Examples 61-70

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Examples 1-10

Examples 11-20

Examples 21-30

Examples 31-40

Examples 41-50

Examples 51-60

Examples 61-70



Wouldn’t it make more sense to have the crosswalks line up?

Well, no.  In this case, the offset crosswalks and accompanying railings force pedestrians to turn and walk toward  oncoming traffic.  If they look up at all they will see oncoming vehicles. If not, instructions are printed on the blacktop: “LOOK LEFT.” Pedestrians, especially those right-hand-side driving foreigners, need these instructions because that is often the opposite of what they are used to.  

This cross walk in London also alerts drivers of the cross walk by the jagged lane markers.















Mistake-proofing for tailgaters. And while we are on the subject of road markings, this is one of my favorites (partly because I suspect the effort is entirely futile). A section of Route 220 in central Pennsylvania between Port Matilda and Bald Eagle (the missing link in I-99) offers accidents galore. It is heavily patrolled by the Police and has lots of signage to help motorist drive safely. But this sign is by far the most novel, because it provides instructions on using some unique markings on the road.  Large white dots are spaced on the road so that if a motorist can see two of them they are not following too close (tail-gating).


turntable2 turntable strobe

Back before MP3’s, CD’s, cassettes, or even 8-tracks, there was an audio storage medium known as a record. Records were played on a “turntable” as shown above. High fidelty audio required that the rate of revolution of the turntable be carefully callibrated.  This was accomplished using a strobe light (shown as a red glow in the photos) and precisely spaced notched rings around the circumference of the turntable.  if the notched ring appeared stationary, then the rotation speed was correct. Multiple rings allowed for callibration at the various speeds. Thirty-three and a third, 45, and 78 RPM were common “formats” for this now antique “storage medium.”

The notched rings provided a simple visual check of proper machine function.


lathe 1

Some crafts people and artists in the process of making wooden bowls on a lathe utilize the same concept. They use a strobe light to allow the wood (which is otherwise a spinning blur as shown in the photo) to appear stationary, or with an apparent rotation that is much slower than the actual RPMs. This allows the artist to see the patterns in the wood clearly.


W. E. Johns reports using the flicker of a flurescent light to creat a tachometer for his lathe

lathe tach lathe tach2

The photo above left shows the markings in the lathe chuck (the part that holds and spind the wood). the photo above right shows the lathe running at 150 revolutions per minute. A full description is available at www.gizmology.net/lathetach.htm


The same concept is utilized in timing light used to tune-up automobile ignition systems. timing light


vibe label

The label shown above is attached to a vibratory bowl that is used to finish steel tools.  In order to create a consistent finish, and to be able to schedule the equipment, it is important that all of the vibratory bowls in the factory have consistent settings and thus consistent performance.  The sticker shown above helps workers to determine if the bowls are operating correctly. The photo on the left was taken with the machine off. The photo on the right was taken with the machine running. Notice that on the fan-shaped figure that  lines labelled 60 and 70 seem less blurry.  This indicates that the “lead angle” of the vibration is between 60 and 70 degrees. Now look at the series of circles running horizontally below the fan-shaped figure.  These show vibration “amplitude.” On the photo at right, you will notice each circle seems to appear twice.  At the circle labelled “2” the two circles created by the vibration do not touch. At “7” the two circles overlap. At “3.5” the circles just touch. This means that the amplitude to 3.5 mm. The label allows the bowls operation to be known easily by any one.



copy machine1 This copy machine makes sure all the levers are in their proper position before the cover can be closed..
copy machine 2  


Even the lowly inter-office envelope has some mistake-proofing.  In the photo at right what can you tell about the contents? First that there is something in there, second, that it is smaller than 8.5 x 11 inches, and third it’s white.

Making sure a reusable envelope is empty before you send your memo can save a lot of embarrassment.

interoffice envelope


liquor spout pour spout

The devices that are attached to these bottles are liquor control systems. They insure that the right amount of liquor is dispensed for each drink  It also tracks the amount so that receipts can be reconciled with inventory.



oxygen connector medical air

Medical gas outlets are designed so that the proper valves will only fit in their corresponding outlets. All of the gas valves have a pin at 12 o’clock the other pin differs in location. The second pin for medical air is at 4 o’clock


buckle wrong


buckle right


My safety harness buckle has a red mark indicating that it has not been locked (incorrect).  When the buckling is complete the red mark is covered.


metolious 2 The rock climbing equipment company, Metolius, produces this “range finder cam.” The cam anchors safety ropes into cracks in the rock.  Notice the green, yellow, and red dots that run along the edge of the cam.  The green dots indicate that the width of the crack is safe for use with this device. Yellow indicates that is cam may be place in the crack for adequate safety but the next larger size cam would be in the green and safer. The red  indicates that the cam is placed in a crack that is too wide and the anchoring of the cam is not safe.



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