bikes (e-bikes) are an exciting development in the technology surrounding electric bikes, they are not for everyone.

While these e-bikes cater to casually cruising around or transporting goods with cargo e-bikes, their functionality regarding mountain biking (aside from the shaft-driven chainless e-bikes) is limited.

As time progresses and technology improves, these bikes should become more popular in other cycling areas.

A significant selling point is that some of these chainless e-bikes use software that adjusts the pedal settings as you ride so that you use your pedal power most effectively, allowing you to go further for longer.

However, for now, many people will remain quite content with their chain-driven bikes (both eclectic and normal).

Curious about the performance factors of e-bikes? Let's compare torque and watts.

Conclusion

While chains provide the best energy efficiency, technological advancements have allowed manufacturers to create alternative ways to power the forward movement of an e-bike.

Some models convert pedal power into electricity and back into mechanical energy, while others use a drive shaft that functions similarly to a regular chain. At the same time, the latest development is a hydraulic system that uses pressurized fluid to turn a motor.

While all interesting takes, technology needs to further improve for these e-bikes to replace the chain-driven variety.

Author

  • Miles Baxter

    Miles Baxter is an engineer with a longstanding love for bicycles, sparked by winning a mountain bike in a childhood lottery. Balancing a keen interest in mechanics with the thrill of biking, his career is a testament to the art of turning wheels and gears into adventures.

    Baxter Miles