I started out with a hexa kit from a spanish supplier. 950kV motors and 9x5 props. Pretty lightweight frame, approx 1,7 kg. Plenty of thrust for climb performance, or stopping a rapid descend. Unfortunately this copter got hit by a flag pole in my backyard, frame damaged beyond rapair...
So I bought a 3DR Quad kit from DIY. Took me some time before I had opportunity to testfly, but now when I am flying it - BOY, it is anything but ballistic... On full battery (Turnigy Nanotech 3300mAh, 35-70C) initially I get some useful climb, but pretty soon the climb is soo poor, well... I gotta be careful with the descents, otherwise I won´t be able to stop it before it hits the lawn (yes, that happened a few times...)
Must be something wrong here! Or...?
Using the standard 3DR set, the little ESC and motors, 10x4.5 props.
All up weight: 1438 grams.
All four ESC manually calibrated
On fresh battery, full throttle, measured with Turnigy power analyzer:
28 ampere, 11.7 volt (approx 330 W).
AC Log shows peak 30A and like 11volt (log file attached)
Holding it in my hand it provides positive climb force.
But as I said, after some minute flight, vertical performance is shit.
Is there an obvious explanation to this???
Replies
Way to stay on it Tomas! This will be a great help for those who buy the 3DR platform, in the future. Most people who are buying the kit frames, don't have the experience needed to troubleshoot these kinds of problems yet, and expect that everything has been optimized to work right out of the box.
heres the vid, couldnt do much cliping. did it all on youtube. Anyone know any free video editing software for windows?
https://www.youtube.com/watch?v=6IxAoA2bu-c
I just realized that is an old video and I dont remember which battery was used, if it was 3s or 4s. Regardless you should expect good performance like that. The best way to trouble shoot a quad, even if you dont have a way to read rpms is to get a meter and test each arm at a time. Make sure you are reading above 100W for the stock setup. That way youll narrow down the culprit. After that you can switch esc, motors , props to see what difference that makes. They way you describe your problem , I'm thinking theres a bad prop somewhere in there. It might not have the same pitch as all the other ones and is pushing less air, youll track it down by seeing the power draw. Hope you get it sorted out.
This is data from the stock components on a 3DR quad
I found this on Jeff's youtube. Its one of the first flights with a heavy battery https://www.youtube.com/watch?v=cqM1GlvFIcI
Tomas, give me some time to cut down a video to a watchable length. I can post a video of a stock 3DR going up like a rocket and also give you some info about min max current draw, thrust, rpm. Let me get it all together :)
Tomas, judging from Allen's improved performance with the 10x3.8 propeller, I would say the issue is because of the stock propellers that come with the kit. The improvement is due to the increase in RPM, resulting from the lower pitch. I think the lower pitch props are more better suited for multicopters, and the higher pitch helps fixed wing craft increase thrust, from forward momentum.
Given this, if you can find 11" or 12" props at that pitch you will see the kind of lifting power you want. My guess is that 11" will be ideal. Keep in mind that as you increase the propeller length, the slower the propeller will get, and the less response you will get from throttle changes. It's like driving a car in higher gear, you get more power, but less acceleration too.
I had a jani quad frame I got a year ago that finally proved to be too fragile. I had the larger motors and 12" props on it and ran with 3000mAh and 5000mAh 3S Turnigy. It was very quick. Then I went to 3DR frame and had to go with smaller motors because the larger ones were out of stock. Used the 10" props from 3DR store but they are really weak so I changed to these carbon reinforced props and will never go back. They are sooooo much better and super stiff and it flies so smooth.
About the performance I noticed the same thing as you. I can fly with my 3S 3000 and 5000 batteries but I get about 5 minutes less flight time and I can't recover from a quick descent like I would like. I figured it was the extra weight and smaller props. It is definitely heavier so I went to nano tech 4S 5000mAh and it flies like a rocket again :)
I feel more comfortable with the extra voltage needed for emergency maneuvers.
Thanks for the response guys!
Chris:
Positive. I might be a newbie in the multicopter realm but I do know the sides of a prop (though I understand this might be a common mistake). Since you yourself have a similar setup (-right? Standard 3DR Quad kit) I would be very interested to know what is your peak current draw and min pack voltage on fresh battery and full throttle. If possible also approximate propeller RPM. That would be great, then I would have reference values to lean on in my troubleshooting.
Allen, actually I did shoot a video yesterday. I´ll post it as soon as I get it out of the camera. And I will consider your idea of a tie-down full battery run. I have five batteries of the kind, and they are new. Supposed to be pretty good batteries, you know.
There are not so many possible reasons for this annoying problem that I can think of. Here´s a few:
At least now I know that this lousy performance is not normal, so I need to troubleshoot further.
And thanks Martin, but I don´t think this is a dimensioning problem, since I use standard kit configuration.
Will keep u posted. Thanks for the support
I have used ecalc to help establish motor, battery, prop, weight combinations http://www.ecalc.ch/xcoptercalc_e.htm?ecalc
It gives approximate results. The propulsion is similar to a boat with fluid. The diameter, pitch, HP, and transmission (Kv) ratio will determine how well it pushes its weight. And how fast.
Post a video showing the performance. Include audio if possible. You/we can learn alot when watching a performance video. Record a maximum vertical takeoff and some horizontal runs at max throttle. If the video starts off with a fully charged battery and the performance decreases within a few minutes you probably have either a bad cell in the 3S pack or your electronics is draining the battery. Can you tie it down and run a full battery pack with a watt meter attached to monitor power consumption? Do you have additonal batteries to compare during this kind of captive test?
I have a quad runing with a 2300 MAh battery and I can lift off like a rocket with a GOPRO camera as payload.
Allen
-
1
-
2
of 2 Next