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A NIMBLE 36-SEATER

30th August 1963, Page 60
30th August 1963
Page 60
Page 61
Page 62
Page 65
Page 60, 30th August 1963 — A NIMBLE 36-SEATER
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ROAD TEST: Seddon Pennine 3 36-seat single-decker bus ALTHOUGH big buses are often attractive as a means of spreading operating costs over large numbers of passengers, they are not ideal for all operating conditions. The increases in length of single-deckers permissible for use in Britain from 27 ft. 6 in. to 30 ft. in 1950, and to 36 ft. in 1961, have drastically reduced the number of medium-sized models produced in this country. They are still the most suitable choice for some conditions, both abroad and on the home market, however, and there must be many operators who would find good use for a bus seating 35 or 36 which has something of the heavy-duty character normally associated with larger models and yet is sufficiently light to make useful savings in running expenses.

The Seddon Pennine 3 seems to be just such a bus. Shorter (just over 26 ft. long), and lighter than the 30-ft.-long Pennine Mk. 19, it employs an inclined version of the Perkins 6.354 5.8-litre engine and a Rootes fourspeed synchromesh gearbox in place of the A.E.C. AH410 6-75-litre engine and five-speed gearbox of the longer model. A front-mounted radiator is used, despite the amidships-underfloor engine position, and the chassis layout differs slightly in several other respects, but much of the larger model's general character remains. The frame side-members are actually -11g in. thicker than those of the Mk. 19 model, of which a road test report appeared in The Commercial Motor, August 22, 1958, the dimensions being 8.25 in. deep, 2-75 in. flanges and -igin. thick for the Pennine 3.

The vehicle was one of an order for 15 being built for the Crown Agents on behalf of the Corporation of Hamilton, in Bermuda. The 36-seat metal-framed frontentrance bodywork was built in what used to be Seddon's coachbuilding department, nowadays formed into a subsidiary company, Pennine Coachcraft Ltd. The all-up weight as tested, 8 tons 4 cwt., was equivalent to a bus with all seats occupied, driver, conductor and two standing passengers.

ENGINE AND GEARBDX The engine and gearbox unit is almost identical with that used in current Commer forward-control 5-ton goods models. The 6.354 is slightly derated, being set to produce 105 b.h.p. net at 2,800 r.p.m. in this application, the maximum net torque of 254 lb.-ft. at 1,450 r.p.m. being the same B42

iat of the Commer. The cylinder block is inclined rds the right at 66° from vertical, the engine lying een and, apart from some minor fittings, below the level of the frame side-members. The change-speed tge is partly above this level, but the body floor is )letely free from any protrusion in this area. -usion of the wheel-arches is small, although this is ly accounted for by a moderately high floor level. Le Moss hypoid-bevel rear axle had a ratio of 6-66 to 1, ;what low gearing for a vehicle of this character, giving m.p.h. per 1,000 engine r.p.m. in top gear. The effect

is not so much one of limited speed, for the 6.354 is a relatively fast-revving unit, the engine being rather "busy "; cruising at 40 m.p.h. calls for just over 2,300 engine r.p.m., at which speed the noise level inside the vehicle is appreciably higher than at, say 35 m.p.h. Fuel economy on rural bus work would almost certainly also benefit from higher gearing, but the present rear-axle ratio does have the benefit of making the bus a good top-gear performer. The theoretical maximum gradient climbable in this ratio is 1 in 24, assuming 90 per cent transmission efficiency and 25 lb./ton rolling resistance.

It was not possible to make an accurate check of top-gear speed in the vicinity of Oldham, but it was still slowly rising with the speedometer indicating 46 m.p.h. on one occasion and seems likely to exceed the 48 m.p.h. figure corresponding to 2,800 engine r.p.m. The Rootes gearbox has decidedly wide ratios, third gear giving only 9-4 m.p.h. per 1,000 engine r.p.m. and a maximum of 26 m.p.h. This means that it seems natural to change into top gear at little over 20 m.p.h. in normal driving, so that the engine is frequently asked to pull at quite low speeds. The 6.354 accepted this treatment remarkably well, running smoothly and comparatively quietly under these conditions.

HILL CLIMBING

When third gear is called for, however, gradients of up to 1 in 12-5 can be climbed, according to my calculations. Practical testing of hill-climbing performance carried out at Buckstones Road, Shaw, tended to confirm this and a theoretical capability of climbing 1 in 6-2 in second gear. This 1-25-mile-long hill has an average gradient of 1 in 12, the maximum gradient being 1 in 6-5. The hill was climbed in 6 min. 30 sec., oddly enough exactly the same time as the Mk. 19 tested in 1958, and the steepest section called for second gear for 2 min. 20 sec. Much of the hill was climbed in third gear at about 20 m.p.h. and the minimum speed on

the 1-in-6.5 portion was 10 m.p.h. The wide gear-ratio step between second and third made progress after reverting to third gear slow initially, but the engine steadily built up speed in a manner somewhat reminiscent of much larger engines. The Pennine 3 did not lend itself to direct measurement of water temperature, but the dashboard thermometer showed only a rise from 80°C. (176°F.) to 81°C. (178°F.) during the course of the climb; the ambient temperature was 13°C. (55°F.). The model obviously has generous cooling capacity; an interesting feature is the use of a motor-driven fan.

Subsequently, up-hill restarts were made on the 1-in-6.5 section in first, second and reverse gears. Those in first and second were made with complete ease; in second there was considerable surging, which took several seconds to die down after the clutch was completely engaged, but 1444 there was never any sense of doubt that the attempt would not be successful.

FUEL CONSUMPTION

Fuel consumption was checked on the six-mile course normally used in The Commercial Motor tests of Seddon vehicles. This lies on the Manchester side of Oldham and is decidedly urban in character, involving as it does six sets of traffic lights and a busy roundabout. Difficulties in installing the test tank and tracing a fault in its operation caused the so-called non-stop run to coincide with the finish of work at a large nearby works and the bus was halted for one minute with the engine idling during this test. This time was not included in the calculation of average speed.

six-stops-per-mile test was made tinder fairer conand it was possible to count the stops at traffic as scheduled stops when they occurred. Time did rmit testing under half-load or no-load conditions, would hazard a guess that normal operation on bus of a country, or even suburban, character might well letter figures than the attempt at a fully laden, )p fuel consumption run.

BRAKES

brakes produced good stopping distances, despite a cy for the rear wheels to lock; on two occasions the id slewed round so that the vehicle came to rest at Lt angle to the kerb. This seemed to be caused by variations in the quality of the road surface rather any fault in the vehicle. The handbrake was 'lady effective and could honestly be considered as a 'al means of stopping the vehicle in an emergency than as a mere parking brake.

results of the brake-fade tests on Buckstones Road iomewhat disappointing. After coasting down the ith the footbrake 'continuously in use to hold the down to 20 m.p.h., a descent lasting 4-5 minutes, a essure stop gave a Tapley meter reading of only cent compared with 68 per cent recorded during the stopping distances. I am somewhat at a loss to it for this, although Buckstones Road is an appreciinger hill than most of the others used by this journal td testing. Smoke from the brakes had begun to be t about half-way down, and most of the deterioration occurred .during the last few hundred yards. .heless, the Mk. 19 version of the Pennine dropped per cent when tested on the same hill, its wider rear linings being compensated by greater weight. The le 3 tested was very new and insufficient bedding-in linings seems a possible explanation.

DRIVING

n a driver's viewpoint the bus was pleasant to . The steering, although not particularly light in n to the front-axle load, is sufficiently high-geared to the need for excessive wheel-turning and many would probably prefer it this way, pirticularly as it lot become unduly heavy when manceuvring. The nship of steering-wheel to seat and pedal positions is ind the pedal actions well judged.

steeply inclined gear lever does not merit similar and it seems unfortunate that the change-speed box )t mounted further forward so as to permit the use ore nearly vertical lever, particularly as there appears no structural reason for this not being done. As it movement of the lever has all the awkwardness ited with forward-control front-engined models the gear lever sprouting directly out of the gearbox, It the excuse of thereby being simpler, which vehicles layout can claim.

actual gear-change action is good, with effective °mesh, and it is probably quite light, although one lot have that impression because one's arm muscles aced at a disadvantage. The positions of the lever various gears are the reverse of that usually applyad this gives one cause for some rapid thinking at Ithough of little consequence to a regular driver. A trity of this kind can, however, be a drawback in ed fleet with drivers constantly changing vehicles. Seddon variable-ratio handbrake lever is well placed mvenient to use, although seeming a little heavy for 1 parking use. The mounting of the instruments teir faces horizontal in the tray in front of the driver ppear haphazard at first glance, but is actually much convenient than some schemes on which so-called have been let loose. The speedometer is not obscured by the steering wheel and the switches, mounted below the edge of the tray and at the side, are all easily reached.

A lever to allow the driver to open or close the entrance doors by means of a flexible cable control is provided to the right of the driver. This is convenient and reasonably light to operate, its most obvious fault being a tendency to rattle when the engine is idling.

The engine mounting is evidently comparatively firm, causing some vibration to be transmitted to the rest of the vehicle at idling speeds and giving rise to one or two minor rattles of the type just mentioned. This disappears as the engine speed rises, however, and the 6.354 gives an impression of refinement in the middle-speed range, when both vibration and noise are at their minimum.

NOISE

The body floor is composed of aluminium chequer plate, which is much less sound-absorbent than other forms of flooring. The noise level in the test vehicle was also raised by the need to have a small trap door open for the piping of the test tank—a lot of noise can escape through quite a small opening. At speed and when accelerating through the gears the Pennine 3 was, in consequence, quite noisy inside, but I had the impression that considerable improvement would not be difficult to achieve by the application of simple sound-deadening measures.

The standard of riding comfort was otherwise good and it was pleasant to see a high standard of interior finish in what is obviously primarily a utilitarian vehicle. The suspension is fairly firm, but adequately damped, and the seats reasonably comfortable, although they would have been improved by more rake on the backrests.

A two-speed rear axle or five-speed gearbox would give greater flexibility of performance and greater economy would almost certainly be obtained with a higher overall top gear, but even with the present transmission the Pennine 3 seems to be a thoroughly practical vehicle. One could imagine operators in this country being interested in it as a replacement for early post-war 35-seaters, when route conditions would not be suited to a larger bus.

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Locations: Manchester

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