Thwaites six-tonne power swivel dumper

By: Tim Dittmer, Photography by: Tim Dittmer

Date: 01.04.2011

The Thwaites six-tonne power swivel dumper has a sturdy, basic design that makes it suitable for the self-drive hire industry.

The Thwaites six-tonne power swivel dumper is ideal for self-drive hiring.

Controls are comfortable, easy and logical to use
Swivelling skip allows load to be tipped out the side
Easy to access engine and filters
Smooth and powerful
Strong and well-built

Torque from a 70kW Perkins diesel engine motivates the 4300kg dumper to a top speed of 28km/h. A choice of transmissions is available including manual, hydrostatic, powershuttle and powershift. This one is fitted with a four-speed synchronised gearbox, while direction changes are taken care of by a powershuttle shift box that directs the drive to Spicer axles.

Design and maintenance

Thwaites dumpers use components from Perkins, Yanmar and Spicer, meaning parts are usually available from a lot of suppliers.

The six-tonner appeared to be a strong, well-built machine. It is simple to operate and maintain - the seat is mounted to the key lockable cowling over the engine, which lifts up to allow access to the engine and filters.

Skip body

The skip body is constructed from Domex steel and has a flush capacity of 1.65m3, increasing to 3.15m3 when heaped. The dumper is factory fitted with a hydraulic swivelling skip, allowing it to be swivelled around and tipped 90 degrees either side of centre. With this option the clearance under the front edge of the skip when fully tipped is a huge 1100mm compared to the standard model with only 340mm. Two rams rotate the dump body while one larger ram tips it.

Controls and comfort

Climbing up onto the Thwaites is easy with the help of large steps and well positioned hand rails. Visibility to the sides and rear is excellent, but because the skip is in front it restricts your view, especially when loaded.

A steering wheel controls oil flow to the pivot steer rams. The power shuttle shift lever is located on the left side under the steering wheel, while the lever on the opposite side works the indicators and lights. To the left of the seat is a four-way joystick that controls the skip: push forward to tip, pull back to lower and left and right to rotate the bin accordingly.

To the left of the accelerator and brake pedals is a transmission disconnect pedal, which is useful when you want to change gears on the move or increase engine revs to speed up the tipping cycle while remaining in gear for a fast getaway.

Drive time

Even when loaded the Thwaites has plenty of power on tap while climbing up the stockpile. I stopped mid-way up to try a hill start, and the dumper pulled away easier than expected, with little strain. Once at the top I reversed back down with a bit of speed and applied the brakes mid-way. The machine stopped smoothly and quickly.
Even in second gear it performed well, climbing and descending the stockpile.

The power swivel deck is a huge advantage when it comes to tipping out the load because it can be turned 90 degrees to each side, allowing the load to be dumped or spread along the side of the Thwaites while slowly moving forward or back.
It also makes filling things like trenches with drainage metal or sand a fast, efficient job.

I found using the transmission disconnect pedal in conjunction with the throttle while tipping on a slope a bit difficult because you needed to have one foot on the brake pedal and the other on the disconnect pedal, which left no foot for the accelerator. It was easier to select neutral on the shuttle lever and use the foot brake and accelerator to speed up the process.

While climbing piles of dirt it was possible to grind to a stop when one tyre lifted off due to reaching maximum osculation, but by changing the angle of attack and keeping all four wheels firmly on the ground the traction achieved was amazing.

Back down on the flat I chose fourth gear, and from a standstill the six-tonner pulled away smoothly and with ease. A maximum of 28km per hour can be achieved.

The steering is responsive and quick enough for fast manoeuvring while remaining smooth and controllable.

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