[sarguy01]

So, I am in another forum and made a slightly off topic post in my thread. This is how it went:

I made this statement.

Technically, there is always a slight amount of slip, at all times, since there is only a friction connection between the flywheel and clutch disk. But, we won't get into that since that amount of slip is probably less than 1%.

Edit: I should have said, "Technically, there is always a slight amount of slip, under certain conditions, since there is only a friction connection between the flywheel and clutch disk."

This is the reply.

BS. It's zero.
A properly working clutch allows zero slippage while engaged. None.
Locked in a 1:1 ratio.
Real world: 1% slippage would be a huge problem for a clutch.

Sorry, you have misinformation and I felt an overwhelming need to educate.

This is my response.

Let's discuss, shall we?

A clutch relies on FRICTION! It doesn't "lock" in a 1:1 ratio, unless of course it is some kind of clutch that can physically lock. As far as I know, the 7th Gen Civic clutch is not a lock up design. As you know, the clutch disk is sandwiched between the pressure plate and the flywheel. There are no tabs, locks, mechanisms that "lock" the flywheel to the clutch disk. It is FRICTION that holds the clutch disk to transmit the engine's power to the transmission.

Stick-slip phenomenon - Wikipedia, the free encyclopedia Here is a great Wiki article to read up on. It explains stick-slip. "Stick" is what is described when the clutch is engaged. Stick can be overcome by the engine's torque, but there are factors that can affect the holding properties of the clutch. The coefficient of friction can change due to temperature, friction material properties, oil contamination, water, rate of torque application, velocity, the list goes on. You can read some more here: http://www.pemltd.com/pdf/determining-the-static.pdf

If we use the example of driving on a straight and level road, with no wind, hills or other factors, the "stick" of the clutch should not be overcome if the auto manufacturer properly chose a clutch. But, add in those real world factors and the "stick" of the clutch can be overcome. Think of stomping on the gas trying to make it up a hill. The rate of torque changes and it is very possible that it can overcome the coefficient of friction. From the above Wiki article, “If an applied force is large enough to overcome the static friction, then the reduction of the friction to the kinetic friction can cause a sudden jump in the velocity of the movement.” Or put in a different way, if the engine puts out enough torque, the clutch will not be able to hold it and will slip.

The coefficient of friction is what differentiates the holding power of an organic material versus a sintered iron material. Above I mentioned some other factors that can change the coefficient of friction. When the coefficient changes, so does the stick of the clutch and therefore the amount of torque the clutch can transmit without slipping.

Here is some more info on friction and clutches.

Coefficients Of Friction

Friction Materials

This paper is pretty math intense, but it mathematically shows how engine torque can overcome the clutch when sticking. "The sticking of the clutch sustains as long as the torque transmitted through clutch (Tc) remains below the maximally transmittable torque Tmax c..."
http://www.mate.tue.nl/mate/pdfs/4159.pdf

You said that slipping at 1% would be a huge problem for a clutch. To correct you, I said, "Less than 1%". Less than 1% is a range of numbers from .999(repeating)% down to an infinitely small percent. I didn't specify because I don't have the data to estimate this, so I generalized. This percent could be .0000001% over a 30 minute drive at 60 mph (which would be something like .007296th of a revolution) and the percent slip does not mean the clutch is constantly slipping. Simply put, it slips here and there. I should have worded my previous post to be, "The average slip is probably less than 1%". However, even though the percent is very, very small, it still means the clutch is slipping.

Not to start another debate, but the same slip can be found with auto belt systems, tires rolling over the ground, etc. Friction can allow slip.

So, I am looking for some feedback on my post since I feel that forum doesn't have an abundance of technically savvy people. The person I am debating with is a very knowledgeable mechanic. I am not looking to be right or wrong as much as I am looking for some evidence that a clutch does or does not slip when fully engaged (I don't mean always slipping, but will slip under certain circumstances). I am looking for a friendly discussion. I have my flame proof suit on, just in case...