Old Tech thread


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"Dad says that anyone who can't use a slide rule is a cultural illiterate and should not be allowed to vote. Mine is a beauty - a K&E 20-inch Log-log Duplex Decitrig."
- Robert Heinlein, Have Space-suit, Will Travel.
 
Harpo said:
I used a slide rule for my maths ‘O’ Level in 1978. Everyone else in the room used calculators.
Which makes me think I was one of the last people to use a slide rule in their exam.
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I think that you must be. I also took Maths ‘O’ Level in 1978. At my school we were the last year to be taught to use them, then they went back into their packets. I still have mine with it's instructions. In the exams no one used them.
 
In my 'O' levels calculator weren't available at sensible prices. In my 'A' levels they were just becoming available but we still had to use slide rules, and log tables when more accurate results were required.

It was only at university (about 1975/6) that we were allowed calculators but for exams they were not allowed to be 'programmable'.
 
In my very first catering supervisor job, about 1975, we used one of these to add up the float, shift takings, and to calculate the value of the stock-in-hand.
I remember being told off for putting something heavy on top of it, because it cost "nearly 200 quid". Didn't even have a memory function...


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We weren't allowed to use either calculators or slide rules** when I took my Maths O-level.

IIRC, I was the first person in my class to own a calculator -- a Texas Instruments SR-10:

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​
-- but (obviously) I never used it in lessons.

When the SR-10 came out in 1972 in the States, it cost (according to something I've just read) US$149.95 (direct mail price). I find it very hard to believe that my father paid (or would or could pay) anywhere near that amount of money, and it's likely that the UK price, if the SR-10 was sold here, would have been higher (although I'm pretty sure that he brought it back from the US). I can only assume that the SR-10 had soon been overtaken by other models and so had become difficult to sell. Anyway, I seem to recall him saying it cost £30 or so (which was still a lot of money back then, and neither of my parents were big spenders).


** - We were taught how to use a slide rule in the first year at my first secondary school (with an emphasis on working out the order of magnitude of our expected result, otherwise the slide rule would be useless), but when I moved to another town, and thus another school, not a single slide was to be seen.
 
I was digging the garden yesterday and came across what I thought was a T shaped rock about a foot down from the surface.
Rinsing the encrusted dirt off I thought maybe a tee piece union. but a 20 minutes cleaning and dismantling it turned out to be a brass pressure gauge. It works against a spring like those old pen shaped tyre pressure gauges. about 3 inches tall.
Amazing how well preserved it is after what is probably half a century. I unscrewed the indicator cap so you can see the numbering. (90 psi ? )
Anyone have any idea what it was from?
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I would expect it is from a Boiler. To say if that was a steam boiler, and from a stationary engine in a factory, or a locomotive, or a domestic or industrial heating boiler, then we are going to need to know more about your garden and where it is situated. Is it green-field rural, brown-field former industrial, or very urban? (Even what appears to be rural could be old mining spoil.)

BTW if it's either of the latter and your were digging to plant vegetables, then I'd get a soil survey done before you eat them. If it is old mining spoil (which might be Roman or Medieval) or your house is built next to a railway line, or a major road, it could be high in heavy metals such as Cadmium and Lead, or in Arsenic. Far better to build raised beds and fill then with purchased top soil instead.
 
Dave said:
I would expect it is from a Boiler. To say if that was a steam boiler, and from a stationary engine in a factory, or a locomotive, or a domestic or industrial heating boiler, then we are going to need to know more about your garden and where it is situated. Is it green-field rural, brown-field former industrial, or very urban? (Even what appears to be rural could be old mining spoil.)

BTW if it's either of the latter and your were digging to plant vegetables, then I'd get a soil survey done before you eat them. If it is old mining spoil (which might be Roman or Medieval) or your house is built next to a railway line, or a major road, it could be high in heavy metals such as Cadmium and Lead, or in Arsenic. Far better to build raised beds and fill then with purchased top soil instead.
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Historically only Mining, a Brickworks and an Ironworks in the area so no worries there. :)
I'll research soil testing.
 
Astro Pen said:
I was digging the garden yesterday and came across what I thought was a T shaped rock about a foot down from the surface.
Rinsing the encrusted dirt off I thought maybe a tee piece union. but a 20 minutes cleaning and dismantling it turned out to be a brass pressure gauge. It works against a spring like those old pen shaped tyre pressure gauges. about 3 inches tall.
Amazing how well preserved it is after what is probably half a century. I unscrewed the indicator cap so you can see the numbering. (90 psi ? )
Anyone have any idea what it was from?
View attachment 116216
Click to expand...
Might be worth a google image search?
 
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