i need an object to rotate exactly 90?.

i tried this with a func_brush parented to a func_rotating.
i set the max_rotating_speed to 30?/sec and activated the animation with a button. the button resets after 3 seconds and stops the animation. 3 x 30? = 90?. somehow it is not exactly stopping at 90?. it stops at 91? and when i set the button reset to 2.9sec it seems to fit perfect. when i press the button a few times u can see that its still not exactly 90?

i even tried this with a func_physbox and a phys_motor but i cant get it to work perfectly and i really need it to fit perfectly because ive got lasers alinged to the object.

Do you guys know how to fix this problem. i want to release my new map soon.

thx in advance

i used a func_door_rotating. its always rotating 90?
the button reset timer is still on 3 sec and this works perfectly.
map coming sooooooon