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Thornycroft Sturdy Oiler Averages 21.08 m.p.g.

9th November 1945
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Page 37, 9th November 1945 — Thornycroft Sturdy Oiler Averages 21.08 m.p.g.
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Indirect-injection Six -cylindered Oil Engine Gives Excellent All-round Performance. Severe Weather Conditions Make Two-stage Trial Necessary

ONE of the most popular machines in the range of Thornycroft commercial vehicles is the Sturdy 5-6tonner, which, hitherto, has been available only with a petrol engine. As such it continues to give an excellent performance, and undoubtedly lives up to its name in respect of its ability to stand up to the most arduous operating conditions.

That prospective purchasers of Sturdy chassis are now being offered an alternative in power units in the new Thornycroft TR6 oil engine is of more than usual interest, in that the vehicle is the only one in its class at present offered as an oiler having an engine built by the vehicle maker.

Before dealing with the performance of the Sturdy oiler on the road, here is a brief description of the power unit, together with the general features of the chassis, which are similar to the petrolengined chassis specification.

The engine has six cylinders with a bore of 90.49 mm. and a stroke of 104.8 mm., dimensions which give a piston-swept volume of 4.042 litres. Rated at 30.6 h.p., it has a maximum output of 67 b.h.p. at 2,200 r.p.m., and produces a torque of 168 lb.-ft. at 1,300 r.p.m.

Cast in one with the top half of the crankcase, the cylinder block is provided with flangeless dry liners. There is a one-piece detachable cylinder head, and alloy pistons, overhead valves and inserted exhaust-valve seats.

Valve operation is from a single high-mounted camshaft and short pushrods and rockers. There are seven steelbacked, white-metal-lined bearings to support the Crankshaft, and the big-ends of the connecting rods have lead-bronzelined steel shells for the top half and white-metal-lined shells for the lower half of the cap.

A "drowned" gear-type pump is responsible for circulating the oil direct to the main and connecting-rod bearings and overhead-valve gear. The oil returning from the valve gear maintains a level in the camshaft tunnel, the cams dipping into the oil to provide efficient lubrication of the camshaft bearings and tappets. Overflow from the oil relief valve serves to lubricate the drives in the front chain case.

The C.A.V. fuel injection pump is chain-driven from the crankshaft, there being a pneumatic-type governor controlling maximum and idling speeds,. It is an indirect-injection unit, there being a switch-controlled heater plug for starting.

So far as the rest of the chassis components are concerned, these are characterized by their robust nature, the specification being identical with that of the Sturdy petrol-engined vehiclt. A single-dry-plate clutch, four-speed and reverse gearbox, two-piece propeller shaft and worm-driven rear axle comprise the transmission line, the machine being suspended on 2i-in. wide semielliptic springs measuring 3 ft. 4 ins, in front and 4 ft. 2 ins, at the rear, The Girling brakes are hydraulically controlled on the Lockheed principle, and the steering mechanism is of the cam and roller type.

Having in mind the fine performance of the Thornycroft Sturdy with petrol engine, the road test of this oiler was looked forward to with more than usual interest. It was somewhat unfortunate, therefore, that the day chosen turned out to be quite the worst we have ever experienced on any road test. For the most part the wind was blowing at gale force, and this was accompanied by repeated doses of monsoon-like rain storms.

However, we set out to do the hillclimbing first; the gradient being Farleigh Hill, which has an average up-grade of 1 in 27, with a maximum of 1 in 8.4. The observed distance was 1.4 miles, which, from a 'standing start, was covered in 5 mins. 36 secs., giving an average speed of 15 m.p.h. There was no doubt about the manner in which the machine climbed, and even had the gradient been twice as severe the engine would, undoubtedly, have made a strong climb.

The order of changing gear was from top to third at 21 m.p.h., from third to second at 12 m.p.h., and from second to first at 6 m.p.h. Atmospheric temperature was 59 degrees F., and, at starting, the cooling water showed 162 degrees F., which rose 12 degrees F. on the climb.

Rain-sodden roads strewn with leaves are not ideal for testing the stopping power of brakes, but, nevertheless, the figures obtained from 20 m.p.h. were excellent, out and home showing 21 ft. and 23 ft. respectively.

Owing to the extent of the military and other traffic, and the worsening weather, a decision was made at this point to complete the test at a later date, and this was doge a week later.

The first part of the test was carried out in the Basingstoke area, and the second on the Great West Road, starting with fuel consumption. Travelling towards Slough with a full tank we covered 11 miles, which brought us just beyond the town. One change down was made, and we were held up by traffic lights on two occasions. The average speed worked out at 25.7 m.p.h., and the fuel consumed was 500 c.c. less than 5 pints, giving a figure of 21.36 m.p.g.

On the " home " trip we averaged 24.3 m.p.h., and the fuel consumed gave a figure of 20.8 m.p.g., thus returning the excellent average of 21.08 m.p.g. The conditions were ideal, and the average speeds obtained will indicate that we experienced practically an Unimpeded run in each direction.

For the continuation of the braking tests we selected a quiet stretch of road, running off the Great West Road, with a dry macadam surface. From 30 m.p.h. the vehicle came to rest in a distance of 52 ft. in one direction and 53 ft. in the other. The brakes are smooth in action, and we found them to be beynnd criticism in all respects.

Using the same stretch of road we obtained the following figures for acceleration:—From 0 to 30 m.p.h., through the gears, 41* secs. and 54 secs., and from 10 to 30 m.p.h., 332sees. and 50 secs.

Now a word as to the vehicle in general. Being a forward-control machine, the engine cowling comes inside the cab to leave a "well "for the driver.

The engine starts up instantly, even from "all cold." As previously mentioned, there is a heater plug to assist in this direction, and, following its use, a push on the starter button results in an immediate response from the unit.

Whilst the characteristic oil engine " knock " is no greater than is normal in a forward-control cab, it is the only feature of this fine machine, which, if we were being super-critical, we would single out for comment.

As the gear lever is• attached direct to the gearbox, it comes at the back of the cab, being slightly to the rear of the driver. The cab is roomy, and visibility is excellent. During the whole of the test the compartment remained quite free of fumes, and proved itself to be watertight under exceptional conditions.

For a vehicle of its type we found it to possess excellent manteuvrability, and it passed over all types of road surface as a well-sprung machine should. It is our opinion that it is a vehicle destined to attain even greater popularity than has the petrol-engined Sturdy.

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Locations: Slough

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