26 September, 2017 at 15:52 #39671
The throttle difference / current draw with this version maybe slight at best. (Maybe from the lip you’d get an aero effect) Version 3 was more of a “can i build it” sorta thing as it was loosely based off the duct which we received from Australia. Versions 4 and beyond are focusing on making the ducts lighter and increasing lift. Keep in mind that the original Duct from Australia weighed 36-40 grams each!
Note: Currently printing a Version 5 out of PLA and carbon composite.
Also… I’ve switched over to Fusion 360 and OMG is this like night and day. The absolute positioning alone makes learning it worth it.
Here is the new duct template for version 6
Here is what it looks like rendered
Kevin27 September, 2017 at 01:15 #39680
Completed version 6 with Fusion 360
Overall volume should be: 47.88 per meter, I’m estimating the weight to be about 32.3 grams using PETG. That “should” be about a 20% reduction in weight in comparison to V3 and the ducts procured from Flightclub.
Should receive Version-4 from the print shop tomorrow and possibly Version-5 Thursday. Afterwards I’ll review them both and possibly opt to print Version-6 in Onyx-Carbon or PLA-Carbon. Unlike some of the previous work using Sketchup, the Fusion 360 build should be flawless. Even skinned it in carbon fiber, if you take a close look at the photo above.
Added a copy of the .STL below.
Kevin27 September, 2017 at 10:06 #39683
Should I make an 6″ (152,4mm) version of this duct (V6) as well?
Larger props will see a greater lift effect from a duct than a smaller propeller.
Far as I can tell, the BE2217 motors propeller hub (prop adapter) sits 5-6mm higher than that of the Emax RS2300ks’s. The carbon arms and servo setup is just about identical to the mini’s. Can someone confirm this?
Note: The 5″ duct should fit / work with the “baby” tricopter.29 September, 2017 at 21:34 #39720
Reposting 5″, Version-7 here
Made a completely new duct (5″ Version-7) based off the “ideal aero-shape” and a duct specific formula. Wall thickness is 1.2mm (multiple of 0.4mm)30 September, 2017 at 10:24 #39723
Version 7 Printing (Carbon / PLA)
Should have them by Monday or Tuesday of next week.
Kevin30 September, 2017 at 16:06 #39725
Due to bad weather i was only able to perform a limited test flight today. This was to check for stability and hover performance after prop / duct changes. Added the new HQ 6x5x3 bull-nose props and version-4 duct attached to the tail motor.
Note: Other motors (Left / Right) used the ducts from Australia.
Right off the bat hover was better. The Amp draw was reduced from 11-12 Amps to 9.8 Amps! (Can see the Amp draw via the FPV goggles / OSD)
Will have to do a flight without the ducts to get an value of the Amp draw for both 5″ and 6″ props for later comparison with the project.
Edit: Cant wait for version-7 to test out the full flight profile2 October, 2017 at 11:51 #39737
All three have printed (Carbon-PLA of Version 7), just waiting on the shipment.6 October, 2017 at 10:21 #39770
Here is a beefier copy of version-77 October, 2017 at 00:15 #39784
The 5″ V7 installed as of today. (All three rotors) Flight weight 727 grams.
11 October, 2017 at 11:32 #39825
Did some efficiency testing today and came up with the following values:
8.2 Amps @ Hover, HQProp 5x4x3 with 5″ Duct (Version-7), Flight weight approximately 720 grams
8.2 Amp @ Hover, HQProp 5x4x3 without duct, Flight weight approximately 606 grams
7.2-7.3 Amps @ Hover, Gemfan 6x4x3 without duct, Flight weight approximately 608 grams
7.1-7.2 Amps @ Hover, HQProp 6×4.5×3 without duct, Flight weight approximately 607 grams
Note: Values taken from OSD and control rates turned down to allow for more sensitivity over throttle position. Amp draw is the total sum of all attached electronics and motors.
From the values shown above, it seems that the Ducts are making enough extra thrust to counteract their own weight. (114 Grams for all three) Furthermore, the larger prop sizes do indeed have higher efficiency. It stands to reason that when a 6″ Duct (Version-7) is used, the ducts should product more than their own weight in extra thrust. This is due to the larger ducts “lip” surface areaand reduced tip vortices from greater prop surface area in contact with the ducts inner wall.
Beyond this, I can definitely feel the difference with the ducts on and off. The ducts add a bit of automatic stability, making flying smoother and response time slightly slower. Overall I think this makes the tricopter easier and safer to fly. Unfortunately, installing the ducts correctly is rather difficult and time consuming.
Now as for the props used, “Stiff” Three bladed props are absolutely the way to go. Granted the two bladed props are more efficient but the craft feels loose / sloppy. I found that landing / hovering to be quite difficult with the HQprop 6×4.5×2’s. Another thing of note is that the Bullnose prop’s really do make a huge difference as they’ve a larger surface area that’s in close contact with the duct’s inner wall. (<1mm) Tried the Racekraft 5x4x3’s and found that the current draw was 1.5 Amps higher as the props edge facing the ducts wall was very small.18 December, 2017 at 16:29 #40407LitterBugParticipant
Been a while since I’ve been in here. How are the ducts working out? I’m thinking about printing a set out so I can get my mini tri in the air during indoor season. Open props we are limited to 150mm builds, but with the ducts, I can safely fly with the planes without fear of being labled the schredder. Are your latest files posted up?
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