TECH KNOW

GETTING THE DRIVELINE RIGHT

Meritor are looking to maximise efficiency and durability when it comes to driveline specification, and have come up with a solution for some of the tougher line-haul freight tasks.

It is a constant battle for both truck makers and buyers to get the specification just right for the transport task they are needed for. There are so many variables, all of which will interact with each other to effect performance and durability.

This was the issue which Meritor were considering when looking at drive axle specification in prime movers. When discussing the issue with truck buyers, the market was looking for better fuel economy, lower operating temperatures, lower cost, improved warranty and tight fit differential bolts.

At the same time, the drive axle specification has to be suited to a wide variety of tasks, different tasks have slightly different needs. The decision was made by Meritor to offer two options, one mainly for line-haul and another for the vocational. Each would be specified to meet the different demands of each application.

Operators can choose between a straightforward line-haul tandem axle, suitable for clearly defined line-haul B-double and single operations, with specifications designed to maximise efficiency, including pumpless operation.

The vocational drive tandem axle includes a specification for high spec pinion bearings and tight fit crown wheel bolts, and includes pump and diff lock options on both axles. This is clearly targeted to suit multiple applications and in particular heavy duty vocational applications where customers are looking for reliability.

“OPERATORS CAN CHOOSE BETWEEN A STRAIGHTFORWARD LINE-HAUL TANDEM AXLE, SUITABLE FOR CLEARLY DEFINED LINE-HAUL B-DOUBLE AND SINGLE OPERATIONS, WITH SPECIFICATIONS DESIGNED TO MAXIMISE EFFICIENCY, INCLUDING PUMPLESS OPERATION.”

SCAN QR CODE TO FIND OUT MORE ABOUT MERITOR

ZERO MAINTENANCE DAMPING SUSPENSION SERVICING

Like most systems on trucks and trailers, it is important to understand how Zero Maintenance Damping Suspensions work to conduct a service inspection.

Air Movement within ZMD Air Spring in Rebound.

Suspensions that use Hendrickson Zero Maintenance Damping (ZMD) air springs don’t have the same service inspection requirements as standard shocked suspensions. The main difference with these suspensions is that there are no shock absorbers, which ultimately fail or leak.

OPERATION The ZMD suspension system eliminates the need for conventional shock absorbers and integrates the damping function into the air spring. ZMD air springs have an air chamber built into the lower air spring piston.

The air spring chambers exchange air through calibrated orifices in the top of the piston. When the suspension hits a bump in the road, the piston moves up into the bellows, air in the bellows pressurises and moves through the orifices into the piston chamber. The orifices in the piston restrict air flow in the same way as oil flow is restricted by traditional shock absorber piston valves. On rebound, the bellows area increases in volume and the air in the piston chamber moves through the orifices back to inside the bellows. This action provides controlled suspension movement that delivers good ride quality, eliminating the need for shock absorbers.

However, one function air springs are not able to achieve is rebound limiting. Therefore, to prevent excessive axle rebound movement ZMD suspensions use down stop chains.

Hendrickson ZMD suspensions rely primarily on the air spring for suspension control. Therefore, correct ride height, cleaning and inspection of these air springs plays a critical role in suspension reliability. • Important: The specialised ZMD air springs cannot simply be interchanged with standard air springs.

INSPECTION Ensure that mounting hardware, air springs, spacers and down stop chains are in good condition and correct for the designed suspension ride height. Any worn, damaged or mismatched parts may result in damage to the suspension and suspension components.

Look for chafing or any signs of component damage. Look for misplaced air lines that may rub on air spring bellows. Check to ensure truck or trailer ride height is at specification. Operating at an incorrect ride height will place extra strain on air springs and other suspension components.

Ensure that the upper bead plate is tight against the mounting bracket and that the mountings show no sign of movement. Air springs should be cleaned regularly of dirt and dust that may build up around the bead. Any grime in this area will eventually wear through the rubber bellows and cause premature failure to occur.

ZMD SERVICE FAQ

How can I identify a ZMD suspension?

The main sign will be that instead of shock absorbers, there will be chain down stops. There may also be a label on the trailer chassis indicating fitment of a ZMD shockless suspensions. Closer inspection will reveal the words Zero Maintenance Damping embossed above the unique ZMD part number on the air spring bellows.

How do I confirm the damping on a ZMD suspension is correct since there are no shock absorbers to check?

There are no moving internal components in a ZMD air spiring. So, there are no inner parts that will wear out or fail. If the suspension is fitted with the right air springs, that are in working order, then it will be correctly damped.

ZMD Air Spring Identification.

Zero Maintenance Damping Components.

ADOPTING TECHNOLOGY TO BE SMARTER

Smart trucks, smart braking systems, telematics, alongside some, seemingly, not so smart compliance requirements!

We need to be smarter and start using the basics of these smart technologies for simpler, smarter compliance outcomes, says Bob Woodward, Australian Trucking Association Chief Engineer.

It is disappointing how the mandating of some safety technologies is accepted as a ‘well I have to do it’, as long as it’s fitted, from there I really don’t care! EBS is more, much more than that, and as with many technologies, we don’t know what we don’t know.

However, we also need to be willing to have our ‘what we don’t know’ horizons expanded and start to embrace, by learning and implementing, being more receptive and delving more into the unknown, to start asking the questions, what’s in it for me?

Recently, an operator called to enquire about a statement that he had heard operators can extract axle group weights from a Trailer-EBS system. In respect of trailers, the answer is a definite yes, but may not be so readily accessible, if you don’t have the appropriate outputs/displays.

The fact of the matter is ,you can, and by managing some other specific factors the results can be surprisingly accurate. My own experience, has seen triaxle weights within 80 kg of the certified weigh-bridge are consistently achievable.

But the T-EBS system must be appropriately powered, the suspension needs to be correctly setup and the systems configured and calibrated. The suspension must be set at operating ride-height and the suspension eye bushes must only be torqued up when the suspension is at ride height with the brakes released (many aren’t).

Then the T-EBS system lower and upper calibration set points must be configured using actual weigh-bridge masses (with all brakes released). The ATA-ITC produced a Technical Bulletin with input from ITC partners BPW Transpec, Fuwa K-Hitch, Hendrickson, MaxiTrans and SAF Holland (each ITC members) to assist operators. (See QR Code at the foot of this article.)

The fact is, the T-EBS smarts and mass basics are what provides the inputs for electronic brake load proportioning. So, it’s time to refocus and keep compliance requirements simple. Remember, when using suspension-based technologies for mass management, the vehicle needs to be on level ground and the brakes released to get superior results.

With a few basics sorted, is a fully functioning trailer T-EBS smart? Definitely! So, what could go wrong? Plenty, some of the systems supporting EBS leave much to be desired.

The Australian Design Rules ‘Definitions and Categories’ states:

B-Double, a combination of vehicles consisting of a prime mover towing two ‘Semi-trailers’.

Road Train, a combination of vehicles, other than a ‘B-Double’, consisting of a motor vehicle towing at least two trailers (counting as one trailer a ‘Converter Dolly’ supporting a ‘Semi-trailer’).

ADR 35/06 Clause 5.8.2 says, ‘Each vehicle designed to be used in ‘Road Train’ combinations, must be equipped with a special connector conforming to ISO 7638-1:2003, together with a permanent electrical supply system configured for 24-volt operation.

Note 3 adds, ‘This does not prevent fitment of an additional ISO 76382 connector for a 12-volt nominal supply voltage.’

Sounds simple enough, but there are suppliers and operators who don’t seem to (or want to) understand the downsides, a 12-volt supply just doesn’t cut it as an EBS power supply when there are more than two trailers and if you count the converter dolly as a trailer, an A-double has three trailers.

The downsides of reduced voltage (brown-out) can impact negatively. You can get an over-braked dolly, impacting on safety, or the rear trailer wheels lock-up when lightly laden, plus, there’s trailer swing. Whether you call it a road train or a PBS A-double or a B-triple or any other combination, if it isn’t a B-double and has two or more trailers, it’s a road train and the Trailer EBS supply needs to be 24-volt.

So, what can go wrong with an EBS brown-out? Lots, including overbraking and loss of EBS functions on the trailing trailer/s.

IF IN DOUBT. Talk to your relevant T-EBS supplier: HALDEX, Knorr Bremse or WABCO.

SCAN THIS CODE FOR THE RELEVANT ATA TECHNICAL BULLETIN

EFFECTIVENESS OF REFRIGERATION POWER, THE FORGOTTEN FEATURE OF THERMAL EFFICIENCY

Mark Mitchell, Chairman, Australian Food Cold Chain Council (AFCCC) looks at refrigeration effectiveness.

Coefficient of Insulative Effectiveness.

In the world of truck and trailer refrigerated body benchmarking, a lot of time is spent worrying about the K value or ‘Coefficient of Insulative Effectiveness’. This is of course, important, as is any measurement or standard that confirms the thermal quality of a transport asset.

The diagram below explains it well. If a body is built properly using the highest quality materials and techniques, the K value is lower, and the body will reject more of the outside heat from entering the refrigerated space.

This is all great, but all too often the second part is forgotten, which is the effectiveness of the refrigeration system in combination with the quality of the refrigerated body to achieve an efficient outcome.

The refrigeration system must have enough capacity to overcome the heat leakage of the trailer or truck body and the additional heat load imposed from such things as infiltration, product load, deterioration of the insulation material, and equipment load such from fans and lights.

All the good work of building a great trailer body can go out the window with the wrong choice of refrigeration, and conversely the work of a good refrigeration system could all be in vain if connected to a thermally inefficient or faulty body.

A struggling refrigeration system means that the system needs to continuously operate to cope with the heat load, which results in significantly higher power and fuel consumption. Additionally, temperature sensitive goods such as dairy and meat could be affected and wasted in the absence of proper performance.

In addition to testing for airtightness and heat leakage, the Australian Standard AS4982 sets out requirements of refrigeration performance by measuring the time taken to reduce the temperature in a body, and the system’s ability to hold this temperature over time. For a body to achieve a freezer classification (Class C), the system must start at 38°C and reach -18°C within eight hours and hold this temperature for an additional four hours with an additional heat load of 35 percent added.

This requirement establishes the very important partnership between the refrigeration system and the body of the vehicle. It is the only true way of determining if a truck body or refrigerated trailer is fit for the purpose and the temperature requirement it is built for.

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