Drive axle inflation systems might not be the Holy Grail of truck maintenance, but they are in a position to cure a vexing problem. Tire pressure maintenance is time-consuming and costly, but there's no debating the savings from properly inflated tires.
Inflation systems for trailers have proven their value in the market, but such systems for steer and drive axles have proven elusive. The problem with a steer axle is the solid spindle, compared to the tube-type axle used on a trailer. It's easier to route the airline through the tube to the spindle and on into the wheel hub with a rotary union and a stator than to work around a solid spindle. In drive axles, the natural barrier is the axle shaft itself.
Obviously eliminating the need for pressure check at all wheel positions will reduce maintenance costs, while at the same time improving tire life and fuel economy, if the experience with trailer systems is anything to go by.
It will soon be possible to do just that. Currently four suppliers are in the later stages of development of inflation systems for tractors: Airgo, Aperia, Dana and Meritor (PSI). Meritor declined to be interviewed for this story, but the others have offered hints at what's soon to come, or is already on the market.
Tony Ingram, president and CEO of Oklahoma-based Airgo, told us his company will have a system on the market "in the next few months."
"We're still a few months away from commercialization," he says. "We have been working with test fleets and OEs to prove and approve the product and we're nearly there."
All the moving parts and connections are inside the axle housing, with hoses leading from the face of the hub to the individual wheels. Each wheel has a check valve to prevent both tires from deflating in the event one tire blows out.
"Our focus is to work with the OEs and get the system installed at the factory," says Ingram. "Retrofitting is more work and would require some special tooling, so we don't expect to see a lot of activity on that front."
Ingram says Airgo's control system will also be able to sense vehicle load through suspension pressure and will be able to inflate and deflate tires to the optimum pressure for the load, which could a feature well received by fleets that run a lot of empty miles or with declining loads.
"The key factors in the fleets' minds are ease of maintenance, durability and price, though not necessarily in that order," Ingram says. "Our goal is a million-mile seal. We haven't gone that far yet, but we haven't seen any failures that would suggest they won't last that long. We worked extensively with the University of Oklahoma to develop and test the seals, and we very happy with what have now."
The steer axle, like Airgo's trailer system, uses an external rotary union. Ingram says the installation isn't difficult. "The challenge has been getting the OEs to accept it, and some now have," he says.
The Halo tire inflator from Aperia Technologies is a different sort of critter. It's more of a pressure maintenance system than an inflation system, though it can do that too. The bolt-on Halo device uses a small internal pump driven by the rotation of the wheel. Because of its relatively small size, it delivers a fairly low volume of air, but certainly enough to replenish or adjust pressure loss resulting from minor leaks, leaky valve stems, seepage and even temperature compensation.
Reports we have seen show fleets that have tried and tested it are happy with its performance, and say that it does what it's designed to do. The Halo requires no maintenance, and installs in less than five minutes with common shop tools. It's reusable and can be used at all wheel positions except the steer axle at this point.
According to the website, The Halo device is NOT recommended for use on wheels with convex shape such as steer positions. The convex shape of the steer tire wheel end makes the Halo device more difficult to safely mount via a bracket system. "The company is exploring mounting options for steer axles and should have a solution in the future," the website notes.
Joshua Carter, co-founder and CEO of Aperia Technologies, says the company has put Halo through several prototype generations based on testing and fleet feedback.
"Engaging fleets and real industry experts has allowed us to develop the right product," he says. "Without that experience the Halo wouldn't be what it is today."
Dana has been building central tire inflation systems for military and some vocational applications since the 1980s. These are traction enhancing systems, which can adjust tire pressure up or down depending on the need for traction in soft or sandy soils. These systems are generally more than is needed in an on-highway application where only top-up air may be necessary to maintain a preset inflation pressure.
However, Dana has a system in development (as yet unnamed) that leverages the sealing technology used on the military side for an on-highway application.
"We're looking at a sealing technology that's integral with the axles," says Tom Bosler, global director, Product Planning at Dana Holding Corporation. "And not just drive axles but steer axles as well."
Bosler says the seal is the key to making it work. He says Dana worked closely with a couple of seal manufacturers and developed patent-pending technology that would not have been possible just a few years earlier. Between their engineering expertise with axle technology and the new sealing technology, the new system is supposed to have the lifespan that on-highway users are demanding.
"We have about 6 million miles worth of lab testing on the seals since the product was first unveiled at IAA in Hanover, Germany in 2012," he says. "We also have product out on the road in field evaluations."
The system is based upon technology used in the military CTIS system, but scaled down to make it palatable to price-conscious fleets.
"The challenge was to keep as many features and benefits as possible while keeping the cost down to where the total cost of ownership makes sense to a fleet," notes Bosler.
The current version of the product is inflate only, Bosler told us, but added that Dana is working on something that will compensate upwards and downwards.
"It won't be an adjustable system like the military or vocation designs, but it will be capable of temperature compensation," he says.
Bosler, like Ingram, offered little detail on the inner machinations of the seals and the air line routing, except to say Dana has incorporated a way to put air into tires through the axle without external hoses or by pressurizing axles. He did offer that the steer-axle system will use a rotary joint with a cross-drilled spindle.
Dana's system will be an OE-only offering, with a price point based on total cost of ownership and set by the OEM. There are no plans for an aftermarket installation, Bosler says. Dana has not yet announced an actual launch date.
We are aware, as well, that Pressure Systems International, manufacturers of the Meritor Tire Inflation System are also working on such as system, but that's about all we know at this point.
There are externally mounted drive and steer axle system on the market, but they haven't gained wide acceptance in North America as they have in parts of Europe and South America. Ingram says fleets are a bit leery of the external plumbing becoming tangled in road debris or worse, getting broken off.
If maintaining drive axle inflation pressure has been keeping you awake at night, you may soon be able to get a good night's sleep.