The new fabricated boom also allows for internal hose routings for improved protection. “Some customers complain that the auxiliary hoses on the boom/dipper get snagged on branches or other obstructions when operating in woods or confined spaces,” says MacIntyre. “The N Series boom design helps to address these concerns. The hydraulic hoses are routed inside the boom for greater protection. Also, Case rerouted hoses and changed the bracket design where the hoses intersect between the boom and dipper to provide less chance of contact with low overhangs. This modification also provides the additional benefit of lower transport height.”
The boom maintains a proven placement on the machine. “One of the mainstays of the Case backhoe design is the over-center boom,” says MacIntyre. The boom is positioned “over center” from vertical and tilts forward, with the boom cylinder pinned more rearward than non-over-center designs.
“Advantages of the over-center design include better balance and ride, lower transport height, steeper downward digging angles and uniform lift performance throughout the boom lifting heights,” says MacIntyre. “For an operator, this means the boom can lift, lower and reposition an object near the hydraulic capacity of the boom without degradation at deep depths.
“All backhoes on the market lift more at full boom raise, but drop off when they are below grade,” he notes. “The Case over-center design allows a very flat curve, meaning the design allows a backhoe to lift almost as much below grade as at full raise.” This is important when excavating below grade or setting pipe in the ground.
Backhoes can utilize a number of attachments, so hydraulic versatility is an important consideration. “If you want to install any attachment, the Volvo machine is equipped with a single- and double-acting circuit,” says Bargellini. “So you can actually convert from single- to double-acting on the same machine. You can also adjust the flow for those circuits.”
Caterpillar offers similar hydraulic system versatility. “Caterpillar offers a combined function hydraulic line kit, which allows use of one-way and two-way flow attachments from the same auxiliary lines,” says Hershberger.
“Machine performance is driven by many variables, including hydraulic systems, pressures, flows, cylinder sizes and pin locations,” he adds. “The shape of the boom factors into performance areas like visibility, truck loading performance and digging over foundation walls and other obstacles. All of these factors and others, such as hydraulic valve tuning, combine to deliver backhoe performance.”
Such capabilities can differentiate one machine from another. Consider the revamped slew system on Terex backhoes. “The TLB840 is designed with a new slew system that provides high torque for easy backfilling and slewing uphill,” says Wright.
Boom shape and geometry
Some manufacturers offer curved boom designs. “This design aids in machine balance, especially when the machine is being driven at speed,” says Blower. “The curved boom aids in throwing the backhoe weight over the tractor and not having it hang out the back of the machine.”
That said, JCB has chosen to stick with a straight boom design. “JCB has elected to stay with the straight boom open box design, as cylinders, hoses, valves, etc., can be located inside the box, thus protected from site damage,” Blower comments. Balance for roading purposes is achieved by moving items on the tractor, such as the engine, transmission, etc.
“The shape of the boom has no reflection on the machine’s performance in terms of digging or lifting,” Blower asserts. “The geometry of the boom and dipper working together along with the hydraulic cylinders and pressure provide the power and productivity within the backhoe, not the shape of the boom.”
However, Wright believes geometry is important when talking about overall backhoe performance. Terex uses a curved boom that, when combined with the large cylinders, increases digging performance. “The curved boom design also offers operators greater clearance to reach over obstacles and the ability to load closer into trucks for greater productivity,” he states.
Several generations of Caterpillar backhoe-loaders have featured an excavator-style boom. “Caterpillar launched the excavator-style curved boom on our 446 in 1989, then carried it over to our B Series machines (416, 426 and 436) in 1992,” says Hershberger. “At that time, and for years following, most competitors maintained a straight boom design. Today, many have added some curvature to their boom design. Since then, we’ve improved versatility through hydraulics and available work tools, such as the Cat hydraulic thumb.”