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Subject: 
Re: Is this bad design?
Newsgroups: 
lugnet.general
Date: 
Fri, 16 Nov 2001 17:13:11 GMT
Viewed: 
523 times
  
I suspect it's due to the way that plastic parts are made.  They have to
have a draft, or an angle on all vertical walls, in order for them to be
removed from the mold.  Over small distances, or when reinforced in a 3-d
structure, this draft doesn't show up.  However, when you build a long
distance in a straight line (as your bridge decks are), the small angles in
each vertical wall (it may be as small as 1/2 degree) will add up to cause
bowing in the overall structure.

But that's just a theory.

Adrian
--
www.brickfrenzy.com


In lugnet.general, Ross Crawford writes:
Hi all,

I've found the following interesting LEGO behaviour while working on the deck
for my bridge. It consists of (many) plates held together on the bottom by
technic beams. There's a picture of the construction here
http://www.brickshelf.com/gallery/RoscoHead/coathanger/big3.jpg. As you can
see, there's also small plates holding the technic bricks together. The result
I'm getting is shown here
http://www.brickshelf.com/gallery/RoscoHead/coathanger/big1.jpg and here
http://www.brickshelf.com/gallery/RoscoHead/coathanger/big2.jpg. In just over a
metre, the middle of the deck is raised about 1cm. In the context of the
bridge, this is actually a bonus, however I see it as generally a "bad thing".

And further to that problem, The side decks (which are only 4 studs wide) are
exhibiting a horizontal version of the problem, see the pics at
http://www.brickshelf.com/gallery/RoscoHead/coathanger/small1.jpg and
http://www.brickshelf.com/gallery/RoscoHead/coathanger/small2.jpg. You can see,
with the row of 1x6 plates next to the row of bricks, there is considerable
horizontal curvature, in addition to the vertical curvature! And this is
definitely bad for my bridge deck!

Has anyone else experienced this?

ROSCO



Message has 2 Replies:
  RE: Is this bad design?
 
(...) Do you still need draft if the mold has ejector pins? --Bram Bram Lambrecht bram@cwru.edu www.bldesign.org (23 years ago, 16-Nov-01, to lugnet.general)
  Re: Is this bad design?
 
(...) Hmmmm. I would have though if that's the case, it's more likely the slope would be outwards toward the bottom of the plate / brick, causing the curvature to be the other way, ie sunken in the middle rather than raised. It also doesn't explain (...) (23 years ago, 16-Nov-01, to lugnet.general)

Message is in Reply To:
  Is this bad design?
 
Hi all, I've found the following interesting LEGO behaviour while working on the deck for my bridge. It consists of (many) plates held together on the bottom by technic beams. There's a picture of the construction here (URL) As you can see, there's (...) (23 years ago, 16-Nov-01, to lugnet.general)  

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