4 ms·

And how would you propose one gain intuition on what individual pieceparts of a build-to-print submarine ought to weigh, especially given the scale (and relativ

And how would you propose one gain intuition on what individual pieceparts of a build-to-print submarine ought to weigh, especially given the scale (and relative weight) of the thing in error can't easily be gauged by any individual? 10x error is hardly familiar territory if the thing in question is, say, trace heavy metals in a custom alloy. If I gave you volumetrically equal pieces of 6061 and 7075 aluminum--whose difference in density is ~4%--would you be able to intuitively sniff out that something was off? What if those pieces were several tons a piece and your calibrated industrial weighing equipment had a reasonable +/-5% margin of error?

TheSpiceIsLife 7y ago
Is +/-5% really a reasonable tolerance for industrial weighing equipment?
- metaphor 7y ago
  Sure if the industrial weighing equipment leveraged is, say, a weigh-in-motion system with an acceptable GVW tolerance of +/-10% as described in NIST HB 44[1]. In any case, this toy detail was intended to snuff out the grandparent's presumption that 10x error in any arbitrary parameter is obvious. The difference between 6061 and 7075 is offered as a simple thought experiment in that they're both common alloys in industry, yet difficult to discern one from the other despite the latter having a zinc composition that's 20x greater in the best case (6061 = 0.25% max; 7075 = 5.1-6.1%; 20 ~= 5.1 / 0.25) as specified by ASTM B209[2]. Fact of the matter is a contractor was responsible for a build-to-print submarine. A particular drawing specified something-or-other with an off decimal value that escaped human detection during multiple engineering design reviews. Contractor had something-or-other manufactured to the exacting detail specs in said drawing and no doubt was able to provide supporting documentation in the form of material certificates of conformance and lot testing results...but all the precision instrumentation and manufacturing quality control in the world amounts to nothing if the basis of truth is fundamentally flawed...and it certainly didn't help that the only effective opportunity to detect catastrophic design error (not that it's a build-to-print contractor's responsibility to identify such subtle faults) was spot validation of a system-level key performance parameter that wouldn't have been possible until the entire system was fully assembled. [1] https://www.nist.gov/system/files/documents/2019/12/03/00-20-hb44-web-final.pdf https://www.nist.gov/system/files/documents/2019/12/03/00-20... [2] https://www.astm.org/Standards/B209.htm https://www.astm.org/Standards/B209.htm
  - TheSpiceIsLife 7y ago
    Thanks for the extensive reply. I was just curious as I work in metal fabrication but have had little to do with weighing equipment.
  - rwmurrayVT 7y ago
    I believe in this case the issue lies at the planning yard instead of the building yard. Building yards are usually not filled with engineers evaluating the design criteria sent from the planning yard.

TheSpiceIsLife 7y ago

Is +/-5% really a reasonable tolerance for industrial weighing equipment?

metaphor 7y ago
Sure if the industrial weighing equipment leveraged is, say, a weigh-in-motion system with an acceptable GVW tolerance of +/-10% as described in NIST HB 44[1]. In any case, this toy detail was intended to snuff out the grandparent's presumption that 10x error in any arbitrary parameter is obvious. The difference between 6061 and 7075 is offered as a simple thought experiment in that they're both common alloys in industry, yet difficult to discern one from the other despite the latter having a zinc composition that's 20x greater in the best case (6061 = 0.25% max; 7075 = 5.1-6.1%; 20 ~= 5.1 / 0.25) as specified by ASTM B209[2]. Fact of the matter is a contractor was responsible for a build-to-print submarine. A particular drawing specified something-or-other with an off decimal value that escaped human detection during multiple engineering design reviews. Contractor had something-or-other manufactured to the exacting detail specs in said drawing and no doubt was able to provide supporting documentation in the form of material certificates of conformance and lot testing results...but all the precision instrumentation and manufacturing quality control in the world amounts to nothing if the basis of truth is fundamentally flawed...and it certainly didn't help that the only effective opportunity to detect catastrophic design error (not that it's a build-to-print contractor's responsibility to identify such subtle faults) was spot validation of a system-level key performance parameter that wouldn't have been possible until the entire system was fully assembled. [1] https://www.nist.gov/system/files/documents/2019/12/03/00-20-hb44-web-final.pdf https://www.nist.gov/system/files/documents/2019/12/03/00-20... [2] https://www.astm.org/Standards/B209.htm https://www.astm.org/Standards/B209.htm
- TheSpiceIsLife 7y ago
  Thanks for the extensive reply. I was just curious as I work in metal fabrication but have had little to do with weighing equipment.
- rwmurrayVT 7y ago
  I believe in this case the issue lies at the planning yard instead of the building yard. Building yards are usually not filled with engineers evaluating the design criteria sent from the planning yard.