It Doesn't Add Up

Being a hard-core fan of Doctor Who about ten years ago I set out
to make a working sonic screwdriver and did a brilliant job of it.
But somehow I lost both the screwdriver and the plans for it, so
I'm rebuilding it from scratch and memory
What I am now noticing is that I had a 1" diameter part screwed into
a battery compartment made out of a five inch section of nominal
1" aluminum pipe. Supposedly such pipe has an internal diameter of
1.0625" yet the part made out of 1" round aluminum bar fit
perfectly. Is the inside diameter of Al pipe actually smaller
than it's stated value or is bar stock a little larger in diameter
than the stated 1"?
Reply to
Ron Hubbard
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In article , Ron Hubbard writes
B&Q stock them! A few years ago BBC Radio 4 'Dead Ringers' Dr. Who (John Culshaw) rang their Dundee (I think) store and asked for one, amongst other items. After a pause of a second or two the assistant said they didn't have one in the store at the moment. This indicated to me quite clearly that they had indeed stocked them previously. There had probably been a run on them that week. Give B&Q a ring if you're UK-based. Regards, Martin
Reply to
Martin Goldthorpe
Howdy, Martin. I wanted one that works! Using for once that tiny little mind of mine (a mere 136 IQ) I designed the electronics and the ultrasonic transducer-- it took me nearly two years to get it right, but by the time I was finished it could produce 143 dB of ultrasonic sound pressure; enough to turn certain types of screws from a distance of a few inches and even keys in doors. It was a bit bulky because of a battery problem, but that was ten years ago.
Now, with some of those tiny 1 volt to 9 volt DC converters the bulkiness of the battery compartment can be reduced considerably and the thing is-- or when I get through machining another casing-- will be truly pocket-sized. Somehow losing the construction plans off my computer and having to redo it from scratch just amazes me that I had did such a good job of engineering when engineering was the last thing on my mind when I took high school metal shop. It started out to be such a simple project, but I learned a lot of stuff about sonics and acoustics and nearly a half-dozen other areas of science and technology to get it done.
I'm even more amazed in that I did it all out of 1" aluminum bar and pipe, and it all came together right the first time. :-)
Reply to
Ron Hubbard

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