Standard bikes operate on a simple principle. The cyclist’s legs use the pedals to turn the cranks, and power is transmitted to the rear wheel via a pinion and chain. This solution has been gradually improved over more than a century and has proven to be light, efficient, durable and cheap to manufacture. Is it time for a whole new concept?
Biking around the site It is dealt with in detail thought “digital powertrain”. In this solution, the pedal arms drive an electrical generator that converts mechanical energy into electricity. It travels via two wires to the motor, which drives the rear wheel of the bike.
Although it sounds like science fiction, it is not a new concept at all. The first patent for a digitally motorized bicycle was issued as early as 1975, and the first fully functional motorbike was demonstrated in 1995. The first production bicycle with a digital motor was launched in 2012 (Mando Footloose) and is currently working on their digital drivetrain systems By many companies (such as Schaeffler, Pendix, Podbike, Bike2, etc.).
Let’s stop briefly at the term “digital engine”which is sometimes referred to as a “series hybrid drive”, “sequential hybrid drive”, or simply an “electric drive”.
The digital drive offers a number of advantages over the traditional solution. For example, the chain and gears were left out of the powertrain design. This eliminates the need for maintenance, occasional replacement of these components and associated problems. For a digital motor bike, it is sufficient to change the tires and brake pads.
Other benefits of a digital drive
You can also enter a system designed this way Add a battery (or supercapacitor), which you can charge while driving. If you decide to send part of the energy from the pedal to the battery, you can use it later, for example, when starting off at traffic lights or when overcoming small hills.
When driving downhill, the electric motor can act as a generator and the electricity obtained can be stored and used later. An electric anti-lock braking system can be integrated into the motor, and when the bike is stopped, it can lock mechanically.
A digital drive can just as well Improved pedaling technique. The system will allow the cyclist to ride with optimal power and cadence, resulting in the highest possible efficiency. A good example of when changing pedal characteristics can be beneficial is rehabilitation after an injury or disability.
Disadvantages of a digital drive
Perhaps the primary drawback lies in the fact that converting mechanical energy into electrical energy and back into mechanical energy is very inefficient. In a classic bike, where the power is transmitted from the pedals to the rear wheel by a chain, more than 95% of the kinetic energy goes into the forward motion.
The digital engine loses about a fifth of its power to the electric generator and another 20% to the rear engine. An additional 10% can be lost when the step gear is used to properly set the powerband. We have this Almost a loss of nearly half of the energy consumed!
“To give you an idea, with a chain drive you can go 27 km/h on the flat at 150 watts, while with a digital drive you’ll cruise a whole 17% slower (22.5 km/h). Even worse on an incline. At a 5% grade , you’ll go 9.4 km/h with the chain, while with the digital drive you’ll cruise 34% (6.2 km/h) slower.” Cycling reports around , stating that these values apply to an 85kg cyclist with a 15kg wheel.
It has its pros and cons
Of course, it is necessary to take into account the fact that the device guarantees the conversion of movement into electricity and back, weighs more than a chain system. The lightest rear axle motor is more than a kilogram heavier than a normal one, plus we have to add at least another kilogram for the front alternator and wiring.
However, when we add a battery to a digital motorized bike, we create what is called a sequential hybrid electric bike. At the same time, bikes with a digital motor have practically all the components of an e-bike, so it makes sense to equip batteries that provide some assistance and compensate for the extra weight and gearing losses.
It is often cited as a real stumbling block for digital power units efficiency. If the motor does most of the work, digital-drive e-bikes are closest in drive efficiency to sequential-drive e-bikes.
Claude Bernard Student Edgar Tournon He explains in his work, that with its digital drive system, it is possible to achieve an effective engine efficiency of about 75% on a flat track of five kilometers, and if a fifty-meter hill is added in the middle, it will be 62%. The reason for this high efficiency is the fact that the engine can recover energy when decelerating at traffic lights or when driving downhill.
Is it the engine of the future or a dead end?
Not so long ago, many professional photographers were convinced that they would never switch to digital cameras. However, with the gradual technological changes over time, digital cameras have become the choice of professional photographers all over the world. Will the digital drive follow a similar path?
In the case of a solution without a battery, this is unlikely – compared to the series, disadvantages prevail in the form of lower engine efficiency, additional weight and the inability to work effectively on flat or sloping terrain.
But the situation is completely different in the case Digital engine with built-in battery. This solution would be ideal since there is no corrosion, little maintenance, and low operating costs. The system will also be cheaper to manufacture. Currently, it is best applied to cargo bikes, personal vehicles, and rental bikes.
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