Guide written by:
Jeremy, construction site supervisor, Cardiff
If you're into mechanics, you'll know just how often you need to get under a vehicle! However, it's essential to ensure your safety when working. This is why you need a decent jack! Mechanical, hydraulic or pneumatic, let us take you through the lifting solutions available to you.
- Lifting capacity
How to assess your lifting requirements?
When you need to carry out inspection or maintenance operations under a vehicle, it has to be lifted. To achieve this, you'll need a device capable of safely lifting and securing the vehicle in a raised position. A mechanical, hydraulic or pneumaticjackwill let you disconnect your vehicle from the ground to work underneath it without risk.
Sized to suit the required load, a jack - accompanied by props for improved safety - is the ideal companion of any amateur or professional mechanic! They can also be useful to lift other heavy loads: gates, building elements etc.
To work out what you need, nothing could be simpler! Lifting capacities are indicated on each jack. When changing a wheel you don't need to lift the entire weight of the vehicle, but half of it, using a pivot (don't make the common mistake of dividing the total by four!...) So for a vehicle that weighs two tons, you need a jack capable of lifting a ton. Don't overcomplicate your calculations, and always oversize your jack to allow a margin for error!
What different types of jacks are there?
Several types of jacks exist to suit your needs:
- Mechanical jack: also known as the "diamond"jack, this is the type that car manufacturers generally supply with any new vehicle. Working on the principle of the worm drive, it's the simplest type of jack. Sitting on the ground, with a claw tab under the chassis of your car, it allows you to lift your vehicle off the ground with ease. The lifting capacity of this type of jack rarely exceeds 1.5 T. Very useful for changing a wheel, for example, this model of jack is not advised for more complex mechanical operations unless the load is secured with props. The main advantage of this type of jack is that it fits (in retracted position) under most vehicles thanks to its small size (approx 10 cm).
- Hydraulic trolley jack: this is the classic workshop jack. Consisting of a rigid chassis on wheels, a hydraulic cylinder and an articulated arm with a lifting disc, its load capacity is significantly superior to the diamond jack. Most models are suitable for loads from 2 to 3 T, but some jacks for SUVs or trucks can go up to 5 T. Mobile thanks to its wheels, it is also very easy to handle. The cylinder is operated by a manual pumping movement via a handle. Robust and stable, these jacks are particularly suited to mechanics applications and provide a greater lifting height than diamond jacks. However, before you buy, make sure it will fit under your vehicle (in lowered position).
- Hydraulic bottle jack: the principle of operation here is identical to the trolley jack. However, the cylinder is not mounted on a wheeled chassis but fixed on a flat support. Lifting is carried out directly by the cylinder, allowing for much greater load capacities of up to 20 T. However, its shape means it won't fit under vehicles that are low to the ground, and its lifting height is limited by the length of the cylinder, often less than that of a trolley jack.
- Pneumatic jack: for heavy and intensive use! Reserved for experienced mechanics and professionals, pneumatic jacks offer a lifting capacity up to 30 T. Coupled to an air compressor, they come in two main forms:
- With air cushions: generally with two or three cushions, load capacity is limited - on average 2 to 3 T. Fixed or on a wheeled chassis, their small footprint makes them simple and practical to use for an impressive lifting height.
- Hydropneumatic / oleopneumatic: here the technology gets a little more complex. Compressed air serves to pressurize a hydraulic fluid to actuate a cylinder. The shape is similar to a trolley jack, except that it allows lifting capacities of up to 30 T! Lifting height is substantial by default and can be increased by means of extensions. Equipped with all kinds of safety features (failsafe in case of compressed air cut, controlled descent, etc.), this is a real high-end jack.
- Rack-and-pinion jack: for occasional use. These are easy to operate - just turn the crank! Suited to agricultural and off-road applications, it is a robust jack, with simple technology that allows you to lift a machine whatever its ground clearance (4x4s, tractors, trailers etc.). Lifting capacity is substantial and can reach 15 T for larger models.
Final advice before you do any heavy lifting?
When working underneath a vehicle, trailer or any other heavy machine, always make sure you secure the load. Whatever type of jack you use, it must be placed in a stable position, on even, dry ground.
Remember to chooseyour jack to suit the load you want to lift, and consider obtaining props or chocks for extra support.
For private vehicle maintenance, the best option is probably the trolley jack. A little more expensive than the basic diamond jack, it pays big dividends in terms of convenience and will prove is worth in no time.
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Guide written by:
Jeremy, construction site supervisor, Cardiff, 128 guides
Electrician by trade, I first worked in industrial estates where I installed, wired and fixed a large number of electrical installations. After this, I managed a team of electricians for this type of work. 10 years or so ago, I turned to building and construction. From the modest family home, to gyms and theatres; I have been able to coordinate, audit and organise all sorts of construction sites. for 4 years now, I am restaoring and bulding an extrension to a bungalow in the heart of the welsh countyside. My experience in manual work and my knowledge means I am proud to be of service. Terraces, interior design, roofing, plumbing, electricty, anything goes! We have, my wife, daughter and I, built almost everything we have from scratch! So to answer all of your questions, and to orientate and advise you on coosing your tools? Easy!