Well, the house is now insulated, so my thoughts drifted back to spine testers, and converting my arrow straightener to a spine tester.
So I identified a whole load of materials, parts, bracketry, bearings, etc and was just about to hit the 'Buy it now button' when I had an epiphany...
- The amount of money that I was about to spend was not far away from the cost of a second hand commercial spine tester
- It would still only measure to 500 spine as that's what my dial gauge reads to
- That Bearpaw electronic spine tester, brilliant though the idea is, isn't actually doing a lot.
In light of this, I present my new spine tester, made from a set of kitchen scales, an ashtray, two blocks of wood, two pencils, some foreign coins and five pencil marks on the kitchen table:
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Like the Bearpaw tester, you press the middle of the arrow down to the plinth which is set 0.5" below the bottom of the shaft:
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And read the number on the scales:
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And it has a major improvement over the Bearpaw unit as, thanks to the two extra pencil marks on the table, it works on 23" supports as well as 28" ones:
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It's not as good as the Bearpaw one as it doesn't read spine directly. I was going to develop a spreadsheet to work it out but in the end I decided that would be overkill as the equation wasn't complicated:
At 28": spine = 220,000 / weight on scale in grams
At 23": spine = 396,929 / weight on scale in grams
Given that it's an experiment / prototype, it seemed to work pretty well, what with hexagonal pencils as supports rather than frictionless bearings, a 0.5" plinth that was pretty much just eyeballed for height, kitchen scales with a dodgy battery that is only precise to 5g, and test arrows that I couldn't be bothered to defletch:
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The one fly in the ointment was the last Cartel 500, but a bit of research revealed that Cartel do spines different, so there you go.
And the 1716s were crossed out as they were no-name Chinese ones that 1716 was always a guess for anyway, so I threw that reading away.
And if you're interested, here's a look into my brain when it's trying to work out the equations:
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