Rear-discharge trailers make the road-making process much easier for Avijohn Contracting – Words and images by Warren Caves.

Asphalt – a strange word, described as a dark bituminous pitch mixed with aggregates, mainly used for surfacing roads and sealing roofs. Back in the days of our early seafaring relatives, it was also used (without the aggregates) to waterproof the hulls of the ships during the long voyage out from the Mother Land.

That’s probably about as much thought the average person would like to give to this product. But that’s not the case for Avijohn Contracting, a company that lives and breathes the benefits of working with the sticky and sometimes pungent aroma of asphalt.

Avijohn Contracting is a family-owned company that has been in business for over 25 years. From its origins as a civil contracting company in the Sydney metropolitan area, when it predominantly constructed car parks, driveways and plGrant_Engineered_Trailers_Avijohn-Contracting_15aying fields, the company has developed over the past 15 years and now specialises in supplying and laying asphalt for public and private roads, car parks and sports courts etc.

Founded by John and Vicki Kennedy, they were joined in the business by their son Michael after having completed his HSC. The company operates from its office at Cawdor on Sydney’s sprawling south-western fringe, employing 16, predominantly local, full-time crew members.

“We like all our employees to work for us on a permanent basis. We don’t have casuals and this gives us a keen and dedicated team. As a result, we have had employees come over from rival companies attracted by the job security which we provide,” explained Michael.

“We started out in general civil construction work and now have moved more into the asphalt side of things. We cover all of the Sydney metropolitan area, as well as down the south coast as far as Bega, completing highway upgrades and maintenance work.

“The bulk of our work now comes from local councils and governments, keeping us busy and also maintaining a reliable financial base, enabling us to plan and organise our workforce. We are currently an RMS pre-qualified contractor and local government approved contractor, both endorsements being an achievement of which we are very proud,” said Michael.

Avijohn has several tippers and dog trailers in its fleet as well as rollers, skid-steer loaders, profilers and paving machines.

Historically, the company would use either its own tippers or those of a contractor to tip the “hot mix” into the paver for application onto the road surface. However, due to the recent development and introduction of rear-discharge conveyor trailers, the company has introduced this new design into its equipment base with the fleet.

“The conveyor trailer set-up has some distinct advantages over traditional product transfer methods, which we found attractive,” said Michael.

“First and foremost, the use of a conveyor trailer removes the need for raising the body on a conventional tipping trailer to effect the discharge of material. As it is no longer necessary to raise the tipper body, it makes the whole work scene a safer place, through removing the risk of trailer rollover and also the possibility of the raised trailer coming into contact with overhead power lines or low trees. This removes the concerns of many councils over the possibility of impacting with trees, which has been a restricting factor in many job sites.Grant_Engineered_Trailers_Avijohn-Contracting_1

“We also find that on steep or highly cambered roads it is a lot safer and more secure to transfer asphalt with this unit, as the centre of gravity is kept down low throughout the whole process. Another benefit is that we have a great deal more control over the transfer process in relation to discharge rate and placement,” added Michael.

Avijohn’s new conveyor rear-discharge conveyor trailer was manufactured and supplied by Penrith-based Grant Engineered, and Michael Kennedy says that it really hasn’t had to go back to them for anything more than its first service and has performed admirably. Grant Engineered is a family-run business specialising in the manufacture and repair of truck bodies.

Managing director, Grant O’Brien, has established an excellent local reputation for being able to provide bodywork and trailing equipment solutions, working with a variety of materials including aluminium, stainless steel and steel sheet.

The process for discharging material with the latest design of rear-conveyor trailers is via two small air-operated doors at the rear of the trailer. Both these door openings are significantly smaller than the tailgate area of a standard tipper.

“Straight away we noticed a reduction in side spill out in front of the paver. We are now placing the load directly into the centre of the paver’s hopper, right where we want it.

“The conveyor system gives us more intricate control over discharge rates. This is an important factor, as when using a tipper we may unintentionally drop too much product into the paver’s hopper, through the effect of gravity speeding the discharge rate. If this occurs it can result in a “bogging down” of the machine until some weight is rolled out, not an ideal situation for those operating on the road surface reconstruction,” Michael added.

The conveyor design works by a chain driven system of slats rolled over a central fixed platform, which, unlike other conveyor belt systems, results in an even discharge over the trailer length. This gives an even weight distribution from start to finish, and, if the last load of the job has an excess of product left on board, the remainder will not be concentrated at the rear of the trailer. This can occur in a belt-driven conveyor system and contribute to a breach of legal trailer axle weights. In this chain-drive system the remaining load will be distributed over the length of the trailer, allowing even distribution should it be subsequently necessary to cart away the excess material.Grant_Engineered_Trailers_Avijohn-Contracting_20

The trailer has flip-over rear mudflaps to allow the paver to “butt up” to the rear tyres, and the truck at idle will match the paving speed to give an even result. A small amount of braking may be required on declines to maintain the required slow speed to match the correct discharge rate for the paver.

A small diesel tank is fitted for cleaning purposes and for pre-load spraying to avoid sticking. Underneath the rear of the discharge area is a set of coarse brushes, which prevent any product travelling back into the chains and drive.

Avijohn sources its asphalt from five different bitumen plants around Sydney, and the new rear-discharge conveyor trailer is currently coupled to the company’s Freightliner CST 112.

“The Freightliner has a really low tare weight of around 7.7 tonnes, which gives us a payload of around 25.5 tonnes. This is great for our type of work and we find the bogie-axle trailer very manoeuvrable within our worksites. We also load profilings (old road surface cut up) into this trailer, which adds to its versatility, needing only to ensure it is completely cleaned out prior to re-loading with hot mix bitumen,” said Michael.

“While tipper trucks will still play a role in this type of work, the conveyor trailer will surely become a dominant influence in the delivery and transfer of road-surfacing materials in the future.

Satellite tracking and dash cams are installed in Avijohn vehicles, and, as Michael commented, it’s not so much to monitor the drivers, as to improve efficiency by knowing when a load is about to arrive and subsequently being able to have machines and the crew ready for action.

“All our vehicles are fitted with dash cams and these have proven to be an invaluable asset, proving very helpful in apportioning blame to a third party.

“We try to keep our fleet as new as is practicably possible to promote equipment reliability and prevent any breakdowns or delays which could effect the speed of completion of a specific job. If we dig a road up at night we have to be able to fill it before morning. Failing to complete the job on time would reflect poorly on us as a business,” added Michael.

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