The brand new High-Performance Circle (HPC) for Cat® 140, 150 and 160 Motor Graders increases performance, lowers total cost of ownership and improves drawbar durability. Product Specialist, Darren Hodge introduces Caterpillar’s new HPC option.
Through the years, Caterpillar has revolutionised the operation of motor graders with the introduction of joystick controls and a suite of advanced machine control and technology solutions, delivering enhanced operability and productivity.
Caterpillar Product Specialist, Darren Hodge says the new High-Performance Circle (HPC) option is yet another innovation from the globally renowned equipment manufacturer that’s sparked excitement from owners and operators around the world.
“Before we get into Caterpillar’s new HPC introduction, let’s look back at traditional Motor Grader design and past developments that led us to this new innovation,” Hodge says.
“As we know, Motor Graders spread and shape materials to a curvature and elevation design typically in road construction and maintenance. The drawbar, circle and moldboard (DCM) is the prime work tool to complete these works.”
The DCM has many linkages and moving parts to position it in a multitude of positions for precision grading.
The DCM can be lifted and lowered to control blade finish elevation. The blade can also slide left to right for greater reach, while also being able to be tilted fore and aft to assist the material rolling action, for easier spreading.
The main drawbar pivots within the main frame for greater reach in cutting ditches and side/high bank slopes. The circle can be rotated to maintain a desired blade angle of up to 360 degrees, but typically 0 to 50 degrees, depending on blade loads.
“In all, there are up to 10 linkages, ball joints, couplings, sliding surfaces and gears to complete these operations, which all require wear tolerance maintenance, consuming expensive time, labour and parts to maintain,” Hodge says.
“A well-maintained DCM structure will ensure long life and durability of the components and ensure wear between parts is kept to a minimum, ensuring blade elevation position remains stable for accurate surface elevation finish.
“If left unmaintained the DCM can be a costly assembly to repair, and reduced lifetime of components is expected. Wear between linkages, slides and gears left unmaintained results in blade chatter, uncontrolled horizontal and vertical movement of the blade.”
Operators are expected to meet road construction design tolerances for curvature and elevation finish within five millimetres to 15 millimetres, error to specifications. With a worn DCM, the blade chatter can be actually greater than 10 millimetres of blade movement, making it very difficult to meet design requirements efficiently.
“Fortunately, the Caterpillar Motor Grader DCM linkage design makes work a little easier to maintain this structure,” Hodge says.
“All these moving, sliding components can be easily adjusted to maintain a tight tolerance between moving surfaces and all the components include exclusive low-cost sacrificial wear strips, preventing costly parent metal wear out of the ball joints and sliding surface.”
Hodge adds that the traditional Cat design has been “the leader” in providing the lowest cost of operation for the DCM.
“Our G and H Series Motor Graders have shoes that carry the circle within the drawbar and allow for 360-degree rotation by a circle drive pinion and inner circle teeth,” he says.
“To maintain this structure once worn with movement between, circle gear shoes and drawbar assembly required extensive heavy labour under the DCM to remove supporting shoes, maintain shim thickness and adjust thumb screws.
“This much-needed maintenance reduces wear between the horizontal drawbar and or circle surface. As well as between the circle and drawbar, to ensure smooth meshing of drive pinion and circle gears.”
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Sacrificial wear strips are located between the circle shoes and inner drawbar, and between the horizontal rotating surface of the drawbar and circle, requiring periodical replacement when worn beyond reuse guidelines.
With these repairs the grader could spend days in the workshop just to maintain this structure, resulting in a lot of downtime and costly labour and parts.
With the introduction of the M Series grader, this structure was re-designed to significantly lower the time required for adjustment and replacement of wear strips. Called the top-adjust, this drawbar was an exclusive design where the adjustment for wear between the circle and drawbar and replacement of wear strips could easily be maintained from the top of drawbar assembly, saving up to 70 per cent in time and labour costs.
“That’s set to get even better, with the introduction of Caterpillar’s new HPC,” Hodge says.
The HPC design improves machine performance, efficiency, and uptime through increased service intervals and longer life. Meeting grade elevation tolerance in road design efficiently is important to reduce rework on the job. With the HPC, operators have greater confidence in meeting grade elevation tolerance design due to reduced wear between circle and drawbar.
The HPC helps to eliminate hours of monthly planned maintenance for frequent inspection, wear strip replacement and circle shoe adjustments associated with conventional circles. The new design includes increased circle torque, performance, and improved durability advantages, providing a smooth, effortless rotation of blade, further assisting operators to meet road design elevation tolerance.
“With thousands of hours of testing before introduction, the proven design for Motor Graders can reduce service and labour time costs by up to 40 per cent when compared to the previous models,” Hodge says.
The design includes already proven structures and components with the heavy-duty drive system, adopted from the Cat Excavator swing drive and grader worm drive from the Cat 14 Motor. A fully sealed bearing design replaces the open circle and drawbar, reducing maintenance touchpoints, removing exposure to abrasive materials during grading and increasing service intervals and machine uptime. A centrally located grease bank is easily reached to the lubricate circle ring and drive gear assembly.
A readily accessible cover can be removed for periodic wear inspection of circle ring and once worn (likely after thousands of hours), the split ring can be rotated to get an extended replacement interval.
“We expect that within the grader’s first period of ownership, it’s unlikely the swing drive ring replacement will be required, as it is fully sealed, preventing abrasive soil materials in wearing out the components, compared to traditional designs.” Hodge says.
The traditional circle shoes and drawbar to circle adjustment and wear strip replacement are gone, a real winner from backbreaking labour experienced by mechanics.
“The HPC will be a winner with customers using 3D Grade Technology, to reach fine elevation design tolerances in road construction. Although Grade technology can efficiently support the operator maintaining within 5-15 millimetres elevation design tolerance, as I mentioned previously, a traditional DCM design can have greater than 10 millimetres of horizontal blade movement if not maintained frequently,” Hodge says.
“It’s near impossible to achieve road design finish specifications accurately and efficiently with a worn DCM. As such, the new low maintenance HPC design will be a delighter for owners, operators and maintenance personnel.
“3D Grade technology attachments can cost upwards of $100,000, a big investment for owners. But when used to complete road construction with automated controls to finish within tight design tolerances, the job is completed so much more efficiently and accurate saving thousands of dollars in fuel, labour and machine costs.
“The new HPC will enhance the use of Grade Technology saving the customer even more money.”
Make sure to contact a local Cat dealer to learn more.
This article was originally published in the April edition of our magazine. To read the magazine, click here.
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