Twin-engined sweepers face threat from environmental legislation
In a special contribution to LAWE's Millennium 2000 Preview Issue, Roger Hoadley, the founder and Managing Director of Scarab, sets out his view on the potential impact of Government legislation on the design of road sweepers.
Environmental legislation could bring about the demise of twin-engined
sweepers. The effective subsidy of rebated red fuel will surely become an area for the
UK Government to investigate, particularly if the income could help finance
solutions for environmental issues elsewhere.
Any road suction sweeper requires engine power for propulsion, and for their
brushes and vacuum fans. Machines in the 1960s had mechanical drive from the
prop shaft. When the vehicle stopped so did the fan, and as it took several
seconds to spin up to speed again, a long uncleaned strip was left each time
the vehicle moved off.
The industry found the solution was a second, smaller engine to power
brushes and fan, which require some 50-60bhp.
Lorry engines of the early 1970s did not have that much power to spare, so
by 21 years ago, when I was working for Blaw Knox, there were half a dozen
makes of sweeper, all using two engines. But engine efficiency had been
increasing greatly, so that even a small lorry had enough power for the
With the launch of the Scarab Major range we tackled the problem from
another direction, using a Scarab hydrostatic drive to move the vehicles at
low speeds so that the truck engine rpm could be maintained for fan brushes.
Between sites the hydrostatic drive is disengaged and the truck driven in
the normal way.
More recently came the Scarab Maxim, which uses the normal clutch and
gearbox with a mechanical PTO for the fan, but still using the single
chassis engine principle.
Maintaining Scarab’s technical advances is the latest hydrostatic drive
machine, the Scarab Monic, with infinitely variable road speed for city
Initial development has been based on an Isuzu chassis cab which is only two
metres wide, saving 200mm over most 7.5 tonners. The engine drives a pump
which supplies sweeper services and the hydraulic motor which replaces the
gearbox and clutch.
I am convinced that any investigation into the use of rebated fuel will
spell the end for the twin engine sweeper. Other advantages of the single
engine include one tonne greater payload, and more space in the hopper,
because you have no donkey engine, cooling system or extra diesel tank.
The Scarab philosophy indeed translates directly the task that Government
has set manufacturers to ensure that operators have available vehicles that
- more fuel efficient
- less polluting
- less resource intensive
With exhaust emissions being the predominant source of air pollutants from
road transport, and with the main thrust of measures being to cut down on
pollution from vehicles directed to improving exhaust emission performance
of new vehicles, it is surprising that the retention of ‘auxiliary engines’
has remained for so long. The setting by Government of mandatory vehicle
emissions has only applied in principle to the ‘chassis’ and not to the
total vehicle operation.
It is an important fact that the majority of road sweepers individually have
more impact on local urban air quality as their operating pattern is focused
on towns and cities.
Given that air quality problems are concentrated locally the case for
operating ‘single’ engined sweepers is very strong, particularly when the
units can be used predominantly in urban areas.
Scarab has established a complete range of truck-mounted road sweepers that
have low environmental impact, particularly in respect of exhaust emissions,
without any compromise in their roadsweeping performance.