Nice designs, i would like to use a 50mm radial fan with a circular duct and may create a remix of srs5694's design for that.
I toyed with doing that. In fact, my design is based on an earlier effector-and-fan design that I did, which used a 50mm radial fan, before I got fed up with the inductive probe I was using and decided the Smart Effector looked like the best way to do bed probing on a delta printer. Although I've abandoned that effector design for myself, I'm planning to publish it, probably this evening (US Eastern time). You might be able to merge bits from the two designs once I publish the effector.
That said, one reason I didn't pursue the radial fan idea is that placement of the fan seemed awkward. It would either need to lie on its side or be placed upright but extend out quite a way from the effector, with a rectangular duct to link it and the circular duct. It didn't seem worth the effort to me personally to design it – but of course if that's the design you prefer, and if my design helps you get there, then that's great!
Any idea how far away the fan duct should be from the heat block depending on the heat resistance of the material? Is the silicon sock enough to shield a pla/petg/nylon duct when getting very close to the sock?
I don't know for sure, but I can say that I printed my duct in PETG, and it seems to be holding up fine to printing PETG. (I've got an E3D V6 sock on my heat block.) My other printer (a Robo 3D R1+) has a PLA fan duct that's about as close to its nozzle as my fan duct design design gets to its nozzle, and even the Robo's fan duct seems OK. (It looks like it's softened a little, but not much.) I print PETG on that printer, too, so the heat block gets up to 250C or thereabouts.
