Scarab's latest Merlin: a wizard on the streets?

The Merlin XP sweeper is built around the Euro 4 chassis and packs an impressive payload. But does it work its magic where it matters? Dan Gilkes took it for a ride

Street cleaning is an essential part of any council's environmental concerns. But, whether the local authority takes on the work itself, or a contractor assumes responsibility for sweeping, choosing the right machine for the job can be a complex decision.

One engine or two seems to be one of the first questions, with pros and cons for either side of this perennial argument. Having an auxiliary, or donkey, engine means that the sweeper brush is run on reduced-tax red diesel, with just the truck chassis being moved by expensive DERV.

Yet there are those who would say that running the hydraulics from the truck's own engine does not add as much to fuel consumption as the second engine will use. As an environmental aside, there also seems little point in specifying the latest Euro 4 engine in the chassis, if the secondary engine does not have to conform to that standard as well.

But there remains demand for both systems, as evidenced by the fact that even Scarab - a long-time supporter of the single-engine truck - now offers a twin-engined sweeper to those who want one, although that is primarily for overseas markets. Scarab's main interest remains in the single-engined market, with the Merlin XP its latest 7.5 tonne model. The Merlin XP has been designed specifically for the requirements of the Euro 4 trucks on which it will be built. And LAWR caught up with one working for the London Borough of Sutton, to the south of the capital.

As mentioned, the Merlin XP was designed around Euro 4 chassis requirements, taking into account the additional weight that they will carry to cope with achieving emissions regulations. This includes AdBlue tanks and other added technology that can result in a weight rise of up to 60-100kg over Euro 3 models of the same truck. While this sort of weight increase can be largely ignored on a heavier model, on a weight conscious 7.5 tonne vehicle it becomes an important consideration.

Making light work of the design
To combat this, Scarab's designers and engineers went back to the drawing board and created a body that is up to 300kg lighter than its previous 7.5 tonne sweeper, offering at least 550kg more payload than some competitors. The XP in the title means just that: extra payload. On an Iveco or Daf 7.5 tonne chassis, Scarab claims that the Merlin XP with a single sweeper has a potential payload of 2,325kg, while the more popular dual sweep truck can carry 2,115kg.

This weight cut has been achieved by reducing the height of the body, the resulting loss of metal making up the bulk of the weight saving. But the truck retains a competitive 900 litre water tank at the front of the body and the hopper has a healthy 5.5m3 gross capacity, down from 6.2m3. That means a hopper payload volume of 4.7m3, which is certainly competitive against a twin-engined truck.

As with all of Scarab's Merlin trucks, the XP uses the firm's proven hydrostatic drivetrain, which is fitted in the chassis between the regular truck gearbox and the back axle. This transmission design allows the sweeper to be driven to the work site as a conventional truck, with all of the fuel consumption benefits of the latest Euro 4 designs. When ready to sweep, the driver simply engages top gear in the regular gearbox and switches on the hydrostatic transmission.

In hydrostatic mode, the operator controls forwards and reverse direction by the use of a simple lever next to the driver's door, which is perfect for those who prefer to sweep with a head out of the window.

The truck's throttle pedal determines the travel speed. At the same time, the gearbox drives the hydrostatic pumps to power the suction fan and brush system, providing protection from abuse for both the truck's driveline and the sweeper attachment.

The hydrostatic transmission provides travel speeds of 0-20mph and Scarab claims that the truck can tackle the steepest of gradients without losing power to the sweeper or suction operation. That suction system uses a 900mm diameter fan mounted in the top of the hopper, providing a virtually straight through flow of air from the suction nozzles.

Nozzle control
The nozzles themselves are 750mm wide with a 250mm diameter suction hose. Four manually adjustable water spray jets are fitted to the nozzles at 90˚ intervals to provide internal dust suppression. An optional four-jet water boost bar can also be fitted in front of the suction hose for use in extreme conditions. The central wide sweep brush is a 320mm diameter design with direct hydrostatic drive. The brush is fully floating with shock absorbers to prevent bounce. Three-speed control is standard and customers can add a brush pressure control if desired.

The suction nozzle, side brush and wide sweep brush can be raised or lowered independently. This provides a variety of sweeping options: from a 740mm wide suction nozzle only; through a 1,060mm suction nozzle and side brush; a 2,000mm wide suction nozzle, side brush and wide sweep; or the full 2,950mm width using both nozzles, both side brushes and the wide sweep central brush.

The Merlin XP also comes with a lightweight 4m long wander hose with a 150mm diameter, for cleaning gullies and awkward areas. Quick release wander hose points are located on wither side of the body's rear door. All of Scarab's sweeping and suction systems are controlled by a sturdy CANbus panel in the cab.

The panel controls the suction, fan, brushes, hopper, work lights and water sprays. However there is a secondary set of controls on the chassis for tipping of the hopper, allowing closer inspection of the tipping area for drivers. The CANbus panel also displays operating data, including fan speeds, distance and hours swept information, and can be used for system diagnosis in the event of a fault.

The Scarab Merlin XP successfully answers all of the questions asked by the latest emissions legislation. With chassis becoming heavier, to cope with AdBlue tanks and other exhaust after treatment, Scarab has managed to reduce the weight of its sweeper equipment to keep payload for the operator high. Certainly there has been a reduction in the hopper volume, but this has been more than offset by the payload advantage, and the truck will be able to work for a lot longer with the slightly smaller hopper than it would with virtually no payload capability.

As Euro 4 trucks become the norm, an increasing number of local authorities and contractors are going to be looking to maximise the use of their vehicles. If they decide to stay at 7.5 tonnes, Scarab's Merlin XP offers a solution to meet their needs.

Dan Gilkes is a freelance road tester

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