Why are wedge shaped beams being used?

[M110020]

Hi guys. I saw this in one of my Engineering Design slides about embodiment designs and saw these slides using uniform stresses as an example and had a hard time figuring out how is this structure supposed to ensure uniform stress.

Shown in here is taken from the slides I was referring to. What I can't seem to grasp is if the shape of the gondolas are wedges doesn't that make all the stresses concentrate at one point on the structure? I thought that was a bad thing as stress concentration can be extremely destructive for a structure.

Could someone maybe explain it in brief to me or maybe point me in the right direction? Thanks a million.

 

[nvn]

M110020: Good catch. Yes, you are correct. In the first picture, the direction of the taper of the cantilever beam holding the large metal masses is drawn wrong, and would concentrate the bending stress at a point, which could be destructive to the cantilever beam holding the large metal masses. This is just the opposite of the uniform bending stress concept in the second picture.

(By the way, the tie rods supporting the gondolas have very low bending strength. Their tapered or wedged configuration is inapplicable to the uniform bending stress concept. This is because the gondolas tend to work with gravity, whereas the cantilever beam holding the large metal masses tends to work against gravity.)