Design Con 2015

How about some water power?

-January 30, 2013

Electrical and electronic engineers tend to think of power in terms of a few basic parameters: volts, amps, watts, and related units. This makes a lot of sense, given what we’re dealing with and trying to do.

But there’s a whole world of non-electrical power out there, when things need to move. Let’s face it: even your all-battery EV has motors and motion, which means you have to understand mechanical aspects of power application, usage, recovery, and waste.

That’s why the article “Carried by impulse: the physics of water jetpacks” in Physics Today was both fascinating and interesting to me [side note: PT is a great publication, and the articles they post online in front of their paywall are often fascinating].

I had read about these “jet packs” powered by water pressure, but only in high-profile press releases which were long on sizzle yet short on analysis. But this article actually has a detailed analysis of the various forces, angles, and factors which come into play for this unusual fluid-power and motion-control situation. It’s got all the relevant equations, explanations, and enhancements to make it a real learning experience. (You can also see some information, videos, and pricing at the site of a water jetpack vendor, Jetlev-Flyer.)

The analytical article is good in several ways. First, it makes you stop, think, and exercise your analytical skills in a way that is both enlightening while still tied to the basics of force, power, geometry, mass, and other factors which directly or indirectly enter into so many design situations. Second, for many technical and historical reasons, hydraulic power is a major mover in many applications, yet EEs often don’t understand it - or perhaps are even a little scared of it.

That’s too bad, since hydraulic-power systems are increasingly being enhanced with smarter, more-efficient control using electronics, software, and associated algorithms. To do so effectively, you have to at least have a basic understanding of the realities of fluid power. It’s a world where the fluid mass and inertia means that things don’t happen as fast as they do in electronics, yet at the same time the systems are capable of delivering huge amounts of impulse power and impact: just watch a hydraulic hammer in action, and you'll see what I mean.

A good circuit-centric electronic engineer knows his or her “stuff,” of course, but a really versatile one understands principles of physics including fluids, thermal issues, packaging, and reliability, to cite just a few aspects of a complete project.

Are there other non-circuit and non-software areas you wish you knew more about, either to do a better job or to get that job you wanted, or that you have found critical to doing your job?

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