Rant: Spray and gascan nozzles equally idiotic

Last weekend, in a bizarre burst of energy that motivated me enough to spraypaint a rusty old Charmglow grill that had become a certifiable eyesore, I dug up an old can of barbecue-black-colored Rustoleum spraypaint from our garage. Originally purchased to retouch a Yakima Jeep rack with its own lackluster paintjob, the can of paint had been in our garage for maybe a year.

In a development that added insult to consumer-satisfaction injury, I'd soon discover that the nozzle on this spraycan is a Contraption of Infuriation that rivals the Grand Champions of Horrible Nozzles, the nefarious late-model Blitz monsters:

Don't be fooled by the looks of these innocent-looking nozzles. By the time they're through with you, you will stink of petroleum distillates!

I apologize to the engineers who designed these contraptions if they're fans of Machine Design and are reading this. After all, you probably faced innumerable challenges and design constraints when tasked with developing what we engineers call a "liquid pourer" fancy enough to pass Portable Fuel Container Manufacturers Association muster. In fact, I have no idea how such unholy designs come into being. If anyone has some insight, please share.

Anyway, my own nozzle problems with the Rustoleum can became apparent only after I had carefully taped off all my rusty grill's shiny steel parts, sanded the rust away, and determined that I should wrap up the job up within the next couple hours, as there was rain on the horizon.

In short, a genius somewhere decided that some spraycans should have complicated caps with triggers that rock back to shoot like guns, instead of the normal mash-down-valve-to-shoot style of spraycan nozzle. Who knows, maybe they wanted to appeal to gun lovers.

This is what my work area looked like after I tried to use said spraycan — and it exploded:

The situation was actually worse than it looks, as the majority of black paint exploded onto my person. But I wiped myself off with paint thinner and resumed the project ... first by doing an autopsy on the offending contraption:

Upper left, a can of black paint tantalizingly unwilling to relinquish its sweet nectar. Upper right, a stupid piece of plastic that fits over the part of the spraycan most likely to have problems. Lower center, the offending nozzle.

"Why would they do this!?!" I exclaimed silently to myself. You see, the two problems with this overly complicated design are that it 1) Applies pressure on the stem at an angle if the plastic gets even slightly out of whack, which promotes squirting in unpredictable directions if there's not full nozzle-stem engagement, and 2) If the stem manages to get actuated okay, the paint must travel through an overly long L-shaped channel before it comes out ... dramatically increasing the likelihood of splattered dispensing and even full-fledged clogs and sudden explosions when some really big blobs get stuck in there.

In the end, I finished the job by fitting the spraycan with a nozzle harvested from another (normally equipped) can of spraypaint. The nozzle wasn't an exact fit because this industry doesn't standardize nozzles — clearly — so I wrapped the can with a rag as I sprayed.

Sometimes in design, less is more.

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Existing and emerging technologies immediately applicable to product design, as well as industry trends that promise to change engineering.

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Elisabeth Eitel

Elisabeth is Senior Editor of Machine Design magazine. She has a B.S. in Mechanical Engineering from Fenn College at Cleveland State University. Over the last decade, Elisabeth has worked as a...
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