• Genius of the cab designers
Page 23
If you've noticed an error in this article please click here to report it so we can fix it.
have always found it iscinating that the various lassis manufacturers have -oduced so many different lb designs while working to le same strict constraints of ,gislation and dimension.
A classic example of this is e Ford Transcontinental corn3red with the 'New Genera)n" cab on the latest Merce:s-Benz range — two complely opposite ways of thinking, To elaborate on the many fferent approaches made by e various designers to arrive leoretically) at the same result, am using six examples of irrent cab designs from Scaa, Seddon Atkinson, Ford, ercedes-Benz, ERF and Bedrd.
And to find out just how a cab :signer starts work on a new :sign before the drawing board age and its subsequent progss, I went to the Bedford Igineering department to talk Ron Cooper, executive engi:er, Bedford Trucks, cab and m.
the shade
About 10 years ago, the K cab designs were put the shade by the then ew Scandinavian imports. -ivers suddenly realised just hat the other manufacturers id been doing and they liked it. )day, Scania is still recognised ; one of the leaders in )mmercial vehicle cab design r comfort and safety due, in e main, to the notorious wedish safety requirements lating to cab strength which all rries marketed there must eet.
Before starting production ith a new cab, Scania has to tisfy the authorities that the 3sign will meet certain impact sts. The first test consists of a 300kg (2.2001b) cylinder 3ing released from a forward 3ight of 3.0m (9.8ft) and vung at one of the windscreen pillars. This is designed to simulate the effect on the cab corners of the vehicle rolling over.
In the event of a collision, an inadequately secured load will shift forward into the back of the cab. So a similar mock-up with a 1000kg weight is carried out on the rear bulkhead. The final test requires that the cab roof must be able to withstand a static load of 15 tonnes (14.8 tons). This particular test is to simulate a complete rollover or, say, a container dropped during loading.
It should be emphasised that all these tests are made on the same cab. It is not allowed to wheel out an undamaged structure for each part of the test. On top of that, the doors must remain closed during the tests.
Scania cabs consist of a lattice framework of 'tophat' sections, generally closed by a cover sheet, spot-welded to the open side of the section to form a box section. This particular design provides a strong basic unit, whether exposed to bending, tensile or compressive forces.
The framework of the whole cab is, therefore, designed so that the loads occurring as the result of a collision will be distributed over a large part of the cab and not concentrated in the collision area.
Reinforcement
Certain sections, more • likly than others to receive impact damage during their life, are provided with extra reinforcement. This applies to parts such as the windscreen pillars, where reinforcements in the form of channel sections have been welded in.
The outside panel also contri butes to the strength by being connected to the windscreen pillar and the inside of ths windscreen frame.
Reinforcements are provided at the cab mounting points which represent direct point loads. These reinforcements consist either of increased material thickness or of extra reinforcements so that the load from the cab support points is distributed into a larger section of the cab.
The cab of a forward control vehicle is more exposed than a bonnetted type which has the shock-absorbing protection of the bonnet and wings in a collision. Also, because modern cabs are required to be tiltable, the front section must be extremely rigid to accommodate the cab mounting.
A forward control Scania cab (LD81, for instance) is therefore., 'provided 'With two channel, section supports. From these supports, two tophat sections run backwards under the cab floor. These tophat sections and the two supports are joined by means of two gusset plates which distribute the forces arising from a collision over the framework and floor
Different
The way Ford approached the problem of cab design was rather different — they went out and bought one. Before the Transcontinental was introduced, in 1975, Ford policy was one of using as many home-built components as possible.
But when the company decided to attack the heavy end of the commercial market, this policy was changed and Ford went, instead, for existing well-known ..and well-proven proprietary components. The engines came from Cummins, gearboxes from Fuller, axles from Rockwell and cabs from Berliet.