Road Test Bedford VAM
If you've noticed an error in this article please click here to report it so we can fix it.
TRAFF1C congestion in holiday centres, at sports meetings and on routes to many places of interest is playing a large part in the increasing travel by luxury coaches. Often passengers are car owners who do not find motoring for pleasure attractive but demand that luxury and comfort of the coaches they book, should be at least as high as that provided by the private car. The Bedford VAM passenger chassis fitted with a Duple body tested by us recently must be rated high from the point of view of comfort, styling and layout and, being constructed with well-tried components the chassis should prove to be reliable.
The VAM passenger chassis was introduced in June, 1965, after requests from operators for a medium capacity front-entrance coach had been linked with requests from coachbuilders for a completely level frame upon which such a body could be mounted. The result of these requests is a 16 ft. 1 in.-wheelbase chassis with a front overhang of 6 ft. 3-4 in. and a rear overhang of 3 ft. 10.7 in. which is capable of accepting front-entrance bodywork of up to 32 ft. long and 8 ft. 2.5 in. wide ranging from 41to 45-seat capacity, and having a g.v.w. rating of 9.15 tons. Optional power units available are the Bedford 300 Cu. in., 133 h.p. petrol engine or the Bedford 330 cu. in., 104 h.p. diesel engine; the test vehicle was fitted with the latter. Also available is the Leyland 0.400 132 h.p. diesel engine. Three transmission arrangements are available, these comprising the Bedford four-speed constant-mesh gearbox withor without a two-speed axle, or the Clarke five-speed overdrive synchromesh gearbox and single-speed axle as fitted to the test vehicle. The latter arrangement is mandatory when the Leyland 0.400 engine is fitted.
For Engine Changing A pressed-steel ladder-type frame is used and the nearside member of this is swept inwards and down at the front facilitating the mounting of either left-, or right-hand control bodywork. The front cross-member is removable to allow for ease of engine changing and the power unit is mounted vertically and low between the frame members; the drive-line in the laden condition is almost parallel to the frame. A completely new front axle is used having a track of 6 ft. 7.5 in. and a capacity of 4 tons 6 cwt., this being greater by 12.75 cwt. than the actual load imposed on the front axle of the test vehicle. As with other vehicles in the Bedford range, the VAM is fitted with dual-circuit braking using a tandem master cylinder serving separate hydraulic circuits to the front and rear axles. On both the diesel-engined models an air pressure servo is fitted, but on the petrol-engined version a vacuum-servo is fitted. A mechanical handbrake to the rear brakes is standard on all vehicles.
The Duple Bella Venture body is of composite construction incorporating reinforced-plastics front panels, canopy and dome sections. Features of the body are the inwardopening, forward-entrance door with a full-depth emergency door opposite and a waist-depth emergency door at the rear on the off-side. The interior trim is both pleasant and functional. There is provision for 112 Cu. ft. of luggage in the compartment at the rear. The first thing that I noticed on taking up my position in the driving seat at the start of the test was that entrance to the seat called for some effort on the part of the driver. The second and more 'painful was the extremely sharp edges of the seat runners, and at the end of the test I had a nasty gash on the calf of my right leg to remind me that this was so.
For the purpose of the test the vehicle was laden with sandbags representing 45 passengers, when it scaled 17 lb less than its designed weight of 9.15 tons. With the addition of two observers the actual test weight was 9.3 tons.
To simulate the sort of route over which a touring coach would. normally be operating, I chose 15 miles of road starting from Watling Street Café on the AS (adjacent to the junction of M1) and finishing at the church outside the entrance to the grounds of Woburn Abbey. This took in the AS as far as Hockliffe and the A50 from there to Woburn, passing through Dunstable where reasonably heavy traffic was encountered and three stops were made for various reasons. The route is undulating and includes some main road hills. Two tests were completed over this route, one running north at 30 m.p.h. and one south at 40 m.p.h. At both speeds the vehicle behaved perfectly with regard to road holding and general handling. The steering on this machine is accurate under all conditions and the fine control needed when travelling over narrow roads is of the highest order. As is usual with air-overhydraulic brakes, they are a pleasure to use, giving that nicety of control so essential if passengers are to be given a smooth ride. The gear-change lever appears at first to have excessive travel and there is a distinctly rubbery feeling in the action. This seemed to have completely disappeared by the end of the day, and I concluded that it needed some practice if one is to accept it.
Bedford engineers have excelled themselves with the gear ratios of this machine, for it seemed to be right for every type of going and at whatever speed one chose to drive. Only the full throttle test on the M1 showed the high-ratio differential fitted to be a weak link in the set up, for although the run north produced a maximum speed of 70 m.p.h., the leg south rarely saw the clock reading above 50 m.p.h. This pointed to the 330 Cu. in. engine not being powerful enough to pull such high gearing unless conditions are ideal. It may well have been that better results would have been achieved on this southern leg had the direct-drive gear rather than overdrive been engaged. It must be remembered that the particular test vehicle had not been produced for motorway operation; had it been, the Leyland 0.400 engine would probably have been fitted.
On ordinary trunk roads the vehicle was capable of hanging on to the higher gears very well indeed. Overdrive would take speeds from about 33 m.p.h. upwards comfortably, provided that "crashing" acceleration was not needed. Excellent flexibility of the engine allowed fourth gear (direct) to be used quite effectively from about 23 m.p.h. and up to 55 m.p.h. if needed and this gear proved to be the right one for negotiating second-class roads at around 30 m.p.h. when the engine noise level was 'completely unobtrusive.
Acceleration tests proved that if required the vehicle could reach 40 m.p.h. in 45 sec. but the direct-drive test showed that the gearbox must be used correctly if the vehicle is not to be punished. The transmission was extremely rough in direct drive up to about 18 m.p.h. and the time of 89.9 sec. taken to reach 40 m.p.h. from 10 na.p.h, on one leg of this test in this gear told its own story. Subsequent checks made on the performance of other vehicles in this class showed that the VAM is an average performer with regard to acceleration. Full results of the tests can be seen in the panel.
Fuel consumption proved to be again about average of most other vehicles tested in this class and the figures of 16.05 m.p.g. running at around 30 m.p.h. and 15 m.p.g. at up to 40 m.p.h. were achieved without resorting to freak methods such as coasting or hanging on to higher gears than were needed for correct progress to be made. Proof of this is seen in the tables where the average speeds are shown. For the 30 m.p.h. run the speedometer never read above 35 m.p.h. and, in fact, most of the time registered 32 to 33 m.p.h., the average returned over the 15 miles including stops, being 30 m.p.h. For the 40 m.p.h. run, when the speed was never allowed to exceed 45 m.p.h. and was kept so far as possible to exactly 40 on the clock, an average of 37 m.p.h. was returned.
During these tests I found the vehicle very pleasant to drive quite apart from one or two nasty noises emanating from the bodywork around the underside of the entrance step. One point which will endear the vehicle to those unfortunate passengers who are prone to travel sickness, is the almost roll-free ride that it gives. This characteristic is helped considerably by the angled dampers on the front axle.
Riding as a passenger at a later stage of the test, I found that this condition was not confined only to the front end, but that at any position in the coach including the back seat, a ride that should not upset the tenderest stomach was enjoyed.
Also at this time I had a chance to assess the effectiveness of the heating and ventilation systems fitted to the vehicle. Heating and demisting are provided by a Smiths system, and ventilation is by sliding top sections in the windows between the rearmost pillar of the entrance and the sloping pillar above the rear axle. From this point to the back of the coach individual jet vents are fitted in the roof served by air intakes situated in the roof panel above the sloping window pillar. Even though there was a very cold wind blowing and the ambient temperature was only 10°C (49°F), the interior of the vehicle was easily kept at 16°C (60°F) and it was not until the door was opened that one realised just how cold it was outside. Additional ventilation by opening roof-lights is provided.
Moving on to the motorway full throttle test, two points stood out in favour of the bodywork. The first of these was the almost complete absence of wind-noise even when the vehicle was travelling at 70 m.p.h. The second was the fact that although this test was carried out in the. dark and with a good proportion of the interior lights switched on, there was little interference with the vision afforded to the driver and in fact the blind provided behind the driver was not needed. Some idea of the steady ride that the VAM gives can be assessed from the fact that, owing to Vauxhall Motors fitting a test tank that held only four pints, it was necessary to measure out the fuel and top up the tank whilst the vehicle was in motion. Bedford project engineer Winston Wright who accompanied me on the test managed to do this without spilling a drop, even when travelling at high speed on the motorway.
Results obtained during the brake tests proved that a driver should never get into trouble through not being able to stop. Footbrake tests produced good results. From 30 m.p.h. a total distance of 43.3 ft., from the time the pedal was pressed until the vehicle came to rest, was recorded. This gave an average retardation of 20.7 ft/sec'. From 20 m.p.h. average retardation was 17.4 ft./see. The handbrake produced a Tapley meter reading of 43.5 per cent from 20 m.p.h.
A hill-climb test was completed on Bison Hill at Whipsnade. This hill is 0.75 miles long with an average gradient of 1 in 10.5 and a steepest gradient of 1 in 6-5. When l tried to take the temperature of the engine coolant at the start of the climb I stumbled on a snag in the body design. It is absolutely impossible to pour water in the radiator filler without using a hosepipe. Now I think this is bad because it prevents topping up at the roadside, makes anti-freezing difficult and in general stops a proper check on coolant level being made. Because of this I could not get the thermometer into the water. The dashmounted temperature gauge, however, recorded no change in the temperature of the coolant during the climb.
A total time of 3 min. 53.7 sec. was taken to climb to the top of the hill, first gear, which was the lowest used, being engaged for 1 min. 15-6 sec. During the climb the lowest speed recorded was 9 m.p.h. which was the maximum speed obtainable in that gear. The vehicle will, it is said, climb a 1-in-4 gradient with a bit in hand.
A brake test was carried out by Coasting down Bison Hill against the brakes at about 20 m.p.h. and when the speed dropped below that, engaging top gear and driving against the brakes. Taking a total time of 2 min. 35 sec. to descend it was necessary to use top gear for 40 sec. When doing a full-pressure brake-stop from 20 m.p.h. at the bottom of the hill a Tapley meter reading of 75 per cent was recorded, which was only 8 per cent lower than the best figure recorded when the brakes were cold.
Returning to the steepest section of the hill, the handbrake was tested for its ability to hold. This it did easily and it was also capable of bringing the vehicle to a standstill very quickly when it was applied whilst the coach was allowed to roll backwards down the hill. A second-gear start proved to be impossible but in first the machine moved off with complete ease. Turning round and facing down the hill the handbrake was tested again in the same manner. On both occasions it passed with honours. Reverse gear starts were a simple proposition without any undue slipping of the clutch.