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 
Technical & Industrial
Page 62
If you've noticed an error in this article please click here to report it so we can fix it.
ERF Demonstration
ON Wednesday, at the FVRDE, Chobham, a demonstration of the ERF spring-powered parking-brake system was given before a large party of engineers and technical journalists.
Prior to the demonstration, COMMERCIAL MOTOR was able to carry out evaluation of the system, and a report on this appears on page 72 of this issue. Brake efficiencies recorded on this occasion were unsatisfactory and, as reported, the vehicle was returned to ERF for attention. On Tuesday the vehicle was again submitted to COMMERCIAL MOTOR for evaluation and the following results were achieved;—
Service brake from 30 m.p.h. and 65.5 ft. total stopping distance, 66 per cent Tapley meter: from 20 m.p.h. and 60.75 ft. total stopping distance, 61 per cent Tapley meter. Spring brakes only, operating on both axles of the tractive unit, produced on this occasion average Tapley meter recordings of 25 per cent.
The Ministry of Transport brake tests carried out during the proposed yearly vehicle inspections are to be done at 25 m.p.h. and figures recorded from this speed were: service brake 50.1 ft. and 65 per cent on the Tapley meter; spring brakes only, 26 per cent, and spring brakes with third-linecontrolled trailer braking, 52 per cent Tapley meter.
A fade test carried out by driving the vehicle at full throttle in fourth gear against the brakes at 20 m.p.h. for one mile produced from 20 m.p.h. a total stopping distance of 47.75 ft. and a Tapley meter reading of 57 per cent. As this test was carried out at the FVRDE at Chobham it was possible to use the test slopes which have 1 in 4 and 1 in 3 gradients.
Whilst the spring brakes alone failed to hold the vehicle on the 1 in 4 slope, it was quite a simple proposition to park the outfit—using the spring brakes and the airpressure trailer brakes—which was grossing just on 30 tons on the 1 in 3 gradient when facing both up and down. Several stops were made on this slope and on every occasion the outfit was brought safely to a halt.