Eliminating the physical connection between the wheel and pedals seems counterintuitive, but there are a few benefits.
Electric bike technology has advanced leaps and bounds in recent years, so much so that the very foundations of the bicycle as we know it are being overhauled. Sure, even the most sophisticated electric bikes still roll on wheels and have rubber tires, as we’re not in the era of flying bikes just yet. Nevertheless, the way power is sent to the ground has evolved quite a lot.
While most electric bicycles still have a physical connection between the pedals and the wheel – either though belt or chain – a few manufacturers are deviating from this traditional method of propulsion. Instead of using a chain, belt, or any physical connection from the pedals to the wheel, these bikes make use of a so-called Digital Drive system, which means that the pedal strokes of the rider operate a generator which then sends electric power to the wheel.
Electrek provides an interesting explanation of how this works by comparing it to the hybrid technology we find in electric cars. In a conventional e-bike, described as a parallel-hybrid, the rider can manually pedal the bike without the use of the electric motor – sort of how a hybrid can still rely on the ICE engine when the electric motor isn’t in use. Conversely, a lot of e-bikes have a hand-throttle, which allows the rider to use only the electric motor. For a more visualized explanation of how a Digital Drive works, check out the video from Cycling About.
We’ve talked about one of these Digital Drive systems before. Schaeffler’s Free Drive system employs a power generator that’s activated by the rider’s pedal strokes. The generated power is then sent to an electric motor powering the bike’s rear wheel. In a Digital Drive System like Schaeffler’s Free Drive, the physical connection between the pedals and the wheel is eliminated, sort of like a series hybrid setup, where in the rider’s pedal inputs are required to operate the electric motor, but eliminating the electric motor – say, in the event of a malfunction or dead battery – will render the bike stranded.
Herein lies the issue of the Digital Drive System, as no matter how high-tech and sophisticated technology becomes, there will always be more points of failure as compared to a purely mechanical setup.
Imagine a scenario wherein you had to ride a Digital Drive-equipped e-bike for 20 miles. Sure, the sophisticated technology and myriad of sensors can tailor each and every pedal stroke to provide maximum efficiency. Sure, the system will be silent, comfortable, and ergonomically optimized – but what if something goes wrong? Say the controller malfunctions, or your battery runs out of juice. You’re left stranded on the side of the road waiting for someone to come rescue you. Whereas if you were riding a conventional e-bike, you could still pedal your way to your destination, albeit in a much more tired and possibly cramped up state.
Don’t get me wrong, I’m not hating on tech like the Digital Drive, and there surely is a place for systems like this. On the one hand, long-tail cargo bikes with extended rear cargo bays can benefit from such a setup, as running a super long chain isn’t exactly comfortable, stable, or safe. On the other hand, compact folding commuter bikes can be packaged more creatively as, obviously, wires can be positioned differently and are much more flexible than a chain or belt drive.
The use of the Digital Drive also enables bike makers to be more creative with their designs. It makes ideas like an all-wheel-drive electric bike more feasible, as well as configurations like a recumbent, rear-wheel-drive bike, or an all-wheel-drive electric cargo trike. Essentially, the sky’s the limit when it comes to setting up a bike, as the limitations of a chain and sprocket are thrown out the window.
Sources: Electrek, EBike 24, Cycling About via YouTube
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Keyword: E-Bike Tech: Could Digital Drive Be The End Of Chains And Sprockets?