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Torque where it counts...

Transmission choice gives power where it's needec oy Grcham Montgomerie

AS IF ANYONE needed reminding we in the UK have a slight discrepancy in gross vehicle weights when compared with the rest of Europe. Thus we have tractive units with ,design weights of 32 tons, 38, 44 and even 50 tonnes all operating in this country at 32 tons gross.

As one would expect, this leads to a tremendous variation in drive-line specification with engine power ranging from around 200 horsepower to 350 plus, all to do the same job as far as this market is concerned. I have been looking at the power unit and transmission options which can be chosen by the UK operator and indicating the balance between top road speed and performance up the hills.

Some years ago — and not so far back either — manufacturers were busily engaged in a power race with many engineers looking at 8bhp per ton and beyond. The oil crisis 'adjusted' people's design aims and now the emphasis is on reduced engine operating speeds with a large chunk of torque where it matters.

Cummins with the E290 and Rolls-Royce with the 1' versions of their 290 and 265 engines are good examples of the trend towards lower speeds. Gardner, of course, is no stranger to this particular way of thinking with the fastest engine currently rotating at just over 1,900rpm.

On the gearbox front, there has been an increasing interest in fully synchromesh boxes moving away slightly from the constant mesh type. True, most of the manufacturers who have followed this line of thought still only list a synchromesh version as an option rather than as standard but it will be an interesting trend to watch in the future.

Companies like Volvo and Scania of course use synchromesh gearboxes throughout and have done for many years.

At the rear of the vehicle, no clear pattern has emerged over axle design with doublereduction, hub-reduction and single-reduction versions all currently available in many permutations with overdrive and direct top gearboxes.

The axle situation was further complicated by the engine manufacturers' move towards lower engine speeds. This left some chassis builders, Seddon Atkinson and Bedford to name but two, without a high enough ratio to maintain a satisfactory road speed at lower engine revs. Thus several had to change their axle specification or in some cases change the source of rear axle. Seddon Atkinson had to develop rapidly a 4.57 ratio for its group axle whereas Bedford changed from SoMA to Rockwell when the Cummins E290 was fitted instead of the Detroit Diesel V8 twostroke in the TM 3800.

In the top weight category, the semi and fully automatic .transmission has got a foot in the door via Allison with Volvo and ZF with DAF and Seddon Atkinson although the ZF models are not yet listed as regular factory options.

The main contender from Leyland for honours in the UK 32 ton category is the Marathon 2 powered by Leyland's own turbocharged TL12 engine. As installed in the Marathon this produces 203kW (273bhp) at 2,200rpm with a maximum torque of 1,055Nm (780Ibft) at 1,300rpm. Although the gearbox is sourced from outside (the Fuller RTO 9509A) the axle is of Leyland design being of the hub reduction type available with a choice of three ratios giving a performance spread ranging from a top speed of 118km/h (74mph) to a maximum climbable gradient of 25 per cent.

Although the TL12 is the standard power unit for the Marathon, Leyland also offers alternatives from Rolls-Royce and Cummins. Originally only the lower power versions from these manufacturers could be specified (eg the Cummins 250) but Leyland has relented on this recently and now the Cummins E290 is available. As a guide to performance, the NHC250 en gined Marathon has a top speed of 99km/h (61mph) and a gradeability of 21 per cent from its 5.524 axle ratio.

The L12 engine in the Buffalo is the same unit as in the Marathon but minus the turbocharger. Brought in to replace the headless 500series engine for this model, the L12 develops 151kW (203bhp) at 2,200rpm. Maximum torque is 775Nm (570Ibft) at 1,400rpm.

A choice of four ratios is listed for the L12 Buffalo which give a wide performance spread. This ranges from the 102km/h (63mph) and 15 per cent gradient. for the 5.524 axle to the 73km/h (45mph) and 21 per cent gradeability for the 7.69 ratio.

At the NEC last year, Leyland launched the TL 11 engine which is based on the long serving 680 unit. (The L/TL 12 engine is based on the AEC 760). The TL 11 produces 156kW (209bhp) and, while this might seem very similar to the L12 output, the argument put forward by Leyland is that it enables them to satisfy the needs of operators who are strongly for or strongly against turbocharged units. Two basic engine desi( serve the DAF range of tr tive units with power c puts from just over 2 horsepower to the 300 p of the top-of-the-range D unit.

The FT 2105DHR is pla for operation at 28/32 tc gross and features a turl charged version of DA long-serving 8.25 litre (E cuin) in-line six-cylinder I gine. As installed in t particular model it_ produ, 150kW (202bhp) at 2,400r with a maximum torque 670Nm (495Ibft) at 1,E .rpm.

As with most vehicles fr Eindhoven, a ZF gearbox standard equipment, in 1 case a six-speed constz mesh AK6-65 with a dir drive top and a GV80 sr ter. The synchromesh sion of this box is listed a factory fitted option.

At the rear, the DAF 2: single-reduction axle is av able with a 6.33 to 1 n only which gives a mi mum road speed of 86kn (54mph) and a gradeab of 18 per cent or 1 in 5.6.

The same engine crops in the FT 2300DHU pia for 36 ton operation but this case an air-to charge cooler is added which permits an increase in power up to 169kW (230 bhp) and a corresponding torque increase to 775Nm (572Ibft).

To cope with the performance increase, the 5K-90 GP constant-mesh gearbox from ZF is specified with its nine speeds and direct drive top. The FT 2300 features a hub reduction axle in contrast to its baby brother with a choice of two ratios, 5.03 (standard) and 4.49.

These give a performance capability of 91km/h (57 mph) and 25 per cent gradeability for the standard ratio with 102km/h (64mph) and 22 per cent being the equivalent figures for the optional axle. Both the 2105 and 2300 models share the same clutch specification, a single dry plate design with a diameter of 380mm (15in).

Moving up the range we come to the two 2800 models which share the same basic engine design with the major difference again being the addition of charge cooling. As fitted in the FT 2800 DKTD, the 11.6 litre (708 cuin) turbocharged engine develops 185kW (248bhp) while in the DKS version this is raised to 229kW (307bhp) both at 2,20Orpm.

The DKTD, which is plated for 40 tons, utilises the ZF AK6-90 constant mesh box with a splitter — again with a synchro option — but the 51 ton gcw DKS version is equipped with the 13-speed Fuller RTO 9513 box. As Fuller does not make a synchromesh unit, there is no alternative for this model.

With the ZF box, top gear is direct with the splitter ratio being 0.82 while the Fuller has an overdrive top gear with a 0.87 ratio. Both 2800 models use the same DAF 2699 hub reduction axle which has a design capacity of 13 tonnes although it is obviously limited to 10 tons in the UK.

The standard axle ratio for the DKTD is 5.53 which permits a road speed of 96 km/h (60nnph) and a gradeability of 23 per cent (1 in 4.5). The corresponding figures for the -6.09 axle are 88km/h (55mph) and 26 per cent (1 in 4).

The 5.53 axle, standard for the DKTD, is the option on the DKS version where it gives a top speed of 81 km/h (57mph) and a maximum gradient of 1 in 4. The standard 5.03 ratio raises the top speed to 100km/h (62mph) while the gradeability is marginally reduced to 23 per cent.

As well as producing right hand drive versions of its European 38 tonne models for the UK market, Mercedes-Benz appreciated the needs of the operator who wanted a 32 tonner pure and simple and the result was the 16195 tractive unit — a vehicle designed specifically for the British operator.

The Mercedes range of vee engines is built on the modular principle ie if you need a bigger engine then add a few more cylinders. Thus the V6, V8 and V10 engines all have a high degree of commonality of components.. (Daimler-Benz claims that 86 per cent of the engine components are identical). To illustrate the point, the engines for Europe whether six, eight or 10 cylinder. share the same bore and stroke dimensions of 125 and 130mm (4,92 and 5.11 in) respectively.

In this country however this applies only to the V8 0M402 engine in the 1626 and the V10 OM 403 in the 1632. As I mentioned earlier the 1619 was designed with the UK operator as the main target and so the OM 401 V6 engine becomes the OM 401X by virtue of an increase in stroke from 130 to 142mm (5.11 to 5.91in) with the bore remaining the same.

Mercedes — like Fiat — has remained a staunch advocate of the naturally aspirated engine and the current vehicle range reflects this philosophy. The flagship of the Mercedes fleet uses the V10 engine which produces 235kW (320 bhp) at 2,500 from a capacity of 15.9 litres (970cuin). 'This compares with the 185kW (256bhp) from the basically similar V8 in the 1626 chassis.

Although Mercedes stick rigidly with ZF for most of the gearboxes, the individual specifications vary considerably around the basic allsynchromesh theme. Thus while the V10 is coupled to an eight-speed range-change box, the V8 is used in conjunction with a 12-speed splitter design. The 1619 chassis is once again the exception to the rule as this uses an eight-speed rangechange box built by Mer cedes.

The standard ratio for the 1626 is 5.22, comparatively high gearing as it permits (at least technicallyl) a road speed of 114km/h (71mph) and a gradeability of 19 per cent. The optional 5.94 ratio limits the speed to 101km/h (63mph). With its 4.64 ratio, the V10 can achieve 105 km/h (65mph) and 29 per cent.

The Dodge C-36T drive line has had a change of gearbox since its introduction as the K3820P in 1973 with a nine speed Fuller box replacing the original Chrysler unit. The engine however is retained. This is a six-cylinder turbocharged unit built in Spain which produces 202kW (275bhp) DIN at 2,200rpm and a maximum torque of 1,010 N m (745Ibft) at 1,400rpm.

At the rear a Chrysler 232N double reduction axle is fitted, a component which the 36T shares with the 38T which is basically the same vehicle but with a Cummins engine fitted. Intended mainly for TIR work, the 38T uses the 258kW (350bhp) SAE NTE 350 unit which puts out a useful 1,440Nm (1,065Ibft) of torque. Its release for the UK has not yet been announced.

The standard axle ratio for the -C-36T is 5.48 which gives the Dodge a top speed of 106km/h (66mph) and a gradeability of 26 per cent. There are two other ratios available which gives a top speed of 114km/h (71mph) or a gradeability of 30 per cent depending upon the operator's priority.

At the 'bottom' of the Chrysler range is the recently introduced C-32T model. Although this is also powered by a Spanish-built turbocharged six cylinder engine, it is not the same unit as fitted to the 36T. Compared with the 12 litre (732 cuin) engine for the heavier model, the engine for the 32T has a capacity of 9.3 litres (567cuin). It produces 157kW (216bhp) DIN at 2,200rpm and a maximum torque of 824Nm (6071bft) at 1,400rpm.

Although Chrysler has gone to Fuller for the heavy truck gearboxes, a homebuilt product is retained for the C-32T in the shape of the 813 synchromesh box which is an eight speed range-change unit with a direct drive top.

Seddon Atkinson sub-divides the 400-series range of tractive. units into two categories — those with naturally aspirated and those with turbocharged engines. Both sectors incorporate three engines.

The lowest power output is that provided by the Gardner 61.)(C at 144kW (193 bhp). This engine is a modified version of the longserving 6LXB and, when announced at the NEC last year, it took the six-cylinder Gardner into the 32 ton category for the first time. The particular 400 which uses this engine — the T32 G6XC — is also the only Seddon Atkinson tractive unit to use a David Brown gearbox. The other models, whether Gardner, Rolls or Cummins powered all call up the nine-speed Fuller RTO-9509A with its overdrive top.

The other Gardner engine to find its way into a 400 is

af course the straight-eight 3LX6. AS installed in the Seddon Atkinson it produces 184kW (245bhp) at a typically Gardner speed of 1,850 rpm. Maximum torque is 960Nm (716Ibft) at 1,000 rpm.

Cummins provide the last naturally aspirated engine in the shape of the NHC-250. Turning to the turbocharged engines, Seddon Atkinson offer two Rolls variants and a Cummins. The Rolls-Royce 265L was the first of the new 'de-speeded engines to go into a 400 series tractive unit, It develops 181kW (256 bhp) at 1,900rpm with a maximum torque of 1,077Nm (792Ibft). This compares with the 210kW (281bhp) of the 'L' rated 290 Rolls engine.

The latest trend towards lower revving engines caused some vehicle manufacturers a few problems because of the lack of a suitable axle ratio. A reduction in maximum engine automatically means a lower road speed unless the axle ratio is made higher and in the early stages the Seddon Atkinson group axle ratios stopped at 5.05 necessitating buying out for a short time. This situation has now been rectified with the SA-13-HR axle having a 4.57 option which gives the company a ratio spread from 4.57 down to 6.12.

With the E290 Cummins engine — another power unit rated at 1,900rpm — the single-reduction Rockwell R180 axle is available as an alternative to the SA hub reduction type although the ratios are very similar, 4.57 against 4.62.

Whatever the power output of a Seddon Atkinson, the clutch specification stays the same. It is a twin-plate type from Lipe-Rollway with a diameter of 356mm (14in).

The power units offered by MAN are a mixture of turbocharged and naturally aspirated, in-line and vee-engines. Of particular interest to the UK operator is the 16.240FT which is the nearest that MAN gets to a genuine 32 tonner being plated at 38 tonnes gcw.

From a capacity of 11.4 litres (696cuin), the naturally aspirated MAN 02566 MF engine produces 177kW (237 bhp) at 2,200rpm. The maximum torque of 860Nm (636 lbft) is transmitted via a singe dry plate 420mm (16.5 in) clutch to a 12-speed ZF splitter box. Two ratios are listed for the MAN hub reduction axle at 5.22 (standard) and 5.94 which give a top speed of 105 and 92km/h (65 and 57mph) respectively.

The addition of a turbocharger to this engine takes the power up to 206kW (276 bhp) at 2,200rpm for the 44 tonne MAN 16.280 FTS, A 13-speed Fuller gearbox replaces ZF for this model which, like the 240, is listed with two axle options. The standard 240 ratio of 5.22 be

comes the option on the 280 with the standard for the latter being 4.64. In standard trim, the 280 has a top speed of 106km/h (66mph) and a gradeability of 60 per cent.

At the top end of the MAN range comes the mighty 19. 330 FT whose naturally aspirated V10 engine provides no less than 246kW (330bhp) from a capacity of 16 litres (973cuin). The RTO 9513 Fuller box is retained for this model although the clutch diameter is increased from 420 to 430mm (16.5 to 16.9).

The 5.94 axle ratio gives the MAN 320 a top speed of 102km/h (63.5mph) and a gradeability of 32 per cent at 44 tonnes gross.

Like the other UK special builders ERF can draw on engines from Cummins, RollsRoyce and Gardner; gearboxes from Fuller and David Brown; and axles from Kirkstall and Eaton. Six and eight cylinder Gardner versions can be specified with the former having a six-speed David Brown gearbox used in conjunction with a two-speed Eaton axle. The 8LXB is coupled to a nine-speed overdrive Fuller box as is the rest of the ERF range whether Cummins or Rolls powered. Apart from the six-cylinder Gardner model, a Kirkstall D85-10-2 axle is fitted throughout the ERF range with ratios varying from 5.04 to 6,11.

Most manufacturers who compete in the glamour category of the UK 32 ton market offer a 'lightweight' and a 'heavyweight' model. Scania however goes one better. As well as the 81 and the 111, Scania also offers the 141.

Admittedly the latter machine is not exactly designed for use at the puny UK gross weight limit but the fact remains that it is still available to UK operators.

Scania engine numbers indicate the capacity of the engine in litres — at least approximately. Thus the DS8 engine specified for the LB81 has a capacity of 7.8 litres (476cuin). It is a turbocharged unit which delivers 153kW (205bhp) at 2,400rpm — a classic example of a 'UK spec' 32 tanner.

The Scania LB111 is also powered by a six-cylinder turbocharged engine but a much larger one: 11 litres (671cuin) to be precise. Hence the engine type number DS11. Net installed to BS Au 141a, this engine produces 206kW (275bhp) with a maximum torque of 1,110Nm (820Ibft) at 1,300rpm.

Scania shares with its cor petitor on the other side Sweden an enthusiasm for fully synchromesh gearbo Again from the point of vie of origin, another similari is evident as Scania uses uni of its own design and man facture.

For the LB81, a ten-spec splitter box is specified whir has a direct drive top gez• The standard axle ratio is 4.E which permits a speed 95km/h (59mph) and a grad ability of 16.5 per cent. 14 two alternative ratios provir one higher and one low giving a performance sorer of 105km/h (65mph) at or end and a gradeability of 1 per cent at the other. The ax permutations of the LB11 are many and various wi hypoid, spiral bevel and hi reduction types all being Ii ted. As a guide to the perfc mance of an LB111 the sta dard ratio of 4.13 permi a road speed of 106km/ (66mph) and a gradeability 30 per cent.

As I mentioned earlier, t[ 141 is not exactly design( for 32 tons gcw havir 276kW (370bhp) on tap fro its turbocharged V8 engin The torque figure is, if an thing, even more impressii being rated at 1,480N (1,090Ibft) at 1,300rpm.

Scania's GR 860 ten-sper box is fitted which, in conjun tion with a 3,88 axle rati gives a top speed of 103kmi (64mph) and a gradeability 38 per cent. As an indicatir of the 141's ability in its d sign weight range, it has gradeability of 24 per ce when operating at just ov 60 tons!

The range of vee engines the Magirus Deutz tracti units are built on a modul principle similar to that us' by Daimler-Benz. Thus ti piston, rings and barrels the V8 F8L 413 for exam are identical to those used the 10-cylinder Fl OL 41 engine.

Both naturally aspiratE the eight cylinder versi produces 170kW (228bh. and 722Nm (530Ibft) torq with the corresponding f ures for the 10-cylinder u being 224kW (301bhp) a 920N m (6751bft) respectivel ZF provides the gearbox for both "Maggies&thou the specification is differe The 232D 16FFS uses a 1 speed splitter box while t nine-speed range-change b is preferred for the 311 19FFS,

The standard axle ratio with the splitter box is 6.4 to 1 which gives a gradeability of 18 per cent and a top road speed of 96km/h (60mph). With a ratio of 5.11, the top speed of the V10 is 103km/h (64mph) coupled to a gradeability of 32 per cent.

Last year Magirus announced two new models, the 256M19FS and 320M19FS. The bore of the modular design was increased from 120 to 125mm (4.72 to 4.92in). This resulted in an obvious increase in capacity which improved the power figures to 190 and 238kW (256 and 320 bhp) DIN respectively.

Long time Gardner users, Fodens have now dropped the 8LX13 from their range so as far as the tractive units are concerned the 6LXC is the only Gardner fitted. Fodens' own eight speed gearbox is fitted but the old worm drive axle has been replaced by a single-reduction Rockwell design with 4.875 to 1 ratio which gives a top speed of 98km/h (61 mph) and a gradeability of 19 per cent.

The 'Big Cam' Cummins is listed as one of the many possibilities for the Fleetmaster. Again a Rockwell axle is specified but with this engine the Foden gearbox is replaced by a nine-speed Fuller RT09509A. The low engine speed of the Cummins and the high 3.7 ratio of the Rockwell give an identical performance capability to the 6LXC version.

The 'L' versions of the RollsRoyce 265 and 290 engines are also coupled with the Fuller gearbox and the Rockwell axle. Thus the Foden gearbox is only used for the 6LXC Fleetmaster while the Foden worm axle is deleted.

Staunch advocates of turbocharging, Volvo has a choice of three basic engine varients for its F7, F10 and F12 chassis. The two Scandinavian constructors share many common features in design. Both fit fully synchromesh gearboxes of their own design, both make a great deal of use of forced induction and both manufacturers use a type number which denotes the cubic capacity of the engine eg the engine in the F7 has a capacity of 7 litres (427cuin).

Starting with the F7 this particular model is available with a choice of two power units, both of which are developments of the TD7OE engine used in the highly successful F86 range. Retaining the same basic design, the engine is available in two ratings, the TD7OG and the TD7OF with the major difference being that the latter is equipped with an air-to-air charge cooling system.

Net installed to BS Au 141a, the F version produces 162kW (217bhp) at 2,400rpm which compares with the 150kW (202bhp) of the TD70G. The maximum torque is 800 and 685Nm (590 and 505Ibft) respectively at 1,400rpm.

The F10 is also available with two engine alternatives.. The TD 100 A is rated at 171kW (230bhp) with the B version producing 207kW (278bhp) both at 2,200rpm from a capacity of 9.6 litres (856cuin). The major difference between the two ratings is the turbocharger boost which necessitates a lower compression ratio (12.5 against 15 to 1) for the higher rated TD 1008.

The biggest engine in the Volvo range — the 12 litre (732cuin) TD120C — powers the F12 which, like neighbour Scania's 141, is a luxury for 32 ton operation. Power is 243kW (326bhp) with a maximum torque of 1,320Nm (985Ibft) at 1,300 rpm. Eight and 16-speed versions of the Volvo synchromesh gearbox are available with steel synchro cones now being fitted to improve reliability.

Bedford is unique in this country in offering a truck powered by a two-stroke engine with the 'in-house Detroit Diesel. The TM3250 uses the 6V-71 while the heavier 3800 is fitted with the 8V-71 as standard. Incidentally the '71' refers to the capacity of each cylinder in cubic inches with the eightcylinder and six-cylinder variants having a 70 per cent parts commonality.

In the 32 ton TM 3250, the 6V-71 produces 160kW (220bhp) while the 8V-71 in the 3800 gives nearly 300 horsepower. Although both engines are pressure charged it is not by means of an exhaust driven turbocharger but by a positive displacement twin-lobe blower.

Although the 6V-71 is specified with a Fuller box, the 8V-71 is unusual in that it uses a 10-speed Spicer splitter box — the only truck in the UK at the moment to do so. With the 5.43 axle ratio, the TM3250 can achieve 93km/h (58mph) on the road with a gradeability of 20 per cent. In the axle field, the TM 3800 is also unique in its choice of the SoMA axle for use with the Detroit Diesel. Recently however Bedford announced another version of the TM3800 using a Cummins E290 engine which must use a Rockwell axle because of the lack of a suitable axle ratio in the SoMA. The 3250 TM uses a single-speed Eaton axle.

The drive line of the Ford Transcontinental is standard throughout the range as far as the component suppliers are concerned. Engines from Cummins, clutches from Spicer, gearboxes from Fuller and axles from Rockwell are featured to give a range of vehicles from 34 to 44 tonnes gross.

Since late last year, the complete range is now powered by the E versions of the Cummins 290, 350 and 370 variants. The HA 3424 has a derated version of the 290 which produces 179kW (240bhp) compared with the 201kW (270bhp) of the 'conventional' E290 in the HA 4427 With the top models of the Transconti chassis, the HA 4431 and 4434, the Cummins engines are both charge-cooled using an airto-water system with the highest powered version delivering 259kW (345bhp). All these power outputs are obtained from the same basic 14 litre (855cuin) six-cylinder engine.

The operator has the choice of both the nine and the 13 speed Fuller gearbox with a 3.7 or 4.11 axle ratio in the case of the HA3424 and 4.11 or 4.63 for the heavier versions.

The latest offering from Renault Trucks and Buses UK Ltd is the TR305. The power is,provided by a charge-cooled version of the turbocharged 12 litre (732cuin) six-cylinder used in its stable-mate the TR280. An air-to-air system is used which has resulted in a power output of 222kW (298bhp) at 1,900rpm with a maximum torque of 1,225Nm (925Ibft) at 1,300rpm.

In contrast to the 280 which uses a ZF gearbox, the latest 305 has a nine-speed Fuller as standard. A choice of four ratios is available for the 13 tonne hub reduction Berliet axle ranging from 6.83 to 5.12 so the operator can have a road speed of 87 to 116 km/h (54 to 72mph).

Modifications to the turbocharger of the 280 have permitted an increase in power from 180 to 198kW (242 to 266bhp).