NEWS & REVIEWS
Scarab, of course, pioneered the single-engine sweeper which uses the vehicle engine to power its suction fan and brushes via hydraulic drive. The absence of the auxiliary engine, its fuel tank and cooling system used on all other sweepers in Ireland means more than one tonne more pay-load and a bigger hopper.The advantages of having only one engine are obvious, but until Scarab came along some 20 years ago the problem had been how to keep the lorry engine running at sufficient rpm to power the suction fan and brushes, while keeping road speed down when moving - yet still retaining normal travel speeds.
The solution was twofold. First came the remarkable increase in engine power outputs, so a relatively small truck had the neccessary 50 to 60 bhp in reserve to power the sweeping services as well as moving along the road. The second development was hydrostatic drive, achieved by fitting a hydraulic pump to the engine and a motor on the drive shaft. While sweeping the Scarab becomes an automatic, with forward-reverse shuttle lever and speed from 0-30km/h controlled by the accelerator. For travel, the Scarab hydrostatic drive is disengaged and the vehicle is driven in the normal manner.
While most contractors now accept hydrostatic drive, as fitted to telescopic handlers, fork trucks, dozers and most compact sweepers, the fact remains that it does cost more. So five years ago Scarab came up with Unidrive, which is based on a 13t to 19t chassis with normal gearbox and fitted with a camshaft-driven hydraulic pump to drive the sweeping services. It competes head to head on price with the twin-engined sweeper, which also rely on the normal chassis gearbox for sweep speed control.
The demonstrator Magnum on a DAF LF55 chassis made its Northern Ireland debut at IWM Newcastle in April, and I was able to try it next day.
It`s an impressive machine when opened up, with a 6.5m3 payload volume in its stainless steel hopper and an 1800 litre water tank against the 1250 litre of a typical twin-engined sweeper which looses hopper space to accommodates its auxiliary engine and fuel tank - not to mention loosing an extra tonne of payload.
Unidrive components are the same as those on the hydrostatic machine, as are features such as steel pipes to replace rubber hoses, manual over-ride on control valves and steel rather than cast suction nozzle boxes. I liked the automatic fan wash which comes with the optional high pressure lance, otherwise it`s fairly easy access above the tailgate.
Some machines induce dislike from first acquaintance, some improve with experience, a few feel just right. For me the Magnum falls into the third category, due to the brilliant DAF LF chassis. Any driver will love the DAF for its low noise, smoothness and cab comforts, while its nine-speed gearbox, light controls and excellent lock make it an ideal basis for sweepers.
"Just use crawler gear and take your time", said demonstrator Tony Lawrence, "and you`ll find it`s easy". And he was right.
The cruise control is used to set engine speed to about 1000 rpm. Switching on the fan and imposing its 45 bhp load makes no difference to engine speed or noise, such are the wonders of electronic diesel control. With 180 bhp available the DAF isn`t even trying, and letting out the clutch in crawler gear produces effortless progress at 1.6 mph.
With both side brushes and centre brush extended the Magnum swept a 3.2m path around a long neglected car park with many loose stones. The surface was left spotless, leaving only a light stain where cement powder had been scatterd on oil spillages. Even this disapeared when the optional high-pressure front water jets were selected, the powerful suction leaving the surface almost dry. On lighter work the machine will sweep happily in fourth gear and full width.
The wander hose is equally impressive, bricks and rocks being lifted from several inches away and light material from up to a metre. In fact the suction is so strong that the fan speed must be reduced slightly to prevent the hose locking onto the ground.
Like most people, I expected a cost advantage from using red diesel for an auxiliary engine rather than the all too expensive white required by the motive power. But because the Scarab has only one engine working in its most efficient torque band it uses less fuel than a twin-engined sweeper with one idling and its auxiliary working hard, doubling friction and thermal losses. In fact the Scarab uses as much as one-third less, according to tests carried out by the Paris municipality.
Mr Lawrence says the Magnum is hard pressed to use eight litres per hour on the heaviest work, which compares with up to 12 litres for a typical auxiliary engine alone and easily cancels out the `red` cost advantage. The Scarab produces lower emmisions and makes less noise, of growing importance as contractors move to the enviromental standard ISO14002. And there is only one engine to fuel and maintain.
The DAF engine is very quiet, like those on all modern trucks. An auxiliary engine produces more noise particularly for the driver, which I find very tiring whether it`s a sweeper or a fridge rumbling away behind my head. And the public is becoming less tolerant of noisy machinery.
The Magnum Unidrive has to be a strong contender for the price-conscious contractor who wants to stay with a manual gearbox yet enjoy the Scarab economy and enviromental benefits. However for following a planer or municipal work the extra cost of Scarab`s hydrostatic drive would be well justified.