While training in Zimbabwe, David pulled an impressive prank on his housemate. Luckily (for David), the guy had a good sense of humor!
In the late ‘70s I was training at the Posts and Telecommunications Corporation Engineering College in Harare in Zimbabwe. There were three of us, Mike, John and myself, from the Police radio section - the Police sent their techies to the PTC college for training. We lived in a police barracks on the other side of town and all of us had cars. John was probably the most staid of us, but nevertheless had a good sense of humour. He hailed from Bulawayo, some 300 Km away from Harare, and drove back home for long weekends or when he had some leave.
In one of the breaks in our course, he had taken a week’s leave and was going home on a Saturday morning. He hadn’t been home for some time and was fairly excited to be seeing his family again.
So Mike and I decided we’d see him off in style. In my miss-spent youth I had learned to make spectacular bombs from match-heads. You get a knife and carefully pare off the coating from all the matches in a box or two onto a piece of plastic sheet. You then get a length of twin-stranded wire and join the two ends together with one strand only – this acts as your fuse or detonator. You place the wire among the match-heads and wrap the plastic tightly around them. You then wrap a bit of aluminium foil round the whole lot, and then tie it up with a bit of string. You then put 12 volts on the wire, the single strand briefly glows red hot and then burns out, in the process igniting the match-heads. You get a spectacular but fairly harmless explosion with a huge cloud of smoke.
I made up one of my devices with about a foot of wire terminating in crocodile (alligator for you yanks) clips. John got an early night on Friday and Mike and I installed my device. We crawled under John’s car and connected it between the switched terminal of the starter (which on cars of that era was exposed) and the chassis. We did use a meter to make sure we didn’t connect to the live terminal and blow ourselves up.
John was up at the crack of dawn and as our rooms were adjoining, Mike and I heard him get up. We heard him lug his case out to his car and we crept out of our rooms. Seconds later there was a loud explosion. We put our heads round the entrance to our corridor and saw John’s car with a huge cloud of smoke pouring from the hood. John knew us well. He got out of his car and looked straight at our heads peeping round the building entrance. “You @#$%^&* bastards!” he yelled at us. It was the only time I ever heard him swear. Once he’d got over the shock, though, he was quite impressed at our ingenuity. I don’t remember how he got us back, but alas it was not with anything remotely technical….
Ah yes, funny how you can easily forget something from your youth, yet the description of the flaming arrow on a wire to the campfire brings it all back. Camp Squanto BSA, Plymouth, Massachusetts . . . 1975 - 1980. Yikes, that was a long time ago.
Naughty yes. I AM a naughty bugger.
Risky...well if it blew up right in your face it might be dangerous, but unless you made a huge one you wouldn't really stand much chance of injuring yourself.
I've always worn glasses but if I didn't I would wear some eye protection when installing one now. But whether I would have done at the time (I was about 19 then, and 54 now) I couldn't say. When you're 19 you think you're bulletproof.....
Wow, your post takes me back. We did exactly the same thing in a YMCA father-child group I used to belong to that was heavy on camping trips. Lots of EEs in the group, so naturally we had to have magical self-igniting campfires at our ceremonies to instill a sense of wonder and amazement in the kids.
The flaming arrow shot from a bow up in a tree was always backed up by a battery and a pyrogenic electric match. Pre-soaking the logs in flammable petroleum distillates didn't hurt either :)
This is similar to a trick used at Boy Scout camp.
The basic idea was to light the nightly campfire by sending an lighted arrow down a slanted wire into the campfire kindling, thus lighting the campfire. For some reason, the leaders decided this was somewhat dangerous (someone had to climb a tree and light the fire) and that it didn't quite achieve the mysterious effect they want.
So they opted to the above mentioned trick without the explosion. Success was achieved by multiple matches and a multiple single strands of wire. I got to set it up each night and turn it on. At the appropriate invocation, a lantern battery and knife switch set the ceremony in motion. It always worked.
Designers of embedded systems need to test and troubleshoot designs by looking at both digital and analog signals, and the analog representations of digital signals. ESC Boston is the place to see mixed-signal oscilloscopes in action.