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HomeScale✈️AircraftScale HeliVario Scale Helicopters › Gearbox dome for extended shaft
07-25-2020 10:57 PM  15 days ago
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Makiedog

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Minneapolis

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Gearbox dome for extended shaft
Ever since I experienced a horrible ground resonance episode for my Cobra's maiden test flight (on concrete), I added a gearbox dome thingy to stiffen the extended main shaft. Now I have no evidence the long shaft was a reason for the ground resonance, but the shake never occurred again. I have also refrained from landing on concrete. What do you guys think?

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07-26-2020 12:27 AM  15 days ago
Notar

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Taxachussetts

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Couple of things. Vario does not like more than 75mm of unsupported rotor shaft above the top bearing in the assembly.
The side frames you have are just stamped out of aluminum, and are not thick enough, or annealed for strength. If you got them from California, they contribute to the vibration as well.
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07-26-2020 12:38 PM  14 days ago
Rojoalfa

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Punta de Mata, Monagas-Venezuela

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Notar The side frames you have are just stamped out of aluminum, and are not thick enough, or annealed for strength.
/
/

I understand that the two frames and the bottom base are not from Vario... Isn't it?

You are explaining that this weak frames act like a resonance box...

Very bad.

/
Saludos cordiales,
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07-26-2020 11:01 PM  14 days ago
Makiedog

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Minneapolis

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I got the Airstar side frames years ago. I doubt they contributed to vibration cos they're well braced to the side walls at both the top front and top rear. Like I said, the shakes never returned ever since I added the dome bracing and stayed away from concrete, I'm just not sure which variable was the original culprit. As you can see, she flies quite well today.

Watch at YouTube

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07-27-2020 12:17 AM  14 days ago
Grimracer

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Eau Claire WI

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those are Aristar side frames.. they are complete garbage.. ask me how i know..

my 212 has a set too.. and they have been a "challenge" to make work. I had to add CF bracing to mine.

If you can make them work.... great.. just be warned.. your going to want to change them at some time...

Looking forward to seeing the bird...

Grim
Michael J Zaborowski
Futaba USA
AMA 124909
IRCHA 5453
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07-27-2020 12:59 AM  14 days ago
Notar

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Taxachussetts

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Makiedog I doubt they contributed to vibration cos they're well braced to the side walls at both the top front
Thats exactly what caused the vibration is the crappy side frames. You just do not have enough experience with people using them to see this. Thats fine, the top dome is a band aid in the mechanics. The frames work fine in pod and boom, but the minute they are in a fuse, they cause the vibration. I should know, i sold quite a few replacement sets when guys put those mechanics in fuselages. But, i am sure yours will be alright.
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07-27-2020 02:41 AM  14 days ago
Makiedog

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Minneapolis

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Joe, risk noted. I'll look at frame replacement or reinforcement. What kind of failure should I expect? Cracked frame?
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07-27-2020 11:14 AM  13 days ago
Notar

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Taxachussetts

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Yes, cracked frame where they bolt to the mounting block on the bottom is common, and where the servos mount as well.
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HomeScale✈️AircraftScale HeliVario Scale Helicopters › Gearbox dome for extended shaft
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