Equipment Details: Free up your hitch

Transportation is not the only reason for driving a truck to the jobsite today. Contractors are using their trucks as mobile power sources, tapping the engine, transmission or electrical power to fire up on-board air compressors, generators and welding equipment.

Compared with tow-behind systems, on-board systems offer a multitude of advantages (see the sidebar below). “The emerging technology is definitely on-board,” says Tom Noland, Ingersoll-Rand’s manager for business development, On-board Power Solu-tions. “It’s rare to see a gas utility towing a compressor today,” Noland says. “Years ago a crew was two or three trucks and six guys. Today that crew has shrunk to one truck and two men. And that crew also needs the hitch to tow a backhoe or other equipment.”

Unlike tow-behind machines that are mostly similar, there is a lot of diversity in the on-board truck systems market. And each system offers different capabilities tailored to a variety of contractors and applications. Some do just air, others electrical power, others welding and some do a combination of two or three. So here’s a look at the major players in this market and what they have to offer.

Natural gas utility crews are the primary customers for Ingersoll-Rand’s on-board air compressors, Noland says. These crews use the air to run tools and pressure test lines. Water and electrical utilities are also using on-board air to do everything from pole jetting to blowing fiber-optic lines or mice through conduit. Service trucks also factor into the customer base.

The company offers rotary-screw, under-deck systems (typically 90 to 185 cfm and 100 to 150 psi) and two above-deck piston compressor systems: the VHP30 (30 cfm/175 psi) and VHP40 (40 cfm/175 psi). “Ours can be PTO or hydraulically driven,” Noland says. Direct-drive PTOs are generally preferred, but trucks that already have hydraulic systems are good candidates. “For the below-deck systems if there is a side-mount PTO and it is accessible we would prefer to use it,” he says. “That would be a typical Chelsea 442 gear box and a short driveline directly attached to the airend. These are all mounted underneath the truck between the frame rails.”

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On four-wheel-drive vehicles where you can’t use a side-mount PTO, Ingersoll-Rand’s solution is to insert a gearbox that splits the driveline so you can operate in the road mode or the compressor mode, Noland says. “But those are rare,” he adds. “A much smaller percentage of the under-deck compressors are split shaft – 5 percent vs. 95 percent side-mount PTO. You only use them when you have a four-wheel drive transfer case interfering with the PTO port or there is no PTO port,” he says.

Ingersoll-Rand can also tap the truck’s engine for electrical power. “You can drive onboard, below-deck generators or welders hydraulically with a belt off the compressor, or using its own PTO gearbox and driveline so you can operate them together simultaneously,” Noland says. “If there is only one PTO available and the customer wants both, we’ll belt drive the generator off the compressor and you can get up to 10 kilowatts in that application and 185 cfm of air. They’re becoming very popular and they provide a very stable 60-hertz frequency that is needed to drive the central plastic pipe fusion machine used by the gas utilities and the waterpipe industry.”

With service trucks as its main business, IMT provides a wide range of compressed air options for its products. “We offer hydraulic and direct-drive air compressors ranging from 35 to 80 cfm with a maximum of 150 psi, both reciprocating and rotary screw,” says IMT product manager Tim Worman. “We manufacture our own and control all the electrical and hydraulic component integration into our body.”

The typical customer for IMT is a heavy equipment service technician working for a contractor, dealer, rental store or tire vendor. And since most of these trucks come with a hydraulic crane, hydraulically driven air compressors often make the most sense. “Hydraulic drives are more selectable as to where you can mount them,” Worman says. “They’re not under deck, so they’re less susceptible to damage. And they’re more compatible with the chassis.”

Direct-drive air compressors, however, are popular in the tire industry, Worman says. “In the tire industry they’re using a lot of air and direct drives are more efficient and don’t have the cooling requirements of the hydraulic systems,” he says. “The biggest advantage of direct drive, though, is that it’s under deck. The configuration of a tire truck limits the amount of storage and, with the compressor mounted under deck, the storage is not as compromised.”

Worman cautions contractors to do their homework before buying a truck they’ll want to configure with an air system. Certain chassis manufacturers run their transmission cooling lines over the PTO opening, making it difficult to mount components there. And some automatic transmissions may limit the amount of horsepower and torque you can draw from them without risking the chance of voiding the warranty.

On its 4000 and 7000 series trucks, International offers the factory-installed Diamond Logic PowerPack 3, a 3-kilowatt AC electrical power solution for anybody who needs mobile power, says Brad Bishop, business line manager. “This would include the construction and utility contractors who are using power tools, lights, portable air compressors or whatever the jobsite requirements are,” he says.

One advantage of this system is packaging, says Rich Glasman, product line manager for truck electronics. “It fits in the battery box, or you could put it anywhere you deem appropriate,” he says. “The utility people tell us that cabin space on a truck is about $100 a square inch and our system takes zero.”

Another consideration is the quality of the electricity, Glasman says. “Our systems provide clean power when you want to recharge,” he says. “There are two different types of power, clean or sine like you get out of your house, and quasi, which a lot of inverters or generators produce. Quasi is hard on batteries. You want to charge with sine. For tools or computers, anything to do with batteries, quasi power will reduce battery life on the equipment.”

Unlike the other systems mentioned in this article, the Oasis brand of on-board air compressors operate off your truck’s battery, either 12- or 24-volt DC. “We provide 10- foot power leads that connect straight to the batter terminals,” says John Williams, president of Oasis Manufacturing. “We recommend customers mount an auxiliary battery as close to the compressor as possible. Then they can cut the power cable to 2 or 3 feet.” Williams also recommends a deep cycle battery like those made by Odyssey.

Oasis compressors give you the equivalent of a 3- to 4-horsepower shop compressor, Williams says. “The big advantage is that you can put them just about anywhere you want,” he says. And you can install them on any size truck, not just 3/4 ton or larger. The compressors can be run with or without air storage tanks, and even without a tank they generate enough air to run a 1/2-inch impact wrench, he says.

The 5-horsepower, 12-volt HP1000 compressor generates 8 cfm at 100 psi and a maximum pressure of 200 psi. The 24-volt version cranks out up to 16 cfm at 100 psi with a maximum pressure of 125 psi. The XD2000 uses a modified 5-horsepower motor with a cooling fan to extend run time and is capable of 90-percent duty cycle.

The units are also portable and can be removed from the truck to get closer to the work area or connected to any 12- or 24-volt DC power source. Air storage tanks are available from 1.5 to 6 gallons in size. (And if you’re looking for a little street cred, the company can couple your compressor with one of its air suspension kits that can turn your truck from a raised to a lowered stance at the flip of a switch.)

For construction and equipment service organizations that need a truck to simultaneously provide all three functions – power, air and welding – there’s the PowerBox 3-in-1 units from Dynamic Power Source. “Many field service trucks have been outfitted with a separate welder, compressor and generator,” says Brian Wilcher, marketing specialist. “We decided to compact all those components into one unit and make more efficient use of the equipment and the work vehicle.

Although the company made its mark initially with self-powered, above-deck, three-in-one units, customer inquiries convinced the company recently to create a new PTO-driven model, the 280HD. This hydraulically powered, above-deck unit puts out 200 amps of welding power, 5,500 watts of electrical power and 20 cfm of air when hooked to a 14 gpm/3,000 psi PTO. The unit is self-contained and weather resistant and, unlike the company’s self-powered models, can be mounted on the side pack of a service body, into the load space or onto a welder platform. The control panel can be attached to the unit or mounted remotely into the compartment of your service truck.

The company also offers five self-powered three-in-one units. “Why use a vehicle’s 400-horsepower engine to do what a 20-horsepower engine can do?” Wilcher asks. These range in size from the 280MP with an 18-horsepower Kohler engine, 5,500 watts of power, 20 cfm/150 psi air, 200 amps of welding power and a 6.5-gallon air storage tank to the 450 Diesel with its liquid-cooled, 34-horsepower Kubota engine, 12,800 watts of power, 30 or 65 cfm/150 psi rotary screw air compressor, 350 amps of welding power and a 10-gallon air tank. The company also offers a two-in-one machine, the 175MP, with a 12-horsepower Kohler engine, 7,500 watts of power, 13 cfm/150 psi air and a 5-gallon storage tank. The self-powered units also offer portability – you can lift them out of the truck and leave them at a jobsite.

As compared with under-deck systems, the rotary screw air compressors from VMAC are even more space efficient in that they’re under-hood mounted. “With the hood closed, you wouldn’t even know the truck has a compressor,” says Michael Pettigrew, marketing manager. The company has also recently introduced the Predatair60, a hydraulically driven, above-deck system.

Customers for VMAC’s systems are primarily users who are repairing and maintaining heavy equipment, Pettigrew says. But with the high-volume capabilities of the rotary screw design, it is possible to run up to two jackhammers on the company’s larger unit. And Pettigew says he has known of customers who used the system to provide their shop compressed air in a pinch.

VMAC’s under-hood systems are belt driven and mounted on a cast bracket that bolts onto the front of the engine. The bracket aligns the compressor with the crank pulley and features an auto tensioner and idler to eliminate side loading. The VR70 provides up to 73.5 cfm and 175 psi. The VR140 provides up to 150 cfm and 175 psi. Installation of the under-hood systems is limited to North-American-built work trucks as each system is engineered to fit specific engines and chassis, Pettigrew says.

The Predatair60 hydraulic above-deck model cranks out 60 cfm and 175 psi and is easy to transfer to other trucks. If the truck is equipped with the proper hydraulics, installation is fast, Pettigrew says. The unit pulls its power from a PTO or a clutch pump. Minimum system requirement is 13 gpm and capabilities range up to about 21 gpm. At 13 gpm, the system will produce about 40 cfm. At 20 gpm you’ll get about 60 cfm.

On-board systems vs. tow-behind
On-board pros:

  • Frees up the truck’s trailer hitch to carry skid steers or backhoes and other machines
  • Eliminates theft risks
  • Eliminates risk of damage to stand-alone unit
  • Eliminates need to drop off unit at the shop or yard before taking truck home for the evening
  • Lower costs – you don’t have to pay insurance, toll charges or license fees on second system
  • Reduced labor in that you don’t have to do preventive maintenance on a separate unit.
  • Easier maneuverability/ tight space access

On-board cons:

  • Some systems are truck specific and can require additional components or expenses when transferred to other trucks
  • Truck can’t leave work area during operation
  • Most systems require a 3/4-ton or larger truck
  • Usually can’t be sold as used equipment
  • Can’t be left at the jobsite while driver runs other errands

Rotary screw or piston compressor
Rotary screw compressors are the newest technology in air compression and develop high pressures and volume instantaneously – no storage tank is necessary. They’re great for high demand applications, and the lack of an air storage tank helps free up storage space. Contractors with high air volume applications such as running multiple jackhammers, pressure testing lines, blowing cable and rock drilling usually favor rotary screw.

Piston or reciprocating air compressors use a storage tank and can’t run wide open full time like the rotary screw compressor, but contractors like them because they’re relatively bulletproof and deliver enough air for most service-truck-type applications – filling tires, powering air tools and such.

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