AT THE HEART OF THE ROAD TRANSPORT INDUSTRY.

Call our Sales Team on 0208 912 2120

all-engined ehicle

22nd November 1963
Page 51
Page 50
Page 52
Page 55
Page 51, 22nd November 1963 — all-engined ehicle
Close
Noticed an error?
If you've noticed an error in this article please click here to report it so we can fix it.

Which of the following most accurately describes the problem?

18-ton-gross articulated outfit DESP1TE all that has been said in this and other journals for a number of years regarding the overall economies to be gained from the use of big, hightorque engines in heavy goods vehicles, there are still operators in 13ritain who prefer to buy low-powered machines at a low initial cost. They obviously do so with the intention of using them for a comparatively short period, and certainly before repair bills become too frightening. As this market undoubtedly exists, manufacturers have some justification for offering vehicles of this type; hence the introduction in 1961 by the British Motor Corporation of Austin and Morris 18-ton-gross tractive units powered by 5-7-litre diesel engines developing only 105 b.h.p. and 255 lb.-ft. torque.

In fairly flat parts of the country, such as East Anglia, this type of vehicle could be used with a certain degree of success. Long-distance running, with the majority of mileage over favourably graded motorways, might also provide a reason for using a vehicle of this type, always assuming that high average speed was not an important requirement. But in normal haulage conditions it is inevitable that the small engine of this design gives a sluggish performance and high fuel consumption, and must make heavy demands on the driver.

This would be the situation with the tractive unit operating at its rated gross train weight of 18 tons. If the vehicle were overloaded the driver might well find himself in trouble. A guide to the capabilities of this vehicle at 18 tons is given by looking at the fuelconsumption and acceleration-performance figures reproduced in the data panel of this test report. The best fuel figure that could be obtained was a rate of 9-3 m.p.g. under full-throttle conditions over the almost-level stretch of /V between Birmingham and Droitwich, this having be obtained at an average speed of 31-5 m.p.h. Over a stretch of undulating main road the consumptic rate increased to 8-0 m.p.g. for an average speed 1 22-8 m.p.h. This run, also, was made under almc continuous full-throttle conditions.

So far as acceleration is concerned, the unit to 82 seconds to reach 30 m.p.h. from a standstill. It was n possible to find a long enough stretch of flat road on whil a true indication of the vehicle's direct-drive accelerati( performance in low axle ratio between 10 and 30 m.p. could be measured. 1 was unable to record these figurc therefore, and the Austin engineers who were with me to me that they had not succeeded on the M.I.R.A. test tral either. • I repeat, though, that operation in really lel4 country and without an overload might be an economic proposition. With time no object, consumption rates 10 m.p.g, or so could even be obtainable with the right ty of driver. On general performance, however, this tracti unit is outclassed. All this was particularly disappointing for me in view )f the very favourable performance of the last Austin ;oods vehicle that I tested, this being the FH-series under:ab-engined 7-tonner (July 5 last), which proved that the 3.M.C. are well aware of the need to provide a high 3ower-to-weight ratio and good driving conditions in modern haulage vehicles.

The B.M.C. FF K360 prime mover was the first vehicle .o go into production with the B.M.C. 5-7-litre diesel .ngine, this basically being a bored-out version of the 51-litre unit which has proved highly successful since its ntroduction in 1955. This larger engine has many mechanical features in common with the original smaller mit although one obvious difference is that, whereas the 5.1-litre engine has a C.A.V. distributor-type fuel-injection pump, the 5-7-litre unit has a Simms in-line pump with pneumatic governor. The external dimensions of the two !ngines are the same and they are interchangeable in various chassis, although (needless to say) the smaller power unit is not available in the 18-ton tractive unit.

In terms of running components, the FF K360 tractive anit has much in common with the FF K340 17-ton-gross unit, both of which have the 5-7-litre diesel as standard, driving through a 13-in, clutch and an E.N.V.-designed five-speed constant-mesh direct-top gearbox and single propeller shafts into an Eaton two-speed driving axle. At this stage the basic specification similarities end for, whereas the 17-ton unit has an axle with ratios of 5.57 and 7-73 to 1, with vacuum-operated shift, the 18-ton model has an electric-shift axle With ratios of 6.14 and 8.54 to 1. There is no single-speed-axle alternative.

Both tractive units have 0.25-in.-thick chassis-frame side members, but those on the lighter vehicle are only 7.625 in. deep, whereas the FF K360 has 9.125-in.-deep members. Because the 1(340 is designed for use with automatic coupling gear, it has one less cross-member than the fifthwheel-type K360. There are suspension differences between the two models also: both have 2.25-in.-wide front springs and 2.5-in.-wide rear springs, but in the case of the lighter model these are 40 in. and 45 in. long respectively, whilst the 18-ton design has 45-in. front springs and 51-in. rear springs assisted by 2-5-in. by 35-in, helper springs. Further more. dampers are optional at the front of the 17-ton vehicle and are not available at the rear of this chassis, whilst the 18-tonner has them as standard at the front with the option, at extra cost, of having them at the rear also. The braking systems of the two vehicles are similar, both having Girling equipment with Clayton Dewandre Hydrovac suspended-vacuum servos. In both cases the rear brakes are 15.25-in. by 5-in, leading-and-trailing-shoe units, but the heaviet model has 16-in. by 3-in, two-leadingshoe front brakes. These are 0.5 in. wider than the front brakes of the 17-ton vehicle and give an additional frictional area of 30 sq. in. Another slight chassisspecification difference is that, although both models have the same type of steering gear, the lighter machine's equipment has a ratio of 20 to 1 whilst the heavier model has 23-5-to-1 gear, giving five turns from lock to lock. The standard tyres on the 18-ton chassis are 8.25-20 (14-ply) but, for an extra £23 2s. 6d., 9.00-20 (12-ply) tyres can be supplied although these do not increase the design gross-weight rating of the vehicle. The standard electrical system is 12V, with two 144 a.h. batteries mounted immediately behind the cab. A 26-gal. fuel tank is standard. The quoted list price of £1,425 includes the FF-type all-steel cab, which contains a single seat on each side of the rather wide engine cowl.

My tests were carried out in conjunction with a Brockhouse 12-ton straight-frame semi-trailer (type KS 1282) with 26-ft. platform body and an unladen weight of 2 tons 12.75 cwt. This appeared to be a very well-built assembly, with a robust all-welded frame and 3-75-in.square solid axle beam incorporating eight-stud hubs and Girling 15-25-in. by 5-0-in, two-leading-shoe brakes. These are actuated through a single-line upright-vacuum system by a Clayton Dewandre S1/687 servo motor, and rod linkage, the servo being mounted within 8 ft. of the front of the semi-trailer in order to keep the length of the vacuum lines down to a minimum and so help to reduce system delay. This Brockhouse design has 3-in.-wide semi-elliptic springs, the eyes and hanger-brackets being fitted with plastics-impregnated bushes to eliminate the need for greasing. Davies Magnet light-alloy single-speed verticalscrew landing gear is standard, the semi-trailer supplied for test having flexibly mounted pressure pads, although wheels are optional. This semi-trailer has a maximum width over the mudwings of 7 ft. 5.5 in., and has 9.00-20 (12-ply) tyres as standard. As optional to the 9-in. by 3-5-in, hot-rolled channel-section main members, pressedsteel members can he used.

The total unladen weight of the Austin tractive unit with semi-trailer was 6 tons 1-25 cwt. and the test load totalled 12 tons 0-5 cwt. With an Austin engineer, myself and the test equipment in the cab, the gross train weight for the test was 18-25 tons---5 cwt. above the makers' recommended figure. The weight distribution was quite good, with the semi-trailer axle carrying only 8 cwt. more than the driving axle. The front-axle loading was low, however,

B 1 8

partly because the coupling centre line was only 6 in. ahea( of the driving-axle centre line

Braking tests were carried out first, while the roads wen dry, and although satisfactory retardations were recordec from 20 m.p.h., the outfit showed signs of instability whet full-pressure stops were made from 30 m.p.h. and excessiv, driving-wheel locking spoilt the results. At the same time, certain amount of braking unbalance caused the tractivt unit to pitch violently. Because of the pitching when making all these stops, :h Tapley-meter readings were produced, the average•.ding from 20 m.p.h. being 81 per cent, whilst that from m.p.h. was 73.5 per cent. The semi-trailer brakes aeared to be 'correctly balanced, as the wheels were ving marks' on the road without locking, but a certain iount of system delay was evident when making stops rn 20 m.p.h. while using only the hand-reaction valve the cab. However, the maximum retardation so )(bleed was good, at 26-5 per cent.

Due to the over-braking on the driving axle, good ctive-unit handbrake figures were obtained from the ne speed, the average maximum figure being 33.5 per at. Hard application of the lever lett 50-ft. skid marks.

In view of the low power-to-weight ratio, I took my first ,I-consumption figures along a fairly flat 20-mile course tween Bidford and Broadway, the only climbs on this ute being of a very minor nature. By driving at up to m.p.h. wherever possible, an average speed of 26-4 m.p.h. is returned for the round trip. The fuel-consumption te was disappointing at 9.1 m.p.g., although the figure ts not surprising in view of the substantial amount of iirect-gear working necessary during the run.

A second main-road test was subsequently carried out er the short undulating course near the Longbridge etory which is normally used for Austin tests. Wherever Issible the outfit was driven at 40 m.p.h., but the average eed for this run was only 22.8 m.p.h., top gear (with :her high or low ratio engaged) having been used for only per cent of the total running time.

This being so, it was not surprising that the consumption te was as heavy as 8-0 m.p.g., and to give an indication of at this engine can do over the same course. the July test the FH 7-tonner produced figures of 12-1 m.p.g. at -5 m.p.h. average speed, and 14.3 m.p.g. at 29.0 m.p.h. rerage speed when cruising at 40 and 30 m.p.h. spectively.

The stretch of M5 used for the "high-speed test sembles a billiards table compared with earlier motor ays. such as the Preston By-pass and the London rmingham MI. Despite this, the road speed dropped to !low 15 m.p.h. on more than one occasion and the aximum speed that could be obtained when heading

n-th was 40 m.p.h., although 49 m.p.h. was recorded on e speedometer once on a slight downgrade when heading

wards Droitwich. Out of a total running time on the otorway of 29 minutes, only 18-5 minutes were spent in p-high. This, again, meant that the fuel-consumption Lte was heavy for a vehicle carrying a 12-ton payload.

However, this is one of the more obvious penalties of iing too small a power unit. Another serious disadvart

ge which is not always considered is that, even under the iost favourable conditions, the engine is always being .orked hard, so its rate of wear must be high also.

The standing-start acceleration times up to 30 m p.h. :corded in the data panel were obtained by split shifting rid are the average results of numerous runs made over long level stretch of road. This same piece of road was sed while •attempting the top-low acceleration runs etween 10 and 30 m.p.h. but, as already mentioned, these Ltempts failed because of lack of road after 84 seconds had een spent without reaching 20 m.p.h. from 10 m.p.h.

At the same time, checks were made of the individual ear speeds and these showed that several of the ratio Dmbinations were so close as to virtually be the same, icluding second-high and third-low, third-high and fourth)w, and fourth-high and fifth-low. Thus, instead of aving 10 distinct gear ratios to help him on his way. the river of this vehicle has only seven effective ratio steps 3 play with. This leads me to believe that a change in the earing of this chassis might improve the overall erfonnance and economy.

Fish Hill, Broadway, was used for the gradienterformance tests, this climb being 1.25-mile long with an verage severity of I in 14.2. During the climb the mbient temperature was 20°C. (68°F.),and the engineoolant temperature before the ascent was 70°C. (153°F.).

The climb took a long time-13-5 minutes—and caused the coolant temperature to shoot up to 88'C. (191°F.). The lowest ratio combination employed was bottom-high; this was in use for 7 minutes, during Which time the speed was approximately 5 m.p.h. Second-low was used for a total time of 5 minutes and slight exhaust smoking was observed during this test.

Because of the low power-to-weight ratio, the engine was working extremely hard during this ascent, as evidenced by the rise in coolant temperature and the fact that the engine cowl on the exhaust-manifold side got so hot that it could not comfortably be touched. The slight exhaust smoking noticed seems to be an unfortunate characteristic of this 5-7-litre engine, for exhaust smoke was a fault with the FH 7-tonner tested in July.

A brake-fade resistance test was made by coasting the outfit down Fish Hill in neutral, using only the footbrake to keep the speed down to below 20 m.p.h. This test lasted approximately 4.25 minutes, and at the bottom of the hill a Tapley-meter reading of 33 per cent was obtained from 20 m.p.h., showing that the maximum efficiency had dropped by 0-48g whilst the pedal travel had increased by over 2 in.

Further gradient-performance tests were made on a short 1-in-7 slope inside the grounds of the Austin factory. Facing up this gradient, a bottom-low restart was made with some power in hand, although the engine stalled when this test was attempted in bottom-high. Facing down the hill. reverse-low proved adequate for a restart, although the engine again stalled when reverse-high was attempted.

Both facing up and down the hill, the tractive-unit handbrake and the semi-trailer vacuum brakes proved powerful enough to hold the outfit by themselves. Facing down the hill, the semi-trailer parking brake also was enough to prevent forward movement although, when facing uphill, this parking brake was only just powerful enough. This Austin model is not among the most pleasant I have driven, the main troubles being the noise of the engine, the need for almost continuous use of the gearbox ane' axle changes, and the very uncomfortable build-up of heat inside the cab resulting from the excessive engine tempera ture and the poor ventilation. Despite its need for frequent use, the gear lever is not positioned to the best advantage. It is too high and rather too far back relative to the driving seat. So far as cruising speeds are concerned, on a gently undulating road it is possible to get up to over 30 m.p.h.; but at this speed the slightest up-grade makes use of the lower box ratios necessary.

Because of its short wheelbase, the tractive unit pitches a fair amount on all but the smoothest of roads but generally the suspension is not too bad for this length of vehicle. The steering is usually satisfactory on smooth roads, with a good castor action, but road undulations do cause a certain amount of reaction at the steering wheel.

Forward visibility is reasonable, but the standard mirrors are on the small side for an articulated vehicle; it is not easy to see both sides of the semi-trailer, which would make reversina tricky with a high-sided semi-trailer. So far as the cab itself is concerned. I have commented unfavourably on previous occasions about its design, from the driver's angle, so will say no more beyond recording my view that the position has not improved.


comments powered by Disqus