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
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228 
A coupling to beat artic roll-over risks
Page 72
If you've noticed an error in this article please click here to report it so we can fix it.
• Articulated vehicle roll-over has been the subject of extensive research in recent months by the Road Research Laboratory. As a result the RRL has devised a coupling—an experimental unit of which has been built by Gloster Saro, the tanker builders, for use in a series of physical tests on the aerodrome runways at Hucclecote, Glos.
Because of the need for a trunnion assembly to absorb the pitch movement between a tractive unit and semi-trailer, an outfit so equipped becomes increasingly unstable as the degree of articulation between the tractive unit and semi-trailer increases. There is also a degree of vertical lift in a kingpin and jaw assembly which exerts no restriction on the semi-trailer when it rolls. These two factors permit several degrees of lateral roll when an outfit is cornered and the decreasing centre widths of the pitch trunnion as the tractive unit is turned lowers the vehicle's roll resistance.
The coupling which has been tested, comprises a fifth-wheel of the conventional type mounted on top of a drawbar trailer turntable ring. To enable comparative tests to be completed, the fifth-wheel is arranged to allow a locking pin to be passed between it and the rubbing plate on the semi-trailer while the ball race turntable ring can in turn be locked to the tractive unit chassis so allowing either to be placed in use. The tests have proved that the elimination of vertical freedom at the coupling and the prevention of narrowing the trunnion hinge centres when the tractive unit is turned, considerably reduces roll, and transmits more of the trailer roll to the tractive unit. This gives the driver ample warning of the vehicle's attitude and also reduces the steering effort required.
It should be emphasized that for the present there is no intention, for reasons of convenience in coupling and uncoupling, and of course unladen weight, to commercially produce the coupling assembly which has been under test.