Finished the Shed structural elements last night; took over two hours, less than three. Marla was an excellent helper and spare hand, spare brain.
In retrospect, we should have left all of the screws slightly loose until all panels were in place -- getting the roof on was six flavors of annoying, trying to torque the shed walls into shape.
The instructions say "Measure diagonally to be sure the shed is square." We didn't bother with this because the instructions made no mention of what to do if the shed were NOT square, which fits in just about right with my experience with the Chinese approach to debugging -- which is to say, they don't. No error reporting, because that might indicate weakness. Bugs? We don't have any bugs! Our tests prove it, see that green light? If you measure your shed and it's not square, clearly you lived a poor life and should just go die now. Hah.
So the shed was not square, but leaving the screws loose until the end would have made it easier to finesse into position. That would have required more forethought than _I_ had going, and would have been something useful for the instructions.
Oh, and don't get me started about the highly accurate placement of holes in this metal shed thingy. Yup. Putting the hinges on, if you tighten two of the three screws, the third screw hole is over half a diameter out of place. That's some quality machining there Lou.
Needless to say, the doors don't hang right yet. Another task for the coming weekend.
I spent the rest of the evening trying to find an IGBT or other transistor shaped device that can (a) handle 600 amps, an arbitrary number I pulled out of my ear that is about ten times the IGBT I use now; and (b) can switch at 100kHz, another arbitrary number, but my current Tesla goes at 168kHz, so 100kHz frequencies seem reasonable.
I found one very nice 600A IGBT on eBay for $47, normally a $470 part, but it switches at 25kHz. In fact, most if not all high power IGBTs switch at the 20-25kHz range.
I do so want to build this massive Tesla in DRSSTC style, though, which means BIG SWITCH. Or, maybe, lots of little switches in parallel, except that IGBTs don't parallel gracefully, not like MOSFETs. But MOSFETs have issues with current dissipation at high voltages.
So the quest goes on.
Posted by Edwin at June 25, 2008 07:42 AM