Know your "circular mils"

[graham-xrf]

I'm going to speculate that the advent of modern technology (computers and the Internet) have made the use of this type of convenience (conductivity proportional to area) much less of a useful thing. Most people are quick to look this type of thing up in an online chart than actually crunch numbers, and if so can do it on a calculator so pi * r^2 isn't tough.

A similar issue, how many people care memorized for small angles:
the tan(x) is approx the same as the sin(x) which is approx x/60? (for an angle x measured in degrees)
Why bother, won't a calculator do that exactly? (@graham-xrf might know why I picked this up)

(Sigh).. You are right!
I guess you got to know me a bit. I don't know quite when I became a precision-minded numeric freak, but folk around me now know that they can't borrow my calculator without getting into a knot over why it does not have an "=" equals button (HP-35S Reverse Polish Scientific)
. The calculator app on my phone is the same.

 

[rabler]

(Sigh).. You are right!
I guess you got to know me a bit. I don't know quite when I became a precision-minded numeric freak, but folk around me now know that they can't borrow my calculator without getting into a knot over why it does not have an "=" equals button (HP-35S Reverse Polish Scientific)
. The calculator app on my phone is the same.

@graham-xrf
I'm a fan of RPN too. I grew up on HP RPN calculators. Made some money in high school writing HP calculator programs for medical lab folks to use for calculating routine laboratory results. I learned PI to the number of digits found on HP calculators. But, flying single pilot IFR, you can't drop the controls to grab the calculator without risking "unusual attitudes" (aka bad things). So anyone that has done navigation in their head knows that if you are X degrees off course and N miles out, N*X/60 gives you how far off course you are, with enough accuracy given the likely error in your knowledge of X and N. Sometimes being quick and close is more important than being accurate

I say that, but most folks currently flying IFR would turn to the fiddling with the GPS and map display before crunching numbers in their head. I'd guess similar logic in sailing. So times change the practical aspects of how folks approach science and engineering pretty significantly. There was a discussion about using gauge (gage?) pins to determine hole diameter, and I could see some of the same progression there in how folks approached it.

 

[graham-xrf]

@graham-xrf
I'm a fan of RPN too. I grew up on HP RPN calculators. Made some money in high school writing HP calculator programs for medical lab folks to use for calculating routine laboratory results. I learned PI to the number of digits found on HP calculators. But, flying single pilot IFR, you can't drop the controls to grab the calculator without risking "unusual attitudes" (aka bad things). So anyone that has done navigation in their head knows that if you are X degrees off course and N miles out, N*X/60 gives you how far off course you are, with enough accuracy given the likely error in your knowledge of X and N. Sometimes being quick and close is more important than being accurate

I say that, but most folks currently flying IFR would turn to the fiddling with the GPS and map display before crunching numbers in their head. I'd guess similar logic in sailing. So times change the practical aspects of how folks approach science and engineering pretty significantly. There was a discussion about using gauge (gage?) pins to determine hole diameter, and I could see some of the same progression there in how folks approached it.

I had got used to the nice high-tech GPS screen with the moving map, keeping track, and warning of zones and potential airspace violations. It gave me the QNH, and there was also the handy GPS "altitude above terrain" thingy for where I happened to be, so I could leave QFE set for the landing field. No need to calculate anything. For insurance purposes, it is classed as an "extreme sport", but I loved it

Re: Gauge pins? They are simply things to love, BUT, to have a set that has all the uppers and lowers by a few tenths, as well as the exact size, comes damn expensive! Double that to have a metric set as well! For the moment, I make do with re-purposed busted end mills that work quite well.

I do have a "small" set of lab gauge blocks, only ever used to check on the micrometers and calipers. My scope (HP54520A) needs to do it's self calibration too, but only after I have discovered and replaced the 3.3V Lithium cell. The signal generator (HP8657A) is also a very old thing, but it works quite fine, and will be "exact" when locked to a GPS gadget I now have the kit for.

By coincidence, I came across circular mils again, this time all about calculating how much current carrying copper area fits into the winding window on the bobbin of a ferrite high frequency transformer.