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Spec Sheet: Motor graders

May 28, 2009 |

Editor’s note: Spec Master delves deeper into the specifications reported in our annual Equipment World Spec Guide. This month’s guest expert: Dan Gillen, product support manager for motor graders, Caterpillar.

Frame type (rigid or articulated)
Articulated motor graders make up the vast majority of machines today – in fact, according to the Equipment World Spec Guide, there are only three rigid frame machines sold in North America. Be aware, however, the articulation joint can be put in one of two positions: in front of the cab and behind the cab. (Caterpillar is a proponent of the behind-the-cab articulation joint position, citing better visibility to the moldboard.)

Operating weight (lbs)
Since weight is a determiner in machine sizes, it tends to be a premier spec in buyers’ minds. But the important aspect of weight is how it’s split on the machine – how much weight is on the rear axle and how much is on the front axle. Typically, about 70 percent of a machine’s weight is on the rear, which gives the machine power and traction; and 30 percent of the weight is on the front axle, which gives the machine control. Be aware of the fine print on this spec – some spec sheets will include the weight of attachments with the base weight, saying the machine is “typically equipped” with these attachments.

<b.Moldboard length (feet)
Make sure you know if the machine gives you the ability to take advantage of the full moldboard length. Some machines have a fixed-position moldboard, so the moldboard slides left or right from a fixed point. Others have a three-position moldboard anchor that can further extend the machine’s reach left or right. A smaller-length moldboard that has the ability to change anchor positions may have more right-left reach than a fixed-position moldboard that’s a bit longer.

Moldboard height (inches)
Combined with moldboard length, this is an indicator of how much material you can carry. Caterpillar says you should also look at throat clearance – this is the distance from the top of moldboard to the bottom of the circle when the moldboard is tipped all the way back. Throat clearance becomes important as the material you’re carrying rolls across the moldboard. If you don’t have adequate throat clearance, that material will strike the circle and fall down to be reprocessed, leading to inefficiencies in productivity and fuel burn. If you put a taller moldboard on a grader, you need to be aware it will reduce your throat clearance.

Moldboard thickness (inches)
This is not a major spec, since manufacturers in the North American grader market typically have a moldboard that is 0.78 to 0.98 inches thick.

Blade lift above ground (inches)
Typically you would only consider this spec when you don’t want the blade to come in contact with any material while the machine is moving. The blade, however, will always be able to lift higher than the lowest point of a grader (usually a transmission or front axle), so your high center point is typically lower than the moldboard cutting edge.

Maximum blade side shift, right/left (inches)
This is an important spec, especially for those who consistently use graders to ditch or slope. As discussed under “moldboard length,” some machines have a fixed side-shift anchor and on other machines you can change the side-shift anchor position and further extend the machine’s side reach.