Scania-Vabis picks models for UK market
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BY A. J. P. WILDING, AMIMechE, MIRTE DETAILS have been announced this week of the models on which Scania-Vabis, of Sweden, plan to concentrate for the British market. The company makes a wide range of commercial vehicles starting with a model with a payload capacity of 7.6 tons and also p.s.v., but only chassis at the top end of the goods range are involved.
Initially, the LB76H tractive unit for 30 or 32 tons gross train weight is to be offered to British operators; imports should start towards the end of this year. A special version has been specially developed for the UK and this is the first goods model to be produced by Scania-Vabis with right-hand drive.
Other special features which have been incorporated to meet British requirements include a changed brake system and an alteration in wheelbase to 9 ft. 10 in.
A normally aspirated 11-litre diesel or a turbocharged version is used in this model, but it is considered by Scania-Vabis that a turbocharged engine will be the more popular in Britain and in this case the type name of the chassis becomes LB76H Super.
In normally aspirated form the engine is called the Dll and the maximum net output is 192 b.h.p. at 2,200 r.p.m. with the maximum net torque 549 lb. ft. at 1,200 r.p.m. Bore and stroke dimensions of the six-cylinder, direct-injection diesel are 5 in. (127 mm.) and 5.7 in. (145 mm.) respectively, giving a cubic capacity of 673 Cu. in. (11 litres).
When turbo-charged, the type name becomes DS11. The turbo-charger is mounted on top of the engine and consists of a single-stage radial-blow turbine and a single-stage centrifugal cornpresser. Maximum net output of the DS11 is 237 b.h.p. at 2,200 r.p.m. and maximum net torque 665 lb. ft. at 1,400 r.p.m.
Both engines are of the same general construction. The cylinder block is integral with the upper half of the crankcase and wettype cylinder liners are used. Twin cylinder heads each cover three cylinders and the injectors are mounted in stainless-steel sleeves which are in direct contact with the cooling water.
All valve-seat inserts are made of a special alloy and both inlet and exhaust valves are Stellite faced. Lubrication is by a system incorporating a constant-displacement oil pump giving 70 p.s.i. maximum, and lubricant is filtered through a strainer in the sump then through a cyclone and a centrifugal filter.
The fuel system includes a Bosch PE6P100 injection pump with mechanical governor and Bosch injectors. The turbo-charged engine has a device on the fuel pump which works in conjunction with the pressure level in the induction manifold ensuring that the fuel input is reduced at low engine speeds to reduce "smoking".
Apart from the engine, the specifications of the LB76H and LB76H Super are identical. The drive from the engine is taken through a 16.5 in.-single-plate clutch and the standard gearbox is a five-speed, direct-top unit with synchromesh on the four highest ratios. Gear ratios are 7.7, 4.35, 2.48, 1.47 and Ito 1, and reverse is 7.14.
As an option, a 10-speed gearbox can be supplied, this consisting of a five-speed main unit and a two-speed, planetary-gear splitter box which divides the gear ratios of the main unit. The splitter box ratios are 1.4 and I to 1, the change is mechanical through a lever in the cab. The standard rear axle is a spiral-bevel unit with air-operate( differential lock and there are alternative ratios of 4.67, 5.13 an( 5.71 to 1. As an alternative a double-reduction, spiral-bevel an single-helical gear unit is available. This can have ratios of 4.9: or 5.91 and also incorporates a differential lock.
For the British market, a special-design brake system is usec and this has MGM spring-brake operating units at all wheel which perform both secondary and parking brake requirements Pressure is supplied by a twin-cylinder compresser and air is store( in two twin-chamber reservoirs. One reservoir is used to feed in dependent circuits for service braking of the front and rear axle and actuate the semi-trailer brakes, whilst one of the chamber in the other acts as a water condenser and separator.
Short hand-brake lever The second half of the latter supplies air to hold off the MGiv spring brakes and upon application of a short hand-brake lever it the cab supplies air to the auxiliary connection for the semi-traile third line and at the same time releases air from the spring brake: through an invertor valve. This provides the secondary systen required under the latest C and U Regulations.
So that the parking brake shall be purely mechanical there is r valve in the system which has a built-in 8 sec. delay so that afte: this time air in the semi-trailer auxiliary line is exhausted. A hand reaction valve is also fitted in the cab for independent operatior of the semi-trailer brakes.
Brake sizes are 16.25 in. diameter all round by 5 in. wide a the front and 7 in. wide at the rear. Total frictional area 798 sq. in.
Steering is by a ZF unit with integral hydraulic power assistance and semi-elliptic springs are fitted. Other details from the specifica lion include 24 V electrics, 10.00 or 11.00-20 tyres and a 44 gal fuel tank.
The cab used by Scania-Vabis is finished to a good standar( and is of all-steel construction. Although the front overhang 4 ft. 2 in., entry is over the wheel and the dimension from th( centre line of the front axle to the rear of the cab is 1 ft. 7.5 in A sprung driver's seat is standard, as also is full heating an ventilating equipment.
Load-carrying versions of the LB76 will also be available an( so will single-drive six-wheel rigids and tractive units.
The designations of the Scania-Vabis six-wheelers which wil eventually be brought into this country are LBS76 and LBS7( Super according to which engine is fitted. These are to the sam( general design as the four-wheelers, the difference being th( addition of trailing wheels. There are the same options of trans mission and driving axle and the same ratios in the latter.
Two wheelbases are made-16 ft. and 17 ft. 3 in. (from centr( line front axle to centre line rear bogie). The rear suspensior provides for more load on the driving axle than the railing wheels The stub axles of these are carried in the ends of substantia beams pivoted from the chassis frame and connected at the froni end to the rear shackles of the driving axle springs.
The driving axle springs are underslung as against top-mounted springs on the four-wheelers and because of the lighter load on thc trailing wheels these have 5 in.-wide brake linings (other sizes arc the same as on the four-wheelers) giving total frictional area for the six-wheelers of 1,130 sq. in. The six-wheel model has noi yet been developed for the British market and no decision has been made on the braking system to be used.