July
20, 1998 Design News
Letters to the Editor
Readers state their views
Metric not costly
I've followed some of the recent letters both pro and
con on metric. Although there may be some initial cost
when first converting from inch-pound units to metric
units, once the changeover is made, when a product is
originally designed in metric units there is no increased
cost at all.
If additional cost were a continuing consideration,
why don't we see countries using metric convert back?
The move to metric is the worldwide trend. Many countries
changed in the 1970s while the U.S. held back. Now we
are among the few nations that remain to convert. In
fact there are benefits to standardization.
American measure is not binary! How about the factors
of 12, 3, and 5,280 for length alone, as well as fractions
of an inch. Or how about the awkward conversions like
8.35 lb/gal rather than 1 kg/l for water density. Also,
computers may use binary, but they still print out for
us in decimal.
We can't buck the fact that our numbering system and
virtually every monetary system in the world is decimal.
I don't see that going away!
Don Hillger
Colorado State University
Designing in metric easy
Regarding the metric controversy:
Metric is rational with units flowing from one measure
to another with few oddities. English units are arbitrarily
arranged with no constant or regular multiples. If the
English units were binary, every unit would be twice
the size of its smaller cousin: 2 inches to a foot;
2 feet to a yard; 2 yards to a fathom (this one is true!);
2 fathoms to a rod; and 2 rods to a mile.
I still can't always remember all the multiples in
the English systems even after working as a toolmaker
and tool designer. Now I work for a multinational company
and find designing in metric much easier.
One writer asked about metric clocks. In the 18th
Century the French Academy proposed a metric calendar
and clock. The yearly calendar would have: 12 months
to the year, 3 weeks to a month, 10 days to a week.
The day would be divided into 10 metric hours (2.4 hours
each), 100 metric minutes to the metric hour (1.44 minutes
each), and 100 metric seconds to the metric minute (0.864
seconds each). The 24-hour day was too well-established
and had just recently been standardized to convince
everyone to throw out their clocks.
The writer should visit the Clock Museum in Rockford,
IL. They have a 5th Century clock from China
based on a 10 hour day, that's 10 hours from sunrise
to sunset. It has cams that set the first hour at sunrise
and the length of the hour for that day of the year.
It must be an amazing clock, but not one I would like
to live with.
English units have lost their chance to dominate the
world, but the English Language is becoming the standard
of business and computers.
Carl Blum
Metric safety concerns
After reading the letters in the 4/20/98 issue about
metric conversion, I have a very important reason (beyond
being irritating) why converting to metric is a problem.
It is the engineer's job to ensure a product is safe. In
most cases, computations are performed on critical aspects
of a product. The "feel" an engineer has for
the calculated values allow him/her to make a judgment
about the correctness of a calculation. In other words,
does the computation "make sense"?
Honestly, I have no idea what Pascal means in the physical
world. However, I can instantly get a "feel"
for a calculated value expressed in pounds-per-square-inch.
Metric conversion will potentially make products unsafe.
Ken Yasinski, CMfgE
Member of Technical Staff
Lucent Technologies
Norcross, GA
A new 'spin' on an old tire
What is so new on the Goodyear Tire (Design News,
5/4/98, p. 80)?
During 1964 I had a Thunderbird 1960, equipped with
these so called Goodyear Double Eagle Tires. This tire
had the regular valve and a soft blue patch for a needle
valve in the side wall. Where are those tires?
Horst Kiepen
Goodyear replies:
The Lifeguard Safety Spare, introduced in 1963 as the
Goodyear Double Eagle tire, was a forerunner to the
extended mobility technolgy used in the Eagle Aquasteel
EMT run-flat tire. The Double Eagle was sometimes called
the "tire with a built-in spare."
The Lifeguard provided double air-chamber protection.
The inner chamber was inflated through a regular valve
in the rim. The outer chamber took air through a self-sealing
rubber valve in the tire sidewall, similar to the valves
in footballs and basketballs.
The tires permitted a motorist to drive up to 100 miles
after air in the outer chamber had escaped due to a
puncture or rupture.
It was a complex process, since most motorists were
confused by inflation pressure requirements for the
two chambers. The tire also was difficult to mount as
a three-piece assembly.
The Lifeguard was used as original equipment on some
vehicles until 1969. Complexity eventually limited its
commercial use. In 1965, Goodyear introduced the Lifeguard
concept in its NASCAR race tires, which still use this
run-flat capability.
Goodyear took a new route with its Eagle Aquasteel
EMT run-flat tire by using a self-supporting tire construction
with reinforced sidewalls to hold the vehicle off the
ground, even without inflation pressure.
Dave Wilkons
Public Relations Manager
Consumer Tires-North America
Goodyear Tire & Rubber Co.
Send us your letters
Got an opinion on engineering? Want to add information
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it.
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Send them to
Letters, Design News
275 Washington St.
Newton, MA 02158
or e-mail them to: jbroderick@cahners.com
Note: Opinions expressed are those of our
readers and do not necessarily reflect the views of
Design News.
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