Dismantling 3 Wheeler Gearbox: Idler in Differential Case

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Discussion Overview

The discussion revolves around the design of a 3-speed gearbox used in three-wheeled vehicles (tuk tuks), specifically focusing on the placement of the idler gear within the differential case and its implications for reverse gear functionality. Participants explore the mechanics of the gearbox, the rationale behind its design, and the potential risks associated with having multiple forward gears available in reverse.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that in three-wheelers, the differential rotates in the opposite direction when reverse is applied, allowing reverse to be engaged in any forward gear (1, 2, or 3).
  • Another participant expresses concern about the safety implications of having all four forward gears available in reverse.
  • Some participants suggest that the gearbox design may have evolved from motorcycle designs, which typically do not include a reverse gear.
  • There is speculation about whether placing the reverse gear at the differential provides any mechanical advantages, such as keeping drive components rotating in one direction.
  • A participant questions the rationale for including the idler gear with the differential, considering the potential lack of advantage in having multiple gears available in reverse.

Areas of Agreement / Disagreement

Participants express differing views on the safety and mechanical advantages of the gearbox design. There is no consensus on the benefits of having the idler gear in the differential case or the implications of engaging multiple forward gears in reverse.

Contextual Notes

Participants have not fully explored the assumptions behind the gearbox design or the specific mechanical advantages it may offer. The discussion remains open regarding the implications of having multiple gears available in reverse.

monty37
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i recently dismantled a 3 speed (tuk tuk) gearbox.But unlike usual 4 wheelers,i found the
idler in the differential case.usually for reverse ,idler is also present in the gearbox .
When i asked i was told that in 3 wheelers when the reverse gear is applied,the differential as a whole rotates in the opposite direction ,so reverse can be applied in any gear(1or 2 or 3).
But i have always read that reverse gear is a single gear having its own gear ratio.
 
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I meant a 3 wheeler gearbox having 4 gears (forward) and one reverse
 
Seems a little dangerous to keep all 4 gears available in reverse.

Two thoughts:
The gearbox (or gearbox design) could have evolved from that of a motorcycle (without reverse). It may just be simpler that way.

Putting the reverse gear at the differential keeps drive components between gearbox and differential rotating in only one direction. Not sure if this offers an advantage.
 
but nobody wants 4 gears in reverse so where is the advantage in keeping the idler with
the differential.Is it because it is a rear engine rear drive?
 

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