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bob from maine
User Rank
Platinum
Re: Spark coil sparks indeed
bob from maine   7/26/2012 2:17:20 PM
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Model-T spark coils could, under the right conditions of condensing humidity, energize the dashboard metal each time the #1 cylinder fired. This made for some very entertaining driving. While in the military, we had HF transmitters of various output power all going through one antenna patch panel. Connecting a 10KW transmitter to a whip-antenna with a 1KW tuning coil at its base usually caused the whip antenna to launch at fairly significant velocity. It also occasionally caused the transmitter power-supply to crow-bar and scare the heck out of anyone standing nearby.

ervin0072002
User Rank
Gold
6Joule cap fully charged = Pain
ervin0072002   7/23/2012 7:52:24 AM
NO RATINGS
 

Ok so let me define pain in electrical engineering terms. 6 Joule cap charged at about 4kV (do the math if you want to know C I don't remember it) shorting it across my thumb and pointing finger. I had a hard time closing my hand for about a week and had no strength on it for a good two weeks. I know there was some nerve damage but then it went away and did not need therapy.... Of course had I shorted that from one arm to the other I might not be here to tell the story ;)?

Oh and then there is the time when I shorted a capacitor of the same kind that had been sitting in a shelf for over three months. Don't you love capacitors that always stay charged and in case you discharged them they go ahead and charge themselves? Only at a couple of hundred volts but still tickles you if you short it across your fingers...

Scott Orlosky
User Rank
Platinum
Does the Chemistry lab count?
Scott Orlosky   7/22/2012 8:14:01 PM
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I loved my chemistry lab as a youngster, especially my alcohol lamp burner - you could really get reactions going with a little heat.  One day I was trying to remove the protective metal cap off the top of the burner (i couldn't figure out why it would rust since it was full of "alcohol" and not water).  Undaunted, I grabbed a pair of pliers, twisted for all I was worth and cracked the glass base severing my index finger down to the tendon. Yowtch!  Five stitches later and a bandage the size of a golf ball on my finger - I returned home.  Never did that again.

JimT@Future-Product-Innovations
User Rank
Blogger
How NOT to measure the length of a battery
JimT@Future-Product-Innovations   7/22/2012 4:50:40 PM
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In the 1990's in Telecom, before LiIon batteries became the normal standard, NiCad and NiMetal Hydride cylindrical batteries were the cell-phone industry's power-source of choice.  These cylindrical cells, just like Lead-Acid Duracells, were only 1.5V nominal, so typically, three were used to engineer a "cell pack" with a safety circuit. 

The battery department design engineers would routinely measure length of these cells using a metal Vernier caliper.  Guess what happens when you measure across (+) and (-) of a battery cylinder with a metal caliper-?

There was not a Vernier caliper in the entire department that didn't have arc-burns on them, and not an engineer in the department who didn't recognize the "pop" and burnt smell after the failed measurement. It got to be a running joke for the battery engineering department.

Island_Al
User Rank
Gold
Re: Lessen in heat transfer
Island_Al   7/21/2012 12:18:50 AM
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Years ago I got back from a 2 month field job, wrote my trip report, and sent it to our shop typist/secretary. I then just gave it to my boss. The next day he brought it into my office and it looked like a term paper with red pencil "spelling", "restructure", "needs clarification", etc notes all over it.  It was not a deliverable paper, but just for in-house future work.  I wrote across the top in caps "SEND TO THE TECH WRITER SHOP INSTEAD OF ENGINEERING.  THEY ARE MUCH LESS EXPENSIVE TO USE" and brought it into his office 5 minutes later, dropping it on his desk. I never saw the paper again. I think he just filed it.


Moral of story: Don't let English majors design electronic circuits (or manage engineers). You can't win in a battle of wits if you are half prepared. - Dilbert (paraphrased).

Tim
User Rank
Platinum
Re: Lessen in heat transfer
Tim   7/19/2012 10:31:32 PM
NO RATINGS
Missed that one.  It should be "lesson"

Bob Salter
User Rank
Iron
Shock & Burn
Bob Salter   7/19/2012 2:36:43 PM
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I watched a young man, a new hire, operate a drill press for his first job at my plant.  He claimed to be experienced, and after turning on the drill and pulling on the feed lever, nothing was happening. After about half a minute, he let the drill bit retract and was somewhat a little confused and amazed that the end of the drill was a bright red color. Before I could say anything, he quickly touched the end of the bit with his thumb and index finger. The smoke that came off was definately not cutting oil evaporating. I explained that in any metal removing operation, if the tool is not advancing and no chips are being produced, you are definately not cutting. When he asked why this drill did not cut, I asked him if he turned the switch to FWD or REV.

warren@fourward.com
User Rank
Platinum
Re: Spark coil sparks indeed
warren@fourward.com   7/19/2012 2:04:39 PM
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I failed to mention that this was in 1966 when the air was still and there were jobs to be had.


Larry M
User Rank
Platinum
Re: Spark coil sparks indeed
Larry M   7/19/2012 1:29:30 PM
NO RATINGS
Warren wrote:  While explaining things he took a metal ballpoint pen and suavely touched the spark in the middle.

Interesting that he had the electrodes exposed. I've built several Jacob's Ladders over the years, usually from discarded 10KV neon sign transformers. They work best if they are in an enclosure vented at the bottom, since they rely on convection airflow to move the arc up from the bottom of the V to where there's really an impressive width.

I've demonstrated this principle by standing above the enclosure and blowing down to hold the arc at an arbitrary spot.

A Jacob's Ladder without an enclosure would only work well if the air was very still.

warren@fourward.com
User Rank
Platinum
This is fun!
warren@fourward.com   7/19/2012 1:18:43 PM
NO RATINGS
I use copper beryllium flat spring material as a spring set to move lenses.  I have to cut it to length then drill holes in the corners in a fixture I made.  While holding the fixture and drilling with a high speed Dremel tool the drill bit went through multiple layers of copper beryllium and through my left index finger.  Then the drill bit came out of the Dremel.  I stood there with a drill bit through my finger and my finger nail with equal amounts of drill bit on either side.

I drove myself to the hospital emergency room and held up my finger and told them, "I think I have a problem."  They took me into a room and the Dr. just unscrewed the drill.  I could have done that!

But for the next week I was pulling out little curlicues of spring material out of my finger.  My finger should have been X-rayed, and I should have kept my finger away from the business end of a drill!

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