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What Is A PTO Driven Air Compressor?

What Is A PTO Driven Air Compressor?

A PTO driven air compressor is an air compressor that’s driven by the power take-off (PTO) of a vehicle. These innovative air compressors are mounted under the deck of the vehicle, resulting in an elegant solution that’s out of sight and out of mind (until you need it!)

Advantages of PTO Driven Air Compressors

DTM70 PTO Air Compressor

Render of VMAC’s PTO air compressor for Ford

PTO air compressors have numerous advantages compared to traditional above-deck air compressors. The advantages of PTO driven air compressors for work trucks include:

  • Mounted under the deck to free up cargo space
  • Reduce truck GVW
  • Rotary screw air end
  • Provide 50-200 CFM of air
  • No separate engine to maintain
  • Fewer moving parts
  • Can be combined with hydraulic systems

PTO driven air compressors also tend to be fairly simple to install, which can save upfitters dozens of labour hours and reduce the purchase cost for operators or fleet managers. With so many advantages, it’s little surprise that PTO air compressors are becoming an industry favorite.

Vehicles Compatible With PTO Driven Air Compressors

PTO driven air compressors are somewhat sophisticated systems because they are designed to integrate with specific vehicles and applications. As a result, not all vehicles are compatible with a PTO system. Air compressor manufacturers have focused on two of the most common diesel work trucks:

  • Ford F-250 to F-750 Diesel
  • RAM 3500 to 5500 Diesel

PTO air compressors have also been built for industrial OEM applications, such as drilling rigs. These PTO air compressors are much larger machines that are typically skid-mounted and can provide over 1000 CFM.

Direct-Mounted vs. Remote (Shaft) Mounted

The PTOs used in the air compressor industry are typically side-mounted PTOs. Like the name implies, side-mounted PTOs are mounted directly onto the side of a transmission. An air end is then attached directly to the PTO or remotely, via a shaft.

Remote Shaft Diagram by Parker Chelsea (Source)

Remote-Mounted/Drive Shaft Air Ends

Space around a transmission can be limited, which means it isn’t always possible to directly connect an air end to a PTO. When that’s the case, air ends (and other accessories) can be remote-mounted using a drive shaft. The shaft essentially acts as a connector, linking the PTO port to an air end that’s mounted elsewhere on the vehicle.

Disadvantages of Shaft Air Compressors

  • Rotating components are exposed
  • Increased fabrication costs passed onto buyer
  • May cause alignment issues
    • Excessive stress & wear on shaft
    • Premature shaft breakdown
  • Can be bulky and heavy

Direct-Mounted Diagram by Parker Chelsea (Source)

Direct-Mounted Air Ends

Direct-mounted PTO air compressors are a more innovative solution that was developed by VMAC and has become a popular compressed air solution. With this solution, the PTO and the air end are directly mounted to the transmission, eliminating the need for a shaft.

Direct-mounted air compressors have several advantages over shaft driven air compressors. Because direct-mounted systems have fewer moving parts, they tend to have a longer lifespan, produce less noise, and are more efficient.

Direct-mounted PTO air compressors, such as VMAC’s Direct-Transmission™ Mounted PTO Air Compressor, are the new gold standard for PTO air compressors.

Fully Engineered Systems vs. Installation Kits

PTO air compressor kits can be purchased in one of two setups:

  • Fully Engineered Kits
  • General Installation Kits

Fully engineered options are designed to work with specific vehicles and have detailed manuals on installation. They are designed by professional engineers who spend thousands of hours designing the ideal system for each individual vehicle. Upfitters are told exactly where each component should go, right down to the individual bolts.

By contrast, general installation kits are available for a variety of vehicles and provide more of an installation guideline than specific instructions. It’s up to the upfitter to take the guidelines and apply them to specific vehicles, determining each component’s exact positioning and what accessories are required. PTO air compressor kits rely on upfitters’ expertise and creativity, so it’s critical to work with a reputable and experienced PTO air compressor upfitter.

Engineered systems come in direct-mounted or remote-mounted options, while general installation kits are only available in remote-mounted options.

How To Find Fully Engineered PTO Air Compressors

Air compressor manufacturers don’t clearly mark engineered and non-engineered solutions, but they are easy to spot if you know what you’re looking for. Engineered solutions will be marketed towards specific vehicle models, such as the RAM 3500 or Ford F-350, and will be presented as complete solutions.

By contrast, general PTO air compressor kits won’t be geared towards a specific vehicle, are marketed towards several different makes at a time, and are displayed as a collection of individual parts. Upfitters are then required to take these parts and engineer them into a working PTO air compressor system for the buyer’s specific vehicle.

4 More Things To Know When Buying A PTO Driven Air Compressor

Render of VMAC’s Direct-Transmission Mounted air compressor for RAM

Comparing PTO air compressor models can be overwhelming. Many of the benefits of these systems are common across all models, such as reducing deck space, minimizing engine wear, and the use of rotary screw air end technology. But various PTO air compressors are far from equal and there are a few major differentiators buyers should keep in mind when comparing models…

Transfer Case Design

Some PTO air compressor manufacturers redesign or heavily modify the vehicles’ transfer case to create the space needed to fit the PTO and its tertiary components. Unfortunately, this may void the OEM warranty on the transfer case and other parts of the vehicle as well.

Manufacturers who recognize the significance of this shortcoming have designed PTO air compressors that work with the existing transfer cases, no modifications required. While this solution requires more sophisticated engineering, with mounting kits designed for specific makes and models, it prevents warranty and maintenance issues for the end user.

Weight

PTO air compressors for work vehicles vary in weight, which can increase GVW and fuel consumption. The chart below demonstrates just how significant these variations can be:

ManufacturerCFM OutputWeight
VMAC 70 CFM150 lbs (wet)
Competitor 1125 CFM407 lbs (dry)
Competitor 260 CFM285 lbs (dry)

More weight doesn’t mean a better PTO air compressor—it just means the parts are heavier. Operators looking for a PTO driven air compressor should find the lightest, high quality system that will meet their air needs.

Read more about weight concerns for vehicles in this article:

Top 5 Challenges Caused By Overweight Heavy Duty Pickup Trucks

Ground Clearance

The first iterations of PTO air compressors had poor ground clearance and not all manufacturers have updated their designs. The last thing an air compressor should do is limit a vehicle’s ability to get around, so operators shouldn’t settle for any system that notably reduces vehicle clearance.

Installation Times

All vehicle-integrated air compressors have two upfront costs: the system itself, and the time it takes to install it. Truck upfitters will factor in the install time when quoting customers, passing the cost onto the buyer. Savvy fleet managers will find out how much of their money is going towards installation versus labor, and may be able to cut costs by choosing a high-quality engineered PTO driven air compressor with reduced installation time.

Read More About PTO Driven Air Compressors

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