Subject:
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Conversion between LDU, inches and millimeters
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Newsgroups:
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lugnet.faq
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Date:
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Tue, 24 Aug 1999 23:13:12 GMT
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Viewed:
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5529 times
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In lugnet.faq, Jeremy Sproat writes:
> Adam, do you have an inch <-> LDU conversion constant as well?
Conversion constants are much more relevant to the stud pitch than the brick
height or width, because brick heights and widths are subject to the error
caused by the fact that LEGO always designs elements so there will be tiny gaps
when assembled, to make them fit better even when marred or dirty.
The stud pitch in LDU is given by Steve Bliss's section of the FAQ answer,
which says that the stud pitch is 20 LDU (LDraw units). That's an exact figure,
because of the LDU's role as a way to make it easier to position pieces at
integral stud-positions when you're building a model in LDraw.
The stud pitch in the physical world is (from my section of the FAQ answer)
7.986 millimeters plus or minus 2 microns. Expressed as a percentage the error
is 0.025 of a percent (or 1 in 4000).
The inch to millimeter conversion is (by international standard) exactly 25.4
millimeters to an inch. That is also an exact figure (by international
agreement).
When you do the math, you get the following conversion factors, each with its
corresponding error term:
1 LDU = 0.3993 +-0.0001 millimeters
1 millimeter = 2.5043 +- 0.0006 LDU
1 LDU = 0.015720 +- 0.000004 inches
1 inch = 63.611 +- 0.016 LDU
- Robert Munafo http://www.mrob.com/
LEGO: TC+++(8480) SW++ #+ S-- LS++ Hsp M+ A@ LM++ YB64m IC13
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Message has 1 Reply:
 | | Re: Conversion between LDU, inches and millimeters
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| (...) This surprises me. *Exactly* 25.4 mm / inch? I thought that the conversion rate was kind of one of those irrational numbers (1) that had digits trailing off into infinity or, failing that, Imelda Marcos' shoe closet. :-, (...) *This* is cool. (...) (25 years ago, 24-Aug-99, to lugnet.faq)
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