Making a mixer

Trailer and body maker Gorica has been established since the early 1990s. We paid a visit to watch a concrete truck being born.

ANALYSIS, PMV

Trailer and body maker Gorica has been established since the early 1990s. We paid a visit to watch a concrete truck being born.

Trucks are so common over the Emirates, it is easy to forget that the many different body styles do not simply come off a production line, rather they are designed especially for purpose.

 Today, plenty of firms with a base in the region produce truck bodies, but few have been as long established as Gorica, who have been in Jebel Ali since the start of the 1990s.

All the steelwork is taken care of on site, and designs for the bodies and trailers are also taken care of at the premises, though dustcarts and concrete mixers are co-designed with partners.

It is this can-do approach to engineering that Paul Austin Price, Business Development Manager, Gorica, attributes, in part, to the success of the company. "Our design and innovation has helped, as we draw all our own plans."

"We can manufacture anything, whatever the customer requirements." he said.

Due to the construction boom, Gorica have a very healthy order book, with, perhaps unsurprisingly, concrete mixer bodies seeing the biggest increase in sales.

"We produce around 80 drums per month of which 65 are concrete mixers" said Denis Gulin Deputy General Manager, adding that while mechanical components such as the gearbox are brought in from Europe, all the heavy fabrication is done in-house.

Chassis

Most of the mixer bodies that Gorica make are assembled directly on the rigid chassis of a large truck. In the past the firm has also built special order machines based on a semi-trailer, but these are rare.

To start, the steel to be used for the drum needs to be a fine grade, due to the harsh life the machine will lead.

Pressing matter

"The metal we are using is special, imported from Germany. It is manganese steel which is used for the drums" explained Paul Austin Price, as the first batch of metal is moved into place by a giant overhead gantry crane.

At the start of the production line, the backplate for the mixer drum is the first, and most complicated piece of metal to be fabricated. A large press shapes heavy-gauge steel in to a concave disc.

A second, more specialised machine used a bearing to roll the sides up be several inches. Next, the steel for the drum needs to be cut, so that the drum and the spiral can be assembled.

Clearly, this needs to be carefully done as the pieces have to fit together perfectly, so extensive use of a computer programme is employed to cut accurately.

This electronic process controls a plasma cutter to obtain perfect shapes. "CNC helps us produce more, faster and more effectively" said Denis Gulin.

The technology behind the cutters at Gorica was developed with software engineers ESAB of Sweden.

Welding

After rolling steel for the mixer drums, the containers are welded in sections, complete with the steel that makes up the mixing screw in place.
 

Initially the parts are tacked in place to hold them, then the unit is moved with the gantry crane on to a large rig with an automatic welder.

The barrel is turned, just as it would be when the mixer is in use, and the auto-welder follows the line as it out-spirals. "This is a far neater and higher quality way of welding, compared to doing it by hand" Gulin said, while indicating the neat, stippled effect of the joined seam, looking not unlike the icing on a cake.

Next, the drum is moved to another part of the workshop where it can be sanded down, and ready for media blasting, in preparation for priming. This is done in order that the paint might stick to the metal, as swarf and other impurities prevent it from bonding to the surface.

Drums reunited

After priming it is time to unite the drum with the rigid chassis truck that will carry it about. Most of the trucks that Gorica deal with are brand new, though any chassis supplied be the customer can be built on, and it is not uncommon to fabricate a new drum, where the old has either worn out or has become damaged in some way.

Paint shop

The red oxide primer is applied and left to set, before final preparation of the body.

Next, the truck makes a visit to the paint shop.

Situated in a sealed block outside the main production facility, the spray booth is modern and extremely clean. Workers wear air-fed masks as the paint used is hard-wearing two-pack, which is good for trucks, but bad for your lungs if inhaled.

The paint is also mixed on site, again with the assistance of computer control to continually get a good match.

"We can paint the truck whatever colour the customer requires, of course, but white is always the cheapest and most common option." Gulin said. Interestingly during painting, the drum is rotated as if the machine was mixing in order that the sprayis applied evenly, everywhere.

Elsewhere in the factory, highside, curtainside, tipper and tanker trailers are built. These are all bespoke, made to the customer's requirements.  While the mixers are built on an existing chassis, the trailers have their own chassis fabricated.

First, the rolled steel is brought in to the factory by a side-loading fork lift. This has an advantage over conventional trucks in that the long and flexing RSJs can rest on the specially designed flanks of the truck. Workers then attach the metal to a series of overhead gantry cranes, which then move the metal down the production line.

This required building onto pre-assembled axles. The difference here is that assembly of the chassis is started with the unit upside down in order that the suspension, axles and brakes can be assembled without the workers getting stiff necks from having to crawl underneath.

Later in production, the unit is easily flipped over, using the power of the massive hydraulic gantry cranes.

Generally, the brakes used on the trailers are sourced from the American manufacturer Wabco.
 

Unsurprisingly, these are heavy duty items and a range of technologies are offered as Paul Austin-Price explained; "Discs offer better braking and heat loss, but it is very difficult to change the mentality of some owners."

The wheel rims are made by Gotrade, a subsidiary of Gorica, and the tyres, particularly for non-road vehicles need to be ordered months in advance. However, providing this is done, supply is steady.

U-body

Walking around the compound, there are a variety of different types of trailer being fabricated. In one area, workers put the finishing touches on a bitumen tanker, while else where welders buzz and crackle on a brace of tipper bodies for moving gravel.

One was a conventional flat-floor unit, but the other was something a little more specialised. "This is a half-U, where the actual body is U-shaped" said Austin-Price "This is a Gorica speciality, similar to tipper bodies used all over Europe."

So, next time you see a heavy truck or trailer on the road, spare a thought for where it came from... and those who built it.

All about mixer trucks

Way back in 1916, an inventor called Stephen Stepanian filed a patent for a mixer truck, though it wasn't for another thirty years or so until they became a common sight.

The ready mix truck maintains the material's liquid state, through agitation, or turning of the drum, until delivery.) The interior of the drum on a concrete truck is fitted with a spiral blade known as an Archimedes screw. In one rotational direction, the concrete is pushed deeper into the drum. This is the direction the drum is rotated while the concrete is being transported to the building site.

This is known as "charging" the mixer. When the drum rotates in the other direction, the Archimedes screw-type arrangement "discharges", or forces the concrete out of the drum. From there it may go onto chutes to guide the viscous concrete directly to the job site.

If the truck cannot get close enough to the site to use the chutes, the concrete may be discharged into a concrete pump connected to a flexible hose, or onto with a conveyor belt which can be extended some distance.

A pump provides the means to move the material to precise locations, multi-floor buildings, and other distance prohibitive locations.

"Rear discharge" trucks require both a driver and a "chuteman" to guide the truck and chute back and forth to place concrete in the manner suitable to the contractor.

Newer "front discharge" trucks have controls inside the cab of the truck to allow the driver to move the chute in all directions. The first front discharge mixer was designed and built by Royal W. Sims of Holiday, Utah.

Concrete mixers generally do not travel far from their plant, as many contractors require that the concrete be in place within 90 minutes after loading.

If the truck breaks down or for some other reason the concrete hardens in the truck, workers need to enter the barrel with jackhammers; dynamite is still occasionally used to break up hardened concrete in the barrel under certain circumstances.

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