Topics
Background
The extended length of the cyclecar requires a corresponding expansion segment in the primary drive shaft. In addition, to implement reverse functionality a new reversing gearbox assembly must inserted between the original gearbox output and the U-joint input in the swing arm.
Layout of extended drive train with reversing gearbox
The gear shift mechanism must also be completely re-engineered in order to migrate from foot to hand control.
Gear shifting
Like nearly all motorcycles, the Moto Guzzi gear shifting is handled by a swivel foot pedal and a hand operated clutch. The original setup uses two swivel arms (one arm is the foot pedal) and three linkage bars to rotate the gear selector in the gearbox.
The concept for switching to a hand-operated sequential shift lever uses a similar linkage arrangement.
When the shift lever A is pushed forward, control arm B moves in the opposite direction (back towards the driver). This motion rotates a swivel C that pushes control arm D forward. Turning linkage then moves control arm E upwards, rotating the gear selector shaft that is a pivot point connected to the engine gearbox. Pulling the shift lever back causes the reverse action.
This sequential shifter only handles forward gears and neutral. Reverse action must be independently triggered since this functionality is not incorporated into the original Guzzi gearbox.
Reversing gearbox
Conceptually, a reversing gearbox deploys four identically toothed gears in a specific configuration.
First two identical secondary gears are linked together but offset. Because they mesh one-to-one, their rotational direction will be opposite from each other. Two primary gears separated by a spacer are placed so that they can slide to engage either one of the two linked secondary gears. A shift mechanism moves the primary gear from the forward to the reverse position. The drive shaft passes through the primary gears.
Reversing gearbox concept with fill plug and shift link
The reversing gearbox requires its own oil and has an independent shift mechanism — separate from the main engine gearbox — that will have linkage located in a reachable, but cannot-be-engaged-by-mistake location.
Because there will be no reverse lights on the cyclecar, a beeper will be installed on the rear section of the chassis that is triggered by the reverse shift lever, much like a brake light switch.
To operate, with the cyclecar in neutral, first the reverse position is selected and the beeper is switched on. Then, using the clutch, the main gearbox is shifted into first gear, but instead of moving forward, the vehicle will begin to move backwards. When motion is completed, the main gearbox is shifted back to neutral, and then the reverse position is returned to forward. At this point, the beeper stops.
