A Bus to Please Passengers and Operators
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ROAD TEST: A.E.O. Renown 71-seat double-decker bus BECAUSE the A.E.C. Renown double-decker was introduced just over two years ago and was, at that, a development of the Bridgemaster integrally constructed double-decker, a road test of the vehicle now—on the first occasion that it has been made available to this journal—may seem of academic interest rather than practical value. It was, however, a useful test, for apart from showing what an operator can expect from the Renown, the figures obtained can be applied to Regent V double-deckers which are available with the same running units—the A.E.C. 9.6-litre engine and four-speed synchro mesh gearbox. The test is also of interest as being the first of an A.E.C. double-decker with these units and the first time since 1947 that an A.E.C. double-decker chassis with this size a engine has been tested by The Commercial Motor; in that case it was a Regent III with an 'earlier version of the 9.6-litre unit and the then. standard airoperated preselective gearbox.
The Renown tested was in fact shown by A.E.C. at the 1962 Commercial Motor Show and since that time has been used on demonstrations throughout the country. In all, 28 operators have actually used this test vehicle on service, these including a number of B.E.T. companies and municipalities including Western Welsh, South Wales, East Yorkshire and North Western, and Leigh, Nottingham and Rotherham. Other users have included Scottish Omnibuses, and some independent operators. Besides these, the vehicle has been stationed at A.E.C. depots throughout the country whence it was sent• out to operators for demonstration and, in all, a total of 50,000 miles had been covered when it came to us. This is what leads me to say that the test might be largely of academic interest, for any operator seriously considering the model for his fleet will have tried it himself or at least had the opportunity. Although the actual vehicle tested was built so long ago, it had been modified from time to time in line with minor detail changes in the design so that it was virtually a current standard production model, the exception being that an in-line fuel-injection pump was fitted to the engine, not the C.A.V. distributor-type pump which is currently installed. There has been no major change to the design since the Renown was introduced and a full description appeared in The Commercial Motor of July 6, 1962. The fundamental difference between the Renown and the earlier A.E.C. Bridgemaster low-height double-decker lies in the adoption of a separate chassis instead of integral construction. The transmission line was changed and on the Renown the engine is mounted at an appreciable angle to the chassis centreline, the front end being to the left and the rear to the right of this line. In addition, the engine is inclined downwards at the rear and the centreline of the cylinder bores leans slightly to the left, away from the driver, to provide more room in the cab.
The main gearbox option is an A.E.C. Monocontrol semiautomatic unit mounted independently, but the model tested had the alternative four-speed synchromesh type which is mounted in unit with the engine. It is interesting to learn that although the model was designed primarily for Monocontrol transmission, only one of the 180-odd Renowns in service or ordered has been specified with the Monocontrol.
From the rear end of the gearbox the transmission line runs just inboard of the offside main chassis member to the input shaft of the rear axle which is offset to the right. Primary reduction in the rear axle is by spiral bevel and secondary reduction (which also conveys the drive from the low level of the axle centre portion up to the wheel centrelines) is by spur gears which are available in alternative ratios. The overall rear axle ratio on the Renown tested was 4.65 to 1, three other options offered being 5-35 to 1, 5-75 to 1 and 6-2 to I.
As will be seen from the drawing in the specification table, the chassis frame is a fairly complex structure. It is built largely from *-in.-thick pressings, the sidemembers being 8 in. deep over most of their length. Aft of the bulkhead an additional member is mounted outboard of the nearside sidemember, and 8.5 in. away from it, to provide the strength required at the step area of forwardentrance bodies, for which the chassis has been designed.
The Renown's suspension differs considerably from that of the Bridgemaster, for whereas the latter had independent front suspension similar to that of the London Transport Routemaster, the Renown has a beam front axle and semi elliptic springs. At the rear, however, air suspension continues to be used, Dunlop Pneuride components with 12-in.diameter three-convolution bellows being employed.
The front axle and springs are, in fact, common to those used on the Regent Mk. V double-deckers and the splitcircuit air-pressure braking system also has principal units identical to those on this model. The front-end sheet metal work is also similar to that of the Regent V.
The vehicle tested had a 71-seat Park Royal body and the kerb weight was just under 8 ton 15 cwt., a figure, incidentally, the same as that of some Bridgemasters. With a payload of 4 ton 5 cwt. of sand-filled sacks placed evenly around the upper and lower saloons, and with driver, two passengers and test equipment, the gross weight was brought to 13 ton 4.75 cwt., which represented the bus running with 70 passengers, as well as driver and conductor. Of the tests carried out, those for fuel consumption and acceleration produced excellent figures, whilst the braking performance was found to be entirely adequate for a double-deck passenger vehicle.
The braking tests were carried out first and the footb rake figures obtained were reasonably good, but on the handbrake tests a Tapley-meter reading of only 13 per cent was obtained because the handbrake lever came right back against its stop before full application. After adjustment by A.E.C. next day, additional handbrake performance tests were carried out and these produced the figure of 23 per cent quoted in the tables, which is good for a 70-seater double-decker. During the stops the retardation was quite smooth, there being no sign of grabbing at any wheel, and the bus kept in a perfectly straight line.
Despite the fact that the highest rear axle ratio obtainable was fitted to the test vehicle, the figures for acceleration were extremely good; with any of the other three ratio options the figures would, of Course, be even better. In the through-the-gears runs all four forward ratios were used and although very quick changes were, made the synchromesh was not overcome, On the direct-drive runs the Renown pulled away very smoothly from 10 m.p.h.
A six-mile out-and-return run on a section of the A6 south of the Luton exit of the M1 motorway was used for fuel consumption tests. This is an undulating circuit c42
with generally gentle inclines but there is one severe section just before the roundabout at the motorway spur. The first four consumption tests were made with a full load, the second four the day after with half the load removed. It will be seen from the consumption analysis table that two non-stop runs were made in each condition. On one of these the vehicle was cruised at between 30 an 34 m.p.h., on the other at around 40 m.p.h., to discover what could be expected when running in built-up areas and on country routes respectively. On the twoand six-stops-per-mile tests each of the stops was for 15 seconds, during which time the engine was left idling.
The figures obtained on the test were very good indeed, and better than one would expect to get with a bus of this capacity—they were about what one would expect with a Continued on page 7,2 bus carrying 10 or so passengers fewer. The high axle ratio benefited the figures for non-stop running, no doubt, but at the same time would have played a part in worsening the figures when stops were made, particularly on the sixstops per mile runs. This is obvious from the low average speed for the fully laden six-stops run and, on this, the speed rarely exceeded 25 m.p.h. On none of the tests was it possible to start off in a higher gear than bottom; certainly on the half-laden runs second-gear restarts would have been feasible with the lower ratios that are available.
No hill-performance test was made with the Renown, but the six-stops per mile fuel-consumption run, when the bus was fully laden. was used to assess brake fade, the final Stop being a full-pressure one from 20 m.p.h. A Tapleymeter reading of 45 per cent was obtained on this, compared with a 54 per cent, maximum obtained on the earlier footbrake tests from the same speed. The small reduction of 9 per cent indicates slight fade, which is only to be expected, and this appeared to be due to the linings. No high-speed fuel consumption run was made because this would have been to little purpose on a vehicle such as the Renown, but the M1 was used to assess the ride at the maximum speed. This was very good and although there was some wind the bus handled well and control was not affected. Maximum speed on the motorway was 51 m.p.h., the maximum in the lower gears being 10, 19 and 29 m.p.h. The Renown handled well in all circumstances, irrespective of loading or road surface. The suspension is well designed and there was little tendency to roll; to assess the worst possible condition, when the half-load consumption tests were made all the load from the lower saloon was removed but only a little from the upper saloon. This meant that the bus was being driven as though the top deck was full and the bottom empty, and even in this condition there was very little roll.
I found the Renown a very easy vehicle to drive, with•the gearchatige lever well positioned and the driving
position very good—the seat fitted had a wide range of both vertical and back-and-forward adjustment. The angle of rake and low position of the steering wheel combine to produce the feeling that one is in full control of the vehicle, and with 6.75 turns from lock to lock the steering is light and manceuvring at low speed is not hard work.
The level of engine noise which reaches the driver is relatively small, but a good deal gets through the bulkhead into the lower saloon and this is a point which should receive attention, for there appeared to be more noise downstairs than in most double-deckers. This is the only complaint that passengers can have, for the smoothness of ride will be generally appreciated. I tried various seats and found the ride good in all of them.
Access to the driving compartment is reasonably good, although once in the doorway it is not particularly easy to get into the seat. This was especially noticeable when the handbrake needed adjustment, because one had to climb over the lever to get into the seat. After the brakes had been adjusted the lever was not so much in the way.
For passengers, the low-set single step provides excellent access to the bus, while the stairs to the upper saloon are well designed, there being seven rises in the spiral staircase.
The Park Royal 8-ft.-wide body was found to be in very good condition considering the 50,000 miles' service that it had completed, and was quite free from creaks and rattles during the test. The standard of finish inside is high, and among the particularly useful body features are a translucent panel in the roof above the stairs and a light set in the body side half-way up the stairs to give adequate illumination at this point both by day and night. There is a useful luggage space underneath the stairs and .the fluorescent saloon lighting is behind white translucent panels above the windows in both saloons.