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> In a book of LEGO history I read, it was explicitely stated that the
> original inch based measures were changed to mm. I don't remember which
> year, but it was a long time ago. The distance between two studs is 8 mm.
I tried the experimental approach, built a long line of 23 x Technic beams 16
assembled with plates and measure the total length: 2937mm
With 8mm distance between studs, the theoretical value is 2944mm, error is
-0.23%
With 5/16" distance between studs, the theoretical value is 2921mm, error is
+0.54%
Though we are closer to metric dimensions, I admit my experiment is not
decisive!
But if you look at the names of parts on s@h pick a brick, you see many
dimensions expressed in mm, and a few clearly implies 1stud = 8mm:
Brick Ø16 W. Cross
Parabola Ø16
Parabolic Reflector Ø24x6,4
Parabolic Reflector Ø48
Philo
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Philippe Hurbain wrote:
> With 8mm distance between studs, the theoretical value is 2944mm,
> error is -0.23%
> With 5/16" distance between studs, the theoretical value is 2921mm,
> error is +0.54%
>
> Though we are closer to metric dimensions, I admit my experiment is
> not decisive!
I'm not at liberty to say too much, but I have actually looked at three real
drawings of LEGO parts, and not even TLC seems to be sure what the
dimensions should be - I've seen the distance between two studs dimensioned
as 8 mm on one part and as 8.018 mm on another!
--
Anders Isaksson, Sweden
BlockCAD: http://web.telia.com/~u16122508/proglego.htm
Gallery: http://web.telia.com/~u16122508/gallery/index.htm
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In lugnet.cad, Anders Isaksson wrote:
> I'm not at liberty to say too much, but I have actually looked at three real
> drawings of LEGO parts, and not even TLC seems to be sure what the
> dimensions should be - I've seen the distance between two studs dimensioned
> as 8 mm on one part and as 8.018 mm on another!
That much? Wow. I figured the distance between two studs should be closer to
3mm, since a LEGO tile is (in theory) 3.2mm thick, and it will sorta fit between
two studs. Or were you refering to the center-to-center distance?
Anyways, one thing you have to remember is that the dimensions on a LEGO brick
will be noticably different from the dimensions on a LEGO brick mold. Depending
on the specific shrinkage rate of LEGO-spec ABS, an 8.018 mold dimension could
result in a post-form LEGO brick with an ~8mm dimension. It's been a few years
since I actually had to know the shrink rate of ABS, but one of the sites I
pulled up on a quick search said it ranges from 0.0024in/in to 0.0165in/in.
Going with the former, an 8.018mm mold will produce a 7.9988mm part. The latter
would result in a 7.8879mm part.
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Purple Dave wrote:
> That much? Wow. I figured the distance between two studs should be
> closer to 3mm, since a LEGO tile is (in theory) 3.2mm thick, and it
> will sorta fit between two studs. Or were you refering to the
> center-to-center distance?
Center-to-center, of course. The stud diameters differ by 0.028 between the
drawings too, creating a diff of the gaps of 0.046 (but the length of the
parts are exactly the same).
> Anyways, one thing you have to remember is that the dimensions on a
> LEGO brick will be noticably different from the dimensions on a LEGO
> brick mold. Depending on the specific shrinkage rate of LEGO-spec
> ABS, an 8.018 mold dimension could result in a post-form LEGO brick
> with an ~8mm dimension.
Well, the drawings are of parts, not molds (and the parts are attached).
--
Anders Isaksson, Sweden
BlockCAD: http://web.telia.com/~u16122508/proglego.htm
Gallery: http://web.telia.com/~u16122508/gallery/index.htm
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