the future

What will bring the future for the clutch?

At this moment there are realy promoting electric cars around the world. But do electric cars need a clutch? NO!

They are directly driven from the engine, the current determines the power deliverd to the wheels.

The elektric cars are yet not very popular, but within 10 or 15 years they will!

presentation: a car clutch for dummies

A car clutch for dummies

View more presentations from Thijs Leroy.

diaphragma spring

The diaphragma spring is works like a regular spring. You press on it and it wil shorten.

they are fabricated of cold rolled springs steel to 50CrV4
life: >1 000 000 operations

more info is difficult to find about a clutch of 1987. Even people is business don't know the spring rate...

Why a diaphragma spring?
A normal spring like we know will be pressed more easy after a period of time. A diaphrama spring does the opposite, it will be harder to be pressed.

clutch assembly volvo 240

In "vraagbaak Volvo 240" I found a drawing of the cluth whith some interesting properties.

pressure group, bearing

The bearing used to push the parts together is a thrust bearing. The part which make conctact with spinning parts will turn together with these parts. The other parts are connected to the lever. But it isn't a rigid connection. it has the possibility to turn around an axis. This is important otherwise you will wring the primary shaft if you use your clutch pedal. This should cause serious damage to your primary shaft.

consequence: gearbox are so engineerd that the bearings will brake before the primary shaft. If you wring the shaft to much you will create some slack in the bearings... your gears in the gearbox will be destroyed!

clutch plate, material

One important thing of the clutch plate is the used material of friction material.
There is a total contactarea of about 440 cm².

the material has to be resistant to the large amount of power.
One of the materials used is a kind of organic material:
Metal-fibres woven into "organic" (CF aramid with other materials)
advantages: long life, operating temperature, hard use possible
used for cars up to 400HP

In the friction material there are some grooves. Whats the fuction of them?
They will drain heat caused by friction, but also by a large pressure.
There will be always microscopic moves between f.e. the clutch plate and the flywheel. The friction will lead to very small particles of organic material. These have to been removed, because they act lik sandpaper for the same organic material.
They will also drain little drops of oil if there is a small leak. !!oil in the clutch will destroy the flywheel, clutch plate and pressure groep!!

more info: www.uucmotorwerks.com/clutch

clutch plate, springs

In the sketch below you see a spring. In the clutch of a volvo 24O there are four of them.

This is just for a smooth ride and is not necessary for the function of the clutch.
The driving part (friction plates and steel plate) of the clutch plate pushes to te springs, the springs will be pressed and they push to the driven part (connection whith the primary shaft).
So if there is suddenly a large power-increase the springs will intercept so the car will accelarte smoothly and not in shocks.

This is why race cars don't have springs in the clutch. It causes a very litte decrease in power a a little delay in power trasmitting.

clutch plate - rivets

The sketch in the previous post shows a couple of rivets. But why do they use rivets?

Especially these who connect the friction material with the other parts of the clutch. Because this is the place where power transmit from one part to another.

If the clutch is in function, so all parts are connected by a large force, the frition plates are pushed between the flywheel and the pressure group. But a part of the clutch plate is pushed between the two friction plates. So there is a friction force between the different parts of the clutch plate. Rivets are necessary to keep the clutch plate together if there is no connection.

Another aspect is that it is useless to disconnect the friction plates from the clutcht plate. If the friction plates are destroyed, the whole clutch is probably at the end of his life.
Its also a very easy connection, no turning tools are required

clutch plate - sketch

connection primary shaft - clutch plate

The connection between these two parts needs a radical fixation, but a axial freedom, but still be able to translate the power from one part to the other.

A good solution is a splined shaft.

It will be a 21x24 splined shaft

the properties: z= 34 (the last unvisible column)

more info: tabellenboek voor metaaltechniek (E31 - p 212)

radius primary shaft

Another imporant part of the clutch is the primary shaft. It's the link between clutch and gearbox.

theoretical the torque produced by the motor is the same torque on the disc plate and the same as on the primary shaft.

calculation:
d= 11,65mm

the real situation: 24 mm

or there is something wrong in the calculations (probably) or there are some properties of the gearbox that influence the radius.

mass flywheel

The mass of the flywheel depends on the motor and the mass of the car.
The calculation of the mass is a part of the engine. A lot of people doing flywheel-tuning. They take weight off the flywheel, the mass declines and the car becomes a little faster?

If the mass declines too much, you will never be able to drive the car.

flywheel - bolts

The main function of the flywheel is keep the motor spinning. It has a weight of 12 kilo. The total weight of the clutch (housing inclusive) is about 19,5kg...

Such a mass will cause a lot of centrifugal force. First a calculation of myself followed by a comparison with the real information.

What's the radius of a bolf if you can use 8?

The centrifugal force is calculated in the mass center. If you count the whole flywheel the mass center is in de middle. If there are 8 bolts, you can devide the flywheel in 8 equal parts. The distance from the center to de mass center is about 200mm.

F(c) = 14 808N (for 1 bolt)

The torque causes a force perpendicular to the radius: F(t) = 1280N

F(tot) = 14 863N

The max shear of a 12.9 bolt is 1080Mpa. (www.werktuigbouw.nl)

the safety factor for dynamic loads: v= 3...6

for the calculation: v=5

result: r= 4,68

this results in 8 bolts: ISO 4017 - M10 - 12.9

If you use bolts with another classe, you will become a larger radius.

more info: tabellenboekje voor metaaltechniek

the car - volvo 240

The clutch I will discus is one of a volvo 240 (1987). It's already an older car, but the principles are the same.
The car is a rear wheel drive one.

properties:
volvo 240 '87
motorcode: B230K (Benzine, 2,3l)
HP: 85kW/116Hp @ 5100 tpm
torque: 192Nm @ 3000 tpm