21 September, 2017 at 03:00 #39585
Throwing one on in ABS now! Thanks for sharing!
EDIT: There are some gaps between the arms and the other parts. I’m using Simplify3D to print.
21 September, 2017 at 03:04 #39586
Kinda reminds me of the Hunter/killer drone form Terminator
Attachments:21 September, 2017 at 07:42 #39589
Sorry about the delay in replying…
As for the arms not connecting, this is an issue with Sketchup and its inability to handle absolute object placement. Trust me I went round and round for hours with this and thought it was resolved. I’ll give this another pass sometime today to see what can be done here.
For now continue printing the duct, unless you’re able to make the fix(s) on your end.
Least that way we’ll know…
-Does the propeller and motor fit?
-Does the propeller spin freely while keeping the air-gap as small as possible?
-Are the arms strong enough to handle the weight of the duct, the torque from the motor and the occasional impact?
-How much does the overall assembly weight?
Kevin21 September, 2017 at 09:16 #39590
I think i fixed the arms, made them a bit taller too…. Have a look at V3.
Thinking of redoing the main duct itself as I feel it maybe too thin at the bottom and too thick at the mid-point. Your feedback would be very helpful here.
Note: Sorry but it attached the same file three times while editing.
Kevin21 September, 2017 at 10:25 #39595
Here is the basic template I used to create the ducts profile within Sketchup. This is later extruded to create the final shape.
Note The little arrow shown on the images, is the area I expect the propeller to spin.
Here is a more refined template that thickens the bottom of the duct, while also removing excess material from the top. Trying to keep the thickness somewhat even from the bottom up, then angle over for the aero-lip. (Both are overlaid in this image for comparison. Blue new, red old) This change should make the duct stronger, lighter and save print material. Please be aware that Duct V3 is still using the first template. Will make an effort to create V4 in a day or so.
V3 volume is 44880 vs V4’s volume of 35518. Another way to look at it is a 21% savings in weight!
Kevin21 September, 2017 at 17:20 #39600
It still appears that these are separate pieces rather than joined.
Not familiar with sketchup to figure out how to make the pieces turn into 1.
Not sure if this helps Sketchup Join
LitterBug21 September, 2017 at 17:30 #39602
Working the issue….
Looks like Google’s freeware is basically crap as it lacks a lot of the functionality that the full version does. Specifical the capability to place and bind objects. Hence “Join” and all the other functions don’t function so well when you can’t strictly control placement of objects. Worse yet, I tell sketchup to make a circle with a diameter of 64mm and it gives me a smaller or larger diameter than whats input. If I still had 3D-Max I’d of completed this project in under an hour and had it right the first f’n time!
If worst comes to worst, i may bite the bullet and learn Blender. But man, that program is so cumbersome it’s not even funny.21 September, 2017 at 17:38 #39603
I find most of the graphical tools cumbersome. I’ve played with openscad in the past but haven’t done much lately. Could probably create a profile then do a rotate_extrude on it to generate the duct. Need to dust off the cobwebs….
LitterBug22 September, 2017 at 08:22 #39614
Was able to have a 3rd party fix the connections and print out version 3! Corrected files are attached below.
Kevin22 September, 2017 at 15:29 #39620
Awesome! I’ll print them up tonight! A couple more recommendations: 1) radius the connections between the arms, duct, and motor mount. 2) make the thickness of the part surrounding the motor a multiple of the print thickness so there isn’t an air gap in it.
LitterBug22 September, 2017 at 17:51 #39621
1) What do you mean by radius ? What would this do ?
2) I am unsure what the multiple would be so I wouldn’t know what to apply here.22 September, 2017 at 19:16 #39622
Completed version 4!
Not sure if this will have the same issues Version-3 has as this is a completely new build. (Verified build via online tools)
File is on my Google-Drive as its about 1MB: https://drive.google.com/open?id=0BzC5WK3Vbi5OLXRwc1hlSHllWWM
Kevin23 September, 2017 at 18:36 #39639
Version 3 installed!
Clearance looks like it’s 0.5 to 1mm. Using 1 mm thick double sided tape on the inside of the duct. Where the prop touches the tape, it’s obviously narrower than 1 mm. Hard to judge really as the motors centering can be a big factor here.
Also take note, the wiring from the servo / motor now runs through the carbon arm.
Kevin24 September, 2017 at 21:29 #39644
Did several flights with version-3 duct and new servo installed (stock PID settings)
This included a basic flight for the tail-calibration and fuction checks.
Overall impression was OMG this is awesome, No tail-wag!
Not saying that the Duct helped but rather that old servo obviously had some issues (before the crash) Nothing i did with the old servo really helped remove the spastic tail-wag. Beyond that, the duct performed great. Had a few print issues with it that needed addressing but once this was resolved it works as intended.
I should receive version-4 from the print-house by Wednesday, flight test it and the decide on further improvements. Once this is done, I’ll opt to have a complete set made of the strongest and lightest material practical. (Maybe nylon with impregnated carbon fiber) Thus far, most of the ducts I have seen / used weight 35-40 grams each. I am hoping to cut this in half while keeping the performance and strenght.
Kevin26 September, 2017 at 14:37 #39668
Managed to get this latest version printed off last night in ABS. Came out pretty decent. I forgot to change to single wall to lighten it up. Will print another tonight. Depending on props and motor height, the duct could be too narrow.
I usually run 6″ props on my mini. Think I will get a dRonin autotunes in with unducted 6″, unducted 5″, and ducted 5″ to see if there is any noticeable difference in the throttle position required for hover.
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