January 19, 2012
A Penton Media Publication
Tune in to EngineeringTV.com
Box-beam tracks
make rides
thrilling
page 20
A NEW TYPE
OF THREADED
INSERT, page 50
POWERING UP
OVER ETHERNET,
page 58
HOW TO
WORK WITH
PLANETARY
GEARS, page 62
Supplying
reliable
quality
components for
the automation
and control
industries
www.altechcorp.com
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VOLUME 84
ISSUE 1
JANUARY 19, 2012
FASTENING & JOINING
A threaded insert
TOUGH
ENOUGH
Authored by:
Jason Deters
Senior Engineer
Process & Technology Development
General Dynamics Land Systems
Sterling Heights, Mich..
for the Marines
Fredserts
give
engineers a
new way to
put bolts in
soft metal.
FEATURES
tracks let
20 Box-shaped
mega-coasters soar
High forces and extreme speeds made
possible by stronger and smoother
box-shaped rails.
In search of an insert
The design team wanted to use threaded inserts, a common practice when putting bolts in soft metals like aluminum and magnesium. Inserts, usually made of a tough
metal like stainless steel, are installed into pretapped holes
and permanently locked in place. Their interior threads
give a strong, wear-resistant interface to install bolts into.
Although engineers have a few basic types of threaded
inserts to choose from, including key-locking, ring-locking, and helical-spring, none met the U. S. Marine Corps
demands. For example, if a conventional insert needs to be
MACHINE Design.com
Resources:
Fredsert offerings and videos, www.
fredsert.com
General Dynamics Land Systems, www.
fredserts.com
Miller Precision Industries, www.
millerprecision.com
For more info on the Expeditionary Fighting
Vehicle scan this code or go to:
http://
machinedesign.
com/article/
marines-geta-new-assaultvehicle-1211
Engineers at General Dynamics Land Systems, Sterling
Heights, Mich., faced a challenge when designing the
Expeditionary Fighting Vehicle for the U. S. Marine
Corps. The amphibious combat craft needed to be made
mostly of a lightweight aluminum alloy so that it would
meet its mission objectives. But aluminum is relatively
soft, and fasteners used to attach components to the
aluminum frame needed to satisfy several requirements.
They had to be lightweight, create watertight seals, lock
in place solidly, resist extreme vibrations and shock, and
withstand extended exposure to saltwater. The Marines
also wanted be able to remove and replace the fasteners
in the field.
50
Edited by Stephen J. Mraz
[email protected]
Fredsert threaded
inserts have been used
by General Dynamics
Land Systems, Sterling
Heights, Mich., on several
military vehicles, including the
Expeditionary Fighting Vehicle,
the Future Combat System for the
Army, and the Joint Light Tactical
Vehicle for the Army, Fredserts also
went into several thousand Humvees
when they were upgraded.
Here are several
female Fredserts
installed in the
sidewall of a
military vehicle.
The four oval
drive slots on
the head of the
Fredsert mate
with drive lugs on
the tool used to
install Fredserts.
removed for any reason, it must be drilled out. This risks
damaging the hole in the parent material. Plus, drilling can
be clumsy and difficult if the insert is not easily accessible.
Another limitation is that inserts typically cannot create air and watertight seals without using a thread-locking
compound. And even when thread-locking compounds
are used, many inserts don’t offer ‘blind’ internal threads,
so there is still a leak path.
And finally, there’s a limited range of standard threaded
inserts on the market, and custom lengths or materials are
typically accompanied by high prices and long lead times.
JANUARY 19, 2012
This lack of flexibility often means engineers must alter
their designs to accommodate available insert sizes or material options.
Faced with requirements it could not meet with commercially available threaded inserts, General Dynamics
began internal design and development of an insert that
would do the job without adding cost. Led by a talented
and now-retired tool engineer named Fred Wheeler, the
team came up with the Fredsert after 12 months of development, testing, and redesign. Ultimately, more than 6,000
Fredserts were installed on each Expeditionary Fighting
Vehicle, and Fredserts have been used on several other
General Dynamics vehicles and weapons, including the
Mk 46 naval-gun turret, the Army’s Future Combat System and Joint Light Tactical Vehicles, the Navy’s Littoral
Combat Ships built by Austal, Mobile, Ala., as well as
more than 12,000 upgraded Humvees made by AM General, South Bend, Ind.
Fredserts’ advantages
A Fredsert combines a tapered thread profile, 100%
thread engagement, cutting flutes, and a flanged head to
create a friction fit with material compression to reliably
lock it in place. External threads are slightly oversized
compared to other inserts and tapered in certain areas so
that they create a friction-fit when installed into the parent material (such as aluminum). And all of the Fredsert’s
threads are engaged with the parent material, much like
the way taps interface with threaded holes. Other inserts
use standard bolt threads that end up with significantly
less contact with the parent material in terms of surface
area.
The flanged head also helps in that it gets torqued down
onto the parent material and contributes to the locking action. Fredserts are designed to exceed the tensile strength
of bolts installed in them. In tests, bolts break before the
JANUARY 19, 2012
50
44 How inventors can move from hopes and
A “million-dollar” idea?
dreams to reality and the marketplace.
threaded insert tough
50 Aenough
for the Marines
MECHANICAL
An inside look at
Fredserts give engineers a new way
to put bolts in soft metal.
Planetary
gearheads
can improve
machine
performance
and efficiency,
and lower
costs. But
proper sizing
is critical.
Power-over58 Giving
Ethernet some muscle
As power-over-Ethernet applications
expand, demands for even more
power are following right along.
Authored by:
Howard Horn
Product Manager
Thomson Industries, Inc.
Wood Dale, Ill.
Edited by Kenneth J. Korane
[email protected]
62
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SBUIFSUIBO
spur gears, have higher torque capacity and
run quieter.
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t4PGUXBSFUPPMTGPSTJ[JOHBOETFMFDUJPOMFU
EFTJHOFOHJOFFSTRVJDLMZGJOEBOEDPNQBSF
gearheads that suit an application.
Micron Motioneering gearhead sizing tool,
www.micronmotioneering.com
Thomson Industries, www.thomsonlinear.com
62
Planetary gearheads can improve
machine performance and efficiency and
lower costs. But proper sizing is critical.
Micron AquaTrue
Planetary gearheads
offer IP67 protection
against harsh
cleaning chemicals
and high-pressure
wash down.
Key points:
Resources:
An inside look at
planetary gears
planetary
gears
MACHINE DESIGN.com
Planetary gearheads are high-precision, motion-control devices that generate
substantial torque for their size, have high torsional stiffness, and low backlash
— making them suited for wide-ranging tasks. For instance, specific types of
planetary gearheads:
r3VOBSPVOEUIFDMPDL
TFWFOEBZTBXFFL
GPSNPSFUIBO
ISJODBS
toning applications. The lubricated-for-life gearheads require no maintenance, and high torque-to-size ratios permit compact envelopes and small
machine footprints.
r)FMQBUUBJOBDDVSBDZXJUIJOBGFXUFOUIPVTBOEUITPGBOJODIPOQMBTNB
DVUUJOHNBDIJOFT
UIBOLTUPFYDFQUJPOBMMZMPXCBDLMBTI)FMJDBMDSPXOFE
gearing provides fast positioning and smooth movement, and sealed gearboxes keep out abrasive dust generated during cutting.
r-JNJUOPJTFBOEWJCSBUJPOBOENFFUTUSJDUCBDLMBTISFRVJSFNFOUTJOTDBOOJOH
tables for cardiovascular patients.
r- FUGPPEQSPDFTTJOHFRVJQNFOUTMJDFNFBU
CSFBE
BOEGSP[FOGPPETBU
speeds up to four slices/sec. Also available are slim, right-angle designs to
JANUARY 19, 2012
62
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JANUARY 19, 2012
MACHINE Design.com
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RS# 103
ON THE COVER
DEPARTMENTS
Box-shaped roller-coaster
tracks at Six Flags Over Texas.
8 EDITORIAL
How to ace an engineering job interview
10 EDITORIAL STAFF
12 LETTERS
16 SCANNING FOR IDEAS
Efficiency lets smaller motors handle bigger jobs
Overpressure valve protects lithium-ion battery packs
20 REPORTER’S NOTEBOOK
30 LOOKING BACK
36 COMMENTARY
Time for engineers to think about unionizing? — Stephen J. Mraz
38 ADVANCED MANUFACTURING
40 BERKE ON SAFETY
When machine operators slip and fall
42 VANTAGE POINT
Agile product development and strong-form product
management — Barry Jaruzelski, Richard Holman
69 ORR ON ENGINEERING
Solving problems in context
70 SOFTWARE PRODUCTS
72 PRODUCT SPOTLIGHT
Pumps & compressors
74
82
83
84
86
86
87
4
PRODUCTS
BUSINESS INDEX
AD INDEX
DATA FILES
CLASSIFIEDS
BUSINESS STAFF
BACKTALK
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JANUARY 19, 2012
POSTMASTER: Send change of address notice to
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Power transmission
for wind turbines
EDITOR’S WEB PICKS
Altra Wind Technology’s new Web
site, www.AltraWind.com, covers power
transmission and motion control in wind
turbines. Sections include rotor, yaw, and
blade-pitch brakes, shaft-locking devices,
high-speed shaft couplings, and access
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safety, and reliability.
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New forum on
materials, adhesives
The Fabrico Forum (www.fabricoforum.
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Mobile apps offer
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RS# 106
EDITORIAL
How to ace an
engineering job
interview
The economic recession has abated somewhat, and hiring is on the
upswing. Now you’re more likely to read about the travails of those interviewing for employment rather than people downsized out of jobs.
In that regard, it looks as though the new trend in job interviews is to ask
brain-teaser-type questions. The practice seems to have been popularized by
hiring managers at Google. According to William Poundstone, author of a
book called, Are you smart enough to work at Google?, that company relies on
such off-beat interview questions as a way of sifting out people who won’t fit
into its culture.
You might wonder what kind of culture a company has if it hires people
based on how they answer a question like, “You are shrunk to the height of a
nickel and thrown into a blender. Your mass is reduced so that your density
is the same as usual. The blades start moving in 60 seconds. What do you
do?”
Apparently Googlites are looking for inventive answers. (One of the best
is supposedly to recognize that small creatures are stronger in proportion
to their weight and that you can probably just jump out of the blender.) Another company that apparently buys into brain-teaser interview questions
is Tesla Motors. Tesla interviewees reporting on the Glassdoor.com site say
the EV maker mixes brain-teasers with queries about fundamental physics,
including: Why do letters in mirrors reverse horizontally and not vertically?
You’re in a row boat, which is in a large tank filled with water. You have an
anchor on board and throw it overboard. (The chain is long enough so the
anchor rests completely on the bottom of the tank). Does the water level in
the tank rise or fall?
Though riddlelike interview questions get a lot of attention, the more important part of a hiring process is probably the questions applicants answer
that resemble the work they’ll eventually perform. People applying for programming positions at Google, for example, must write code during their
interviews. But at any engineering company, sometimes even work-related
questions can seem a bit off the wall.
A friend of mine describes an incident during one such interview at a
control-systems engineering firm: “I extolled my past experience and credentials, but I could tell the guy doing the interview wasn’t convinced. All of
a sudden he eyes me suspiciously and says, ‘What’s the integral of 1 over x?’
To my extreme surprise I seemed to recall it was log(x), and though unsure
I blurted out my answer. He brightened measurably and said, ‘That’s the
question I use to separate out the real engineers!’ I got the job, even though I
could not have worked a control-theory integral problem to save my soul.”
The fallacy with questions that demand mental gymnastics is that they
don’t say much about how the applicant will perform day-to-day work.
“What you see is not always what you get,” says Dean Stamoulis, head of the
Global Executive Assessment Practice for Russell Reynolds Associates in
New York City. He also notes that some of the best candidates don’t make
good first impressions, and it’s important to look deeper than an initial perception. Finally, he advises that sometimes what is not said in an interview
is important as well. “If an interviewee doesn’t mention others he or she led
and name key contributors to past successes, that might indicate he or she is
taking credit for others’ work and ideas.”
— Leland Teschler, Editor
RS# 107
JANUARY 19, 2012
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