Tinyhawk Freestyle tinywhoop duct mod by cudbur

Last crawled date: 3 years, 4 months ago

I don't suggest doing this unless you don't use your Freestyle to... freestyle. However, I was inspired by [wob's work on rcgroup forums](https://www.rcgroups.com/forums/showthread.php?2971472-23DT-the-3d-printed-Micro-130-with-true-ducts-Emax-BabyHawk-Gear ) and wanted that extra flight time on my Tinyhawk Freestyle since I predominantly fly indoors with prop guards. I made a very uninformed first purchase in FPV but it's been really fun designing parts for this powerful little machine. This part is intended to be printed as a single perimeter, using eSun PLA Plus. I haven't bumped or crashed yet and I don't think it'll do well when I do. However, the improvement in flight time and characteristics is undeniable.
Used the [OpenScad file from beta_ready] (https://www.thingiverse.com/thing:1535549/files) to export a mesh with my prop size, and import it into OnShape https://cad.onshape.com/documents/67d5ff334ccb7d63d269cde5/w/75f7bd64f5338fed3d70b237/e/cc452dcbd80d936e181b00bb
From there it took 9 revisions (and some failed prints) to tune geometry and print settings so that the part is as lightweight and smooth as possible. Since it needs mounts for screws, vase mode was not an option. Lots of tiny tweaks were implemented to save weight but retain as much from original OpenSCAD export. One key print quality improvement was changing the quarter-circle inlet. The shallow angle near the top causes stepping, which isn't practical with vase style prints. Therefore, I added a tangential line and kept the same height. Not sure impact on efficiency but I'm happy with improvements already!
duct rev9 weight: 18grams
full quad with 1s battery: 79grams
flight times:
duct v4 - 4:40
duct v8 - 5:30
duct v9 - 7:10
The single part duct replaces the Tinyhawk's top plate, and moves the battery under the quad with a velcro strap. Overall, I removed as much weight as I added. I was getting 3-4 minutes with the prop guards, so this is huge improvement for me. Getting 7 minutes with prop guards is exactly what I wanted when I started this project. I haven't crashed or bumped it yet so we'll see what happens.
I tried a two blade propeller which was more efficient (6:30 flight time on duct rev8), but the tri-blade is much quieter and "grippy." Overall an easy choice when trying to cinewhoop around people. I fly around 60-70% throttle on top of the Taranis thresholding to 90%. The ducts make it really fun and easy to fly slow and stable.
One interesting issue was the printer "stuttering" which caused a lot of added blobs. The root cause ended up being the mesh was too highres and the 8bit microcontroller couldn't process the gcode fast enough. My slicer Simplfy3D doesn't have a minimum step option unfortunately. Solution was export lower res mesh, but not too low that it's facetted.
Info on the most efficient ducts:https://capolight.wordpress.com/2015/01/14/quadcopter-rotor-duct/
What I learned:
-Minimize gap between duct and prop. Place sand paper in the duct and manually rotate the prop to grind it down to length.
-Eliminate all print surface imperfections, minimize blobs and align seams.
-Vertically align prop correctly, 1mm matters