Now let's try that again. I should have thought of this one first.
Here's a simple crackle threading for four shafts, each block repeated just once. It repeats neatly on 20 ends, and we can just double it for a 40-end simulation on a straight threading. You may recognize this as an advancing point twill:
Here it is woven as classic crackle on 4 shafts (ground x, Patern, ground y, Pattern); first, the structure drawdown, then with color:
Now here's the 40-shaft version:
Here's another block treadling, 4-shaft version:
And here's the 40-shaft version:
This concludes my ramblings on crackle simulations for 40 shafts. I'll revisit this topic after I get something onto the loom.