IMPRESSIONS OF
Page 64
Page 65
Page 66
If you've noticed an error in this article please click here to report it so we can fix it.
THE EMPEROR
Road Test No. 43
We Prove the Capabilities of the Latest Vulcan Chassis for Doublesaloon Buses. An Easily Handled Machine of Refined Performance and Modern Design
THE double-saloon bus, having a capacity of about 50 persons, is now regarded as the first line of attack . upon urban-traffic problems. The requirements which must be met in the design, of a vehicle of this class are rigid, both as regards the Ministry of Transport regulations and other obvious demands. In addition, a small over. all height is to-day one of the foremost points to which transport engineers pay attention, on account of the development of bus routes in suburban and rural areas in which low bridges have to be passed under and a detour is impossible. Chassis weight must be kept low to permit well-equipped bodywork to be used, despite the 9i-ton limit.
A little over a year ago the Vulcan Emperor chassis, with a sixcylindered Monarch engine, was introduced. This is designed, when equipped with the standard Vulcan body, to have a total height not exceeding 12 ft. 11 ins. when laden, and comfortably to seat 51 persons —26 on the lower deck and 25 in the upper saloon.
Striking Engine Features.
It will be remembered that the Monarch engine which is employed has been specially designed for this chassis by the Vulcan concern, in collaboration with Mr. Ricardo, the
well-known expert. It possesses various striking features, including two cylinder blocks, having three barrels' each, which are of the " wet " type, made–in the form of centrifugally cast liners. A novel feature of the engine is the extent to which the cylinder barrels are carried below the top of the crankcase.
n38
A seven-bearing crankshaft, with 3-in, main bearings and 2i-in. bigends, gives an extremely sweet-running engine with an absence of vibration. This feature made itself apparent within the first few-miles a our road test.
Details of Weights.
By arrangement with The Vulcan Motor and Engineering Co. (1906), Ltd., Crossens, Southport, we took over an Emperor chassis, weighing 3 tons 15 cwt., and laden with test blocks and ballast to the extent of 5 tons 3 cwt.; in addition, the total was increased by 3 cwt. which represents the weight of the driver and our representative. The total weight thus proved to be 9 tons 1 cwt. on the weighbridge. Calcifiating for 51 passengers at the' officially recognized average weight of .140 lb. apiece, this leaves a balance of 2 tons 2 cwt. 1 qr. for body allowance. It will, therefore, be realized that the vehicle was laden to a tOtal representative of service conditions; in consequence, the data obtained during the test represent the figures normally obtainable in every-day service.
After checking the weight, the chassis was taken on to a first-class arterial, road, and subjected to general test, particularly in connection with controllability—a vital factor for a double-saloon bus destined for urban work,
The rani-and-roller-type steering proved to be finger-light at all speeds, even on bad cobbled surfaces, which abound in the smaller roads in Lancashire. An opportunity was taken for testing braking and acceleration on the good surface, thus eliminating, so far as possible, wheelspin due to road irregularities. During the braking tests it was found that a restrained application of the pedal and lever was all that was required to bring the 9-ton 1-cwt. vehicle to rest in 111 ft. from 35 m.p.h., whilst from 20 m.p.h. 27 ft. was the distance required— approximately its own overall length. The Dewandre servo and master adjustment point were very accessible. The hand-brake sufficed to hold the chassis uphill or downhill on a gradient of 1 in 6, and neither brake independently caused any tendency to "snatch."
Acceleration Tests.
During the acceleration tests from rest, upward gear changes were made at 7 m.p.h., 15 m.p.h. and 30 m.p.h., these speeds representing the convenient maxima on the indirect ratios. In each case it was possible to force the speed a little higher, but there was no purpose in doing so, and the engine was allowed to pull the next higher gear so soon as it attained the apparent peak of the power curve. On top gear the speed range was 5 m.p.h. to 42 m.p.h. A very pleasant cruising speed proved to be in the region of 30 m.p.h.
• A quick-acting stop affects the rotation of the driven member of the single-plate dry clutch, and so soon as we hadacnuired.-the knack of regulating the clutch-pedal travel • to suit the circumstances of the moment—either an upward or downward change—it was possible silently to engage all gears and with very little physical effort upon the lever. The travel of the lever knob did not involve any appreciable change in the driving position, so that the most common changes in bus work, " 3-4" and " 4-3," could be effected time after time without involving fatigue.
Quietness was certainly noticeable on all indirect ratios, and this harmonized well with the silence of the engine. When accelerating on top gear the hiss of the air passing into the carburetter intake was the most prominent sound ; therefore, it may accurately be said that a high standard of silence has been attained in the construction of the Monarch engine.
Climbing Capabilities.
To test hill-climbing capacity, we directed our course from Crossens to Parbold Hill, -which has a long, trying gradient with an indifferent surface, it being a long stretch of 1 in 7 with slightly steeper gradients at various points during the ascent. Owing to road-repair work over a large section of the road and our unfamiliarity with the hill, it was essential to keep down the road speed at the foot of the gradient. This caused second and first gears to be used for longer periods during the ascent than would normally be the case, so that it was a more stern test of the engine. At the top of the hill a halt was made and the water in the radiator header tank was found to have attained a temperature of 208 degrees F. This
followed .3 mile at three-quarter throttle in first speed, a restart having been made on a 1-in-7 section.
Our test for fuel consumption was made over first-class and secondclass urban roads at an average §peed of 18.9 m.p.h. There were two stops and four gear changes, three to third and a further one to second speed, in the 6.7 miles, which were run on a measured gallon of fuel. This was poured into a special test tank ; the main fuel feed from the vacuum tank was, of course, discon
fleeted. The test tank was reputed to hold one gallon, but we ignored this and specially measured the fuel so that there should be no query as to the accuracy of the quantity.
This fuel-consumption figure was obtained with a carburetter setting of : Main jet, 150; compensator, 145; choke, 31. This setting, of course, obtained throughout the other specific tests, for which figures are given in these pages.
Semi-elliptic springs, working without auxiliary dampers, are em ployed for the suspension of the Emperor chassis. Carrying a total burden of 5 tons 6 cwt. they, proved to be well suited to the work, and, although they were sufficiently supple to give easy riding, there was no undue rebound action, neither was there pitching.
During the course of our tests we kept a watch upon the behaviour of the chassis frame when passing over irregular surfaces. There was but little movement on the part of the main longitudinals. These are braced by very rigid cross-members, whilst the principal channels are no less than 11 ins, deep and 34 ins. across the flanges.
Amongst the more important general chassis dimensions are: Wheelbase, 16 ft. 6 ins.; front track, 6 ft. 32-t. ins.; rear track, 5 ft. 10i ins.; height to top of frame (laden), 1 ft. 101 ; ground clearance up to rear axle, 10 ins.; ground clearance below offset axle pot, 6 ins.; overall chassis length, 25 ft. 64 ins.; overall width, 7 ft. 6 ins.