A Real Transmission
The five-speed manual transmission is fairly
standard on cars today. Internally, it looks something like this:
There are three forks controlled by three rods that are engaged
by the shift lever. Looking at the shift rods from the top, they
look like this in reverse, first and second gear:
Keep in mind that the shift lever has a rotation point in
the middle. When you push the knob forward to engage first gear, you are
actually pulling the rod and fork for first gear back.
You can see that as you move the shifter left and right you
are engaging different forks (and therefore different collars). Moving the knob forward
and backward moves the collar to engage one of the gears.
Reverse gear is handled by a small idler gear (purple). At all times,
the blue reverse gear in this diagram is turning in a direction opposite to all
of the other blue gears. Therefore, it would be impossible to throw the
transmission into reverse while the car is moving forward -- the dog teeth
would never engage. However, they will make a lot of noise!
Synchronizers
Manual transmissions in modern passenger cars use synchronizers to eliminate the need for double-clutching. A synchro's purpose is to allow the collar and the gear to make frictional contact before the dog teeth make contact. This lets the collar and the gear synchronize their speeds before the teeth need to engage, like this:
Manual transmissions in modern passenger cars use synchronizers to eliminate the need for double-clutching. A synchro's purpose is to allow the collar and the gear to make frictional contact before the dog teeth make contact. This lets the collar and the gear synchronize their speeds before the teeth need to engage, like this:
The cone on the blue gear fits into the cone-shaped area in the
collar, and friction between the cone and the collar synchronize the collar and
the gear. The outer portion of the collar then slides so that the dog teeth can
engage the gear.
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