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A GOOD TIP FOR STABILITY

26th October 2006
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Page 42, 26th October 2006 — A GOOD TIP FOR STABILITY
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Which of the following most accurately describes the problem?

OPERATIONS Safety: Inclinometers

A toppling tipper is hardly a good advert for the health & safety of your operation.

In a special test CM examines two stability warning systems which can help maintain your

equilibrium — and your

reputation. Report by

Brian Weatherley. 0 ver the past five years Commercial Motor has written more than its fair share about artic tipper stability. And when it comes to offering advice on tipping safety we remain convinced that while you can build a trailer to the recommended IRTE Class A standard (which lays down that the trailer should remain stable with the body fully raised while on a side slope of up to 70), tipper operators shouldn't use that as a target to aim at when they're tipping on uneven ground!

The simple fact is that when it comes to stability, tipping trailers respect only one thing: gravity. With this in mind, anything that can tell the driver that he's about to raise a tipping body on uneven ground deserves attention from a health & safety perspective.

CM recently looked at two such systems, from Transport Support and PM Onboard, to see what they have to offer.

Test procedure

The purpose of our test was simple: to find out how each system works by simulating a modest side slope — without running the risk of actually turning a trailer over in the process.

For a test surface we used the relatively flat surface of the steering pad at the MIRA test track at Nuneaton. First we laid down a long strip of scaffold boards to create Our sideslope, gradually increasing the slope by adding more boards.We then drove each of our two artic tippers onto the strip so that one set of wheels was resting on them.A simple but effective way to create a side-slope and, more importantly, we didn't have to raise the body.

As we added another layer of boards we recorded what the stability indicators were showing us in the cab of each truck. Working closely withTim Pulford, consultant at MIRA's Vehicle Dynamics department, we were also able to measure the level of the steering pad and whether each vehicle was perfectly level to start with.This enabled us to come up with a 'true' side-slope figure for each artic.We then compared this figure with the angle indicated in the cabs.

In an ideal world we'd have taken our base measurement at the same point on each trailer. We placed our electronic spirit level on the rearmost chassis cross-member on the Fruehauf semi (which had the PM Onboard system). However, the Stas trailer supplied with theTransport Support kit featured a shrouded rear end so we were forced to use the rear under-run bar (see comments, below).

By checking both vehicles for level in a static condition for our 'control' reading we feel we have accounted for any difference between the two measuring points.

Finally, even though the MIRA steering pad looks perfectly flat, we measured a base slope of between 0.142' which we have allowed for in the final readings.

Looking over the figures we're impressed by how closely the angles recorded in the cab displays matched our measurements on the chassis. Equally reassuring was that both incab readings were on the 'safe' side of our 'true' reading; ie, they 'over-read' rather than 'under-read' the side slope.

The in-cab reading from the PM Onboard system was closer to our measured figure. but Transport Support felt that the use of the rearunder-run bar as our measuring point (rather than the cross-member used with the PM system) could have affected the in-cab reading. TS director Carl Griffiths explains:"Our sensor is fitted to the chassis cross-member at the rear of the vehicle and as such monitors any side-to-side movement within the chassis... we have documented evidence that the sensor which we use is accurate to +/0.02°."

It's also worth noting that the TS system display reads to the nearest half degree, so it might well have rounded up the actual figure.

In any case, the automatic ram interlock on the TS system prevents the driver from overriding the stability indicator. Having programmed it to default at 3' on our test trailer it worked as advertised and the loud "Danger! Stand clear! Unsafe vehicle!" audible warning couldn't be ignored.

The auto tailgate device prompted the same alert when we tried to raise the body with the tailgate closed.

PM Onboard's Mark Bottomley reports that similar interlock features can be built into the company's Tipwatch equipment if the operator wants them.

However, he adds that current feedback from PM customers is that right now they prefer the drivers to retain full control and that to them the warning device is the most important part of the system.

Driver feedback

Hanson owner-driver Bal Dhillon and regular Longthorne driver Neil Edmundson knew each other before this test as they work out of the same Bradford Leeds Asphalt coating plant, run by Hansons. Both are strong advocates for their respective systems -and both these experienced drivers clearly put safety first. We asked them if they'd feel comfortable raising the bodies of their respective trailers with one set of wheels on our scaffold boards. Having taken a look at the 3.3-3.4' side slope created by three lavers of boards both immediately said no.

Dhillon told us:-I wouldn't be happy with that, especially with an older trailer. I've seen them go over on building sites.The trailer does get fatigued and it's frightening to look it.

Edmundson approvingly remarked that -you can't switch the alarm off'. Dhillon points out that being able to ensure he is on level ground when being loaded also "saves a lot of grief" with uneven loading. Commenting on stability indicators in general and the PM system in particular. Edmundson told us:"I think they're all right. I've not used it a lot and I've still got to get a feel for what it's capable of but if it's half as good as the rest of the kit PM has come up with it can't he bad.

"We've had PM weighers for years and they've been excellent. Anything that contributes to health and safety is obviously going to be a good thing. The key is knowing what it's saying to you— and the fact that you can't alter it." Operator feedback Mark Longthorne of Hebden-based Longthorne Transport told us:"It was a bonus as we ordered three new vehicles with PM kit [the PM1300] and the stability system came as part of the package.You do find some quarry operators are asking for stability systems [on visiting vehicles] so it will he useful. If a driver is not sure it can be a helpful indicator, but at the end of the day it's always got to be down to the driver having some common sense."

Gary Sleet, assistant unit manager at Hanson's Ripon quarry and Bradford/Leeds asphalt operation, worked closely witb.TS to develop its stability system to Hanson's needs.

"l decided we'd fit one to a vehicle and spoke to Bal [Dhilloni about it and he was picked to have it installed on his truck and reviewed it with the guys froinTS," Sleet reports. We did a lot of work on it— we weren't keen just to have an alarm. We've taken a lot of feedback from Bal and we love it" Mike Whitaker, Hanson's unit manager at its Ripon quarry and Bradford/Leeds asphalt operation, alds:"We entered it into the Quarry Products Association Best Practice awards and it won a Certificate of Merit. I believe it has the potential to enhance safety across the industry and we're hoping all our new franchise holders will fit inclinometers."

Features: Transport Systems

• Ram extension automatcally stops at preset side tilt angle • Solid-state electronics should be reliable • Clear voice warnings alert driver to danger • 'Tailgate locked' warning • Rear-view colour monitor

How it works

At the heart of the Transport Systems inclinometer is the original 'little black box'. This solid-state, digital, three-dimensional sensor is fixed to the tipper chassis and measures side slope angle. It is mounted as close to the hinge bar as possible so that the body angle is accurately recorded.

The sensor is connected to the indicators in the cab by a high-quality 16-way connector. The operator or driver presets an angle of side tilt into the system via the control and display mounted in the cab; if the preset angle is reached during tipping an impressive array of warnings come into play.

TS, believing that drivers have enough to look at already, fits a 'stern-voice' audible warning as well as indicators. At the same time an interlock is activated which prevents the ram from being extended further. The alarms cannot be silenced or over-ridden. Neither can the tipping operation be resumed until the body has been settled on the chassis and the 'body up' sensors have been deactivated. A 'bleep' sequence also Informs the driver of the degree of lean (eg, two bleeps followed by a gap then two more bleeps would be two degrees).

Carl Griffiths says this kit offers "enhanced safety in any circumstances". Roan also incorporate a 'tailgate-open' sensor. With a tai gate activated from the cab a dangerous condition can arise if the body is raised with the gate locked. At a preset body angle the driver is informed accordingly.

In this case the three-dimensional sensor is mounted on the body— an infrared rear view camera can be specified too.

• Typical cost is 2770 for standard system inc fitting; interlocks available on application.

Features: PM Onboard

• Measures stability as well as side slope • Uses existing load-cell performance to provide information • Does not automatically lockout, allowing driver discretion (but can be locked) • Audible alarms at preset values

How it works

The PM system works from two sources; the load cells and an inclinometer. PM uses CANbus technology to read all four cells and provide information on what the vehicle is doing when it is tipping rather than simply registering the tilt angle.

The inclinometer supplies parallel information. The 'safe' degree of side tilt is entered as a percentage of load transfer from cells on one side to the other. If the cells on one side were reading 100% of the load you would be right in thinking that the tipper was going to topple! PM recommends about 40% transfer to keep you out of trouble.

A touch screen in the cab allows selfdiagnosis and adjustments. Thrust on the cells at the base of the ram indicates that the body is raised and the system starts up. An audible alarm will sound at a preset 3° but this f igure can be changed. In the standard system there is no lock and the driver can continue to extend the ram after the alarm point has been raised although an interlock can be incorporated if desired.

A rear-view camera is included. Mark Bottomley says; "It's hard to sell CANbus but it is this technology that allows us to provide such useful dynamic information."

• Typical cost is £450 on top of PM's standard weighing package inc fitting. The PM 1300 on-board weighing system, at £2,500, includes TipWatch as standard.

CM verdict

In Citl's book, any device that can prevent the calamity of a toppling tipper deserves serious consideration; we think both systems have a lot to offer, not least because they are sensitive to even the most seemingly innocuous side slopes.

The PM Onboard system is a natural extension of the company's proven load-cell and on-board weighing technology, not least in terms of accuracy and reliability. It also provides dynamic information based upon what's happening as the body is being raised.

The TS system combines a tried-and-test inclinometer with strong 'add-ons' like the ram interlock so the driver is not only warned of an impending incident but is stopped from making it worse. Ultimately, which system you go for will come down to buyer's choice. But the fact that well known fleets like Longthornes and Hanson are investing in stability indicators should register with all tipper operators.

Aside from the risk of injury caused by a tipper rollover and the inevitable HSE investigation, there's the cost of recovering the truck and loss of use. So the price tag of a stability system must be seen in that broader context.

As 1 lanson's Gary Sleet puts it:"Ifyou've invested up to i100,00 in a new truck and trailer why would you want to let it go over?"

CM 's thanks go Hanson and to Ken LongthorneTransportfor the loan of their vehicles and to SGB's depot at Birmingham for providing us with the scaffold boards. EXPERT'S VIEW

We were joined on this test by Angus Spooner, now an independent consultant but previously in charge of Crane Fruehauf's tipper and skeletal divisions. He spent 36 years with the Norfolk-based manufacturer and was heavily involved in stability testing of tipping trailers.

"Tipping stability is a mobile problem," he says. "A loaded tipper with the body down may be completely stable on a 20° ground side slope, but with the body raised to tipping height, it's perfectly possible for it to topple over on a ground slope of no more than 1°.

"Today most tipping trailer manufacturers offer a chassis that will allow the trailer to meet the I RTE Class-A side tilt standard. If you operate one with that spec you should have a built-in safety margin. However, it's worth considering that a tipper not designed to meet the Class A or B standard could fall over on a perfectly level surface if it were tipped to its full height fully loaded.

"Remember that the problem is not confined to 'sticky' bads. Consider the easiest of loads, like dry grain through a grain sock, and think what drivers are prone to do -tip up the body and scarper for a cup of teal "The PM system seems to get to the heart of the problem by measuring what is actually happening to the vehicle. Load transfer from one side to the other during tipping is what turns trailers over and the PM equipment should tell the driver whatever the side slope. But remember, the ideal tipping surface will always be flat, firm ground.

"The system from Transport Support on the other hand offers an impressive array of alarms to alert the driver to impending disaster and stops the ram extending automaticallya strong safety feature. It also includes a useful automatic tailgate warning and has clearly been developed in close working cooperation with its customer: in this case Hanson.

"In any case, set the parameters so the alarm is not simply a warning of the inevitable."


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