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 Post subject: Blade flyer builds a Goblin 630
PostPosted: Thu May 23, 2013 6:46 am 
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To whoever is interested, this is going to be a continuing post about my progress building a Goblin 630. It’s going to be a low key “blog style” posting with few words and at least one picture per building session to document my progress as I enjoy the building process.

I am also going to be posting build questions from time to time; and please interject comments as you feel the need.


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 Post subject: Building Session #1
PostPosted: Thu May 23, 2013 7:04 am 
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Let’s get the un-fun stuff over at the beginning. I took every threaded item be it male or female and rubbed them completely clean with 91% alcohol. Not so bad while watching some season ending shows on the PC.
Two questions came up as I was inhaling the alcohol fumes: Should I take apart the factory assembled pieces so I can personally Loctite every bolt? The edges of the carbon pieces don’t seem too sharp. I’m thinking I should file down the edges on a case by case basis, and not go hog wild with my Dremel & files. I will be rounding the edges as I route the wires.
Here is the uninspiring photo of all the cleaned hardware:
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 Post subject: Re: Blade flyer builds a Goblin 630
PostPosted: Fri May 24, 2013 7:24 am 
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Location: Caldwell, TX
Definitely disassemble everything to clean and Loc-Tite. My kit came with pretty rough and sharp edges on my CB. If your isn't bad, I wouldn't take the time to do it. If anything just check for sharp edges where wires are going to run and take care of those with liquid electrical tape or filing or sanding.

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 Post subject: Building Session #2
PostPosted: Fri May 24, 2013 10:21 am 
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I had the house to myself for the day so I got a nice long build session today.

I wanted to continue with the un-fun items. So I disassembled the factory assembled items, cleaned, inspected, lubed, Loctited, and reassembled as needed. Interesting, many of the Allen bolts are 0.060” socketed, and not metric. A improvement I made over the factory assembly, was in the tail rotor assembly. The thrust bearing in the tail rotor grip had minimal grease, and the bushings in the grip links had none. I did a light packing of grease to the thrust bearing, and thin film of grease to the bushings. It’s “like butter” (SNL) now. I need to buy a second 4mm Allen wrench so I can disassemble the main rotor head, but that can wait.
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After spending so much time with the un-fun items the rest of the evening’s assembly went quickly.
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The design & manufacturing quality is truly inspiring. This thing is built like a high precision tank. The gears have twice the width of my Subaru WRX manual transmission 2nd gear (the one that gets the most punishment).
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The assembly comes together without the need for adjustment. No main shaft play, no way to adjust the gear meshes because none is needed. I added a minimal amount of grease to the main & drive pinion and worked the grease onto the faces of the teeth then wiped away any residual grease that was not where it was needed. The delrin plastic gear is very close to being perfect, after a few flights the plastic will have reformed into a perfect match to the pinion. I plan to recheck this when I replace the motor gear with a lower ratio tooth gear in the near future.
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 Post subject: Qunatum motor
PostPosted: Fri May 24, 2013 11:15 am 
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Minor irritation with the Quantum motor.

1. If your $200 product is mounted with screws, why don’t you include the required screws?
2. If HeliDirect combos this motor with the Goblin 630 kit; and every purchaser of said combo is going to need to find their own mounting screws. Why can’t HeliDirect include the <$1 of screws in the combo?
3. If the shaft length of the motor is extended, why isn’t the pinion flat also extended?
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 Post subject: Build Session #3
PostPosted: Mon May 27, 2013 12:03 pm 
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On Friday I had another nice long build session.

It’s starting to look like a helicopter.

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A huge tail rotor pulley (27 tooth). I’m probably going to change this to the 26 tooth pulley in the future so I have the option of using <2100 headspeed. After I get some real headspeed numbers, I’m planning to gear the motor pinion so the governor has the widest range of head speeds available.

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Remember when I was amazed at the size of the tail fin? I only have 9/16” clearance when the main skids are flat. This may be because of the issue SAB had with boom strikes on the first batch of 700’s. I can see myself landing tail fin first most of the times with the Goblin 630.

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I just love this powertrain.

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The canopy fits like a glove.

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I couldn’t hold myself back. I had to put the canopy on.

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 Post subject: Final build post
PostPosted: Tue Jun 04, 2013 12:33 am 
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Well it’s been a long time without a post. When I last left you the airframe was finished and the electrical installation was about to start. Being that electrical installations can be tedious, I thought it would be best to hold off until everything was installed, then do an overview posting of the installation.

SAB’s manuals are pretty good in describing where to route wiring. I took their lead with a bit of full scale avionics style in wiring. The white wire wrapping is spiral wrap that we use in full scale avionics. “My” KC-135R & C-130 have a lot of the avionics wiring covered with this, to keep the wiring organized. The SAB manual had the servo wiring CA’ed to the shell and I liked the idea, so I used it. Spektrum says to have the remote receivers >3” apart. They are a little less than 3” but I think they will do fine.

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I wanted the space around the iKon to be as clean as possible; but also support the wiring. The only real challenge in wiring the Goblin 630 is getting the orange wire bundle from above the powertrain plate to the underside. There is five wire-leads inside that orange bundle, Rx power #1, Rx power #2, throttle, tail servo, and governor. Take note of where the tail boom ends through the upper slot; how does that wire bundle get through?

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Very carefully. You can see that the tail boom is seated correctly against the black screw; but that doesn’t leave much room for the five wire-leads. It’s snug, but not pinching.

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There is a little bit of loose wiring under the iKon mounting plate; but it isn’t much, and it allows me to easily unscrew the iKon mounting plate so I can easily remove the tail boom if needed for transport.

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Every avionics install has an ugly part. You have to bundle wire interconnects somewhere. The two loose connectors are Rx power #1 & #2 these get directly connected to the Rx LiFe battery and safetied with interconnect covers that are easy to put on and remove. I could add a fail-safe switch; but that just adds to the build cost. Maybe in the future.

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I’m not happy with the tail servo wiring. I just haven’t figured out what I’m going to do yet. I want the servo wiring interconnect to “break-away” if the tail boom separates in a crash. I need to figure out a wire protection scheme that adds minimal bulk to give the belt as much space as possible. This is not to say that the space is cramped, I just don’t like mixing my chocolate (wiring) with my peanut butter (moving belts).

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Going forward from the rear of the battery tray is the throttle and governor wiring. You can see the governor circuit board in the middle and the red governor sense wires going to the motor wires. I need to cover/wire-tie the sense wires a little better.

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The Hobby Wing ESC just fits the ESC tray. There is ~3/16” space above the capacitor pack and the frame member. I didn’t take a picture of it, but the heat-sink of the ESC is completely open to airflow through wide openings in the side frame (it’s blurry, but you can see the holes in the picture). There is a hole in the canopy directly under the ESC so airflow goes past the ESC.

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There are many reasons to buy a Goblin; I wanted the most visual helicopter I could afford. I am happy with the results. The weight of my Goblin 630 is 7.40 lbs. (3.357kg) without batteries, and 10.41 lbs. (4.722kg) with two 3700mAh 45C 6S LiPo motor batteries, and a 3200mAh 10C 2S LiFe Rx battery. I’m using such a large Rx battery because of the current draw spike that the Savox servos can pull.

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Setup: I setup the ESC using the DX6i and listening to the beeps. It’s easy if you first read the manual before attempting to do the programming. The eight second very soft start mode works very well. It reminds me of the start sequence of a Pratt & Whitney PT-6 turbine engine that I have worked on for many years. One downside to the very soft start is there is a delay from when you turn off throttle-hold and the motor starts turning. If you hit the throttle-hold in flight, you are committed to doing an autoing landing. The iKon governs the ESC well. Testing the governor while connected to the PC, and without blades, the motor RPM was within <5 RPM of the set RPM (1900 & 2160RPM).

The iKon is very easy to setup with the PC wizard. With the new firmware for the iKon I was able to set the gyro gain through the PC software. This freed up my sixth channel on my DX6i so I can switch through all three flying style setups; and uses the auto-level feature of the iKon. You may be asking how I can switch through three setups using only one channel; through the magic of mixing. Here is a link of how to do it. I have the aileron D/R switch, switch from flying style #2 (position 0) and flying style #3 (position 1). I have the large flap/gyro switch set so if the switch is up (position 0) the aileron D/R switch works normally. If the flap/gyro switch is pulled toward me (like the throttle-hold switch) to position 1 the iKon goes into flying style #1 no matter where the aileron switch is set. I have flying style #1 setup as auto-leveling & beginner sensitivity. Flying style #2 & #3 can be set to sport and (hard) 3D sensitivities. The DX6i only has two flight modes. So I can only set two governor speeds. With the very soft start, I don’t miss not having a “normal” mode. I just set two “idle-up” speeds (1900 & 2160RPM). I use 2160RPM because that is optimized for the stock gearing with my motor. After a few dozen flights I plan on buying a 22T pinion for 2100-2300RPM and a 18T pinion for <1900RPM if the head allows low RPMs.

Now it’s time to get this baby into the air.


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 Post subject: Re: Blade flyer builds a Goblin 630
PostPosted: Tue Jun 04, 2013 6:10 am 
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Fantastic job and writeup! :thumbup:

I look forward to the maiden flight report.

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 Post subject: Re: Blade flyer builds a Goblin 630
PostPosted: Thu Jun 06, 2013 12:18 am 
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JustPlaneChris wrote:
Fantastic job and writeup! :thumbup:

I look forward to the maiden flight report.


Thank you for the kind words.

Today I did the first flight of my Goblin 630. It was very light flying, just taking it easy. I was shaking a wee bit because; here I was controlling a flying lawnmower (4.3hp motor with a huge blade), and I really didn’t want to destroy this model that I have looked forward to for so long. In fact I had the very strange feeling that I was “in” Real Flight or Phoenix just flying the pixels I have spent so many hours doing. While within this feeling, I thought what the hell let’s fly this heli around like I like to do while chilling on the PC. Just letting myself meander, here and there. I also had a little angel speaking to me, “Todd, don’t do anything stupid. There isn’t a red reset button with this model”. The flight lasted ~5 minutes, and was over too soon; but was also relaxing, exhilarating, and deeply satisfying. It’s rare that I feel privileged to own something; I paid for it. But flying the Goblin gives me the same feeling I get when I go fly camping with my Beech Musketeer. The Goblin and the Beech are flying machines that have been designed by talented people that really know their craft. I guess that is why I feel privileged to fly these machines.

Here is the boring video. Please don’t watch it. Really it’s that boring. I shot it on an iPad even. The place I thought it was pointed turned out not to be correct. Save yourself from the five minutes of boredom. Ok, I do like the sound of the Goblin. You could just close your eyes and listen to the video. Yah, if you are going to watch the video, just close your eyes and listen.



I only had one issue today. I had initially set the motor timing to 0 degrees to try to make the motor as efficient as possible. This had the effect of making the motor really bog down. It didn’t seem like it was “on the governor”. I didn’t know if it was a governor, ESC, or timing issue. Working through the problem, I came to the conclusion that I just needed more power. The governor was working with the blades off; why didn’t it work with them on. So I upped the timing to 3.75 degrees. This increased the RPM a bit, and confirmed that I was not “on the governor”. Funny how a little prop syncing troubleshooting experience can find itself applying in weird places. I increased the timing to 7.5 degrees, and bingo, the motor/governor was happy and efficient. The motor was ~120 degrees temperature after the flight at 2160RPM.

After the five minute flight I put in 5442 mA into the LiPo battery (balanced charged). My little 100watt charger took 90 minutes to parallel balance-charge the two 3700mAh 6S batteries. It will do for now. But I’m in the market for a pair of 500watt chargers that can take a 24vdc input (improved efficiency).

I also found out that my Goblin doesn’t like <~2100RPM. If I go below 2100RPM the tail bobs up & down. I’m going to try to correct this side effect without buying the HPS head. But I will probably be buying the HPS head/26T tail pulley/18T motor pinion sometime this summer.


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 Post subject: Re: Blade flyer builds a Goblin 630
PostPosted: Thu Jun 06, 2013 7:28 am 
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Location: Austin, TX
Todd, it wasn't that boring! Congrats on a successful maiden. :)

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Chris Boultinghouse


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