Top tips for road grading in South Africa, from the motor grader experts at KH Plant.
When it comes to using your motor grader, every road grading job is different, with a unique set of variables that must be taken into account. Even those who’ve clocked up many hours operating a motor grader will say it takes time and patience to master the job.
Fortunately, the motor grader is a versatile machine that’s fit for many tasks, from mixing asphalt to grading shoulders. Although each task may require different manoeuvres and tricks, some general tips can improve overall safety and help you achieve the best performance.
General operating tips for grading roads
Master motor grader operators will tell you that it’s vital to visualise the steps involved in each procedure. See the finished task in your mind’s eye and ask yourself questions before you start – for example, do you need to fill low spots or cut high areas, and where will any water source fill in or drain out?
As well as visualising each task, general advice for operating motor graders includes the following tips:
- Avoid moving material more often than needed.
- Trimming is made much easier with good compaction. Use some weight on the blade to steady it, rather than being overly concerned with having material on the blade while trimming
- Get familiar with the five blade movements that are made possible by the hydraulic controls, as they’re suited to different tasks. Some tasks require a combination of some or even all of the blade movements. Know what you want your blade to do before lowering it. Know the settings, and consider your angles and heights.
- You can choose to have either a loose blade, for mixing or spreading loose material, or a tight blade, for reshaping an area by cutting down into it. Most of your jobs will need these two options at different stages.
- Similarly, the moldboard can be lifted from both sides so the blade is at a level height (for levelling an area, for example), or you can have just one side raised, if your surface needs to slope.
Road grading and maintenance tips
Potholes are a major problem on South African roads, and can cause serious motor vehicle accidents.
Depending on the quality of a road’s surface materials, cover material can become displaced, creating ruts in the road and causing material to accumulate on the shoulder in places like traffic stops, hills or other areas where drivers tend to accelerate.
To start
To dress the road, there needs to be some moisture, whether from recent rains or hosed from a water truck. Ensure there is good drainage. The road crown should be in straight sections, while the curves should have super elevation.
Road grading tips for straights, slopes and bends
For a straight road, the wear surface should rise at about a 3 percent slope from the shoulder to the road centre. Of course, you need to take the gravel type and area’s rainfall into account. Curved roads need to be flat, but with an incline that has a 6 percent slope down to the inside of the corner.
Trim cutting edges with a torch to keep them straight. Alternatively, you can drag the cutting edges along a smooth concrete surface, provided the blade is still fairly new and not worn too much. Check for wear, as you may need to replace them to avoid wear on the bottom of the moldboard, which would reduce the support needed for your cutting edge.
Shape the road crown. If you still have enough moisture on the ground, you can cut lightly in the spring.
Road grading tips for ditches and surfaces
When the surface is hard and dry, you can drag the cutting edge along the surface, but set it at about 90 degrees to the surface.
With ditches, consider the soil and road type, as well as the right of way. A rough guide is that they should be about 5 centimetres, or 2 inches, lower than the road wear surface.
In areas with high rainfall, elevate the road surface to avoid having water run beneath the road, which can also cause potholes.
Before grading, you need to choose the right speed and moldboard angle. Go slow for delicate work; fast if you’re removing rocks from a road surface. Use a smooth motion, by making use of the many moldboard angles (between 10 to 45 degrees), rather than just bulldozing your way forward.
How to fill potholes (and keep a grader stable)
Cut to the depth of a large pothole. To ensure it doesn’t form again, don’t fill it with loose material. That won’t last under traffic wear. When doing maintenance, it’s best to have the centre-shift lock pin centred, with the drawbar and circle also centred beneath the mainframe.
To keep your machine stable, the mainframe should either be straight or articulated only a little.
Prevent the machine from bouncing by having the mainframe articulated towards the mouldboard’s ‘toe’, at about 1 to 1.5 times the tyre width (around 2 to 5 degrees).
Cutting and moldboard position for grading roads
To begin, the moldboard top should be about 5 centimetres ahead of the cutting edge. Adjust this position according to the material and other variables. Remember that tipping the moldboard forwards or backwards changes depth of cut across the entire moldboard.
As for wheel position, the top of the front wheels are usually leaned in the same direction that material comes off the moldboard. When the windrow gets heavy, they should be leaned in the direction of the windrow.
When working on side slopes or ditches, the front wheels should be in a vertical position. To ensure the front-axle doesn’t reaching its oscillating limit when you’re using articulation to work across a slope, lean the wheels down the slope. Wheel leans can also help an operator make steering adjustments without having to take hands off the hydraulic controls.
Be careful. If you use the full rear tip, you could run into penetration problems. If the cutting edges are worn, doing so could also damage the moldboard bottom or pivot area.
Over time, each operator develops an individual style and instincts, along with a knack for doing certain jobs. Start slow and steady, be patient and persistent, and you’ll master the art of road grading.
For information about the range of refurbished Caterpillar 140G, 140H and 140K motor graders available from KH Plant, contact us online or call one of our representatives on +27 83 274 4882.
