Tales from the High School Shop V

Ever licked a running spark plug?

So I'm teaching ignition systems and start out by figuring out what kind of voltage we need to fire the plugs. Then how to get that voltage from just a 12V battery.

I demonstrate how moving electricity through a coil creates a magnetic field (using a clear compass on the overhead projector), and I demonstrate moving a magnetic field through a coil creates electricity (using a galvanometer). We talk about how the size and number of loops dictate how we can step up the voltage to make whatever voltage we want.

I hook up a 9V battery, ignition coil, plug wire and plug, and demonstrate how the magnetic field has to be ~moving~ to get electricity, and it won't spark if the battery is always connected - we need to make and break the connection to move the magnetic field.

I offered if anyone wanted to try touching the spark plug and see what the increased voltage felt like. One thing led to another, and a couple kids dared another to put the coil wire across his tongue. Properly grounded, of course - for that proper "complete circuit" thing.

"Um, ok....." as I run my legal liability through my head "but I'm not connecting the battery - you can do it yourself or get one of your lackeys to do it, but I'm not doing this one."

So, his buddy hooks it up and gets the deed done.

He said it felt like licking a 9V battery, but 1000 times worse.

I figure he got off easy. We'll teach MSD next week.

I will never forget the time I got shocked by an MSD.

Through thick insulated spark plug pliers.

And the usual Blue Latex Gloves.

And my pants. (The leg, fortunately!)

And the painted fender.

MSD believer, I am! The kicker was that it used the keys in my pocket as a waypoint, so you can add two more layers of cloth to the list of insulators that it went through.

My favourite was pointing the timing light at the fan and going "Holy E36 M3, your fan isn't turning"

Every semester I could get a fellow student to stick his finger in the fan.

Shawn

BTW SkinnyG: If you ever talk to Al Laitenan from Steveston High, ask him about the time he set his shop coat on fire.

I haven't seen him since I left the coast way back. But I'll keep that in mind. I just set my shop coat on fire last semester. Again. The ones at Mark's have too much polyester - not enough cotton. That, and I should have watched where I pointed the torch.

He was cutting the exhaust off a car on the hoist.

A chunk of metal fell into his shop coat pocket and he didn't notice until it was too late.

Much hilarity ensued.

Shawn

I made a low order thermite reaction on the shop floor once by ignoring the no-steel-on-this-grinder rule cuz the aluminum grinder was inconveniently too far away...

Jay_W wrote: I made a low order thermite reaction on the shop floor once by ignoring the no-steel-on-this-grinder rule cuz the aluminum grinder was inconveniently too far away...

never thought about that...I never switch wheels between metals. Wonder how close Ive been to disaster?

When I first got my free push mower running I had to kill the motor by pulling the spark plug wire. I only did it once with my bare hands. I didn't think the magneto or whatever mowers have was that strong lolz.

I once pulled the coil wire off my Cadillac to kill it - and that thing was fitted with an MSD. They really do fire multiple sparks.

My freshman year shop teacher had us all stand around and hold hands then he handed someone the lead for a lawnmower spark plug and had the other end of the chain ground themself. Yeah, after that demo, I avoid coil wires like it's nobodies buisness, and if I have to play with em, I'm still leary of them when using insulated tools to disconnect them.

never thought about that...I never switch wheels between metals. Wonder how close Ive been to disaster?

Depends on how much aluminum dust is on the floor and how much of a savage you are when you're grinding that flashing off!

skruffy wrote: When I first got my free push mower running I had to kill the motor by pulling the spark plug wire. I only did it once with my bare hands. I didn't think the magneto or whatever mowers have was that strong lolz.

If you ever go into a small engine repair shop to ask what's wrong with your mower, and the mechanic tosses you a part, saying, "Here's what you need."...

...don't catch the part. It's likely a charged capacitor!

We used to do that every day.

Careful. There are big enougt capacitors to kill you.

Yeah, in my Electronics class: "This is a 1Farad Capacitor. You lick it, you die."

I did the capacitor thing to a kid in my high school shop class. Un beknown to me the vice principal was standing behind me at the time. I turned white with fear when I saw him, He turned red from laughing.

Looks like some of you failed the safety unit in shop.

NEVER GRIND ALUMINUM!

Sanding wheels, flap discs etc are find but never a stone.

The aluminum plugs the pores, the stone can't breathe and it heats up. Eventually it will come apart.

I hope you've got a good dental plan.

Shawn

Never heard of the aluminum/stone overheat thing. I guess I'm a lucky person.

I was parts manager at a forklift shop for a few years, the favorite trick around there was to run a wire from the ignition coil high tension lead to the springs in the seat (yeah, this was a long time ago). The unsuspecting victim would climb on board, turn the key, then get it in the ass and the hand at the same time. I learned to first lift the engine cover before operating ANYTHING.

The shop guys once ran a wire from an idling forklift to the service managers' doorknob, he was OK with jokes like that. What they didn't know: the general manager came in through the other door and then tried to go out of the shop door. Of course he got bit but good. the funny part was the idiot kept grabbing the doorknob like he expected something different. He must have grabbed it five or six times before he got the idea. By the time he got out the door, the wire was long gone and everybody was working industriously.

I've never been hit by a MSD but the actuators that I build at work run on 120v @400Hz and I've been bitten by the source voltage for them many times... and I mean MANY times 120 @60hz doesn't hurt all that much but the 400 makes me say some very bad words

Trans_Maro wrote: Looks like some of you failed the safety unit in shop. NEVER GRIND ALUMINUM! Sanding wheels, flap discs etc are find but never a stone. The aluminum plugs the pores, the stone can't breathe and it heats up. Eventually it will come apart. I hope you've got a good dental plan. Shawn

In my time didn't call them "units", but "periods". It was OK, though, because it was an all-boy school..

The first day, the woodworking teacher said, "Now boys, let's talk about safety around power equipment." .. Then he held up his hands. Four and a half of his fingers were missing. 'Nuff said.

Then, in electronics, the instructor simply told us: "This is solder. It looks like regular wire, but when it's hot, it will burn the beep out of ya.". We got the message.

The drafting guy took a lower key approach...

He just told us not to get graphite on the floor when sharpening our pencils on the sandpaper strips that we..

Gawd, I just realized how old I am.

SkinnyG wrote: Yeah, in my Electronics class: "This is a 1Farad Capacitor. You lick it, you die."

One of my friends in high school used to amuse himself by charging a one-farad cap and using it to blow giant holes in aluminum foil.

In reply to NYG95GA:

I'm 33 and I have slipped on graphite on the floor from drafting pencils and sandpaper. It's not been all that long. Although at one of my high schools they were excited because they had just gotten this brand new program Autocad. That was what '91 or '92. Something like that. My shop teacher did something similar, but he was only missing two fingers. In my electronics classes the biggest cap we had was a 1/4 farad, still enough to kill ya. But, I did have a fun time with a pencil lead and the test bench one time. Put a current through one at about 40V and a couple amps and you can vaporize the clay and graphite right into a finger. I found that one out the hard way.

Edited for more story.

My junior high metalwork teacher was a Scot from the old country.

His safety lesson consisted of the following:

"Right lads, listen up. NEVER STICK YOUR FINGER ANYWHERE YOU WOULDN'T STICK YOUR DINK!"

I still have all my fingers

Trans_Maro wrote: "Right lads, listen up. NEVER STICK YOUR FINGER ANYWHERE YOU WOULDN'T STICK YOUR DINK!" I still have all my fingers

And your dink as well, I assume...

NYG95GA wrote:

Trans_Maro wrote: "Right lads, listen up. NEVER STICK YOUR FINGER ANYWHERE YOU WOULDN'T STICK YOUR DINK!" I still have all my fingers

And your dink as well, I assume...

A new meaning to "don't get it on your hootus"

NYG95GA wrote:

Trans_Maro wrote: "Right lads, listen up. NEVER STICK YOUR FINGER ANYWHERE YOU WOULDN'T STICK YOUR DINK!" I still have all my fingers

And your dink as well, I assume...

My wife keeps it in her purse