2-20
CHASSIS MODIFICATIONS
D
AILY
4x4
Base - May 2007
Print 603.93.761
Modifying the Rear Overhang
S
)
Towhook for mid-axled trailers
The use of central axle trailers implies the use of tow hooks suitable for this purpose.
The values of the trailer loads and of the permissible vertical loads are contained in the technical documentation of the manufacturer
of the tow hook or on the production data plate (e.g. DIN 74051 and DIN 74052).
There are also tow hooks with special type approval, whose values are greater than the ones mentioned in the above standards.
These hooks may in any case be subjected to restrictions depending on the trailers used (e.g. drawbar length). In addition this can
imply that the rear cross member should be further reinforced and a subframe runner of larger size be fitted.
-
mobile connection with the towing vehicles takes place via a towing device.
-
The drawbar is not connected to the frame so that it is free to move and therefore able to transmit vertical torques.
-
Depending on its construction, part of the overall weight will be borne by the towing vehicle.
-
For mechanical attachment devices designed for mid-axled trailers, the Dc, S and V values are defined by the following equations:
Dc
=
g
⋅
(T
⋅
C)
(T
+
C)
=
(kN)
V
=
a
⋅
X
2
l
2
⋅
C (kN)
D
=
representative value of the class of jaw (kN). This is defined as the technical reference force for the horizontal force between the towing vehicle and
the trailer;
g
=
acceleration due to gravity (m/s
2
);
T
=
maximum weight (in tonnes) of the towing vehicle;
T+S =
maximum weight (in tonnes) of the towing v the vertical load of a trailer with a centre axle;
R
=
maximum weight (in tonnes) of the trailer;
S
=
value of the static vertical load (in tonnes) which, in static conditions, is transmitted to the point of attachment.
S must be
≤
0,1
⋅
R
≤
1000kg;
C
=
sum of the maximum axle loads (in tonnes) of the trailer with a centre axle at maximum load. It is equal to the maximum weight of the trailer with a centre
axle less the static vertical load (C = R - S);
V
=
value V of the intensity of the theoretical dynamic vertical force;
a
=
for the equivalent acceleration at the point of attachment, as a function of the rear suspension of the towing unit, use the following values:
-
a = 1.8 m/s
2
for air suspension;
-
a = 2.4 m/s
2
for other suspension types;
X
=
length of the load surfaces (m);
l
=
theoretical length of the drawbar (distance between the centre of the drawbar towing eye and the centre line of the trailer axle (m));
X
2
/ l
2
≥
1 if the result is less than 1, use the value 1.
Example for calculating the class of towing gear for trailers with a centre axle
Let us consider a 65C15 vehicle with maximum weight 6250 kg that is to be used to tow a mid-axled trailer weighing
3500kg with S = 250 kg, load surface length of 5m and theoretical drawbar length of 4m.
Therefore, from the data
1. S = 0.25 t
2. C = R — S = 3.5 - 0.25 = 3.25 t
3. (T + S) = 6.25 + 0.25 = 6.5 t
4. X
2
/ l
2
= 25 / 16 = 1.5
we obtain:
D
c
= 9.81 x (6.5 x 3.25) / (6.5 + 3.25) = 21.3 kN, and V = 1.8 x 1.5 x 3.25 = 8.8 kN
Summary of Contents for DAILY 4x4
Page 1: ...DAILY VEHICLE 4X4 RANGE BODYBUILDER INSTRUCTIONS L I G H T R A N G E ISSUE 2007 ...
Page 4: ...Base May 2007 Print 603 93 761 Update data ...
Page 8: ...Base May 2007 Print 603 93 761 Index of section ...
Page 10: ...1 2 GENERAL SPECIFICATIONS DAILY 4X4 Base May 2007 Print 603 93 761 Index ...
Page 28: ...2 4 CHASSIS MODIFICATIONS DAILY 4x4 Base May 2007 Print 603 93 761 Index ...
Page 110: ...2 86 CHASSIS MODIFICATIONS DAILY 4x4 Base May 2007 Print 603 93 761 Chocks ...
