hairyspin
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I've been hacking around with this cooling flap vent which opens to the trailing edge of the model's wing. To avoid airflow exiting the airway mixing with airflow from the top of the wing, there are folding gussets hinged to the flap and to a fillet upstand on the wing. The gussets fold flat together when the flap is closed down to minimum:–
As the cooling vent flap opens, the upper (blue) gusset moves away from the lower (purple) gusset and both have to be rotated just enough to meet again along the hinge line between them. The long way would be to rotate each gusset until they meet nicely: much fiddling and lots of exasperation, repeat a number of times until fully animated!
I've tried a Look-At constraint on the lower gusset, looking at a dummy linked to the upper one, but that doesn't suit since it rotates the constrained gusset off its hinge line with the wing fillet. There has to be a solution!
The answer is ridiculously simple. Both gussets have their pivots aligned with the Z axis pointing directly along the hinge lines:–
If the pivots point in opposite directions, selecting and rotating both together will move the middle edges together (or apart) simultaneously:–
Easy peasy and it works as well in both Max (illustrated) and Gmax.
As the cooling vent flap opens, the upper (blue) gusset moves away from the lower (purple) gusset and both have to be rotated just enough to meet again along the hinge line between them. The long way would be to rotate each gusset until they meet nicely: much fiddling and lots of exasperation, repeat a number of times until fully animated!
I've tried a Look-At constraint on the lower gusset, looking at a dummy linked to the upper one, but that doesn't suit since it rotates the constrained gusset off its hinge line with the wing fillet. There has to be a solution!

The answer is ridiculously simple. Both gussets have their pivots aligned with the Z axis pointing directly along the hinge lines:–
If the pivots point in opposite directions, selecting and rotating both together will move the middle edges together (or apart) simultaneously:–
Easy peasy and it works as well in both Max (illustrated) and Gmax.
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