Subject:
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Erroneous Use of Technic Beams?
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Newsgroups:
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lugnet.build
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Date:
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Mon, 19 Feb 2001 23:32:59 GMT
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Viewed:
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442 times
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Erroneous Use of Technic Beams
or
Ode to a Technic Quandary
Hi all,
Every now and then, with a large creation or something that has joints
or limbs holding large components, somebody mentions that they use
technic beam in lieu of regular bricks in order to reduce the overall
weight of the supported member - the obvious assumption is that the
technic beam, which incorporates holes, weighs less than a comparable
brick. For some dorky reason or another, I got to wondering whether
that was a valid assumption.
The impetus behind using a technic beam is that the holes replace some
of the sidewall. The volume of sidewall it removes is equal to the wall
thickness times twice the area of one of the hole circles: or
(1) V = 2 * (Pi * R^2)*w.t. = 2*Pi*w.t.*R*R
However, the technic holes are actually cylinders that extand across the
width of the brick. If the wall thickness of this cylinder is the same
as the sidewalls, then the amount of volume added can be approximated,
as a rough lower estimate, as the circumference of the hole times the
wall thickness times the width of the brick between the sidewalls:
(2) V = (2*R*Pi)*w.t.*W = 2*Pi*w.t.*R*W
(In actuality, the added volume would be more than this - it would be
equal to the area of the "outer circle" defined by the hole radius plus
the wall thickness, minus the area of the inner circle corresponding to
the hole diameter, time the wall thickness times the width of the brick,
or V = ( Pi * ( Router^2 - Rinner^2) ) * W. However, using the formula
above is an easier lower bound, which underestimates the amount of added
volume, assuming a correct value of the wall thickness)
Comparing formulas (1) and (2), it is clear that the technic beam is
only lighter than the regular brick if the amount of volume removed is
greater than the amount of volume added. This is the case if R > W.
The two can be compared empirically: Consider the radius of the technic
hole: it is exactly one stud in diameter. How wide is the amount of
added brick? Well, since you can attach a studded piece on the bottom
of a technic beam, it, too, is exactly one stud across. On this basis,
the two bricks should weigh exactly the same.
There are, in actuality, a couple of other factors that should be
considered before the final vote is in:
(a) The above argument assumes that the wall thickness of the cylinder
is the same as the thickness of the sidewall. Is this the case?
(b) The studs in a technic beam are hollowed from the top, removing
some of the volume from the piece. The studs on a regular brick are
hollowed from the bottom; the radius of their hollowed section is
smaller, though.
(c) Regular brickes have the tiny pillars that extend the height of the
brick, and every-other pillar has a cross-member support
(d) The technic holes actually have a recessed rim to accomodate half
the central ridge on a technic pin. This removes some of the volume of
the cylinder.
(e) The technic brick has a larger raised LEGO logo on top of its studs
than the technic beam's, whose is in the recess of the stud.
(f) And, of course, there are many variations of the LEGO brick
throughout the years - I in no way vouch for the brick I've been
examining to represent the current design.
So, all that being said, has anyone actually weighed the a brick and a
comparable technic beam to compare them? My gut feeling is that the
technic beam still weighs less, but not by dint of the hole, per se;
rather, due to the fact that the technic beam design eliminates the
weight of the full pillars found inside a regular brick.
Can somebody weigh a technic beam and a regular brick of the same length
and post the results? Obviously, the longer the two pieces are, the
better and more noticable the discrepancy will be, since the proportion
of brick that is in the narrow endwalls is minimized in larger pieces,
and the combined sum of any difference will be more easily measured.
Regardless of the results, it's been an interesting mental exercise ;)
shaun
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Message has 2 Replies:
 | | Re: Erroneous Use of Technic Beams?
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| (...) <snippage of major proportions> (...) I only have two non-technic 1x16's, but I have a fair number of technic 1x16's. 10 technic 1x16 bricks weighed in at ~1.92 ozs, so figure 0.192 each. 4 regular 1x16 bricks weighs ~0.85 oz, which means (...) (24 years ago, 20-Feb-01, to lugnet.build)
| | | Re: Erroneous Use of Technic Beams?
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| (...) This is a great thought. Now I wonder if at some point I mentioned it to you (as part of my quest to build a gun my Fuji Power Armor could hold). The funny thing is, as soon as you started I saw where you were going- the hole removes but the (...) (24 years ago, 20-Feb-01, to lugnet.build)
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