SMOOTHING THE COMMUTER RUN

The site, roughly 20km west of London on the M4 is one of the country's most densely trafficked road and it was essential that the contract which covered the partial reconstruction and resurfacing of both carriageways of the 3km stretch of the six lane motorway stayed open for traffic.

A number of sections of the motorway's slow, or crawler lane had collapsed and required complete replacement. This involved the excavation, and recycling, of the 300mm thick concrete base.

The sub base was then excavated to a depth of 400mm and screened before being relaid in 225mm thick lifts and compacted by McArdle using a Cat CB-534 double drum vibratory compactor.

The managing director, Jim McArdle, is a long time Catophile, 24 years in fact. He claims that the purchase of the CB-534 enables the company to provide its customers with a complete equipment package from a single source for all their earthmoving needs. The current McArdle fleet comprises D6Hs, D250Ds, a fleet of twelve 20 to 50t Cat excavators, including three of the new 300 family machines.

'We buy Cat because they represent excellent value. They offer the right performance, the right economy, are backed by the right support from our dealer and at trade in time, offer the right resale values which makes them easier to sell than most of the competition,' said McArdle.

'The CB-534's variable compaction rate has proved to be a major advantage on road reconstruction works and we have complete confidence that the 10.2t machine can meet the very strict Department of Transport compaction specifications.

'The unit has three independently selected amplitudes so the operator can choose the level that best suits the lift thickness and material on which the machine is working.

'We particularly like the way the eccentric weight system positively locks in place mechanically to ensure the position of the amplitude setting. This also allows the matching of the weight rotation to the drum rotation which improves mat quality,' said McArdle.

The amplitude settings give a choice of 3.6mm, 7.9mm and 10.4mm while the centrifugal force range varies between 4,021kg and 12,043kg. High on the 'like list' is the huge tractive effort provided by the unit's double drum hydrostatic drive which was very handy on the restricted M4 contract.

'The relatively short sections of the carriageway which had to be excavated meant that the compactor needed plenty of traction to climb in and out of the pits.

'Another feature that wins favour is ASC (Automated Speed Control). This is a simple electric over hydraulic control that maintains the forward, or reverse, ground speed selected by the operator; it also keeps mat disturbance to a minimum by smoothing out direction changes. Our operator was impressed with the high degree of all round visibility provided by the units pivoting control console,' concluded McArdle

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