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500 size Apache Gunship Build

F106DeltaDart

Well-known member
#61
Yeah, that is definitely one part that I can't afford risk on. Luckily, the side frames are just thin pieces of sheet aluminum, so it's actually pretty cheap.

Did get around to finishing up the weapons tonight. The Apache finally has some teeth :D.
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PsyBorg

Wake up! Time to fly!
#63
Wow you did an awesome job on the Hellfires mate. They look pretty real. How soon before you think this will be air worthy?
 

F106DeltaDart

Well-known member
#64
Wow you did an awesome job on the Hellfires mate. They look pretty real. How soon before you think this will be air worthy?
Thanks Psyborg! I was originally hoping to have it ready by September 16, so I could take it to the Heli Madness event in Abilene. It all depends how long it takes to get the side plates cut for the gearbox. One of my dad's friends is going it in his free time, so its not necessarily a quick turnaround item. Also have the tail pushrod to figure out, which will be interesting. Definitely planning on flying before October though.
 

F106DeltaDart

Well-known member
#65
Finally finished up the last of the paint and decal work. Time to start setting up the mechanics while I wait for the gearbox parts. Might also take a second look at actuating the Horizontal stabilizer.
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PsyBorg

Wake up! Time to fly!
#67
That looks incredible mate. I see the engine nacelles are hollow, are you planning on something in them like lights or smoke?

I also wonder.. did they change things on aircraft? The last military aircraft I saw had them "Not a step" warnings plastered all over them. I only notice because of the lack of yellow and red in various places. This is Army so I don't know if they did all that or not.

Can't wait to see this in the air though. Tell them machinists to get a move on :p
 

F106DeltaDart

Well-known member
#68
That looks incredible mate. I see the engine nacelles are hollow, are you planning on something in them like lights or smoke?

I also wonder.. did they change things on aircraft? The last military aircraft I saw had them "Not a step" warnings plastered all over them. I only notice because of the lack of yellow and red in various places. This is Army so I don't know if they did all that or not.

Can't wait to see this in the air though. Tell them machinists to get a move on :p
Thanks man, no plans for anything in the nacelles for now. It's heavy enough as is, and I wanted it open to provide some cooling flow to the ESC/servos. I will probably install some ducting plates so that you won't be able to see all the way through though.

As for the no step warnings, they are much less common on choppers, especially since there are handholds/footholds everywhere for maintenance and the preflight. Most of the warning placards are up by the TADS, and they are just small black text, no yellow or anything. You did remind me that I still need to paint the fuel cap though. It's the one red patch of color on the Apache. Also still have to add on the lights.
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Also, I got word that the parts are done, and shipping out today! Should have them in hand soon!
 

F106DeltaDart

Well-known member
#69
Small note on progress. I've been working on a few additions to the build including an actuated H-stab. One big issue recently has been the ESC. I originally had a Castle edge 100 set aside for this project. However, the ESC is too wide to fit in the fuselage if mounted on the side of the frames. And, with the RX, FBL unit, H-stab servo, and rudder servo taking up most of the space too the rear, there just wasn't enough places left to put it. Instead, I ordered a more slim
Castle Talon 90 that should fit without issue. I have also been routing cables to the front for the bind port and FBL USB access. With how difficult it is to insert the mechanics into the frame, I want to minimize any removals as much as physically possible..
 

PsyBorg

Wake up! Time to fly!
#70
Awesome so we may be seeing a maiden in short order then? Hopefully you will get some air time on it before the weather turns foul and too windy to put something like that in the air. Good luck setting up the new tail drive as well as fitting the esc in a happy place.
 

F106DeltaDart

Well-known member
#71
Finally got everything setup for the first flight last night. The new ESC barely fits in the fuselage.. Got my swash phasing set, tail rotor throw calibrated, and all directional checks looking good. So, I decided to try my first hover. I throttled up and got the rotor to full speed and pulled pitch. As soon as I was expecting it to lift off, it sharply rolled right, and the blade tips contacted the concrete. I hit throttle cut immediately and got it back on its gear, and went through my swash setup again. Inputs and phasing looked good. So, I decided to go for a second try, and it ended with the same result. Not sure what is going on. Thinking that it would be the narrow wheel base combined with the raised tailrotor, making dynamic rollover very easy. Anyone ever dealt with anything like this? I'm wondering if a degree or so of left mast tilt (like many full scale helis) would help mitigate the issue... I may also try flying on our fabric runway from the club. The reduced friction should allow it to skid sideways (rather than catch and flip) much more so the small foam tires on pavement.
 

F106DeltaDart

Well-known member
#73
Well, I pulled power and got it light on the gear today. However, as soon as I started pulling pitch, RPM rapidly decayed. It would seem that the little Xnova 890kv motor was just not up to the task of lifting such a heavy machine. I wish I could download ESC data to check on it, but of course the Talon 90 has no logging :p. I decided to order a Scorpion instead: http://www.scorpionsystem.com/catalog/helicopter/motors_4/hk-32/HK_3226_900/. Same KV and shaft diameter, much more power. Hopefully this will finally get this bird off the ground.. An expensive solution for the issue, but it will be worth it to finally get airborne.
 
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PsyBorg

Wake up! Time to fly!
#74
Well in my book this one is worthy of better components. You have put a lot of effort and detail into this not to mention time and money so a few extra dollars will add to the value and longevity. Great job on this :applause: and as the rest of the community I really want to see this in the air.
 
#75
Dude, amazing work. I would love more info on the hardware, maybe some more pictures. I've only built a 450 scale MD500. I love the focus on the model first and the hardware second, I find that very interesting.
 

F106DeltaDart

Well-known member
#76
Thanks guys! Flynn, I'll get some photos tonight since I have the mechanics out of the airframe. I've been focusing on the model part for two reasons. First, the mechanics are generally pretty straightforward, and not that interesting. There's not a lot your are going to do that is atypical on that end. However, I guess this one is pretty different in that respect.. Second, is that its a pain to get the mechanics out of the fuselage, so I try to minimize that process as much as possible. Here is the breakdown on the mechanics. It started from a Trex 500ESP kit, but hardly has any of those original parts now. Here are the modifications:

-Special side frames were included from the kit to lower the tail boom
-A smaller diameter 120T main gear was included with the kit to fit inside the narrow fuselage
-This smaller low tooth-count gear increases the gearing ratio, so it requires a lower KV high-torque motor
-This makes things EXTRA difficult running a 4 blades head, which requires a low headspeed (~1700 rpm)
-The instructions specifically call out NOT to use a 12T pinion or less on the motor because it could damage the gear, making it even more difficult to get the correct headspeed (Most Trex 500s runs a 1600kv motor, I run a 900kv)

-The drop down tail is designed to be belt drive. Personally, I am not a fan of belt drive tails on scale helis. There is always a bit of lag/slopiness associated with a belt drive that takes away from making a model look scale in the air. I found a guy on RCgroups who sold a special drop down gear that allowed me to convert to Torque tube.
-Then there was the raised tail gearbox. It started as the RC Aerodyne part: http://www.scaleflying.com/Torque-Tube-Conversion-Kit-500-size_p_2645.html, but it had a max tilt angle of 45 deg, and the Apache's tail is at about 74 deg. I designed some new side frames for the gearbox and had them laser cut.
-Also changed the pitch bellcrank to the other side of the gearbox to accomodate the right-side Tail rotor. Got that from here: https://shop.microhelis.de/Crank-Arm-for-500-Size

Specs:

Head: Align 500 size 4 blade
Tail rotor: CNC Helicopter 500 Apache Tail Rotor
Blades: eHirobo CarbonHobby 425mm scale blades
ESC: Castle Creations Talon 90A
Swash Servos: 3x Align DS515m
Tail Servo: MKS DS8910A+
FBL Controller: iKon2 with Bluetooth (I can adjust every setting from my phone without needing to pull the mechanics!)
Motor: Orginally planned as an Xnova 890kv 2820, proved too weak. It was originally designed for a 4 lb heli, and this beefy bird weighs in at about 7.15lbs... I have a Scorpion 3226 900kv motor on the way with a lot more power (1770W vs. 1000W). Hopefully that does the trick.
Batteries: 2 x 3S Roaring Top 3700mah in series. These barely fit under the cockpit with maybe 1mm to spare. Cramming all of this stuff in a small gunship doesn't leave much room.. I have a Huey and an H-34 on the bench that I'm looking forward to with all of their internal space.
 

F106DeltaDart

Well-known member
#77
A few photos of the mechanics. The pushrods that runs back past the intermediate gearbox is connected to the horizontal stabilizer when if is in the fuselage. Although the wiring looks like chaos, there is some organization. The USB cable is routed from the FBL controller so that I can perform software updates without removing it from the fuselage. The other wires running forward attach to the pan/tilt for the gun and TADS.
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F106DeltaDart

Well-known member
#78
New motor installed and is ready to go! I missed the window for flying this evening, and the forecast for tomorrow has 17mph wind.. so maybe maiden will be Wednesday? Took the opportunity tonight to get a photo with my other chopper projects as well

Standing ready to fly:
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The squadron:
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Waiting patiently on the assembly line:
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PsyBorg

Wake up! Time to fly!
#79
Sooooo Jealous..

That's an awesome set of helo's you have there. The only one missing in that bunch I would want to add would be the Cobra. Will be interesting to see what you do with that Jolly Green Giant when that is done.
 

F106DeltaDart

Well-known member
#80
Sooooo Jealous..

That's an awesome set of helo's you have there. The only one missing in that bunch I would want to add would be the Cobra. Will be interesting to see what you do with that Jolly Green Giant when that is done.
Funny you say that.. I actually have a 470 size Cobra sitting on the shelf as well. So many projects, so little time :p. I also have some Trex 700 mechanics in reserve for scratchbuilding a Bell 525.