(0) Item

Need Help? Call us at (800) 776-9315

What is a pulley?

Posted by Crystal Carr on 6/26/2018 to News

Have you ever heard of a simple machine? It’s something you might have been quizzed on in middle school, but don’t worry, just by reading this blog you’ll get a gold star for the day! Every day, you interact with simple machines, from opening your bedroom door (wheel-and-axle doorknob) to using a knife to slice your bagel (wedge).

They're in your car, your home, and even your own body. Here, for instance, is a lever:

Occasionally, when someone calls Phoenix Pulleys Bearings & Belts, and I answer with “Phoenix Pulleys, how may I help you?”, they panic. “The police? Oh no, I called the wrong number! I'm so sorry to bother you!” And then I say, “Pulleys, pullllleeeeys, they’re the round things that spin.”

Maybe not the best explanation ever, but it’s a turn of phrase I find effective.

In reality, a pulley is a “wheel on an an axle or shaft that is designed to support movement and change direction of taut cable or belt, or transfer of power between the shaft and the cable or belt.”[1]

So, ALL pulleys require three things in order to function as anything other than a fashionable paperweight:

1.       A rope, cable, belt, or other flexible long piece of material.

2.       A cylinder-ish piece of solid material (This would be the pulley.

3.       Something to hold the pulley in place so that it can turn. For idler pulleys this a bolt through the bearing or bore adapter. Drive Pulleys use a shaft.

Most discussions of pulleys refer to block-and-tackles, which are used to lift heavy weights across long distances with.  Like, say, in a drawbridge, or on a boat. Generally, the more block-and-tackles you set up in a system, the easier it is to lift the heavy weight[2].

pulleys at the top of a drawbridgeblock and tackle pulleys


HOWEVER, this is not where our pulleys are typically used, except for perhaps our rope idler pulleys.

What our pulleys do, is transmit and increase power or speed across long distances. In a simple pulley system, you can swap a small drive pulley for a large drive pulley, and cause the small v-groove idler pulley to spin faster without changing the revolutions per minute of the motor.

Most of our pulleys are not used in a simple pulley system, though. Take a look at your mower deck the next time you mow your lawn, and observe the intricate and beautiful dance of v-groove drive pulleys, v-groove idler pulleys, and backside idler pulleys. They require multiple v-groove idler pulleys and backside idler pulleys working in concert to provide you with a deadly-fast spinning blade to massacre your overgrown grass.

Stay tuned, we’ll be tackling mechanical power again soon!



[1] https://en.wikipedia.org/wiki/Pulley has some great diagrams if you want to find out more about pulleys, primarily block-and-tackle

[2] If you’ve ever gone to a children’s science museum, you’ve probably seen the pulley display. It usually has a couple of chairs and some increasingly elaborate block-and-tackles. A little kid can pick up their “hefty” parent using one of these contraptions.

Add Comment