1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160 
Stability system reduces jack-knife or rollover risk
Page 17
If you've noticed an error in this article please click here to report it so we can fix it.
Sudden red air-line loss on a trailer can lead to an artic jack-knife, but the Haldex EB+ trailer brake control system combats this. Brian Weatherley reports
• by Brian Weatherley
Disc-brake and braking component manufacturer Haldex has produced a CD video that demonstrates its EB+ trailer brake control and dynamic stability systems. The five-minute CD can be used in most office PCs, and kicks off with a look at the problems of sudden red air-line loss on a trailer and the potential dangers associated with it.
EB+ CONTROL
Using an unladen artic on a test track, the sudden red-line failure is demonstrated with 'live-action in three separate modes:
• With the FRS-equipped trailer showing the emergency brake function by spring brakes only—where air is exhausted out of the brakes and the mechanical spring park brakes applied. As the red line is lost, the trailer wheels instantly lock-up creating clouds of smoke, while the trailer swings (usually to the kerbside) creating vehicle instability and the risk of a rollover or jack-knife before coming to an eventual halt.
The truck is then left creating a potential obstruction on the road while the flatspots created on the tyres by the locked brakes are also graphically illustrated!
• The second scene shows the antic operating with Haldex's EB+ and relay emergency valve (REV) and a five-pin ISO 7638 connector. As the red line is dropped, the emergency brakes are still applied but through the service portion—which retains full ABS control, preventing wheel-lock-up. The artic pulls up in a controlled straight line, but remains immobile, again potentially blocking one lane of the carriageway • In the final scene the vehicle loses the red-line while operating with Haldex's EB+ with REV system and a seven-pin connector. Now, although the brakes are still applied, the EB+ senses the condition and that there is still reservoir capacity and gives braking control back to the driver, allowing him to manoeuvre the vehicle onto the hard shoulder or into a lay-by. Thereafter, it applies the emergency park brake.
The vehicle cannot then be moved until the red line is re established. This, says Haldex, is the optimal system for trailer makers and operators.
EB+ STABILITY
The second part of the video shows the Haldex EB. stability control system to good effect, using a pair of laden artics with stabilising safety out-riggers completing a variety of bpi manoeuvres including: • 20m radius circles III 100m radius turns
• 100mm/50m 'Q' turns • Lane avoidance manoeuvres
These are designed to reproduce typical tight European motorway slip roads, UK roundabouts and sudden emergency lane changes which, if tackled incorrectly, can all cause an artic to roll over suddenly.
Using the EB+ system across the trailer axles, the artic's lateral acceleration is monitored to determine whether one side of the trailer is approaching 'liftoff', which ultimately leads to a rollover. In the video, the artic with the system disconnected is seen passing the point of no-return with the wheels on the outriggers making contact with the runway. Without the outriggers, the artic would have completed a full rollover.
However, with EB+ connected, as the trailer approaches lift-off, EB+ senses the lateral force, applies a limited amount of braking and monitors any differential deceleration between the trailer's wheels as the load balance changes—if found, it applies an increased level of braking, slowing the vehicle down until full stability is regained. Once the system senses that the lateral acceleration has reduced, it fully releases the brakes.
In the video the artic is shown on the limit of adhesion negotiating the manoeuvres. Haldex says that the purpose of the track test is to ensure that the system does not operate prematurely. EB+ stability is available as a line-fit option on all semi-trailers whether they are equipped for EBS-operated drums or discs. However, to get the full benefits from an EBS combination, the operator must use an ISO 7638 seven-pin connector.