Don’t Work Under A Jack

4WD Tips      December 8, 2013      David Wilson

There’ll likely be more than one time in the driving career of the average driver when they have to use a jack. It might be to replace a flat tyre or to service a vehicle. In either event it pays to be safe. Just recently the State Attorney General John Rau put out a reminder of the dangers of jacks after the crush death of a South Australian man in suburban Adelaide. He said “Under no circumstances should anyone work under a vehicle supported only by a jack”. He went on “Since 2000 there have been 46 fatalities of Australians who have been crushed while working under a vehicle supported by a jack z4root apk latest version download“. That’s a shocking statistic but it doesn’t also include those injured.

With a 4WD and using a 4WD as it was intended the risks posed to us are even more perilous. Firstly consider the mass of the vehicle, with the average wagon or ute tipping the scales at around 2 tonnes plus. Add that to the terrain you might be on when trying to correct an issue and the danger is omnipresent. So what can you do to prevent the risk of injury or death?

Jack selection is pretty critical. The standard jack that comes with a vehicle I think is better than most people will give it credit for, it’s far from perfect but it’s a good start. Provided the vehicle hasn’t been grossly over-accessorised and therefore become heavy to the point of being over-GVM, a standard jack will work in a variety of situations and enhanced with some simple accessories. Let’s look at some typical jacks that might be of interest and how they might perform in the field.

Hi-Lift or Kangaroo Style Jack – This used to be a mainstay of many a commercial vehicle fleet but today I reckon they’re useless. Not only are they incredibly dangerous to operate, but they’re also heavy and large, so finding a safe place to store them is difficult. A Hi-Lift has a lifting stem around 1200mm high with a lifting tongue activated by stroking a long tubular handle that “walks” its way up the stem with a mechanical pin action. There’s both a forward and reverse gear. The base plate and the stem are not fixed but rather floating (albeit secured with a split pin so they can’t come adrift), to allow the angle of the jack to change as the vehicle is raised and also to compensate for uneven ground it’s sited on. This creates an instability once the vehicle’s wheels leave the ground and make the process highly dangerous. Designed back in the 1950’s when vehicles had square bumpers made of steel, the Hi-Lift is about as useful as “tits on a bull” on a modern 4WD with plastic aero-shaped bumpers. Sure some will argue that a vehicle with a steel bullbar will likely have Hi-Lift slots installed to facilitate its use, but the danger is still there of the vehicle falling awkwardly off the jack. The other point worth mentioning too is that a Hi-Lift needs a mighty effort from its operator. Whilst the lever action provides a mechanical advantage in gearing terms to overcome the mass of the vehicle you’re lifting, you better make sure that you weigh at least 80kgs and be 180cm tall or more once the wheels come off the ground, because the effort required to use the jack is extraordinary. I’ve seen folks of slight stature left dangling from an elevated handle unable to complete the arc of the handle because they can’t get any leverage. They deserve to be consigned to the scrapheap of history.

Bullbag or Exhaust Jack – I was once a firm advocate of these jacks, an inflatable vinyl bag that you position under a vehicle to do the lifting. It works by holding a rubber cone on the hose end of the jack hard up against the exhaust tip of your vehicle. As the exhaust gases flow into the bag it slowly rises like a scone in an oven lifting the vehicle to the chosen height. Its best terrain for operation was either sand or mud, where the broad surface area of the bag spread the weight of the vehicle more effectively than a standard bottle jack with a tiny footprint that might simply disappear into the mire. A bullbag is really a 2 person operation, a person holding the cone on the exhaust and another sitting inside the vehicle keeping the engine speed at a fast idle. Now the real kicker with a bullbag today is that they largely won’t work on a modern vehicle and especially a diesel. Modern diesels run very sophisticated engine management systems and they work by monitoring engine diagnostics. The back pressure the bag creates in the vehicle’s exhaust pipe, once the bag fills to the point of lifting the vehicle, will likely be enough to trick the engine management system into thinking there’s a fault and it’ll likely stall the motor to prevent perceived engine stress or failure. So just at the critical point where the vehicle is about to be raised the jack stops working. If you had a pre-common-rail motor you might be able to use a bullbag, but when you do make sure the bag is protected from any sharp objects either on the ground or under the vehicle (bolts/screws/sharp edges). I used to use a couple of pieces of carpet to offer the bag a bit more protection than the flimsy vinyl patches it came with.

Trolley Jack – This style of jack is really one best suited to a workshop environment. In that environment they are really, really good. The jack employs a scissor action to do the lift, the jack’s base is on wheels (so its perfect on concrete to manouevre), a hydraulic pump lifts the locating plate with an easy stroke on the long handle. There’s plenty of different sizes to accommodate different weights of vehicles. I have seen some of our clients use them in the field and whilst not ideal on imperfect surfaces they can be made to work with a bit of leveling.

OEM Service Jack or Bottle Jack – The OEM (Original Equipment Manufacturer) bottle jack that came with the vehicle is useful because of its compact size. You’ll be able to locate it under the vehicle in a variety of positions (observe the illustration on the jack body or refer to the owners manual for location points). It’ll either have a wind-up action or lever-stroke to operate. When you do the lift you’ll notice there’ll likely be around 3 stages, as the stem extends, then extends and extends again to achieve its maximum service height. Used in conjunction with a sturdy base (a piece of timber or steel say around 300mm square), it’ll do what most people need in relative safety. Just watch out for the small locating plate/head at the top of the stem and make sure when you bring it in contact with the vehicle that it lifts running straight and true. I often will take a second bottle jack when I’m traveling so I’ve got 2 to use in tandem if need be to complete a chore.

Whatever jack you are using the simple message is to make sure that the ground you are operating on is preferably flat and firm and that you keep yourself out of the way if the vehicle falls off the jack. If you must get under the vehicle only do so if the vehicle is supported by stands and even then make sure the job is secure!!!

From Left: Bottle Jack, Exhaust Jack, Trolley Jack and Hi-Lift Jack



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