Chrome parts for your car

Imagine a pile of art critics debating the merits of a given painting without knowing the difference between blue and red. Imagine judges at a dog show not knowing their labradors from their spaniels. Silly, right? Yet you’ll find an infinitude of vitriol spilled over why only idiots would prefer low-end torque or high-end horsepower or is a measure of how much something wants to rotate or twist. Kind of like force, but going in a circle. Here in the US (sorry Mitch) we measure torque in pound-feet (lb-ft), which leads to an easy explanation: imagine a wrench that’s 1 foot long with 1 pound of weight hanging off the end of it. If you’re the bolt at the business end of the wrench, you’ve got 1lb-ft of torque applied to you. Want more torque? apply more than 1 pound of force out on the end of your wrench, or get a longer wrench. There’s more than one way to end up at the same amount of torque: both [2 lbs] X [1 ft] and [1 lb] X [2 ft] equal Ignoring specific units for a second, power = torque X rotational velocity. Let’s go back to our 1-foot wrench. Say you’re putting 1lb-ft of torque on it, and spinning it at at 53 rpm. You’d be making 1/100th of a horsepower (hp). Not too impressive.

So how do we get more power? Kinda like before, you’ve got two options: more torque or more rotational velocity (RPM). Both 2lb-ft at 53rpm and 1lb-ft at 106rpm equate to .02 hp.

A key point to take away is that power is the result of torque

The easiest way to wrap one’s head around the concept of less torque but more power is to use gearing. As a quick refresher, one can use gearing (or pulleys or chain-drives) to reduce rpm, but increase torque. For example if I run 20 lb-ft or torque at 100 rpm through a 2:1 gearbox, I get 40lb-ft at 50 rpm out the other side. For the moment, we’ll assume we’re working with idealized geartrains, meaning you don’t lose any power to friction or the like.

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