# 1
Do you really need a fancy electric bicycle?
Everything you need to keep your healthy life is to continue to use your traditional muscle driven bicycle, but not a lazy electric vehicle. The claim that this is the only way to make our commuting easier is just a sweet poison. Yes, there are different issues with the existing mechanical solutions for bicycle transmissions, but let's check them out.
In principle, the bicycle transmissions are divided into two main categories - non-variable and variable.
The non-variable transmissions from the first category have a constant gear ratio provided by a driving and driven sprockets and are popular due to the simplicity of construction and reliability. They are also the most popular on the traditional bicycles and are known as a single speed and fixed transmissions. However, all these simple transmissions have a common issue - they cannot cover adequatelly the whole range of application. If the transmission ratio is too low (typically for the fat-bikes or city BMX) then it is useless for the normal cruising speed and opposite - if it is too high (typically for the old classical bikes) then the cruising is OK, but the start, acceleration and climbing are very difficut. The fans could say "Who cares!?", but at least your knees will cry for mercy! By the way, why these smart fans don't begin driving on a fourth (or even fift, six etc.) gear their cars?
The variable transmissions:
The first and most popular group in the category of variable transmissions are those, which use the derailleur for shifting within a set of gears (sprockets). The principle of action for switching within a set of sprockets (driving and driven) through the derailleur is relatively simple. For this type of variable transmissions, the gears are manually selected by the user, where the derailleur transfers the chain to the selected sprockets and then the gear ratio remains fixed according to that choice until the next change. So, in order to switch between two desired gears combinations, the derailleur moves the chain successively through the sequential cogs in the given set. Thus, to achieve the desired, adequate, and optimal gear in this group of variable transmissions, may take a considerable time and if the situation varies more dynamically, then the change becomes ineffective or makes no sense. In that case, the increasing number of combinations between the driving chain wheel(s) and driven sprockets, also increasing the problem of choosing an optimal gear. Moreover, the wide variety of gears is rather unusable in real terms at the endpoints due to the significant angular deviation of the chain line, which leads to extreme wearing of the sprockets and the chain. The big difference in the radius of the chain wheels, in case of rapid and frequent switching under load has a shock-hopping effect, causing considerable discomfort and is not only unsuitable for practical use, but can simply destroy the transmission in a very short term. In addition, the variable transmissions with derailleur have a demanding setting and maintenance.
The second most popular group of variable transmissions are the so-called gear hubs, which are based on toothed gears and/or ratchet mechanisms. The most common are the gear hubs mounted in the rear wheel hub, but there are also such, which are intended for mounting as a mid-drive (often combined with the motor). Usually these solutions suffer from a limited space and have a complex and expensive construction, wherein their reliability is not at the required level, and the maintenance is more difficult.
The third group of existing solutions in the variable transmission category are working by gearing the chain on moving segments, that shrink or expand around the central axis, so that the formed circle (driving, driven, or both) provides a change of the gear ratio. The change can be manual or automatic through a mechanism designed for this purpose. The displacement is by slots, mandrel or by cogs rotating around axes, located around the central axe. The construction of this group of solutions inevitably implies empty spaces during the expanding of the segments, wherein the more the extension is and the less are the elements, the more these spaces increase and cause uneven operation and overloading of small sections of the chain, which leads to uneven movement and higher wearing. In addition, shifting from one gear ratio to another is typically slowed by at least one turnover needed to align all segments of a particular orbit.
There are even more innovative solutions using spheres, bearings on a shaft, CVT like or even magnets, but they all are extremely expensive and difficult to maintain.
In fact, most users thinks, that gear shifting is slow and complicated or is incomprehensible action at all. In reality, a very small cyclists' percentage are able to manage adequately gear shifting, to achieve the optimum balance between the desired physical exertion, speed and changing terrain situations, and therefore they are tended to make significant compromises and not to change gears even if they have them installed, but just leaving at some average position and driving. The optimal application of the transmissions requires in fact a change of the gear ratio between the driving and driven shaft according to the conditions and the possibilities of the propulsion force, which determines usage of variable transmissions. The typical situations, that require this, are starting, acceleration, terrain uphill riding or maneuvering (cornering, lane change, slalom, etc.) and this is valid especially for the city bikes.
Just try to recall in your mind a typical daily journey moments in which at start the surrounding cyclists are making a strange body figures while trying to overcome the starting resistance or these in hurry who while trying to accelerate are stepping up on the pedals or these who are doing the same above on the small bridges over the canals or these who are "very smart" by keeping to drive at lower gear all the time to be ready to overcome the above challenges, but making a crazy cadence on a flat even road while trying to keep the cruising speed of the normal commuting flow.
The all above challenges and issues logically leaded to invention of Automatic Cycling Transmission drive - ACT-drive.
So, very soon you'll have the right healty solution - ACT-drive. Something more, with ACT-drive you'll have the chance to revive your robust OMAFIETS and to continue your healthy city commuting!