Safe Transport for Children
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By Laurence J. Cotton, M.1.R.T.E.
Dennis School Bus has Many Safeguards for Passengers: Carrying Full Loud, it is Smooth, Stable and Easy to Handle, and Stop.-start .Work has Relatively Little Effect • on Economy HE risk of accident to passengers is greatly reduced in the latest Dennis Triton 22-scat school bus, because measures have been taken to provide safe trartOort for high-spirited children and to afford comfort when crippled or delicate children are carried. This bus has been designed basically for the London County Council, and following successful prototype tests, a contract has been placed for a large number. One of the production models was supplied for test. The Vilkitilation windows, made to prevent a child from 'putting its head through the opening; arc high in the .body and the sliding-door controls are arranged to deter a child from operating them. With entrances on both sides of the body, the passengers can be collected from either kerb. Safeguards include non-slip rubber wearing steps on the floor and entrances enclosed by guard rails.
To provide comfortable travel, .long semi-elliptic springs with Girling shock absorbers are provided at both axles and the seats, with tubular frames and Dunlopillo squabs and backs, are scaled-down versions of " adult " units. Provision is made in the door widths and seating plan for disabled children travelling in wheeled or carrying chairs. Normally the chairs are wheeled up ramps and manoeuvred into position between the seats, and stanchions, with grips, are placed on each side of the two entrances for. children to hold when being lifted into the vehicle.
The Triton is a 10-ft.. 6-in, wheelbase forward-control, chassis with a full bulkhead which separates the driver from the saloon. Easy access to the driving compartment is essential, because the driver is often • required to help the attendant in lifting a crippled child into the bus. This accessibility is provided by a low -step on the front overhang, and a
wide, forward-hinged door. A glass panel is let into the lower part of the near-side door.
High performance is not required.
smooth travel, reliability and sturdi
ness being preferred. For these reasons the vehicle is equipped with a standard moderate-sized side valve petrol engine, single-plate wet clutch and straightforward non-assisted braking system. Developing 70 b.b.p. at 3,000 r.p.m. and 161 lb.-ft. torque at 1,500 r.p.m., the engine is supported on resilient mountings and connected to the silencer by a metallic hose.
The wet-type clutch is not novel in Dennis design and in the Triton it assures progressive take-up in the transmission. It shares the lubrication system of the engine and gearbox, the latter being a conventional spurtoothed unit bolted in conjunction with the engine and clutch.
Long Springs A two-piece propeller shaft, with Lanchester-type damper at the centre bearing, conveys the,, drive to the hypoid gear of the rear axle. This is a fully floating unit with outrigged springs to reduce frame height. In a small bus it is unusual to find springs 4 ft. 2 ins, long at the rear and 3 ft. 4 ins, long at the front, but such is the equipment of the Dennis. The frame is parallel and level from front to rear and the fuel tank and spare wheel are .carried on the rear overhang to avoid restricting the central entrances.
The risers at the entrance are low, and if the seating and roof height were conveniently arranged, the Triton would•be most suitable as an ambulance for adult sitting cases.
Easy Climbing The test load of 18I cwt., which represented 22 children of about 7 stone average weight, possibly erred on the generous side. After fitting test instruments and an auxiliary fuel tank, the Triton, was driven from the weighbridge at Guildford and headed towards the Devil's Punch Bowl, climbing the long gradient to Hindhead in good style. The high power-weight ratio and 5.57 to 1 final drive are planned for local operation and it follows that hill-climbing ability is exceptional. It is not a high-speed vehicle, but it can cruise comfortably at 40 m.p.h.
IsTuteombe Hill, a notable gradient near Hindhead, was selected, the test being made difficult by sharp bends which cause the 1-in-5 section to be approached slowly. With the power available, this presented no difficulty, so a stop-start trial was staged at a point where, in conjunction with the camber of a by-road, the incline was
in 41. There was no jerk when the vehicle moved away from this point and there was power to spare on the hand-brake lever when halting on this gradient.
After this test came a long climb from the valley back to Haslemere and the Triton was just about warming to its task at the top, with a radiator temperature of 165 degrees F. and engine oil at 128 degrees F., against 41 degrees F. ambient.
Apart from its smooth riding and good cornering characteristics, the
bus can be rnanceuvred through narrow lanes with ease and sharp bends can be taken without need for reversing. An opportune moment for measuring the turning circle was presented on one of the Hindhead parking sites, Although the test vehicle had been selected at random, the stops had been correctly set to specification, the wheel-turning circle measuring precisely 42 ft. on both locks. The swept circle of the body was about 45 ft.
Acceleration is rapid, as was shown when, with well-timed gear changes, the bus reached 30 m.p.h. from rest in 22.1 secs. and in top gear accelerated from 10-30 m.p.h. in 23.8 secs. There was no pinking at low engine speed during the latter test and pick-up was smooth. Many drivers will prefer to use the full torque range instead of making early gear changes.
During braking tests a sharp pull on the lever locked the rear wheels on a clean and dry concrete road. Tapley readings of 37-38 per cent. were recorded in these efforts. With such efficiency there would be
no difficulty in passing a 1,ehicle examiner's test. The foot brake was
also highly effective. Using a Webley pistol to determine stopping distances, the vehicle was halted in 29 ft. from 20 m.p.h. and in 57 ft. front 30 m.p.h., with the rear wheels locking for up to 10 ft. at the higher speeds.
The varying incline of the hill from Milford to Guildford is normally a test of gear performance. Usually, with commercial vehicles, top gear can be engaged for short intervals and the remainder is a part-throttle pull in an indirect ratio. The Triton, however, climbed in top gear—the speed increasing on the more favourable sections.
Fuel-consumption trials were conducted on a 10-mile out-and-return section of the London road, where there was little difference in economy between straight and multi-stop running. The first test, which would be representative of transferring patients from hospital to a convalescent home, was made at a moderate speed with a fuel-consumption rate of •12.4 m.p.g. Then followed a repeat trial over the same route with a stop at every mile. There was little difference in the amount of fuel used, the return being 11.85 m.p.g.
Four Stops Per Mile When collecting or delivering its small passengers at their homes, the school bus might be stopping every few hundred yards, so a third test included halts at every quarter-Mile. It was during this trial that the smoothnes,s of the transmission was again apparent. After 30 or more stops in rapid succession, operating the clutch about 100 times before
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gear changing, the driver is apt to engage it fiercely. With the relatively light pedal action and the smoothness of the wetted friction members of the Triton, the driver is unlikely to give his passengers a rough ride even at the end of a difficult day. After the final stop in the third trial, the engine was switched off and 8.i pints of petrol were put into the test tank to fill it to overflow point, and a return of 9.15 m.p.g. resulted. In normal service consumption would be lower, because the vehicle would start empty and increase its load. whereas on test it carried a full load throughout_ Blanking Beneficial Running temperatures were taken on return to Guildford, after 70 miles' driving. The radiator water was 146 degrees F., indicating that a. blind might be beneficial in cold weather, because no thermostat is fitted. Engine, clutch and gearbox have a common supply of lubricant and this was moderately cool, with a temperature of 126 degrees F. The oil in the hypoid axle registered 114 degrees F'.
An inspection of the Triton chassis, commencing with its 6-in.-section frame, six cross-members and sturdy components, shows that it is built to last. It is not a high-performance bus, but its general economy, manceuvrability a n.d ease of handling are admirable.