[Coco] Schematic for external PIA, cart protoboard.

[Richard E Crislip]

On Sat, 7 Feb 2015 22:43:12 -0500
Gene Heskett <gheskett at wdtv.com> wrote:

> You have an idiot for a shop instructor, certified!  You realize of
> course that putting water on a magnesium fire only intensifies the
> burning about 100x?  It will steal the oxygen out of the water and
> make a fine fine show.
> 
> I hope the furnace was outside else it could have taken the whole
> building.
> 
> I learned about that the easy way, I was taking lessons on gas
> welding from a guy in Iowa City, circa 1956 or so, who had a card
> carrier strip folded up in his billfold with every welding
> certification known to the military, about 4 feet long when
> unfolded.  
> 
> One evening he allowed as how he was going to show us how to weld
> magnesium. With a smith wrench no less.
> 
> I thought, yeah sure and made sure I had my sunglasses handy, aka
> the goggles with the #5 ND lenses.  The item in question was a big 6
> Mercury outboard engine block that had over heated a bit after
> tossing a rod out thru the side & drainig the water.  But he had all
> the broken mag bits, very carefully fit them back into the hole in
> the side of the block and then proceeded to make some really nice
> beads of mag rod all the way around in all, tight enough it should
> have held water again.  After he had suitably impressed the 6 or 7 of
> us, and discussed the heating technique he used with the smith
> wrench, he then said that it was known that this block was warped far
> beyond an possibility of ever line boring it for oversized bearings.
> IOW it was junk.
> 
> Then he said this is what happens when you get it too hot and laid
> the cone of the flame from a #5 tip on a corner of the block.  Took
> about 30 seconds to start the fire.  Knowing he was going to do that
> is probably why we were out on the sidewalk 20 feet from his shop.
> When it lit, he advised us to stay upwind and just watch the show as
> he had no way to put it out that didn't cost way more than the block
> was worth.  10 minutes later the Iowa City FD showed up with a couple
> pumpers and a 10k gallon tanker.  We had a hell of a time convincing
> them that the last thing they ever wanted to do was put water on a
> magnesium fire. 
> 
> It burned thru the sidewalk which had seen better days 40 years back,
> and about 2 feet into the dirt before it was used up.  So the city
> comes by and writes him a ticket for destroying city property.
> 
> It wasn't, it was grandfathered into the land when his father had
> bought it 50 years back, but the judge read the city a couple verses
> from the city version of the bible when he arrived in court to fight
> the fine, he had a contract with a local cement peddler to replace
> that whole blocks worth of poor dangerous sidewalk, dated 3 days
> before the fire, and pictures showing the newly laid sidewalk that
> had already been done by the time of the court date.  The judge was
> duely upset at having his time wasted.
> 
> Yup, I have quite a list of BTDT's.
> 
8-) We did not try to douse it with water. We shut the furnace down and
let it do it thing. It was inside the building. Your description of your
teacher's demo is reminiscent of the thermite grenade demo we
participated in at Tan-San-Nhut. It reduce a fairly large compressor to
a puddle of molten slag in seconds. That was quite a show too. We had
one on top of all the mainframe computing equipment in the data center.
Two for the cpu. I was hoping nobody nodded out and hit button 8-O.