I-153 main gear question for tech savvies here

[McHilt]

Hi,

I was studying the main gear of the I-153 recently to find out what causes the rotation of the strut during retraction in the wheel-well. It looks quite obvious but somehow I can't figure what actually causes the rotation in this case.

the picture shown below is a kinematic representation of the main gear of the Chaika:


Any of you have any clue or insight?...
thanks

Here's another pic: