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 Clutch 2
We've gotten into the habit of always thinking of a coupling as a detachable connection preferably one that can be used without tools. That's not always the case. The connection between two shafts that are not
exactly aligned can also be referred to as a coupling, for example, when using a dry joint. A plumber is happy enough if a pipe connection can be loosened and tightened again using an open-end wrench or pliers
without having to replace any existing seal. Even a double socket can be referred to as a couplng.
In a sense, a dry joint like this can also dampen vibrations in the drive system, such as those caused by the crankshaft accelerating during the power stroke. In the clutch, these vibrations are dampened
by the coil springs shown in the image above. Less common, but still possible, is rubber between the internal gear and the pad carrier. By the way, here you can also see a type of gearing that's more common
in cars, located in the middle.
Another thing that stands out is the rather complicated design of the pad carrier. There are spring-loaded components in between. All of these factors together ensure that the pads fits perfectly against its
respective steel partner, even if the two are not perfectly parallel to each other. Yes, and the rivets used to secure the pads must not protrude under any circumstances due to pad wear.
That wouldn't be such a big problem on the side of the pressure ring, because it, along with the clutch cover and the diaphragm spring, makes up the automatic clutch assembly and gets replaced anyway.
But the flywheel on the other side, you'd really like to find it grooveless. It is individually balanced, certainly, but one would prefer not to have to install a new one. It also makes the repair more expensive.
So, if the clutch tends to slip, take it to the work shop as soon as possible.
So, that covers the basic setup, at the very top of the list. No, we haven't explained everything about it yet. On the right is what's called the central release bearing. Here, the hydraulic pressure from the clutch pedal
is directed straight to the annular piston of the slave cylinder, which then presses against the diaphragm spring via the ball bearing clearly visible in the image above.
| Unlike newer models, older clutches were not allowed to run when the clutch was not
engaged. |
The top image also clearly shows where the force from the release bearing is directed when the clutch pedal is pressed, namely, toward the flywheel. So not only the membrane spring is actuated, but the entire
crankshaft is also pushed away from the transmission. This puts a strain on their axial bearings. A driver's tendency, for example, to keep the clutch depressed for long periods during red lights eventually becomes
detectable in the axial bearing and can result in a major engine repair.
| Master cylinder and slave cylinder with a gear ratio |
Although the central release bearing simply eliminates the need for a lever and directs force more centrally onto the tips of the diaphragm spring, suppliers of these components emphasize that any potential
repair is now easier. Of course, the opposite is true. It must be clear that you can only replace this part if the engine and transmission are completely separated. Below you can see an externally mounted slave
cylinder, which can, of course, be replaced without such a labor-intensive disassembly, even though it probably needs to be unscrewed from the bottom and screwed back on the top of the transmission.
Below, you can see what happens if the release bearing blocks and you simply continue to use the clutch. Don't be fooled by the black lid, it doesn't belong there. Instead, pay close attention to the fine tips of the
diaphragm spring that come into contact with the release bearing. With the bearing in fixed position, these are sanded down until the release bearing can be pressed into the automatic clutch without engaging
the clutch.
Inside the vehicle, you usually notice this when the clutch pedal doesn't return to its original position. It simply gets stuck when pressed, and even the least technically inclined person knows that something
has happened. So what do you do in a situation like that? If you have the appropriate insurance, the vehicle must be towed. Unfortunately, newer cars have a kind of safety feature. You can no longer start the
vehicle if a gear is engaged. This is what we were told by confused drivers who, after such an incident, claimed that the car had taken on a life of its own and sued the manufacturer.
So you absolutely must press the clutch to start the car. However, that actually means more uncertainty. Let's assume the admittedly unlikely scenario that your engine stops working right at a railroad crossing
and won't start again. Back then, you could save yourself by putting the car in first gear and using the starter. With a intact clutch, that's no longer possible today.
With a modern vehicle, you only stand a chance if you outsmart the clutch switch, for example, by keeping the clutch pedal depressed, even though there is no actual clutch function. That works but only if the
switch is located on the clutch pedal. But maybe your car is old enough, too. In any case, let's practice driving without the clutch for now—but only if your engine is running smoothly without any unusual
noises.
To be more precise, it's driving with a clutch that won't disengage. If the engine is cold, you'll need to warm it up by starting it without selecting a gear, as a one-time exception. And then we'll start
with the worst-case scenario: the driving in the city. Turn off the engine, shift into second gear, and start moving when the way is clear. The car starts to jerk and eventually picks up speed if you don't
press the gas pedal too hard. Of course, you need good reasons for doing something like that, because it's not exactly good for the car.
At the traffic light, simply shift out of gear in time and coast while braking lightly enough that you might still roll up to the light while it’s green. Then you'd have a chance to shift back into that gear without pressing
the gas pedal. If you arrive when the light is red, stop and see above. Stay in second gear, even if you want to maintain your cruising speed. For once, fuel consumption doesn't matter.
You should plan your trip through the city so that you encounter traffic lights as infrequently as possible, that is, head as directly as possible toward the outskirts, even if that means taking a longer route overall.
On the motorway acceleration lane, take second gear right up to the edge of the redline, then, without applying throttle shift smoothly yet decisively straight into the highest gear. Of course, the car struggles a bit
with acceleration at first, but take it from an experienced driver without clutch, after that, you're all set.
Of course, this tip also applies to any other problem with the clutch mechanism, including the pull-cable connection. While hydraulic actuation initially offered the advantage of self-adjustment, and thus being
maintenance-free, the simple cable linkage has since caught up in this regard. Let's take a look at that in the image above and the ones that follow.
The first two pictures of the automatic adjustment show the connection in brand-new condition, first in the disengaged position and then in the engaged position. What stands out are the balls that, when the clutch
pedal is pressed, wedge the inner cage against the wall. If you compare the top two images with the bottom two, you can see how the cage has shifted downward as wear has increased.
This is ensured by the clamping ring, which sits directly on the cable's core with slightly greater friction. When you release the clutch pedal, it pulls the cage downward. You could say it feeds more cable to the lower
lever, causing it to be deflected further downwards, in both the actuated and unactuated states, compared to the upper one. The pull-cable connection leading upward is also a bit tighter and no longer curves quite
as nicely.
Important to know: Without adjustment, the pressure point of a clutch would move upward as wear increases, that is, it would move away from the floor panel. As the clutch disc wears down, the release bearing moves
toward it because the direction of movement in the automatic clutch reverses. That is why the purely mechanical connection requires more rope.
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