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Goblin 280 SAB Heli Division - Goblin 280 Helicopters


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Old 07-19-2019, 06:19 PM   #1 (permalink)
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Default Nick in belt (after crash)

I recently had a spectacular crash, my daughter witnessed it. She said I hit an invisible bird! I was basically hovering straight out about 50’ when there was a horrible noise, I think my canopy was ejected and my beloved fireball fell to the ground.

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The carnage was pretty bad. The canopy was ok, but the tail (plastic one) was broken at the tail end. Both DFC arms were broken, one link missing. All 4 servo arms were snapped and the tail pushrod was 20’ away and was cracked from twisting it lengthwise. It was still in one piece but really spongy if you twisted it... One blade was snapped in 1/2, the other intact.Click image for larger version

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So... I’m rebuilding, I’m checking over the belt and find a small nick. Should I replace it or see if I can get a bit more out of it.
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Old 07-19-2019, 06:24 PM   #2 (permalink)
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Some would replace it. Some wouldn't.

I would run it and watch it. I take risks. Especially on micros.

What's your tolerance for risk?
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Old 07-19-2019, 06:33 PM   #3 (permalink)
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Originally Posted by JimJW View Post
I recently had a spectacular crash, my daughter witnessed it. She said I hit an invisible bird! I was basically hovering straight out about 50’ when there was a horrible noise, I think my canopy was ejected and my beloved fireball fell to the ground.

Attachment 804201

The carnage was pretty bad. The canopy was ok, but the tail (plastic one) was broken at the tail end. Both DFC arms were broken, one link missing. All 4 servo arms were snapped and the tail pushrod was 20’ away and was cracked from twisting it lengthwise. It was still in one piece but really spongy if you twisted it... One blade was snapped in 1/2, the other intact.Attachment 804199
Attachment 804197


So... I’m rebuilding, I’m checking over the belt and find a small nick. Should I replace it or see if I can get a bit more out of it.
You already know the answer to your own question.......

“Pay me now or pay me later “ ...... 😉
Ah Clem likes this.
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Old 07-19-2019, 06:38 PM   #4 (permalink)
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Quote:
Originally Posted by JuanRodriguez View Post
You already know the answer to your own question.......

“Pay me now or pay me later “ ...... 😉
Good analogy. How much is a new belt?
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Old 07-19-2019, 06:52 PM   #5 (permalink)
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Good analogy. How much is a new belt?
Don’t know as I don’t own that heli (or any other Goblin) . But I can tell you one thing on a “generic” level ..... the cost of that belt is going to be MUCH lower that another crash if the damaged belt lets loose in flight ......
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Old 07-19-2019, 07:30 PM   #6 (permalink)
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From what you described, that heli is in need a total re-kit. With the super low parts count why not go for the havoc pnp and have a cool looking new bird 👍
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Old 07-19-2019, 10:04 PM   #7 (permalink)
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From what you described, that heli is in need a total re-kit. With the super low parts count why not go for the havoc pnp and have a cool looking new bird 👍
Re-kit?! I only asked because belts were expensive. Otherwise the blades and DFC arms were the biggest loss. I was a little shocked at the cost of the DFC arms...
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Old 07-20-2019, 06:08 AM   #8 (permalink)
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My bad, in that pic it looked like everything but the frame was broken or bent. Have you checked the main & feathering shafts yet? I’m curious how well they hold up.
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Old 07-20-2019, 06:32 AM   #9 (permalink)
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My bad, in that pic it looked like everything but the frame was broken or bent. Have you checked the main & feathering shafts yet? I’m curious how well they hold up.
I checked the feathering shaft; I can feel (Not see) the slightest wobble when I spin it. The main shaft, I haven’t taken out to check. I’ve almost got it back together & was planning on checking the vibs in the log instead of pulling the shafts out.
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Old 07-20-2019, 09:03 AM   #10 (permalink)
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These Goblins are expensive to buy and expensive to repair..... that's why I never bought one.....

If you "feel" the shaft bent, you're most likely going to have vibration issues....

Why not do the repair right the first time (including the belt) ??

If the parts are too expensive, an option would be to sell it and move on to something more affordable.....
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Old 07-20-2019, 09:09 AM   #11 (permalink)
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^^^^^^^^^^^^^^ what he said.. this small heli will nickle and dime you do death... they give you the permanent tail wag for free. I looked at how much I had in mine and I could've had a really nice 550.
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Old 07-20-2019, 02:34 PM   #12 (permalink)
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Yeah, they are expensive but it is a nice size bird for me. It’s small enough to fly at a nearby park and solid in the wind. I was just taken back by the cost of the DFC arms...
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Old 07-20-2019, 03:40 PM   #13 (permalink)
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Bk hobbies has the belt and arm for $8 each. And they have everything in stock so you wouldn’t have to go to multiple vendors
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Old 07-20-2019, 05:49 PM   #14 (permalink)
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Switch to the aluminum dfc arms. They stay in one piece unlike the past that crack every crash.
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Old 07-20-2019, 06:40 PM   #15 (permalink)
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Bk hobbies has the belt and arm for $8 each. And they have everything in stock so you wouldn’t have to go to multiple vendors [IMG class=inlineimg]https://www.helifreak.com/images/smilies/thumbup.gif[/IMG]

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Switch to the aluminum dfc arms. They stay in one piece unlike the past that crack every crash.
I went with Dave at AnythingHeli, he had everything including the aluminum DFC arms 😉
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Old 08-30-2019, 07:12 PM   #16 (permalink)
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Ahhhhhhrrrrrrrrrgggggggg!!!

It happened again! Spontaneous Helicopter Explosion.

Basically the same thing happened today, I was flying, the heli wobbled then parts all over. Then dropping straight down.

I’ve come to the conclusion that I’m:
A) doing something wrong.
B) one/both of the DFC arms are popping off. (Both of the ball links are MIA, have the aluminum ones now)
C) the servo arms are breaking. I’m using these: https://www.anythingheli.com/gear-pr...taba-align-bk/ (only one broke this time)

It looks like the main blade hit the tail breaking the tail off (again)
The canopy was ejected off (again)

Any ideas, the heli is not being flown hard and headspeed was at 3800. Super un-nerving, any suggestions?
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Old 08-31-2019, 12:15 AM   #17 (permalink)
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First of all no don't use a belt with a nick in it.

I get this notion that your tail is coming undone on you. The likely cause is not enough tension on your tail belt. Can you show me a video of it after you repair it illustrating belt tension whilst pushing on it. If it's not tension check for side play on the tail shaft. Are there any tail belt marks on the tail gear or the sides of the cf plates?


Can you give me some more photos, if I can see it I can take a really great guess. Not just the tail but the entire heli especially after disassembly.
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Old 08-31-2019, 12:18 AM   #18 (permalink)
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Replace your tail shaft as gp right now also.
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Old 08-31-2019, 07:58 AM   #19 (permalink)
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First of all no don't use a belt with a nick in it.

I get this notion that your tail is coming undone on you. The likely cause is not enough tension on your tail belt. Can you show me a video of it after you repair it illustrating belt tension whilst pushing on it. If it's not tension check for side play on the tail shaft. Are there any tail belt marks on the tail gear or the sides of the cf plates?


Can you give me some more photos, if I can see it I can take a really great guess. Not just the tail but the entire heli especially after disassembly.
First, thanks for your insights, I’m scratching my head on this. I’ll try to do a video when I get it back together to show the tension.

So you think the tail is coming out first, because the belt is too loose? I don’t think that lines up with what I’m seeing & hearing just prior; in both cases there was a bobble of the head like a cyclic gain issue, then the canopy is spit off, then dropping straight down. I haven’t heard the belt slipping and was just practicing flat level flight with simple turns.

In both times, the boom was broken in about the same place, about 1-2 inches from the tail (I’m using the plastic boom) One of the main blades, in both cases was broken in half, tip nowhere to be found.

This second time, the tail hardware was damaged, the pulley flanges were folded over, the tail pitch slider wheel, was cracked and the bell crank was broken. A tail blade and the tail fin were damaged also. And the new belt was broken, I replaced it with the previous crash.

Both booms have a line or crease where it looks like the blade struck it. The first it is less distinct, while the second is well defined. So that leaves the question of how did the main blade hit the boom?

I hadn’t thought about your proposal, that the tail is coming out. The first time it happened, the tip of the boom was just broken off & the tail was still in the second instance the boom was detached.

To try to test your idea, I re-inserted the boom to check if it was possible to deflect it enough for the blade to hit like it did. It doesn’t seem likely unless the tail came completely out..

I hope all that doesn’t come out as I’m not accepting it as a possibility. I think it is, I just don’t understand it yet if it is.

I’m not sure what you mean about tail marks on the carbon fiber plates. It’s a Fireball, the only carbon is in the tail-fin and main blades. There is some on the tail guide pulleys. Does that show something?

Right now I’m leaning towards option C, the servo arms are breaking. Only one broke in this crash and coincidentally that would allow the blade to strike the boom as it did. I still need to evaluate my idea with the DFC links in place. I’m tentatively ruling out B because I’d think it would be widespread in the Fireball and Mini-Comet if they came off easily.

I have the same servo arms on my Mini-Comet but have only flown it a handful of times. (Not That I’ve flown the Fireball more than 20-30 flights) I’ll ground my M-Comet for now & plan to replace the servo arms with something else on the fireball.

I’ll check all my shafts for straightness too.
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