The concept of V-shift (by Vecter proto engineering) is a design where each drum track is located on an individual drum section, and the various drum sections are linked to each other by springs in such a way that the sections can rotate against each other. This design creates the possibility to pre-engage the upcoming gear, before extracting the current driving gear. When engaging the upcoming gear, the drum section for the currently engaged gear is preloaded by the spring, but can’t extract due to the gear being loaded by the drive torque. At the moment the upcoming gear starts driving, the current driving gear is being unloaded, at which point the preloaded spring creates a big enough torque on the drum section to disengage the current driving gear. This results in a smoother and quicker gear shift than possible with a traditional design selector drum.

How does it work?
By separating the drum tracks of the individual forks, it is possible to allow a phase lag between the tracks. This phase lag will be comparable with the degrees of drum rotation needed for one shift action. By coupling the drum tracks with a spring to the selector shaft, a phase lag can be realized during the shift. When shifting, the upcoming gear can be selected, whilst the current driving gear won’t be extracted due to the gear being loaded with the drive torque causing a bigger load than can be overcome by the spring force acting on the drum section. Once the upcoming gear starts driving, the current selected gear will be unloaded, and the spring will force the drum section, and as such the shift forks, (back) to the desired neutral position. The required stiffness of the spring is related to maximum time allowed to disengage a gear.

In this preliminary layout, two separate drum sections are joined with a torsional spring to a central selector shaft. Each track is supported by a bearing to the drive shaft. The maximum phase lag between the tracks is limited by the notch on the flank of the barrel. The working principle is comparable with a twin barrel system. However, instead of having 2 individual selector drums, only one selector drum with split drum sections is needed. In this concept a spring force returns the drum section to the desired neutral position when the previous gear is unloaded.