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Pulleys

What are pulleys and why buy one?

When we buy something it’s either because we want or need the item. We buy emotionally if we want something and practically if we need it. With a pulley it fulfils a practical need and solves a problem.

Pinterest PULLEYS Photo

Specifically the problem of how can you lift something safely and with minimum effort, repeatedly if needed?

Let’s deal with safety first, you will not wish to injure or strain yourself lifting items and in the days of no win no fee you certainly will not want your staff doing it either.

The mechanics of how a pulley works (which I’ll cover later in the post) means that it can be used repeatedly with less heavy lifting required by the user.

Lifting a weight with a pulley

A pulley is basically made up of, typically, 1, 2 or 4 wheels around which the rope or chain will be wrapped and it’s the science behind the way a pulley works that makes it easier to raise and or lower heavy objects.

The way the pulley operates means that your body strength can be multiplied by 2 or 4 times depending on how many wheels the pulley has.

How does a Pulley give you a lifting advantage?

Mechanical Advantage ExplainedWith just one wheel you actually have no extra lifting advantage because if you want to lift a 20kg load up you will need to pull down on the rope/chain with an equal 20kg force using your own strength. The only real advantage of a single wheel pulley is that you will be pulling down on the rope and can therefore use your bodyweight to help and this is certainly easier than lifting the item up from the floor. This will also reduce the chances of back injuries and enable you to pick up awkward shaped items as long as they are connected to the pulley securely.

With a simple single wheel pulley, to lift something up 2 metres from the ground you will be required to pull down on the rope an equal 2 metres.

The pulley really starts to come into its own when you have a 2 or more wheel pulley, because with 2 wheels and the rope looped around them correctly you effectively halve the force (strength) you need to put into it to lift the same weight. So the 20kg weight mentioned above would now only require a downward force of 10kgs.

There is one slight draw back or trade off in this halving of the effective weight and that is you would now need to pull the rope down 4 meters to lift the object 2 metres.  So it’s a little bit like riding a push-bike up hill in a lower gear, it is easier to pedal but you have to do more revolutions.

The extra distance you need to pull the rope is because with two wheels even though you still have one one rope, the way its wrapped around the pulleys makes it like having two ropes that need to move two meters each.

The Science Bit

The technical term of how a pulley is advantageous is known as “Mechanical Advantage” and is an expression of the lifting “multiplier”. So as the mechanical advantage increases the effort needed reduces, though the distance you need to move the rope will increase by a proportionate amount.

So in an extreme example an 8 wheel pulley would only require an effort of 1kg to lift an 8kg weight.  It’s all about being efficient and using the pulley like a lever effect.

SEE SAW 220

If you ever went on a see saw as a young child with your Dad you obviously wouldn't weigh nearly enough to be able to lift him up if you were both sitting equidistant from the centre of the see saw. However if your Dad was 4 times your weight and sat 4 times closer to the middle you would be able to see saw each other perfectly. You would be moving up and down 4 times as far as him and it’s the physics of force over distance that evens it out.

This is exactly the same as you pulling the rope four times as far with a four wheel pulley. (Anyway that’s enough science)


Check out our YouTube Video

We made a short promotional video about Pulleys to compliment this article.

Our Range of Pulleys

At Ironmongery Online we have an incredible range of pulley wheels and systems for you to choose from.

Whether you are making repairs around the home or installing building work to your business premises don’t take a chance on inferior products get top quality pulleys made using proven techniques.

Our products and our rapid delivery service have proved invaluable to our customers time and time again as our rating on the independent website trust pilot shows.

Take a step by step look our superb product range here.

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