This discussion puts me in mind of why I joined ARSC a couple of years
ago: Finding myself in a constant process of reinventing wheels, I
thought that I might benefit from the experiences of others that had
already gone down a similar path. I was right. Thank you.
KRAB Archive: www.krabarchive.com
On 10/26/2018 12:29 PM, Richard L. Hess wrote:
> Your approach using area was counter-intuitive to me on the first
> pass, so I decided to "check your work" and used my intuitive approach
> which was to actually count turns (mathematically). The answer came
> out the same.
> However, there is a minor error in your assumptions (not the formula).
> It is a deep dark secret that North American tape thicknesses are the
> base-film thickness, not the overall finished tape thickness (measured
> in mils), while the Japanese and some European tapes have their
> overall thickness listed in a nominal number of microns.
> Fortunately, Del Eilers and Bill Lund put together a wonderful
> resource for 3M tapes, found here, and there is an equally wonderful
> table in the same location provided by Friedrich Engel for BASF, AGFA,
> and associated tapes. Alas, the Ampex tape list does not contain that
> Here is a brief listing of overall tape thicknesses from 3M
> categorized by "Play" Standard, Long, Double, and Triple. This should
> work in a fixed pitch font. No tabs included.
> Numeric Thickness Designations
> “Play" nominal mil micron Japanese
> Standard 1.5 50.0 50
> Long 1.0 35.0 35
> Double 0.5 25.0 25
> Triple 0.5 18.0 18
> Actual Measurements
> "Play" actual mil micron 3M Type
> Standard 1.92 48.8 111
> Standard 1.93 49.0 201/2
> Standard 2.08 52.8 206
> Standard 2.06 52.3 250
> Long 1.27 32.3 150
> Long 1.43 36.3 203
> Long 1.51 38.4 207
> Double 0.85 21.6 200
> Triple 0.67 17.0 290
> On 2018-10-26 5:19 AM, ROBINSON Stuart wrote:
>> That assumption was stated in the original example.
>> The tape thickness is a variable in the formula on the spreadsheet.
>> Best, Stuart.
>> Archival AV Technician,
>> School of Scottish Studies Archives.