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It is difficult to evaluate intangible benefits, but the aispension and brake systems are both features which Mr. 3tooke considered to have been fully justified in service. kpart from the obvious passenger-appeal of greatly mproved ride, the suspension had virtually eliminated the 'teed for body maintenance. Failures of diaphragms had leen confined to three instances of internal abrasion of an early design since superseded.
Tyre wear had not proved to be noticeably greater than sn an orthodox-front-engined double-decker. The wear of 'vont lyres was a little greater but this was largely attrisuted to the higher front-wheel loading due to the increased 'Font overhang, and it was counterbalanced by reduced vear of the rear tyres. Gloomy predictions of heavy frontyre wear due to the independent front suspension have iot been confirmed, despite the Wulfrunian's ability to :orner at relatively higher speeds.
In terms of direct operating costs, the disc brakes are somewhat more expensive than drum brakes, sets of pads being as yet both costlier and shorter-lived than conventional linings. On the other hand, the fact that a semiskilled fitter with an apprentice and labourer can change all the pads on a bus during one hour of the night shift, as mentioned by Mr. Brockington in his article in last week's issue, does much to counterbalance the apparent doubling of relining expenditure on materials.. How much the immeasurably greater factor of safety, particularly in terms of resistance to fade, afforded by the disc brakes is worth, obviously cannot be measured only in terms of cash.
Much of the territory covered by the West Riding concern is hilly and many routes include long descents, generally on fairly straight roads with moderate rather than very steep gradients. These invite comparatively rapid descent and consequent, continuous or frequent intermittent use of the brakes with little assistance from the use of low gears. Brake fade is thus a particularly serious defect for any bus which operates in the area and, prior to the advent of disc brakes on the Wulfrunians, all too common a problem.
It has been found possible, by deliberate provocation, to induce mild fade with the disc brakes, but this required what would normally be utterly reckless driving, and efficiency was quickly regained as soon as the brakes were rested. With drum brakes, fade can very quickly be induced, and testers investigating this aspect of brake performance regularly find that efficiency has not been fully restored after a I0-minute stop.
The advantages of the braking system are not confined to fade resistance, however. With drum brakes, it is normally necessary to use all the braking power available to provide an adequate standard for emergency stops. With the Wulfrunian, Mr. Brooke told me that it was more a matter of "how good dare we let it be ", bearing in mind the possible danger of sudden full braking to standing passengers. In practice the maximum line pressure for the brake system is set at 80 p.s.i., which enables 0.65g braking to be produced.. The margin held in reserve is indicated by the fact that the line pressure could go up to 100 psi. The unorthodox suspension and brake systems must not be allowed to divert attention from other aspects of the Wulfrunian's performance in service, however. Uniii the past year or two, the Gardner 6LX engine has been less common in bus fleets than it is in goods transport because operators favoUring the Gardner unit have considered the smaller-capacity 6LW adequate for their purposes. Although many 6LX-powered buses, mostly with large seating capacities, are now on order, few operators yet have sufficient operating experience to make valid comparisons of fuel consumption figures -possible. The West Riding Wulfrunians, which are powered by this unit (set to develop a maximum of 125 b.h.p. at 1,700 r.p.m.) are returning 9.9 m.p.g. • This is a good figure for double-deckers working over busy, hilly routes, particularly as the vehicles seat. 75 passengers and weigh approximately 8 tons-8 Cwt. unladen. Figures for other types of double-decker in the fleet are as follows: A.E.C. Regent Mk. III, 8.9 m.p.g. ; Guy Arab (6LW, engine), 10.4 m.p.g.; and -Leyland PD2, 10.0 m.p.g. The comparison of these must be qualified slightly because of variations in. conditions of operation, weight and seating capacity of bodywork, but all refer to 50to 56-seaters weighing less than 8 tons, few if any of which are working more intenSive. or arduous services than the Wulfrunians. It is clear that the 6LX is as fully capable of maintaining the reputation of the LW series of Gardner engines in terms of fuel economy in the passenger field as it is in goods vehicles.
An interesting aside on the fuel consumption figures is the fact that one Wulfrunian operating on the flat, less intensive routes operated by the company in the Selby area has returned 13 m.p.g., which is actually a better figure than the fleet average for single-deckers of 12.2 m.p.g. The overall fleet average is 11 m.p.g.
The Cave-Brown-Cave heating and ventilating system has proved most effective. Almost completely automatic in operation, it provides a comfortable atmosphere inside the bus, with ventilation without draughts and heating thermostatically controlled to maintain the temperature within a predetermined range. It has a valuable side-effect of completely eliminating the common problem of nicotine-laden condensation in the upper saloon, with its staining effect on the paintwork. The system has been found to require very little maintenance, one of the few operations very occasionally required to eater for large differences in ambient temperature is to divert the air flow through the radiators by changing the position of deflector plates. This can be done very quickly without tools.
The bodies on the West Riding Guy Wulfrunians have, with two exceptions on vehicles acquired after experimental v40 use in other fleets, been built by Charles H. Roe Ltd., us
a metal-framed structure of Park Royal design. 1 general appearance of the more recent vehicles has alte only slightly from that of the prototype, and I think it I reasonably be said that the somewhat box-like froi aspect gives a slightly misleading impression of the c siderable refinements to be experienced by the passem • In fact, the front-end design has been the subject o comparatively major modification from a functional pc of view. in the original design the overall width of bodywork remained at its maximum throughout the len of the .bus, including the front overhang. In wet weat it was found that the front offside cab window beca Seriously obscured by spray thrown up from the fr
wheel. The production vehicles have the bodyw. tapered inwards slightly over this section, so that the wi at the extreme front is slightly rediaced, and this has b found lo overcome the spray problem.
Another modification in the same area concerned driving position. Originally this was deliberately arran to be as close to the windscreen as possible, with a w range of nnobstucted vision as the main objective. Sc difficulty in sensing the position of the vehicle on the ra was experienced, however. Interrogation of drivers to the conclusion that the absence of any part of vehicle's structure from the driver's field of View when was looking straight ahead was the cause of this. entire driving position Was accordingly moved back sc 9 in. and it is generally agreed that the earlier difficul have disappeared. .
Road Impressions
I was able to gain first-hand experience of the Wull niart in its current form, both as passenger and dri' The standard of ride obtained was most impressive, the more so because the vehicle was empty. The NA Riding Of Yorkshire, like other areas where the cou council has a large. mileage of heavily trafficked roach maintain, has a generous quota of uneven surfaces. have a personal theory that many of this area's roads h never fully recovered from the damage they suffered the winter of 1947. Be that as it may, the Wulfrur completely took the sting out of the bumps but nc " wallowed " as might have been expected with a relatir tall vehicle with this capability.
The ride was not, in fact, ultra-soft by private standards, the removal of the auxiliary surge tanks fr the front suspension having made it more firm than original design, without any tendency to harshness lac introduced. Standing on the front platform or sitting at the extreme rear of the upper deck, it was not possible to find the "bad spot" at some part of the vehicle usual with most double-deckers. Particularly noticeable on the upper deck was the marked reduction in the sway normally to be expected when seated in this position on a badly surfaced road.
When I took the wheel, I was surprised at the absence of that feeling of slight. instability which is usual in tall vehicles and by no means uncommon even in small delivery vans. The explanation probably lay in the virtually instantaneous action of the suspension system in resisting roll, which is, I feel, one of the main sensations upon which a driver judges his actions and matches them to the characteristics of the vehicle.
Another factor which undoubtedly has its effect on this impression of stability is the steering. The very noticeable negative camber angle of the front wheels may have a strange appearance but it is evident that the suspension and steering geometry have been carefully thought out to combine precise, responsive and comparatively light steering. With 55 per cent of the unladen weight carried by the single front tyres, a strong understeer effect might have been expected. As the front axle load is 4.7 tons, even in this condition, this effect might have been combined with heavy or unduly low-geared steering to produce a bus that required hard work to get it round corners. In fact, it was one of those by no means common vehicles at the wheel of which one rather looks forward to main road cornering.
The Burman recirculatory-ball steering box and the remainder of the linkage evidently have a high Mechanical efficiency, so that the steering is never unduly heavy. The variable ratio effect makes it necessary to do some fairly rapid wheel turning as full lock is approached, but as the bus is inevitably moving slowly then, this is preferable to the heaviness that would otherwise be expected.
The vehicle I tried had the latest brake system, with a dual brake valve supplying air to two diaphragm-type actuators coupled to hydraulic master cylinders, one operating the front and the other the rear brakes. As mentioned in the article in last week's issue, the pedal pressure has been loaded slightly to discourage unnecessarily severe use in normal service. In practice, I found the firm " feel " preferable to an unduly light pedal pressure and the effort required was no more than is usual on a private car. I expected some delay effect from the air pressure system, but could barely detect any and I can only attribute this to the relatively small capacity of the air pipe lines as compared to a vehicle with direct air brakes.
The transmission on all the West Riding Wulfrunians is through a fluid flywheel and a four-speed semi-automatic direct-acting epicyclic gearbox. The gearbox is electropneumatically controlled from a small gear lever operating in a miniature gate mounted on the steering column. As is general with units of this type, restrictors are fitted in the air lines to slow down slightly the take-up of the brake bands and produce a smooth gear-change. Originally these were intended to permit full-throttle continuoustraction upward gear changes, but Mr. Brooke told me that lining wear on the hands had proved to be severe.
The degree of restriction was accordingly reduced, and drivers instructed to pause in neutral and count up to three when making upward changes. I found in practice that counting up to two, giving about a 2 sec. pause, gave perfect gear changes, despite the Gardner engine's tendency to be a little slow in losing speed. Experimentally flicking the lever straight through without lifting my foot off the accelerator _gave a slight jerk, but, much to my surprise, this was less than is often experienced on buses with the greater degree of restriction. I have the impression that the initial period of slip caused by this is followed by a rather fierce take-up, perhaps due to a heating effect or possibly because the oil film which may at first persist suddenly disappears. The setting used by West Riding certainly appears to be preferable in service and might even suit the same type of gearbox in fully automatic form.
With my left foot unemployed and a brake pedal which required no rndre than moderate pressure, it seemed oddly incongruous to find an accelerator requiring a definite effort to depress it fully at speed. This was at least partially due to the well-known characteristics of the Gardner system of all-speed governing, but the position and movement of the mushroom-type pedal did not suit the anatomy of my foot or ankle very well. This was the only actual complaint I could level at the vehicle from a driver's point of view and this is to some degree a matter of personal preference.
The West Riding company's experience of the Wulfrunian appears fully to justify the decision to depart from conventional vehicle design practice, with the probability of further gains in terms of low maintenance costs as the vehicles become older. I returned from Wakefield with the impression that West Riding had made a very sound choice for the conditions of operation on its routes. Moreover, .1 felt that I had in some ways had a glimpse of some of the features which must one day become normal on public service vehicles. Bearing in mind the experience of Midland Red as well as West Riding, I feel convinced that disc brakes should before many years replace drums on most of the heavier commercial vehicles. Particularly in regard to suspension, the Wulfrunian may well prove to have set the standard by which others will be judged for some time to come.