![]() |
Barry's Coilguns |
|||||
Discovery Coilgun
|
Observations from an ExtraThese are my notes as a bystander ("consultant") during the video production in Arizona.
Danger: High VoltageI thought the whole project was a smashing success, and the coilgun was totally reliable. Sure, some of the extra bits didn’t perform exactly as they wanted, but I still think the coilgun clearly demonstrated its immense power and that one could believably scale it to stupendous size to launch things into space.
That would have been okay, but when it switched to safe mode, one bank of capacitors still showed a full charge. So Basil emoted under camera about how dangerous this was – we couldn’t fire it, we couldn’t discharge it, and we couldn’t safely approach it to repair it. I worked out the RC time constant to be 5 hours, meaning it would only reach safe voltage levels overnight (3RC). Of course the crew is on a schedule and can’t wait that long.
G-Force Meter
Working at night in the desert was an interesting experience too, with flashlights among the cactus with coyotes howling in the not-so-distant dark. However the g-meter never did provide readings that seemed really reliable. Finally the aluminum disk got somewhat caved in by the forces and stress involved, and Tod switched to a thicker disk for which the g-meter was not set up. I double-checked the design engineer's math and it all looks correct. The readings do seem quite high, but they may well be plausible. However, two “identical” back-to-back shots had g-meter readings of 5093 and 7785 which is a substantial variation. Also one low-power shot had a g-meter reading of 9999 which seemed unlikely. For corroboration, Dr Angel took the bent disk back to his lab where he hopes to determine how much force was necessary to bend it that amount. Ballistics Gel
Shooting Vertically
Subsequent vertical shots held together better. However, the fragile mirror always broke. This could have been due to impacting the hard desert floor. Or perhaps, more likely, as the ones who knew how it worked believed, the mounting scheme allowed a bending stress across the silicon, causing it to crack. ScienceI never did hook up my oscilloscope. It became apparent that any extra equipment could only slow down production of a schedule that was very time-constrained. The whole crew worked from sunup to sundown, using every bit of daylight time they could in this extremely scenic location. The special effects crew worked even longer. You simply must see the pictures taken by Tod and Neil and others. My only regret is that very little science could be done on the coilgun. We did not get accurate readings of things like voltage, current, waveforms, mass and velocity. I collected what details I could but it is difficult to put quantitative numbers on its performance. Also we never did get a chance to crank it up to maximum power for one last shot. Oh well, I guess that means I need to build my own, right? I came away with some good ideas about things that worked well on a coilgun. Not the least of which is the copper arrowhead slider for commutation. Overall the coilgun was very successful, very impressive, and will make a great episode. I know it will get a lot of attention from the coilgunning community when it finally airs. I can’t wait to see the finished product. Cheers, Barry |
|||||
|
||||||
Last Update 2017-12-11
©1998-2025 Barry Hansen |