(The purpose here is to teach by examples of how not to do something. For better news about business, including good products, see http://www.keithsketchley.com/goodnews.txt.)
Vibration breaks the camel's back
The rear hatch release solenoid on Chrysler minivans is a wire-wound solenoid with one end of the wire connected to power and the other end to the metal case of the solenoid which is screwed to the hatch structure to provide a ground path. The ground end is simply wrapped around a tab on the end of the solenoid case that fits such that the wire loop is retained. But the tab has sharp corners, the wire is soft, and shock load is high when the hatch is slammed shut. So it fails. This is another case of a detail ruining a reasonable part design - the combination of using wire wrap, the tab radius, the nature of that wire (for conductivity), and the loading in that particular application does not work. What lessons can be learned here?
In contrast, General Motors designers knew their engine control computer, used in 1980s models, had to withstand a shock load from slamming the glove box lid. (They'd put it in a location protected from moisture - behind the glove box. That worked well except on one small car design whose firewall didn't keep a coolant leak from getting into the area - the computer had not been designed to resist engine coolant.)
Have you experienced the carafe of a coffeemaker being sensitive to spilling if tipped too far? Ever noticed that some carafe's are not sensitive? (For example, a five-year-old specific Sunbeam model is very sensitive, a three year old Mr. Coffee not as sensitive. And a newer Black & Decker model not sensitive.) I can see why the better of the first two examples isn't sensitive, from an understanding of how fluid flows - the difference is subtle but definite. (The Black & Decker carafe has a more rectangular spout, obviously different.) So, how much is it worth in product sales over the long term to spend a little extra effort to do a better job of spout design? (I don't see any difference in manufacturing cost between the first two examples, and doubt there is much in the more rectangular spout. Definitely negligible compared to the frequent redesign of the machines for styling and feature fads.)
It gets worse:
The Oster Model 7995-33 coffeemaker has a bizarre spout - a quite narrow spout then a wider quite shallow depressed area that can't handle much volume either. The narrow central spout area might be fine for a 4-cup coffeemaker, assuming people only use small cups, but on that 12-cup design it is guaranteed that people will spill coffee.
And the reservoir filling area on top of the machine is very shallow, so difficult to use without spilling water.
With several fancy brewing control features, it retail for $100 - for that you'd expect a proper design for usability.
Spilling coffee, and water
A common problem with coffeemakers is that the swing-out filter basket compartment does not stay fully closed. The latch may be very weak or not have a clear detent thus prone to users not getting it closed. One model leaks water unless pressed closed. How can that be avoided?
By eliminating the feauture - make the lid over the water tank cover the entire top of the coffee maker. Simple and more economical to make (net, as it does require a mechanism to move the hot water spout out of the way of the filter basket). Credit whoever makes the Black and Decker brand (this year it is Applica) for doing that with their DCM600 series. The same model whose carafe is well designed for pouring.
But debit them for putting two holes in the back wall of the water compartment, so that if the water poured into it hits the back wall some will spill out. The holes may be an attempt to limit over-filling if the carafe is not used to measure the water (I don't see a fill level line clearly marked). Doesn't seem the designers thought that one through, nor tested it much. (Ideally the water overflow should come out the front so the user is aware of it.)
And be aware that some models including the DCM600 do not have an automatic shutoff of the heater. That is going too cheap.
Won't final test catch design problems?
Once I purchased a compact computer keyboard on clearance. It used a function shift key to enable page up/down (awkward), giving some letter keys a dual function. The price was low, which I assumed reflected that it was an oddball configuration - but I thought I could make use of it.
I hooked it up my computer, and discovered it had two letter keys labelled Page UP, none labelled Page DN - but the lower of the two Page Up keys functionned as a Page DN key.
How, I asked myself, could that escape the design, testing, and manufacturing system - wouldn't it be obvious?
I checked how the key was made - the letter and the Page UP were molded in (and had to go together), so it wasn't simply a case of the wrong label being stuck on the key. Someone had designed the mold incorrectly, probably starting by copying the definition of the other key but only getting as far as changing the letter.
How could it be missed in test?
Assemble the product by placing the letters in the right locations, or automatically from bins with the particular part number for the location. Then program a machine to push that key and look for the expected output from the keyboard. All seems fine to the hasty.
That's one problem with mass production - get it wrong, push the production line GO button, and thousands of units spurt out, all wrong. The economics of that are powerful!
So how do you prevent that and still be efficient?
Paper Cutter fails at "Job 1"
I purchased a paper cutter. The Staples "DuoTrim" had many nifty features. But it failed at Job 1 - it couldn't cut paper cleanly! Duh?
Can opener also fails
OneTouch produced a nifty manual can opener.
And a big turn handle, which people with weak hands need.
It appears to have the wrong diameter of star wheel, so does not clamp the can enough to reliably turn it. Perhaps a case of using the wrong parts bin.
Its usefulness to me is mostly for my shown-n-tell bag, for presentations such as this link.
And over in Detroit....
The Tick-Tock Tach
Popcorn all over the place
Go to for my pedantry on corn poppers.
Poorly aligned switches fool user of clothes dryer
And on an instance of the classic "Whirlpool Type I" clothes dryer, commonly sold as Kenmore and other brands:
- the permanent press setting has a trap. The dryer knob can be in a position that runs the motor but does not turn the heater on. The symptom is that the timer is not progressing (the desirable feature in low-price form advances the timer based on outlet air temperature to avoid overheating clothes, as outlet air will be cool until clothes become drier). The user does not realize that heat is not turned on because there is audible action - the drum motor turns.
With honourable mention to Chrysler designers of the mid-1990s Caravan, whose headlight system has a nifty automatic off feature, keeping the headlights on for long enough to get out of the vehicle and see your way to the door of your residence. But don't depend on it to avoid battery depletion - if you stop the vehicle and turn the engine off but do not remove the ignition key and do not get out, as you might if watching something, using your computer, or just listening to nice music, the lights will stay then on and if you've been in the habit of using them as daytime running lights you won't notice them.
They Did Not Understand Food Chemistry
I've praised the makers of Shreddies cereal for their sly "Diamond Shreddies" new product introduction spoof.
But they also produced an actual product "Vanilla Shreddies", whose food design failed to appreciate taste combinations involving basic chemistry of taste (at least for Keith's mouth).
(And the current fad of cinammon in cereal doesn't work well either - I'd best go back to Red River cereal (hmm - was that flax, the latest food fad?). Nor did Lemon Coke (works better in Pepsi which is sweeter, but the reverse is true of vanilla flavour). And there was Blueberry Pepsi, quite a bad idea. :-) I'm coining the phrase "Gratuitous Marketing".
Not User Friendly
Walter Shawlee gets pushy in his articles Gratuitous Technology and User Hostile Interface
They Missed The Concept
The makers of a nice ruler put divisions of a quarter centimetre on the metric side. (OK, I'll explain - fundamental to the metric measurement system is dividing by tens, so the ruler should have divisions of tenths (1 millimetre) or fifths (2 milimetres). OTOH, fundamental to the Imperial measurement system is dividing into fractions, such as 1/2, 1/4, ....
Small things >> complete failure, or worse:
- The Prophone CD directory returns "not found" if you enter the street name as Blvd with a period, as many sources of such an address would list it, but finds the listing if the period is omitted.
- it is common for a number such as membership or card or such to not be accepted if the spaces or hyphens on the physical card are included in the entry on a web site.
Note a common thread of very misleading result - none found, thus a communication of invalid number or no account/membership, when the problem is really a mismatch of expectations on entry format. (Couldn't software designers at include a caution about entry format limitations in the error message? Naw, if they were that smart and conscientious they'd do it right - be foregiving of variations as some software designers indeed do.)
How to do better
One good aid to ensuring a complete usable product is Requirements Definition. Here's an article emphasizing one aspect. Call Keith to engage his knowledge from experience and principles including limitations and pitfalls.
Keith Sketchley's intellectual property, version 2013.02.19
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