Mercedes-Benz introduce special version of 30-ton tractive unit for Britain
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Ai important feature of the forthcoming Commercial Motor Show will be the presence at Earls Court of a large number of manufacturers from across the Channel. Additional evidence of the importance that European makers are attaching to the British market is given by the fact that a number are to build special models for this country.
Mercedes-Benz of Germany is a good example. It has developed in conjunction with its British distributors, Nortnand Commercial Vehicles Ltd., a special version of the LS 1418 and an example will be making its debut at the Show. The LS 1418 is a semi-forward control tractive unit for operation at 30 tons gross train weight and has a similar mechanical specification to the LPS 1418 forward-control model. No doubt the alterations will relate to both when they are sold in Britain. There is no change in the general mechanical layout of the model, the Daimler-Benz OM 346 sixcylinder diesel producing 180 b.h.p. net at 2,200 r.p.m. driving through a five-speed synchromesh gearbox to a two-speed rear axle.
Main changes The main changes to the design are to the chassis which has been shortened and lowered to enable the tractive unit to be matched to standard British semi-trailers. The wheelbase is unchanged at 10 ft. 6 in. but the rear overhang is reduced by 5 in. compared with the previous model This enables the fifth-wheel turntable to be mounted 7 in. farther forward and chassis height has been reduced by 4 in. To provide this lower frame height the rear spring camber has been changed and the maximum deflection reduced from 8 in. to 5 in. Unladen height at the turntable centre is now 42.5 in. The braking layout has been revised to meet UK regulations and at the same time the brake lining area has been increased from 535 sq. in. to 698 sq. in. An airassisted hydraulic system is used and the front axle and the rear axle are on separate circuits with independent master cylinders and air servos. A light-laden valve is fitted at the rear axle to reduce the effort in the servo for this part of the system when the vehicle is running unladen or part laden. The hand brake is a purely mechanical unit to the driving axle and the shoes are actuated independently of the hydraulic system.
Secondary brake system So far the layout described is as the previous design, the changes being concerned with the addition of a secondary system. To meet this requirement Type 15 brake chambers are fitted at each side of the cross shaft in the hand brake linkage. These are brought into use on application of a handreaction valve in the cab and at the same time air is fed to the semi-trailer auxiliary connection. To ensure that too much braking effort is not applied at the wheels, valves are incorporated in the system so that the main and secondary systems are not operated at the same time.
A lot of effort has been made to ensure that lag in brake operation is reduced to a minimum. All air pipes are 15 mm. diameter and relay valves are fitted at the termination of all feeds for the semi-trailer.
Also to be shown at Earls Court for the first time will be the latest version of the Mercedes-Benz LPS 1418 tractive unit which was introduced at the last Frankfurt Show. This has the flat-front cab, the general design of which is followed for all MercedesBenz forward-control models produced for the Continent. The mechanical specification is similar to that of the LS 1418 but although the show model will have right-hand drive the chassis has not been modified to suit British requirements.
The third tractive unit to be featured on the Mercedes-Benz stand will be an LPS 2020 twin-steered tractive unit which is sold in Germany for operation at 38 tons gross train weight. The second-steering axle on this model is set close to the driving axle and an uprated version of the OM 346 engine producing 210 b.h.p. net is used, this driving through a ZF six-speed gearbox.
A final exhibit by Mercedes-Benz will be an 0.302 coach. A 45-seat de luxe version will be featured and this is a model with which Mercedes-Benz plans to enter the British market. The model does not meet current British regulations in some respects such as front axle ground clearance and exhaust position but it is said that the design will comply fully with British regulations when changes in hand become effective. The 0.302 has an OM 327, 175 b.h.p. engine located vertically and longitudinally at the rear and this drives through a five-speed synchromesh gearbox; there is an optional eight-speed gearbox.
Wheelbase is 19 ft. 2.3 in. and overall length of the coach is 36 ft. Power steering and an engine exhaust brake are standard on this model and the show chassis will have air suspension. A right-hand model will be shown and this has forward entrance and the emergency door is on the offside rear.
More details of Mercedes-Benz plans to enter the British coach market should be available next week.