Boats don’t really do
But reverse gear is needed to be able to
slow the boats down.
When there are passengers on board, and
you are coming into a mooring, you need brakes.
sort of reversing gearbox?
You’ve guessed it. One
that requires the least friction.
And there is a
superb option. The epicyclic or “sun and planets” gear
You just push a lever to go forwards, pull it back
to go backwards. In the middle is neutral.
No clutch or
meshing of gears. It’s a delight.
beauty is that when in forward, no gears are meshing.
mechanism is just a spinning mass. Like a flywheel.
gearbox does not waste any power.
In reverse –
yes – all the gears are spinning – and there is a
But the boat is being braked.
gearbox should be sited on the propeller shaft.
shaft is already busy with the toothed belt pulley and probably
with a starting handle.
with the epicyclic gear box is that gear changing is achieved by
When the planet ring is held, the planet wheels have to spin and rotation is reversed.
could be that you already know all about the epicyclic
Many bicycles use a three speed mechanism called the
But have a look at
There are 3
parts to the mechanism. Two are fixed.
The ring gear is fixed
to the propeller shaft. The “sun” gear is fixed to the
For forward gear, the planet carrier ring is clamped to the ring gear and propeller shaft.
This locks the gear teeth of all three components together. They rotate as a single unit.
For reverse, the planet gear ring is released from the ring gear and held stationary.
The sun gear now causes the planet gears to spin.
The spinning planet gears now rotate the ring gear in the opposite direction.
Just put a brake onto the planet carrier and you have reverse gear!