A8M Aerial HK heavy assault model from Terminator 3 - Page 4 - RC Groups
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Dec 31, 2012, 01:19 PM
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kahloq's Avatar
Just found this on youtube. This is exactly the way Im trying to set things up. Its also good to see that yaw control is NOT needed on the rear fan unit. Only the two front fans are tilted for yaw control....the rear fan along with the two forward fans are tilted together for forward/back(elevator) control.

Sweet....that also eliminates extra complicated work on the main vehicle as I do not have to include yaw control at the tail.
take a look and see for yourself.

There is another video by this guy(whos from Italy) that shows the tilt directions of all fans while his machine is stationary on a table.
HK Drone 0.5 - Indoor FlyTest (0 min 32 sec)

I would like to note that this is the same layout I have on my small test bed unit.
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Dec 31, 2012, 05:00 PM
even better:
HK Drone 0.5 - Mixer Test (1 min 16 sec)
Dec 31, 2012, 05:13 PM
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rimshotcopter's Avatar
FYI: I did that mix on my very first tricopter, the tilt on the tail is not needed and the traditional tricopter mixing is not required.
Dec 31, 2012, 05:15 PM
i could see where itd be useful in FPV to keep the platform level while moving forward. but i agree
Dec 31, 2012, 06:12 PM
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kahloq's Avatar
Originally Posted by rimshotcopter
FYI: I did that mix on my very first tricopter, the tilt on the tail is not needed and the traditional tricopter mixing is not required.
Which just makes it that much easier for me build the tail end of this monster HK I'm working on because I had come up with a pretty nice design to have the tail fan on both yaw and elevator axis. But, not having to include the mechanism to tilt the rear fan for yaw removes a lot of the components, removes weight, and lowers the complication factor a good deal.

However, I need to incorporate the elevator tilt on the tail fan because the "real" thing had that. Its easily seen in several of the movies that the tail fan is tilting forward and back so I have to replicate that whether or not its needed for elevator control.
Jan 01, 2013, 12:05 PM
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kahloq's Avatar
Ok....so....here's a video of basically the first tests done with the small edf unit machine. This edf tricopter is being used to figure out any issues with the setup and design before completing the big terminator beast.

Before this video...I had done a quick test with another battery and I was able to get it off the ground and maneuver it some. However, as I'll describe in the video.....these edf motors are super amp hungry.

We all know that edf's tend to use more juice then a prop setup. Yet, its been done before to good results(see videos posted above). In this machine's case, the motors are consuming so much amps so quickly that the voltage is sagging on the battery to the point one motor stops running.

I know this thing can get off the ground because it did it once before on a different battery and I was only at half throttle, but with the battery in the video, it just doesnt seem to be a high enough C rating to do the job.

So..either two batteries in parallel will be needed or much higher C rating ones. I dont want to do two 5000mah batts on a ship this size as thats extra weight I dont know if this setup can lift.
I state in the video that when the voltage gets too high, one of the motors cuts out. I meant to say amp draw gets to high.....which in turn makes the voltage sag. I also say some about C capacity....which...while I am sure you figure out I mean rating, I just want to clarify.

small ducted fan tricopter test1.MOV (3 min 52 sec)
Last edited by kahloq; Jan 01, 2013 at 12:11 PM.
Jan 01, 2013, 12:09 PM
what battery (mah + c rate), and what exact EDF units?

could be that you just need a higher c battery
Jan 01, 2013, 12:47 PM
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kahloq's Avatar
The edf units are wemotech midi 70mm. I agree that I probably just need a higher C rating battery. The one used in the video(merely for initial testing) is a 20C. So..yeah....gonna need at least a 35C or better. And if I have to get some, might as well go 65c since Ill need the exact same batts in my airworld me-262
Jan 01, 2013, 01:43 PM
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kahloq's Avatar
Hooked a different set of batteries and tried another test. I used two batteries in parallel this time....two nanotech 4s 3000s 25-50c. Still had the same problem. Obviously the low 25C constant rating is causing a bottleneck.

Seems strange since the very first test I did before the video was made was using an old rhino 20c 4900 4s and it lifted off the ground without a motor shutting down. Wish I had setup the video cam for that one, but, doesnt much matter since the lower C rating batts in general just arent allowing the vehicle to function right...or could be one of the 4s 3000's just is sagging right off the bat and the other one just cant make up the slack.
Jan 01, 2013, 02:05 PM
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Just a guess - maybe the motor wires are too thin and don't transfer the whole power from the battery?
Jan 01, 2013, 02:16 PM
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kahloq's Avatar
Ok...hooked up the first battery again from before any vids. This is a mere 20c rhino 4900 and as you can see in the video, the craft did leave the ground.
What is strange though is the first time I used this battery, I hadnt even calibrated the esc's yet on the FC board. It was manageable to keep control.

However, this time, it wasnt. I think the problem now partially anyhow, is simple balance. I believe the battery pack will need to be further forward as the rear fan seems to be trying to lift more weight respectively then the front two. During this test, even when the front of the vehicle lifted off the ground, I was holding almost full forward elevator on the radio.

Also need to make some landing legs that are longer and much closer to the edf units so when the thing tilts to one side dramatically or too far backwards, the motor bell housing doesnt scrape the floor/ground. You'll see an example of this in the vid.

BTW....seeing as this lowly 20c 4s 4900 kept all the motors running and got the thing to lift off so to speak, the battery wires to/from esc's etc are not too thin. The motor wires themselves(motor to esc are quick thick also.

small ducted fan testbed vid2.MOV (2 min 15 sec)
Jan 01, 2013, 03:21 PM
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kahloq's Avatar
A third test. I moved the battery pack forward a good deal. It got off the ground ok this time and this is with the same battery as last video and hasnt even been recharged. So the wires bein g too small isnt an issue and C rating, while higher would be better wasnt soo much an issue either. Probably just the other batteries are getting old.

If it were not 10 degrees outside, I give it a try outside for more room, but, at least progress is being made.

small edf test3.MOV (1 min 35 sec)
Jan 01, 2013, 05:15 PM
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kahloq's Avatar
After doing a some research on the jetscreamer 1400 motors..............ive had them for like ever and never used them.....I was reminded of the fact that they can run on 5s. Now the question is.....can the rear fan motor take 5s or will it smoke LOL!?!?!

This may be my overall answer. If I can use 5s, then the amp draw should be lower and the battery shouldnt sag near as much under load. Plus...more thrust output The other question is.....would the edf units themselves hold up to the stress of 5s? Wemotech housing and rotors should, but the fan unit at the tail isnt a wemo. So two unknowns....lol...unknow motor/fan housing!!!

Its done quite well on 4s....so I'll probably give it a shot once Im back from vacation. Will be leaving town thursday afternoon so wont get time to mess with the setup much before then.
Feb 26, 2013, 06:51 PM
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How is the build going? It has been a while since we saw and update.

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