Announcing the newest version of the Raptor 140! Its main objective is to fly over 120km(75mi) at 115kph(71mph) and send signals (including video!) over 3km(1.9mi). It should be ready to fly early February 2014. Anything you see in my design that I should reconsider?
Estimated Raptor 140c Stats:
Weight: 2100g (4.6lbs)
Max Flight Time: 100min (1hr, 40min)
Max Range: 120km (75mi)
Stall Speed: 35kph (22mph)
Cruise Speed: 115kph (71mph)
Max Speed: 145kph (90mph)
Radio Range: 3.5km (2.2mi)
Energy Carried: 289wh (20,100mAh at 14.4v)
Drive Power: 850w
Meters per Watt/Hour: 450
Features of the 140c (improvements over 140b in parentheses):
Airframe:
-MyGeekShow's Raptor 140: 140cm Wing Span
-CG at 26cm from nose (very, very balanced, almost zero reflex)
-EPP foam construction
-5mil Laminate covering
-Aluminum Motor Mount
-Additional laminate to strengthen leading edge (allow for rougher landings)
-6.4m (21ft) of carbon fiber (had 4.5m) (add additional rigidity)
-5cm x 48.5 elevons for low drag control surfaces
-Laminate elevon hinges (more strength and durability than packing tape)
-14cm winglets for visibility and lift improvement
-Integrated steel launch hook, closer to CG (better bungee launches)
-Parachute ring (allow parachute recover system)
-Velcro battery retainers
-PET plastic battery covers
-Plastic flight controller cover
-Precipitation 100% sealed (can fly in rain)
Flight Systems:
-433mhz EZUHF radio system (500%+ radio range improvement)
-32g servo (additional pull strength and durability)
-1250kv motor, was 1450kv (slower rotation as it is switching to 14.4v from 11.1v)
-24 3.6v Li-Ion 3.3Ah cells in 4S6P, aka 289watt/hours (20.3Ah at 14.4v) Raptor 140B carried 111watt/hours
-10x6 carbon fiber folding prop (140B had a 10x7 due to higher kv motor)
-4.7cm aluminum prop hub
-Wiring lanes in airframe (improved wire management)
-4 Ferrite Filters (cleaner transmissions and reduced interference)
Avionics:
-1080 HD Mobius camera (was 720 808 #16)
-FPV tx 1.3Ghz 400mw
-APM2.6 flight controller
-3DR Current Sensor
-3DR uBlox GPS with compass
-1w 900mhz 900RDF telemetry (had 0.1w telem)
-FAA style lighting (improved visibility)
-3A BEC (provides power to telemetry, camera, etc)
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Learn More:
Raptor Details: http://www.mygeekshow.com/theairplanes/Raptor140.html
USA Trip Details: http://www.mygeekshow.com/usatrip/
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Filmed, Edited, Produced and Published by Trent in Arkansas, USA
Comments
Marius and Gary: A 14in prop should be able to fit before it starts making its own space :)
So... according my calculations, my prop's "travel potential" should be a calculated 170kph, or the perfect potential travel of the prop at full throttle:
1450kv motor at 11.1v = 16,095rpm
16,095rpm @ 7in pitch = 112,665in/min = 107mph = 172kph
170kph "travel potential" assumes roughly 50kph "worth" of drag at that speed. (i.e. motor outputs 170kph, and the raptor achieves 120kph) This is consistent with what I've seen with real life testing. When I move the Raptor140b to full throttle, the prop will "travel" at 172kph, while the real airspeed is 130kph.
To achieve 170kph "travel speed" at 14.4v, with this 14x12 prop, I'd need a 646kv motor. Maths:
14.4v x 646kv = 9,296 RPM
9,296 RPM @ 12in per rotation = 111,549in/min = 106mph = 170kph
My main concern is that 170kph of "travel speed" with a 14in column of air is TOTALLY different than a 170kph of "travel speed" with a 10in column of air...
That would be very, very interesting to test. Even on the 140b with 11.1v would use a 837kv motor with a 14x12
Thoughts?
Really stepping up! looking forward to seeing what kind of range you do get, I have a slight concern that going to UHF for the controller might be a bit of overkill, since you will most likely be out of FPV range and definitely out of eyesight, although I suppose you could rig it to be able to power down the FPV transmitter when you are out of its range to conserve battery. Looks like I may have to alter my shopping list for my own Raptor!!!
Trent, looking forward to it. How did you arrive at your cruise speed?
Slow motor big prop is the way forward for endurance. Also making sure the wing is pitch perfect helps along with as light and smooth as possible. But you knew that. As you increase performance launching gets trickier as you do not want to add more power than you need as thats more weight than you need. The landings will run further as well. So get those spot landings happening ;-) You don't want to run into a tree or a wall. Also add a ladder to the check list, and a chainsaw.
What is the largest prop size that would fit on the raptor 140? From what I am reading and from other peoples long range flights (700kv and 14inch prop), the larger the prop and with really low Kv motors is the best way to boost efficiency. Some even go as low as 370kv on their techpods.
Marius
Mecha: Yeah... the cold just hurts all around. Luckily I'll be doing the USA trip in the summer!
Michael: Yes, I've improved the process somewhat since, and have looked into the strip approach. Really, I don't need rigidity that goes with the shape of the wing as it has the entire wing shape as support, only need the wing flex to have support. I'm considering/working to implement this in the future. Your walk through of how to do use it is perfect. Thank you for the tip!
You can also fill the slot with a bit of gorilla glue, and wet the spar, and push it into place, wipe off the excess, and apply tape over the length for 8-24 hours so it cures flat and strong. Sand if it bubbles out past the tape/not flat.
When using the flat carbon fiber strips, don't cut a "v", and fill with glue, as in your build videos, but rather cut a straight slot, perpendicular to the surface of the wing, as deep as the CF strip is wide, and cut only just wide enough 1-2 mm to tightly fit the flat CF strip. After a test fit and trim, apply glue (I like gorilla glue for this) to the flat sides. Very little glue is needed. Apply some tape along the length to hold it in place while it cures, and to allow the glue to form smoothly (it expands) if you are not ready to immediately apply the laminate (usually done after some of the electronics are added.)
Recommendation: Dump the *round* carbon fiber wing spars, at least for everything but the main spar.
Use *flat* carbon fiber strips, and embed perpendicular to the surface of the wing. Glue in place tightly, then mono/econocote over the wing surface. You will not need even 1/3rd of the spars to make it equally (more?) strong. Less work, less time, less cost, and less weight, and very likely stronger.
Make sure you don't forget to include the reduction of capacity due to the cold weather. your capacity will be most likely reduced about 500mAh per cell in bellow freezing temperatures
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