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FF-THE-PEG TIPPER
Road test of Austin 7-ton Tipper reveals acceptable performance and good off-the-road traction but unsatisfactory braking characteristics and disappointing interior of an externally
stylish cab
By John F. Moon, A.M.I.R.T.E.
ALTHO.UGH its performance is acceptable, the engine well-proven and the chassis frame arid running units ' sufficiently robust for the job, the current Austin FF K140 7-ton tipper has two important design failings. One of these is the braking .system, which has been improved to some extent since my initial testing work showed it to be badly balanced. The other is the cab, which, in spite of an attractively curvaceous exterior, has an interior which is poor, even by present-day British standards.
Development History
The original Austin 7-ton chassis was introduced in July, 1955, as a " B.M.C.." and had a wheelbase of 12 ft.,
a 5.1-litre diesel engine, four-speed gearbox, two-speed axle and power-assisted steering as standard. In September of the following year this original model was joined by a 10-ft.-wheelbase version, a 13-ft. 4-in.-wheelbase chassis having been introduced earlier. The current 7-ton range, of which there is also a Morris equivalent, was put on the market in May, 1958. Mechanically very similar to the original models, chassis in the latest series have the present FF cab, single-speed axle and unassisted steering, wheelbase options being the same as before.
A further step in the history of B,M.C. 7,tonners was the announcement in September, 1960, that the shortwheelbase chassis could be obtained with a choice of tipping gears and bodies fitted as original factory equipment. Edbro and Telehoist assemblies are aVailable, the bodywork in both cases being of all-steel construction with a Capacity of 6 cu. yd. The Edbro body, as fitted to the vehicle tested, is operated by Edbro 2L.N. front-end ram • gear, whilst the Telehoist-bodied tipper has Telehoist S.L.7 underfloor-ram equipment. The Telehoist body has fixed sides, whilst the sides of the Edbro body are hinged and removable.
Clear 7-ton Payload.
When the standard 8.25.-20 (l2-ply) tyre equipment is fitted the recommended gross solopweight rating is 10.25 tons, but this can be increased to 11 tons gross—giving
a clear 7-ton payload—if the optional 9.00-20 (12-ply) Lyres are fitted. This size of tyre was on the test vehicle, as were also the optional E.N.V. five-speed constant-mesh • gearbox, Eaton 16500 two-speed rear axle (with which • helper springs are standard equipment) and Hydrosteer power-assisted steering.
Models in the current series of B.M.C. 7-tonners have
Girling hydraulic braking system boosted by a Clayton Bewandre Hydrovac 'suspended-.vacuum t.ervo, as opposed to the upright-vacuum servo of the original 1956 design. It is likely that the disappointing—even potentially dangerous—braking performance 1 experienced when I first tested this 7-ton tipper was due partly to the use of this type of servo, which, properly used, gives very good braking. But if the system is in any way poor the power of the servo tends to aggravate whatever fault is present. In the case of the Austin the fault has been—and still is, to a certain extent—incorrect balance
between the front and rear brakes. The short wheelbase can hardly be blamed for this.
Well Styled but Spartan So far as the latest cab is concerned, it is obvious that styling took precedence when this design vas developed. Externally, there is no doubt about it being nicely shaped, but the inside is very spartan. The rake of the rear panel is such as to make it easy for the driver to bump his head against the back of the cab when he sits back in his seat; the upper line of the windscreen interferes with the vision of tall drivers; the door-sill line is high; balanced-drop windows—which are difficult to operate—are used in the doors; diminutive exterior rear-view mirrors are still fitted (although larger mirrors are offered at extra cost); and, despite the shape of the facia-panel assembly and that of the box pressing above the windscreen being suitable, no glove lockers or cubbies are incorporated. Stowage is restricted to narrow, but deep pockets in the cab sides immediately ahead of the doors, plus an area under the passenger seat.
• Furthermore, the interior width at seat-cushion height is little more than 6 ft., so the cab cannot be called roomy by any stretch of imagination. There are other irritating points about the design, such as the four riveted clips
recently added to stop the windscreen falling out when travelling over rough surfaces, but which also make a windscreen change complicated. Admittedly, the driving seat is adjustable, both vertically and longitudinally, but even the range of adjustment available makes it difficult to compensate for the relative positions of the pedals, the steering wheel and the windscreen.
When I tested this tipper originally, earlier in the year, I complained about the fact that the cab doors would not open through more than 40'. This complaint has been attended to by repositioning the cheek straps, and the doors now open through nearly 750. This makes access to the seats decidedly easier, although the high sill line is still a disadvantage.
At the start of the first test at Longbridge I found the tipper had been loaded with 5 cu. yd. of coarse gravel and sand, and in this condition its gross weight was 10 tons 18.5 cwt. It was a cold day, but the roads were dry, so I decided to carry out braking tests first.
It was immediately obvious that the front brakes were hardly doing any work at all, whilst excessive rear-wheel locking showed there was far too much power at the rear brakes. Although the roads were dry, 1 had to apply a n8 certain amount of steering correction when sliding to a stop, and I dread to think how the vehicle would have reacted had the same manceuvres been carried out on a wet road.
The braking performance was obviously below par, and as a result of my comments "first-aid" measures to improve the braking system were taken. The size of the front wheel cylinders was increased from 1.375 in. to 1.5 in. to give a higher proportion of the overall braking effort to the front brakes. Wider-angle wedges at the rear brakes were tried 15° instead of 13°-hut this move did not have the desired effect. However, treating this change to the front brakes purely as an interim measure, I agreed to carry out further braking tests, having first been assured that production vehicles would in future incorporate the larger front-brake cylinders.
The modification effected an improvement so far as braking from 30 m.p.h. was concerned, the average stopping distance from this speed with the new system being reduced to 63.5 ft. from 74 ft., while the Tapley-meter average was slightly higher at 66.5 per cent. instead of 64 per cent. Rear-wheel locking was reduced also-from 60 ft. to an average figure of 46.5 ft.--but the vehicle still pulled viciously to the right, and after one stop I finished up with the 7-tonner on full left lock.
The changed system had the unaccountable effect of increasing the stopping distance from 20 m.p.h.: the final figure from this speed was 29.5 ft. instead of 26.75 ft. and the Tapley-meter average the same as from 30 m.p.h.66.5 per cent. (it had been 77 per cent. on the first test). Similarly—although nothing had been done to the rear brakes other than to fit a new set of the standard Ferodo DM8 linings, the handbrake performance was slightly reduced, an average figure of 41 per cent. resulting, compared with 46 per cent., whilst the rear-wheel sliding distance had been increased to over 45 ft., having previously been 30 ft.
Following the original series of braking tests, 1 conducted a short fuel-consumption test over a hilly, six-mile circuit of A44I between Alvechurch and West Heath. The severity of this course was such that third-low had to he used when ascending on of the hills, and again when turning round at the half-way point. I was not too surprised, therefore,..at the resulting rather heavy fuel consumption rate of 13.2 m.p.g., particularly in view of the comparatively high average speed of 27.7 m.p.h. which was achieved without at any time exceeding 33 m.p.h.
I then drove the tipper south to Broadway for hiltperformance tests on the 1.25-mile-long Fish Hill. This is quite a severe climb, with an average gradient of 1 in 14.2 and several sections of 1 in 10.5. The run out to Broadway was made at a brisk pace, and although I experienced some difficulty changing gear because the gearchange action was stiff (this eased off. later) and the lever too far behind and to the left of the driver, I found the vehicle handled quite well, the power-assisted steering making it tempting to corner quickly and the suspension— which was undamped—giving a firm but smooth ride.
The climb up Fish Hill was made in an ambient temperature of 5=C. (41'F.). and before making the ascent the engine-coolant temperature was found to be 76"C. (169"F.). The Austin driver took the 7-tonner up the hill in fine style, and at no time did the road speed -drop below 10 m.p.h., the lowest ratio combination employed being third-low, which was engaged for 5 minutes 30 seconds out of a total climbing time of 6 minutes 54 seconds.
It was obvious that the engine was getting fairly hot during this ascent, because the well-insulated engine cowl —which normally kept most of the heat and noise out of the cab—was getting pretty hot on the passenger .(exhaust-manifold) side, and when I took the filler. cap off the radiator at the top of the hill copious quantities of coolant gushed out. :By the time I could insert my thermometer the coolant .temperature had dropped to 82C. (181.5'1.). which suggests that operation in air temperatures of 32C. (90'F.) and -above might produce cooling
system boiling if a lot of hill work is involved. .
Fish Hill was then descended in neutral, while I kept the footbrake applied in order to restrict the speed to 20 m.p.h. The descent lasted four minutes, and by the time I neared the bottom of the hill I was having to exert aboveaverage effort on the pedal. At the bottom I gave the brakes all I'd got, and managed to produce a Tapleymeter reading of 37 per cent., showing efficiency, to have been halved by this rather severe fade test (this was with the original braking system, bear in mind). There was some increase in pedal travel, and slight smoking from the rear brakes, but there was no obvious signs of the front brakes having got very hot. On this occasion the rear wheels did not lock.
Next I drove the tipper back up the hill and stopped it on one of the I-in-10.5 sections. The brakes had cooled down by this time, and I was able to hold the tipper quite easily on the handbrake, following which several smooth second-high restarts were made. From this gradientrestart performance it is obvious that, with this two-speed axle, restarts on slopes more severe than 1 in 4 will be perfectly possible. Even allowing for the fact that the five-speed gearbox currently being offered in this vehicle
• has a higher bottom gear-6.923 to 1 compared with 7.41 to 1 (a change effected to avoid overloading the standard rear axle when the more powerful 5.7-litre diesel engine is installed)—gradients of at least 1 in 4 should still be a reasonable proposition for restarts.
Acceleration tests were carried out on a level piece of road near the top of Fish Hill. The high axle ratio was engaged throughout the standing-start tests, for which second, third and fourth gears were employed. Low ratio was used for the direct-drive runs. The figures obtained are good for a standard vehicle running at this weight, and the engine and transmission were quite smooth during the direct-drive tests. The maximum speed of the vehicle was found to be approximately 50 m.p.h.—which to my mind is quite fast enough with the present braking system Maximum Traction
The tipper was then taken into a disused quarry to obtain a guide as to its rough-country performance. It was able to negotiate short, but severe, rock-strewn slopes with ease, and the suspension and frame flexibility ensured maximum traction at the rear wheels and maximum directional control at the fronts. Unfortunately, the spare-wheel is stowed horizontally beneath the frame, immediately behind the cab, and the ground clearance beneath the carrier is not good. As a result the carrier got knocked out of shape
after it had clouted a not-very-big rock.
I tooksome more fuel consumption figures on the way
back to Longbridge, tisjng a fairly level ten-mile stretch of road between Broadway and Bidford. This relatively easy route was completed at an average speed of 30 m.p.h. without driving at above 35 m.p.h., and 5.15 pints of fuel were required to top-up the test-tank, showing the consumption rate to have been 15.5 m.p.g.—better than the earlier figure. but still rather heavy for a 1962 7-tonner.
The standard Austin FF K140 7-ton tipper chassis-cab. with four-speed gearbox, single-speed axle and unassisted steering costs £1,182, and the standard tipper, with similar mechanical specification and either Edbro or Telehoist 6
cu.-yd. body and ram, is listed at £1,427. Extras fitted to the test vehicle are priced as follows: five-speed gearbox, £60; Eaton 16500 two-sped axle. £168; steering servo, £33.5s.-. 9.00-20 (12-ply) tyres, £34 2s. 6d.: and flashing direction indicators, £8. The 5.7-litre diesel engine, which produces 105 bh.p. at 2,400 r.p.m. and 255 lb.ft. torque .at 1,750 r.p.m., is available at an additional, cost . of a mere £10 providing the five-speed gearbox is specified also.