Why do the Bafang Mid-drives rotate upwards (if loose)?

[dhdallas]

Why do the BBSHD, BBSO2, etc rotate upward against the downtube when they loosen? Shouldn't the forward rotational force of the axle push the unit downwards?

 

[PDXzap]

When viewed from the right side the motor is trying to turn the chainring clockwise and there is an equal force trying to turn the motor counterclockwise.
It's the same when a person walks. Your legs are trying to push the earth behind you but the end result is your body moves forward because the earth has way more mass. When climbing stairs, your legs are trying to push the stairs down but the end result is your body goes up.

Here is a Google search of "equal and opposite reaction".

 

[dhdallas]

When viewed from the right side the motor is trying to turn the chainring clockwise and there is an equal force trying to turn the motor counterclockwise.
It's the same when a person walks. Your legs are trying to push the earth behind you but the end result is your body moves forward because the earth has way more mass. When climbing stairs, your legs are trying to push the stairs down but the end result is your body goes up.

Here is a Google search of "equal and opposite reaction".

Ahhh...I should have known that! Thanks!

 

[Feliz]

I think it's Newton's third law, for every action there is an equal and opposite reaction.