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L. J. COTTON, M .I.R.T.E.
Powered by a 90 b.h.p. Engine, the Chevrolet 10cwt. Van Has Rapid Acceleration, High Maximum Speed and a Braking System Designed for 100 Per Cent.
I.IKE the light vans,produced in .,this country, the Chevrolet ' '10-cwt. model is based on the contemporary American car. chassis. There is, however, a vast difference b,-+---en the British and American products, in that the power unit appears out of proportion when compared with the modest-sized home-produced engine. It develops 90 b.h.p. at 3,000 r.p.m., has a 31-in. bore, 3i-in. stroke, and a capacity of
3.55 litres ...
Many interesting comparisons can be made between the cOnstruction of this six-cylindered power unit and modern British design. The singlepiece cylinder block and crankcase have full-length water jacketing and the drop-forged crankshaft is retained by four steel backed babbitt-lined shell bearings. A harmonic damper of the rubber-tometal-bonded pattern is attached to the front of the.. camshaft. Babbitt metal is also used for the big-end bearings.
Cast-iron pistons, of slipper-skirt pattern, each have two compression rings and one oil-control ring, all the rings being above the gudgeon pin. In the lubricating system, the connecting-rod big-end bearings are dipper-fed at low speed and jets of oil, from offshoots of the, gallery pipe, are directed into the scoops at higher, revolutions.
This system ensures an ample splash feed to the cylinder malls and small-end bearings. The overhead rocker gear . is lubricated, from a metered pressure supply, whilst the main .. hearings . are fed by full . . . .
pressure .. .. .
. Arrangements are made in the water passageways' of the one-piece cast-iron cylinder head for nozzle-jet
cooting -of -the. valves. The centrifilial 'water NMI), is belt driyeA:i,,., ' The single-plate clutch, of .7.1i sq. ins, frictional area, has an asbestoscomposition' facing. Co' mbined: to form a unit, the engine; eititch. and: gearbox are retained in the.,, chassis: • by a four-point rubber mounting. In the gearbox, all the gears . arc; machined with helical teeth. and synchronizing arrangements are: incorporated in the two higher ratios.
The drive between the gearbox and axle is taken through an open propeller shaft with mechanical universal joints and a hypoid final
drive unit in the semi-floating rearaxle assembly. The final-drive ratio of 4.11 to l affords a maximum speed of over 70 m.p.h. A twopinion differential is employed in the final drive.
The .brakes are applied through hydraulic means and the selfenergizing shoes have facings of exceptionally large surface area. The area is such that with full load the ratio, is in the order of 75 sq. ins per ton. Other features of the chassis include reei rcurato ryball steeri and threaded spring shackles.
The all -metal body is open to the driving compartment and the two doors at' the rear are shaped to conform with the curve of the body. Although greater, in overall length than home models, it has a payload space of only 150 cubic ft. The bonnet, and fairing account for a good proportion of the overall length.
1 collected the van from the General Motors • works, Southampton. The payload, comprising a number of road springs, was placed forward in the body to prevent it sliding during the brake tests. The rapid acceleration from rest made me wonder whether they should not have been"secured to the floor. For a goods mode!, the acceleration was remarkable, and on tarmacadam it produced wheelspin.
After leaving Southampton Docks I drove towards Winchester in search of a site to check acceleration and_ braking, a suitable stretch being located between Eastleigh and Otterbourne. The liveliness of the power-unit, together with the
swift and easy changes made by means of the steering-column gear. selector, encouraged me to exploit the flexibility of the van.
Although low gear produced a smoother .result, it could be driven away from rest .emPloying the intermediate gear without harm to the transmission.
Second gear proved useful for rapid acceleration to 44 m.p.h., and trials from rest were made with a
brief period in low gear, followed by a quick change to the next ratio, which was held until 40 m.p.h. was reached. With the large-capacity power unit and -.well-timed gear changes, there was no difference in results in either. direction.
From rest, 20 m.p.h.. was reached
in 3 secs., 30 m.p.h. in 6.2 secs. and 40 m.p.h. in 10.2 secs. Topgear trials gave similarly outstanding results, from 10 m.p.h. to 20 m.p.h. taking 4 secs., to 30 m.p.h. 8.6 secs. and to 40 m.p.h. 14.4 secs. It was obvious that the Chevrolet had ample power to spare.
The load had by this time moved towards the rear doors, and the first braking test brought the springs smartly forward to
collide with the rear of the driver's seat. Emergency application of the brakes locked the rear wheels, but an even retardation without skidding was attained by slightly less energetic use.
After a series of trials the latter method proved to give the best results, and no matter whether the brakes were applied at 20, 30 or 40 m.p.h., consistent performance, equal to 100 per cent. efficiency, was obtained.
At the end of these tests I drove towards Meon stoke, through Bishop's Waltham. A second-class road in poor state of repair between the two villages demonstrated the suspension to be equal to the occa sion: In fact, the springs, shock
absorbers and steering were all severely tested during this part of the course, and remarkably little •road shock was transmitted to the steering or body Rejoining the A.32, road at Meortstoke,. I drove to Privet.f and turned towards Petersfield. Soon after leaving Petersfield the County border Was crossed, and I was heading for South Harting, in West Sussex, to climb the mile gradient, which has an average incline of 1 in 12.
. There were several sharp sections, one of which was recorded on the Tapley meter as I. in 7. This was no obstacle, and the major part of the ascent was made in top gear, with brief lapses into the intermediate ratio
Nearing the summit, I found that the rough-surface car-trials hill was still negotiable, so the van was driven to the foot of the hill in preparation few a more difficult climb. This hill called fol more technique to turn the sharp corners at any speed above 15 m.p.h. hut once again the Chevrolet made light work of the hill Although the running tempera ture of the radiator was 150 degrees F andthe day temperature 53 degrees F., there was a mere 3-degree rise in the water temperature during the climbs.
Descending South Harting Hill at 35 m.p.h., the rear of the van tended
to wander when cornering This happened again on .a straight stretch between Peterstield and Horndean, when I was endeavouring to reach the maximum speed Up to 60 m.p.h the Chevrolet was perfectly behaved, but at 65 m.p.h. the rear began to wander, and at 68 m.p.h. I gave up the. attempt. Normally, the van driver would not experience this deviation from a straight course.
21.8 m.p.g. at 30 m.p.h.
Having been driven more than 50 miles, the van was sufficiently warmed up for the consumption trials. • An initial run was made, starting from rest, and running con-tinuously fot 10 miles-at a maximum speed of 30 rn.p.h This produced a consumption equivalent to 2L8 m.p.g.
A second test, over the same out and-return course, with four 15-see. halts to every mile, inireased the consumption rate to 14.3 mpg This run was made at an average speed of 26 m.p.h
Driving at a steady speed through Portsmouth, and returning to Southampton, 1 was able to observe the easy handling and other fine details of the Chevrolet The cab is well planned for easy access, and the steep slope of the bonnet, together with the large windscreen, affords good visibility
Aftei driving to Southampton in a vehicle in which theinstrument panel was obscured from view by the hub and spokes of the steering wheel, I appreciated the three-spoke flat-top hub of the Chevrolet wheel, which gives a view of the entire panel
A check on the Southampton weighbridge showed the rear axle to be carrying 11 tons, whereas the rated capacity of each tyre is 91 cwt.
I returned the van after having completed almost "100 mites during the day. -Although.one of the longest, it was also the fastest trial I have vet conducted.