Hi I’m new to python and have been following a youtube tutorial to make a fan rotate. The blades of the fan have a bone attached with a custom property called rotation1 which was originally set to 1 but is now set to 100. I have copied the path into the driver and the tutorial said to use the expression var * frames. However this rotated the blades very slowly. So I changed the expression to 1.01 * var * frames. This rotates the blades a lot faster but is still a long way of the 2200RPM that a case fan spins at. Going higher or lower than 1.01 slows the rotation and same with altering the custom property of the bone. How do I go about writing an expression to get the desired 2200RPM
i’m no animator, but RPM = rotations per minute. So if you are animating at 24fps, you need ~37 full rotations per second, which means you’ll have more rotations than frames, which would give the impression (visually) that the blades are rotating backward very slowly.
Yes I realised this and I have done a test render at 60FPS and I am also doing one at 120FPS using keyframes on the time line. Adjusted for the relevant FPS of course. Realistically 60FPS will be fine but I want to compare the two before deciding. But the final project that I have in mind will have 7 of these fans and be quite long. Which would be a hell of a lot of work using keyframes. So I am asking if I can do it using a driver for each fan and how would I go about writing an expression for the driver.
While I did not find how to create a driver for this I did learn that I can do it through the graph editor.
Select the object you want to rotate and create a key frame. Move to the 1 second frame and rotate the object by the desired amount then create another keyframe.
Open the graph editor and select both keyframes by pressing A
click key on the file menu of the graph editor and then select interpolation mode and chose linear.
this is so the object rotates at a steady speed instead of building up the speed at the start.
with both keyframes selected and the mouse over the graph editor press N
go to the modifiers tab on the window that pops out and chose the cycles modifier
on the before drop down box select no cycles
on the after drop down select repeat with offset
Since I am only learning blender it took me days to find that out. I hope this helps someone in the future. Also remember like stated on the other comments to set your FPS for the project higher than the revolutions per second. Otherwise you will end up with it being jerky or appearing to spin backwards.