<<  <  Page 2/3  >  >>
User Rank
Re: Spark coil sparks indeed
warren@fourward.com   7/19/2012 1:07:16 PM
That reminds me of my high school physics teacher.  He brought in a Jacobs Ladder and had it working on the table while he talked.  While explaining things he took a metal ballpoint pen and suavely touched the spark in the middle.  By my calculations, if the transformer driving it was putting out 20kV the middle of the spark was 10kV.  He got sick leave for three days after it knocked him very painfully backwards into the chalk board.

sensor pro
User Rank
Re: Burned fingers? Sure!
sensor pro   7/19/2012 11:26:32 AM
while working on Argon Opthalmic laser tubes I also had some problems with my wedding ring. Numerous shorts and also beal diflections. All this until my lead engineer recommended one of two solutions: remove the ring or get divorced.

Well, I'm still married.

User Rank
Burnt fingertips
OLD_CURMUDGEON   7/19/2012 10:45:33 AM
In the early years of my engineering career, I was charged w/ the design of several high power rf (tube) amplifiers.  More than once did I smell the unique odor of "rf-cured bacon" extending from my hands.  After a while, I played it more safely, using an NE-51H neon bulb securely taped to the end of a plastic wand about 3 feet long.  Much safer tool to investigate "hot spots" on the chassis. 

Specific incidents?  Too numerous to mention & too long ago to account accurately.

Larry M
User Rank
Spark coil sparks indeed
Larry M   7/19/2012 10:14:26 AM
In my early teens someone gave me a spark coil from a Model-T Ford. This device contains a transformer and mechanical vibrator in an elegant wooden box with dovetailed joints. The vibrator chops the incoming 6 volts DC. The resultant square wave feeds a step-up transformer to produce about 10KV.

I decided to make a Jacob's Ladder by attaching two bare wires configured in a V-shape to the high-voltage terminals. The trick to this is adjusting the spacing so that the arc will jump across the V-gap at the closest point. Localized heating of the air causes the arc to be blown upward across the widening gap.

After three or four power off-on tries at getting the spacing right and having it too far (no arc) or too close (insufficient heating). I decided to try moving the wires while it was on.  Had I picked up a plastic-handled screwdriver from the bench, all would have been fine, but none was at hand. Instead I picked up a plastic-handled hunting knife which was on thw workbench, without noticing the rivets which passed through the plastic handles and blade.

When I touched the hot electrode and received the shock, my arm jerked upward over my head and I released the knife. It flew the 20' length of the workshop and stuck (Jim Bowie style) in a wooden bookcase at the end of the room. I couldn't have thrown it better had I tried.

It was a good thing I was working alone at the time.

Old Man
User Rank
High Voltage
Old Man   7/19/2012 9:55:10 AM
One of my first jobs I was tasked to build and debug a complex high voltage TWT switching power supply.  The voltages I was working with were +20kV to -20kV and some supplies were as much as 2kW, more than enough to kill you.  I asked my boss what safety proceedures were in place and he told me, "Don't die." (this was a very small company)  As cautious as I was I would recieve mild to moderate shocks most days.  To help prevent the moderate shocks, a technician and I developed the 'wand of power', basically a long plastic stick with a ground wire attached to the end, and used it to pre drain the capacitors before working on a board.  This job was hair raising, electrifying and definately memorable!

User Rank
Re: Lessen in heat transfer
MaruaderMan   7/19/2012 9:38:48 AM
Sorry to be a nit-picker, but you also need a "lessen" in spelling.

User Rank
Lessen in heat transfer
Tim   7/18/2012 9:58:36 PM
As an engineer, i have had my fair share of experiences with errant voltages and shocks from contact with incorrect wires, but my only real injury was due to inexperience when I started my first job out of high school.  At the company, rookie engineer projects were usually completed through the build process with the engineer working with the necessary support personnel to physically complete the project.  My design called for a bracket of steel bent into a certain angle and then drilled and tapped.  The technician that I was working with explained that they usually complete brackets like this by heating the bend point cherry red and attaching a clamp and bending the bracket into place.  I said no problem and the tech left for break.  I attached the clamp, began heating the steel and when it was cherry red, i grabbed the clamp and immediately learned that heat transfers through steel quickly.  I missed the step that stated to attach the clamp after the metal was hot.  I still have the burn scars to remind me of the heat transfer capabilities of steel.

Charles Murray
User Rank
Re: Exploding meter
Charles Murray   7/18/2012 5:25:49 PM
ttemple: "...holding the meter, with the leads hanging down, with the charred spot square in the middle of my shirt..." Sounds like a classic Wile E. Coyote picture. The only part missing was the burn marks on your face.

User Rank
Where to begin?
NadineJ   7/18/2012 2:02:37 PM
The fact that I have all ten fingers is remarkable.  I'm always amazed when my fingerprints reappear.

I've defintely burned and sliced off my finger tips several times.  I think it all started when, at the age of 12, I put a sewing machine needle through my right index finger.  All of the adults panicked but the nail eventually grew out.

User Rank
Exploding Switchboard
akili   7/18/2012 1:16:37 PM
I had a problem with the 100A three-phase feed to the earth station servo system. I traced the problem right back to the main station distribution switchboard, well beyond my pay-grade at the time.  With the chief electrician in charge reading out the maker's instructions I followed his every word to remove and inspect the contact carriage. According to the book by means of a "special feature" it was supposedly safe to do this operation off-load but with the rest of the switchboard on-line.  We had never used that brand of switchboard before and we took the instructions at face value.  "Remove locking screw A" - OK.  "Raise latch lever B" - OK.  "Grasp carrier firmly, lift and pull out" - BANG!  When our eyes and ears returned to normal I was unhurt and had not received an electric shock but my hand was covered with that lovely bronze sheen from vaporised copper.  The switchboard was wrecked and we never used that brand again.  Surprisingly they are still in business.  No names, no pack drill...

<<  <  Page 2/3  >  >>

Partner Zone
Latest Analysis
Advertised as the "Most Powerful Tablet Under $100," the Kindle Fire HD 6 was too tempting for the team at iFixit to pass up. Join us to find out if inexpensive means cheap, irreparable, or just down right economical. It's teardown time!
The first photos made with a 3D-printed telescope are here and they're not as fuzzy as you might expect. A team from the University of Sheffield beat NASA to the goal. The photos of the Moon were made with a reflecting telescope that cost the research team 100 to make (about $161 US).
At Medical Design & Manufacturing Midwest, Joe Wascow told Design News how Optimal Design prototyped a machine that captures the wing-beat of a duck.
The increased adoption of wireless technology for mission-critical applications has revved up the global market for dynamic electronic general purpose (GP) test equipment. As the link between cloud networks and devices -- smartphones, tablets, and notebooks -- results in more complex devices under test, the demand for radio frequency test equipment is starting to intensify.
Much of the research on lithium-ion batteries is focused on how to make the batteries charge more quickly and last longer than they currently do, work that would significantly improve the experience of mobile device users, as well EV and hybrid car drivers. Researchers in Singapore have come up with what seems like the best solution so far -- a battery that can recharge itself in mere minutes and has a potential lifespan of 20 years.
Design News Webinar Series
10/7/2014 8:00 a.m. California / 11:00 a.m. New York
9/25/2014 11:00 a.m. California / 2:00 p.m. New York
9/10/2014 11:00 a.m. California / 2:00 p.m. New York
7/23/2014 11:00 a.m. California / 2:00 p.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Oct 20 - 24, How to Design & Build an Embedded Web Server: An Embedded TCP/IP Tutorial
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6

Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Next Class: 10/28-10/30 11:00 AM
Sponsored by Stratasys
Next Class: 10/28-10/30 2:00 PM
Sponsored by Gates Corporation
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2014 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service