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Old Nov 08, 2012, 05:21 PM
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A8M Aerial HK heavy assault model from Terminator 3

Terminator A8M Aerial HK heavy assault model

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Recently, I saw a video of some guy in Russia having done the two turbo fan design seen in T1, T2, T3, and T4.
After seeing that and having this project in my head for awile now, I just had to do my own...except it'll be the 3 fan A8M Aerial HK heavy assault model version seen at the beginning of T3. The tiny HK-drone shares the same layout which was seen near the end of the movie which was designed and built by the US Airforce after having purchased Cyberdyne.

Here is link to the short thread with a couple vids of the Russian guy's version.
http://www.rcgroups.com/forums/showthread.php?t=1739605

As a note...this thing will NOT be small. To get an idea of size...the turbo fan ductings will be made using Home Depot 5 gal buckets as a base and using motors spinning 11x7 3 blade props...basically a shrouded rotor design.
As a comparison, the largest ducted fan unit commercially available on the market is 127mm that Im aware of. A Homer bucket has an internal diameter of 280mm at the point where the 11x7 props will be situated.

Originally, I had posted this in the VTOL section which isnt even part of the multirotor subsection at all.....and that area has very little traffic. The reason I'm moving it mostly here is it definitely falls into the multi-rotor designation and I may need help from time to time to figure stuff out.
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Old Nov 08, 2012, 05:24 PM
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Initially, I had wanted to do an EDF version to as closely as possible, replicate the "real" thing. However, the limited size of even the largest edf's would have kept the scale of the entire vehicle rather small...and Im not exactly looking for small to say the least. I am estimating this thing will be well over 7 feet wide,

Also, a BVM edf system costs insane amounts of money for just 1 and is still only a 116mm diameter fan unit running 10-12s. Each fan system costs upwards of $1400. So thats not even an option at all. 3 of those would be a turbine motor. There's no way I'd try to build a vehicle as unconventional as an HK using that kind of setup with that much money.
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Old Nov 08, 2012, 05:26 PM
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So...this is what Im trying to replicate
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Old Nov 08, 2012, 05:27 PM
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The power system for this is going to be 3 Rimfire .60 size 650kv motors on 6s. These will be mounted inside the Home Depot buckets obviously, but not at the top. The top of the buckets are a bit wider then an 11" prop, but not wide enough for a 12".

Each duct unit will be able to rotate some...forward/backwards.... for control movements...at least thats the plan. A flight control board will most likely have to be used for the motor esc's themselves in conjuction with radio mixes for the tilting of the fan housings. Additional gyros may need to be employed on top of the fc board for that purpose.

The motors have been ordered and should be here at the end of the week.
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Old Nov 08, 2012, 05:29 PM
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Since this will be a rather large vehicle when done, I will need to figure out a way to make the thing tranportable.

Everything will have to be hand made, so its not going to get completed in just a couple weeks.
However, I also have a small y-shaped aluminum frame to test out the fc board and tilt ducting ideas before installing the much larger units on the main project. So...I will make posts about the smaller test bed along the way as I scratch build the HK. The small one will be using 70mm edfs and will function basically the same...just no elaborate body.

As a side project, I also have the Hobby King y-3 tricopter with the heli canopy, but my main focus will be the big hunter killer vehicle
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Old Nov 08, 2012, 05:36 PM
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After thinking about the tranportability issue, Ive opted to make the "wing" as two separate pieces that bolt to the "fuse" and have aluminum tubes running thru the fuse into each wing pylon. So..instead of a 7 - 8 ft wing assembly to cart around as one unit, each side will be about 4 feet. This will make assembly at the flying location a lot easier to.

If anyone has seen some of the larger pattern ship type 3D planes, you'd get the idea of the separate wing pieces bolted to the fuse.
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Old Nov 09, 2012, 05:35 PM
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From wingtip to wingtip.....errr...ummm.. rotor housing to rotor housing across the vehicle.......Im expecting about 8 feet wide.
The home depot buckets alone are 12" wide....so those alone are 2 feet.

Because of the size, I may need to hide a couple of extra fan units inside the "wing-pylons" just for lift. Wont know till I get the thing framed up and the electronics installed. I wont be covering it or adding ANY scale shapes and details until Ive got the thing actually capable of flying. I should have a rough fuse section and center wing areas somewhat done in maybe 2 weeks. I'll then need to add the anhedral wingtips plus the homer buckets with motors and build out a dual boom tail section.

Before even trying to test fly the basic setup, Ill be setting up a much smaller y-frame tricopter but with ducted fans to test control ability with tilting the forward two ducts.

I do have the anhedral wingtips framed up now.
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Old Nov 09, 2012, 06:08 PM
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Just to give an idea of size, here is the bare wingtips along side the rotor shrouds(home depot 5 gal buckets).

The props are 12x8x3's to give a size comparison. I'll be using 11x7x3's inside the buckets.

Obviously in the end, the entire vehicle will be painted steal/chrome/grayish. The buckets wont look like buckets either.

The pics are illustrating the two forward fan units btw.
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Old Nov 11, 2012, 11:50 AM
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Motors havent arrive yet as I had expected. So.....ran to hobbytown and bought a bunch of bass and balsa wood to use for the twin tail boom assembly.

Right now....I also have mega scale hitec MG servos with 10mm outshafts on order for use with tilting the two front fan shrouds(homer buckets).

Ive been trying to figure out how I can rig up a dual axis movement rig for the tail fan shroud(also a 5 gal bucket). Pretty easy to do one axis, but both?

Anyone with ideas please chime in...remember, this has to work for something 12" diameter in between two tail booms. The rudder(yaw) axis probably wont need to tilt more then 15 degrees
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Old Nov 11, 2012, 02:04 PM
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wowzers.....7-8' tri ? that will awesome to see fly ..

Terry
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Old Nov 12, 2012, 06:09 PM
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Well...looks like the motors for the HK wont be here till this coming thursday or friday

So...in the meantime, I've started putting the small testbed tricopter turned EDF mule together.
This is a y-600-3 flying spider frame I got off Ebay for $30. Landing legs have spring load which is nice.

So...just like the big main project, this test mule will have two tilting front fan housings and the rear unit will also tilt....but via elevator instead of rudder input like the forward two.

This unit will be used to test how well I can control the aircraft actually tilting the two front fans opposite direction instead of using a yaw tilt setup on the rear fan unit and having the forward two static hard mounted.
My entire setup that will be used programming wise will be dione on this small scale version before even trying to test fly the big one when I get it done.

Just FYI, the rear fan unit has obviously not been installed yet. The two front ones are wemotec midifans with jetscreamer 1400's. The rear unit is also 70mm, but an off brand but quite similar and its got some no name motor in it. All fans run on 4s.....while the jetscreamers COULD be run on 5s, the rear motor would probably smoke pretty quick.

A couple pics....
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Old Nov 13, 2012, 07:39 PM
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Got more done on the small testbed mule. Rear fan unit is attached now. Ive also programmed the v-tail function in the radio since the rear fan is on elevator and the two fronts are on rudder.

This allows the two forward fans to also tilt in unison to help forward or rearward motion while also allowing the rear fan unit to aid the rudder "opposite" tilt directions for yaw correction. I hope that makes sense.

Basically, if you input rudder left stick, the forward left fan unit tilts the thrust direction about 20 degrees max towards the front of the vehilce which pushes that side backwards. The right front tilts the fan so the thrust is aimed somewhat towards the rear which also tries to push the right front forward.
With the addition of the rear fan and it now with v-tail setup, when left rudder is input, the rear fan also tilts so the thrust is aimed slighty to the rear of the craft. This gives two fans trying to push the centrifugal center of the vehicle in a circle arc towards the left, while the left fan unit is trying to pull the front left backwards. This turns the vehicle in a yawed, but level left. Well, thats the idea anyhow.

Everything opposite for right rudder. I'll get some pics of the craft in a day or so with the rear fan setup. I need to get a new power pack for my vid cam too, so once I get that, I can take some video trying to demonstrate what Im talking about.
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Old Nov 24, 2012, 07:14 PM
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Sorry for the delay in posting, but its that time of year where holidays get in the way.

Anyway..... got some work done on the larger fan ducts for the big version. I painted the Home depot buckets in aluminum color. Large spray paint can is only $4.

As you can see in the pics, the wood cross mounts are securely fastened to the walls of the duct with L shaped brackets also found at home depot.

The central wood mounting plate as been duplicated on the underside JUST in case I need additional thrust power, but I wont know that till much further along.
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Old Nov 24, 2012, 07:19 PM
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Here is the bottom side of the duct. You can see the duplicate wood mount plate glued in place. Aside from adding structural rigity, as mentioned I can mount another motor facing down on it. I placed another motor in there just for illustration purposes. It is not currently bolted on. It is, however, the same kv as the main motor units and will also run on 6s.

That being said, it'd be a lot easier to buy 3 more of the rimfire .60 650kv motors and mount them if needed since the x mount piece would already fit the bolts that are already installed in the wood plates. Cost wise, though, those turnigy Sk motors add nothing to the total espenditures. I dont have 3 of them though, so the tail fan unit wouldnt get one of thats the route I went.
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Old Nov 24, 2012, 07:25 PM
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Now...as far as mounting the ducts themselves to the main wing pylons of the vehicle, I will be using giant scale servos from hitec. In addition, the hitec servos will be mounted within an aluminum servo block that has ball-bearing support on the output shaft. This takes the load OFF of the servo spline itself. All the weight of the duct, motor, esc etc will be carried by the aluminum servo block and bearing.

Here is a picture of what Im talking about.....the duct will be bolted directly to the round aluminum hub thats already pre-drilled. Pretty nifty.

Robot guys use these all the time to isolate the servo itself from the actual mechanical moving pieces.
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