Jig or Protractor?

[ConradH]

I think playing area is a bit dependent on they type and age of records. My classical tends to have a larger inner radius... unless it doesn't. If you gather up some typical records that you listen to, and measure them, that's probably a good place to start. You'll find my template generator has a button labeled "typical", and those numbers are from measuring a bunch of records from my own collection. One can get obsessive about this stuff, and compare different alignments with the Elison spreadsheet, but honestly I don't know if you'll hear a difference. It's just an enjoyable pastime.

 

[Nat]

I'm not convinced at all that a lack of computers is any impediment to excellent and intelligent design. The existence of superb machinery of all sorts designed and made before computers existed would seem proof to me. Computers do make some tasks much easier, but much of what they can do can also be done by humans, just more slowly, and with many, many more designers. I use to be in optics, where computers have made an enormous difference in making lens design faster - rather than enormous numbers of people calculating and drawing ray diagrams, which takes a long time, a computer can do it quickly. The use of computers made the the late 70s and 80s explosion of cheap zoom lenses (which have many lenses that have to move relative to each other) possible, but quite a few zooms had been designed using traditional methods before that.
It is also worth keeping in mind that slide rules and abaci can do complex calculations relatively fast, even compared to calculators, though the level of meaningless precision is vastly lower.

 

[ConradH]

I agree, but when doing things manually there's a tendency to stop when the job is done sufficiently well. There's not much incentive to explore 37 other possible approaches, whereas with spreadsheets and the like a curious engineer is more likely to explore other possibilities. Of course you still need a curious engineer. "the level of meaningless precision is vastly lower" is a wonderfully true statement!

 

[ripblade]

Meaningless precision also means that a larger safety factor was built-in to the margin of error. These days it's so tight that real manufacturing limitations can't keep up, leading to more failures through no fault of the maths.

 

[AvFan]

I use arc protractors created by @ConradH's arc protractor program and find them particularly useful. It can be in iterative process when combined with some of the Vinyl Engine tools such as the Overhang Shift Calculator. I too measured a bunch of my records and their inner grooves ended sooner than the "standard" inner groove null point so I mostly use Lofgren B to minimize overall error/distortion.

I do like the parallax feature of mirrored protractors. Is there a way to etch one of Conrad's arc protractors on a mirror? Could the protractor be printed on a transparency then somehow attached to a mirror?

 

[ConradH]

You can print on transparency film with no problem but I've never tried putting it on a mirror. In theory you can print to just about anything, so there's probably a way to print on a mirror or even etch it. People who make optical targets do that sort of thing all the time, but it's expensive and probably not available to the likes of you or I. You could do toner transfer to a polished metal plate, but I don't know how the accuracy would hold up. People make circuit boards that way.