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 
ogie-lift to beat
Page 73
Page 74
If you've noticed an error in this article please click here to report it so we can fix it.
he bog bogey by Graham Montgomerie sIGLE-DRIVE with bogie lift can double-drive for grip." So ran the Hine of a report I prepared for CM's Tary 24 issue on a paper given by Nylin of Scania. With unladen ers especially, the problem of Lion on loose surfaces is well known, Scania claims that the principle of e lift can help a truck out of most Itions. I have just sampled such an it in typical conditions and the worked extremely well — :nigh I still needed a tow on one Lsion.
he truck in question was a Scania 85 HB36 three-axled tipper fitted an all-alloy body by Welford Truck ies Ltd of Stoke-on-Trent. Two nples were, in fact, on hand; one n and the other empty. This was so I could test the effectiveness of the e lift when empty and assess the ormance when laden without the I for loading and unloading as the n vehicle was within, an ounce of the on limit.
iple in Operation
principle the idea of bogie lift is !mely logical. If the trailing rear is raised the extra load is trans ferred onto the drive axle. This has two effects: the obvious one is the increased load on the drive axle and its benefit to traction, but, by virtue of the movement of the lifted trailing axle above the drive axle, the corresponding load on the front axle is reduced. This decrease in front-axle load is important as it lowers the tendency for the front wheels to "plough on" in the turns.
The actual method of raising and lowering the trailing axle is very simple. A hydraulic ram, powered by a pump situated between the main longitudinal side-members forces a transverse beam down onto the leading end of the pivot' arm (see diagram). This movement is ,controlled by the driver from inside the cab and the amount of lift is infinitely Variable.
A single switch controls the pump — "up" on the switch means "up" for the bogie lift and vice versa with the "hold" position in the middle. A green indicator light tells the driver if the hydraulics are working. As soon as this goes out the bogie is either fully up or fully down dependent on where the switch is. By releasing the switch it returns automatically to the "hold" position giving the driver infinite control over the height of the trailing axle. If a driver feels he is losing traction in the three-axle condition he can raise the trailing axle and transfer all or part of the load on to the drive axle as he wishes.
Terrible but typical
The off-road part of the test took place in a Blue Circle quarry in Derbyshire where it had rained continuously for about four days so the surface condition was decidedly tricky — but the Blue Circle trucks carried on as usual so the conditions could be described as typical.
As I mentioned earlier, two Scanias were available for the test. The unladen one used to experiment with the bogie lift, was loaned by A lien's of Hilton near Derby and was identical to the Scania demonstrator supplied by B & W Motors of Nottingham which was fully laden.
It must be admitted that I managed to bog down the Scania where not even the bogie lift and the diff-lock could help. In trying to avoid some of the deeper ruts in the wet clay surface I strayed out on to some loose sand and the rear bogie sank almost without trace. I tried the bogie lift to no avail and even tipped the bOdy. to transfer a little more load on to the drive axle, but with no success.
The truck was almost settling under its own weight without the digging action of the spinning wheels. The drive axle had sunk so far into the soft sand at this point that the diff casing was resting on the ground, which made any further attempts rather pointless. The assistance of a Belaz dump truck was needed to return the Scania to more solid ground. In fairness to Scania I must mention that the ground was so soft at this point that it was difficult to 'cross on foot without sinking in.
On the wet clay, if there was any hint of decreased traction I used the bogie up until the grip returned with complete success.
Shorter wheelbase
One extra advantage of the bogie lift was a "reduction" in the wheelbase when in the raised condition where the vehicle became in effect a two-axle machine. A quite dramatic reduction in the inner circle was achieved from 9.1 to 7.0 m (29 ft 9 in to 23 ft 0 in). In tight yards this could be very useful.
I took the B & W Motors Scania 85 out on to the road to form an opinion of the handling on made-up roads and to check on the fuel consumption. A circuit of around 75 miles was picked which was split roughly 50-50 between motorway and A-road running. Travelling from the quarry to Sheffield via Chesterfield on A61 the 85 averaged 3.08 km/1 (8.7 mpg) for an _average speed of 45.1 km/ h (28.0 mph) including some stop-start traffic work. On the return leg of the circuit on M I the average fuel consumption was 3,35 km / 1 (9.4 mpg) for an average speed of 76.4 km / h (47.5 mph).
The 85 was fitted with a 10-speed splitter box consisting of a five-speed main gearbox and a two-speed pneumatically operated planetary unit. It was not one of the best splitter gearboxes I have tried as the half change took rather longer than I would have liked to engage. Full changes were fast and accurate but if a downward split was made on a gradient, the delay before engagement meant the vehicle had lost so much forward motion that another change became necessary. In practice I rarely made split changes on the hills, preferring to use the facility on the level.
The gear lever was smooth and precise in action but required a longer left arm than I possess to reach comfortably when in second and fourth gears.
I have long been a fan of Scanias when talking about steering as I rate their application as one of the best. With 4.4 turns from lock to lock, the 85 was easily manoeuvrable, the power assistance making light work for the driver. One irritating point about the wheel itself was that the top spoke of the threespoke design obscured the rev counter in the straight-ahead position. The new two-spoke design first shown at Brussels this year will solve that problem.
The pedal layout of the Scania 85 was first class. I have often commented upon trucks where the brake and clutch pedals are mounted far too high up for