Admit it… Most engineers are so busy its hard to step back and smell the coffee. That’s why many of us get that “deer in headlights” look when a conversation steers into humorous territory. Lighten up a bit and enjoy some of the pleasures if life… Like Doughnuts!
Why did the doughnut go to the dentist?… To get a filling
What do you call a pastry that is a priest?… A Holy Doughnut
I was on a diet, but I doughnut care anymore.
While you are wondering why you are reading this and possibly about the wide array of doughnut choices, the nerd side of your engineer brain is thinking, “hmmm, wonder what is better… the doughnut or the doughnut hole?” …and it all goes downhill from there as your mind slips away from the serious stuff.
Since we are on this downhill slope, lets steer this descent just a bit. Just how would you choose which is better?
On the surface, pun intended, it appears there is more sugar glaze on doughnut holes than on a doughnut.
Lets take a look at the surface area and define a few base dimensions. An ideal doughnut shape would be represented by a torus and the doughnut hole would be a sphere. If you set a hole radius, r, of 20mm to match the doughnut radius when looking at its cross section, then set the doughnut plan radius, R, from centerline to 2r or R=40mm, the result could be pretty similar to a standard doughnut. Now lets compare some differences with these dimensions in mind.
Several references will give you equations for volume and surface area for these shapes. I found a few in The Mechanical Engineering Reference Manual for the PE Exam (or MERM). The area and volume equations for a sphere and torus found in the appendix are reiterated below.
Crunch a few simple numbers and the results are;
So now what? If you divide the volume of a doughnut by that of a hole, you will get 9.42… So roughly, you’ll eat nine and a half holes per doughnut. Now if you eat that many holes, then you’ve eaten that number times the surface area of each hole, or 47,374 cubic mm of doughnut hole surface area.
Think about that a minute and compare it to the doughnut surface area of 31,583 cubic mm from the table. Divide the doughnut surface area by the equivalent doughnut holes surface area. The doughnut is 67% of the surface area of doughnut holes when eating the same volume of dough. This means less glaze on the doughnut. If you are a “sugaraholic” like me, then you definitely want the holes, where all other variables are equal.
Ok, you may be thinking this is a bit silly, but consider all of the work someone else spent constructing the Federal Specification for Fresh Doughnuts, then dare to call me silly! Nonsense you say? Check out Federal Specification EE-D-575B! It was revised on July 24, 1979 from a previous version issued on October 14, 1964.
And now you know, “the rest of the story”, as Paul Harvey would say… Krispy Kreme anyone?
Now go give your boss a doughnut and go back to work!
***On a serious note, I would like to send out our deepest sympathy and prayers to the US police force and their families who protect our livelihood with their own lives. We have no idea what you go through and want to extend a huge THANK YOU for all you do. You have our full support!