DAF CF65, CF75, CF85 Series . Manual — part 1085

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General

CHASSIS

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1. GENERAL

1.1 REPAIRS TO THE CHASSIS

-

Any welding, aligning, drilling and wheelbase

alteration activities that are not described in

this workshop manual or in any of the latest

releases of DAF's Chassis Guidelines must

be authorised by DAF.

-

Following chassis repair, the cause of the

chassis damage should be rectified.

Welding
-

Chassis welding may only be carried out by

welders holding a valid EN 287-1 certificate.

-

For welding operations on the steel grade KF

375 chassis, the welding electrode must

meet one of the following standards:

-

Slag inclusions and other contamination in

the welds are totally unacceptable.

Note:

Welding on a chassis constructed of high-tensile

strength steel grades KF 420, KF 500 and KF 600

is strongly advised against.

If, however, you do wish to weld a high-tensile

strength steel chassis, contact must always first

be sought with DAF.

The welding electrode must meet the standard:

ISO 2560:

E 515 B 24(H)

DIN 1913 (January 1976): E 5155 B 10
EN 499

DIN 8529:

EY 5066 1.5 NiNoB

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To repair cracks in the chassis, proceed as

follows, taking account of the guidelines given

above:

1.

Remove all parts restricting a clear working

area.

2.

Thoroughly clean the crack so that the

course of the crack is clearly visible.

3.

Drill a small hole at the end of the crack. This

will prevent the crack from continuing.

4.

Thoroughly grind out the crack on both sides.

5.

Take the necessary precautions to prevent

damage to electronic components. Place the

earth clamp as close as possible to the weld

and avoid bridges.

6.

Lay a bead on one side of the ground-out

crack.

7.

Gouge or grind off the material at the back of

the bead (see the arrow) so that the new

weld material is clearly visible.

8.

Finish-weld the X-seam in the usual manner.

9.

Fill in the drilled hole.

10. Grind down the new weld so that it is flush.

Take care not to grind the chassis flange in

the process.

11. The beginning and end of a weld should not

curve inwards (see the arrow).

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12. Round off the chassis flange at the edge of

the weld.

Straightening

Do not forget your own safety during

straightening operations. When

working with presses, take care that

parts cannot fly out.

The straightening of a chassis demands a high

degree of craftsmanship as in every case of

damage, an individual assessment must be made

to establish whether or not straightening would be

a sensible measure.

Deformations found after accidents will mainly be

of the following 6 types:

-

chassis is bent sideways

-

chassis has a double sideways bend ("S-

bend")

-

chassis sags

-

chassis bulges upwards

-

chassis is twisted

-

chassis is out of square.

In many cases, the damage will be a combination

of two or more of these basic deformations.

In general, the deformations should be dealt with

in the sequence shown above, although some

combinations can be dealt with in one

straightening operation.

When deciding whether or not to straighten a

chassis, you must consider not only the degree of

chassis bending but also the angle of a bend.

If there is a sharp angular bend or fold in the

chassis, the material in that area is likely to be

severely deformed.

If such a chassis were to be realigned to its

original form, there would be a high risk of

overstretching the already weakened material

and causing a crack to develop.

"Cold" straightening
The general rule for cold straightening of a

chassis is that the degree to which the chassis

should be forced back beyond the straight line is

equal to the degree to which the chassis is bent.

For example, if a chassis is bent by 10

, the

chassis should be forced back by an additional

10

 beyond the straight line.

This means that in total the chassis is forced back

20

.

Cold straightening is done with forces ranging

from 40 to 100 tonnes. Therefore, work as safely

as possible.

Particularly when working with auxiliary tools and

aids, you are advised - from a safety point of view

- to attach them correctly.

100mm

R=1

R=1

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"Warm" straightening
DAF chassis should not be warm straightened.

Heating can cause grains in the material which

will adversely affect the material properties.

General
For every straightening operation, all stresses in

the stiffer parts of the chassis, for example in the

tandem axle attachment cross member, should

be relieved. If this is not done, these stresses will

later cause new distortions or cracks in the

chassis.

It is obvious from the above points that

straightening is a highly specialised job for which

the specialist involved bears full responsibility.

Always contact DAF when in doubt or for

complicated "straightening operations".