14181, molding problem

[anothergol]

It's the second time I have to deal with this nasty wing part that keeps bending up, trying to flatten it in hot water, etc. But now I've found out why it's bending. The studs are probably slightly too far appart or something, or there isn't enough plastic to make it solid. But in any case, if you place tiles like on the left over this part, it's gonna bend upwards. While if you do it like on the right, no problem.

[bonox]

There has to be some tension created between rows of studs to make parts stick together. That's what clutch means. Pulling together of studs on one side will cause the part to curl in that direction - and for that part, the flange cutouts on the lower side so it will fit over studs means there is very little resistance to bending. It's moment(s) of inertia are very low. In your second case, you are isolating the tension loads along the long axis of the part to just the studs, rather than building between studs, so you don't get the curl problem. You could possibly eventually see curl about the shorter axis, but its moment is higher due to the flange at each end.

for the 2x2 tiles , you may well get worse curling when using the version without the centre post.

edit: speeling arrors

Edited July 25, 2016 by bonox

[anothergol]

for the 2x2 tiles , you may well get worse curling when using the version without the centre post.

I'd expect less curling *with* the center post, no? Because that post pushes the studs appart on the opposite directions(?)

In any case, that part is missing some solidity structure underneath.. or not:

Yeah the cuts in the side flanges seem to be the cause, *however* you will see that Lego predicted this and added 2 rows of bars joining the posts. Either they predicted wrong and it would need the third row to have those bars, or there is really a precision/molding problem, because those bars aren't doing their job.

Also interestingly, that part's old version (2413) doesn't have the side cuts - I'm gonna try that one.

Edited July 26, 2016 by anothergol

[Vedauwoo]

you see the same effect using 1x2 bricks on a baseplate.....like a long wall, but successive rows or thickening the wall with some 1x6 or 1x8's flattens it back out.

[bonox]

I'd expect less curling *with* the center post, no? Because that post pushes the studs appart on the opposite directions(?)

that's what i said, but mine was the double negative ;)

Sorry for my choice of words