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Weighty Issues

“You could pretty much stand on the back of that trailer and I could tell you how much you weigh,” he retorted.

Countway equipped his truck and trailer with a TruckWeight on-board weighing system – the very first system to be installed by the local supplier, in fact – and he says he has only exceeded his gross vehicle weight once in the six years since it was installed.

“A stick flew up and bent one of my levelling valves,” he explains. Knowing Countway is vigilant about compliance, the inspector let him off with a warning.

Countway is one of a growing number of log truck operators who has made on-board weighing devices a must-have piece of equipment.

“I’m lost without it,” he says. “I don’t have to worry about going across the scales and being overweight and I can max it out.”

Countway said no two loads of wood are the same, as density and water penetration could make two seemingly similar loads cross the same scale at vastly different weights.

“This takes the guesswork out of it,” he said.

The obvious advantage of an on-board weighing system is the avoidance of overweight fines. But Peter Panagapko, president of TruckWeight manufacturer Smart Scale Technologies, says the real payback comes in the form of improved productivity and maximizing payload. Panagapko cites one forestry study that showed transporters routinely leave 5-8% payload on the table to avoid running overweight, which costs them $10,000 to $20,000 per year.

“There are significant savings in being able to maximize each payload,” he says. The other benefit is being able to avoid scale fees at commercial scales as well as the time and fuel spent travelling to certified commercial scales.

“What drives a lot of the purchasing decisions is the fact they’re spending money on out-of-route miles and scale fees,” Panagapko says. “This will eliminate the half-hour of travelling it takes to check weigh a load and the $10 scale fee, so it doesn’t take long to pay for a unit.”

Smart Scale’s TruckWeight system, manufactured near Halifax, N.S., is one of many available on the market at a wide range of price points.

Scale manufacturers use various techniques to determine weight. Some, like TruckWeight, use axle-mounted strain gauge sensors on mechanical suspensions to measure weight based on axle flex. Air sensors are used for air suspension systems (one sensor is required per axle group or levelling valve), and a combination can be used on units that have both air and mechanical suspensions. Other suppliers, such as Vulcan On-Board Scales with a Canadian office in Port Coquitlam, B.C., use strategically placed load cells, which measure weight more like a bathroom scale.

“For logging, we’re mainly using load cells beneath the bunks, fifth wheel load cells underneath the fifth wheel and air sensors on the trailer air ride suspension or truck air ride suspension,” Vulcan’s Bryce Molander tells Canadian Forest Industries. “We can do any suspension: spring, air ride or walking beam, it doesn’t matter.”

The weighing method employed also influences price, ease of installation and cost of repairs, so customers would be well served to shop around and compare the various systems that are available.

John Hughes, vice-president, business development with Rice Lake Weighing Systems, producer of the Precision Loads line of scales, says most log haulers prefer less expensive solutions since they’re used primarily for compliance. Precision Loads offers both an air system and a load cell system. The load cell offering, Hughes notes, is “a little more accurate and about four to five times the cost.”

Some of the least expensive options in the market consist of air sensors and a primitive, mechanical gauge with a dial that gives a rough idea of weight.

“If a guy is pretty good with the interpretation of that, he can usually tell if he’s road legal or not,” Hughes admits.

Truckers who are fussier about their weights, however, can find a solution that’s accurate to within 0.5% of gross vehicle weight (GVW).

Panagapko notes the accuracy of today’s on-board scales is impressive, considering even certified in-ground scales can have a variance of 1,700-2,000 lbs based on informal studies conducted by Smart Scale.

Over the years, on-board weigh scales for logging trucks have become easier to install, more robust and even more accurate. Vulcan’s Molander says the costlier load cell-based weigh systems are typically accurate to within 0.5% of the vehicle’s GVW. But in certain configurations they can cost up to $12,000 installed.

On-board weigh systems have become commonplace in B.C. and Alberta, where Molander estimates 85-90% of log trucks are so equipped. He said interest in the technology has been increasing in Saskatchewan, Manitoba and Quebec, while Ontario lags. The recession put the brakes on orders for many suppliers, but as the economy has recovered, Molander said interest in on-board weighing solutions is once again picking up.

The systems are easy to use, even if the technology that goes into their design is far from simple. The sensors read weight practically in real time and display it on a hand-held or cab-mounted display so the driver or loader is constantly aware of the vehicle’s weight. Most systems allow the operator to display weights by axle group or GVW. Some developers are now working on adding telematics capabilities that will transmit real-time weight data back to the office.

Nova Scotia trucker Richard Countway equipped his truck with a TruckWeight on-board weighing system. Photo courtesy James Menzies.

The forestry sector has been among the earliest adopters of on-board weighing systems, and as a result, manufacturers have had to upgrade their systems to deal with the harsh environment of off-road logging.

“They’re pretty durable systems,” Molander says. “They’re good to plus or minus 50 C temperature-wise. We’ve had load cells on some logging trucks for 20 years, and some trucks don’t last that long.”

Molander said corrosion is the biggest concern, and in response, Vulcan has replaced metal connectors with those made from nylon to reduce their exposure to salt and other contaminants. He suggests spraying any connections with a rust control product and to keep any grease fittings properly lubricated. Panagapko said the most common maintenance-related problems can be traced back to damaged air suspension levelling valves, as Countway found out first-hand.

“If you have an air sensor on there it’s important the levelling valve is functioning properly,” Panagapko warns. “If it’s not functioning properly it will throw the readings off and if that’s the case, the levelling valve has to be replaced. Levelling valves are maintenance items on trucks and in a lot of cases have to be replaced every five years.”

Strain gauge sensors on mechanical suspensions typically have to be replaced every five years, but Panagapko says it’s an easy and inexpensive procedure. The installation of the systems is also fairly simple, at least for those with some technical know-how.

In TruckWeight’s case, strain gauge sensors are attached directly to the axle using; you guessed it – Crazy Glue.

Those who’ve invested in quality on-board weigh scales generally seem happy with their purchases. But there are a ton of options out there, so the best advice is to shop around and choose a system that will deliver the accuracy and reliability you need at the price you can afford.

James Menzies is executive director of Truck News and Truck West magazines. He produced this article for Canadian Forest Industries.