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Thunder Tiger Raptors 30-90 - Imperio > RAPTOR 90 what caused this? OS 91SZ blew a bushing!
 
 
iher
Heliman
Location: mexico

In mid flight my os91sz on my RAP 90 SE stopped. it felt like I bogged the heli after one to many tic tocs.
I checked the glowplug and it had weird looking tiny brass color pellets around the glow filament.
I had never seen this so before starting it again I took it apart
I found the piston and head FULL of dents and it was missing half of the lower bushing on the connecting rod.
ITS A DISASTER.
Why would a bushing break and start bouncing all around damaging everything?

Has this happened to any of you...how is this preventable?



Blade CX + Trex SE + (x2)Shuttle ZXX w/os46FXx + Eslayer wing + Raptor 90SE+ Futaba 9ch H
08-18-2008 05:41 PM
 
 
storman1969
Senior Heliman
Location: Timmins,Ontario

I think this is an issue with OS.. that bushing wears quick. What is funny is why does it break???

And how does it get on top of the piston...

Sorry for your luck...

Keep your eyes in the sky I might be Flying Yeeeeeh!!!!
08-18-2008 07:00 PM
 
 
iher
Heliman
Location: mexico

I agree. The breaking is weird.

After putting some thought into it and analyzing all the parts I think what could have happened is this:

The fan got loose. This play allows the main axel of the engine to move back. Then the arm started to rub against the back plate and the motor casing (there is a grove where the arm passes all around the engine casing). This might explain a certain overheating and maybe this allowed the bushing to move outside the arm, thus hitting against the back plate and breaking ( you can see the rubbing and a big scratch on one side)

The 1/3 rd of broken bushing probably bounced all over the place denting the arm and the underside of the piston, then was pushed by the air and nitro through the piston intake and stayed in the combustion chamber until it was reduced into small enough pieces to be expelled into the pipe……when I shake the pipe I can hear the metal tiny pellets that where spat out by the exhaust port. These little metal shavings are like little spheres, this means they actually melted!

Blade CX + Trex SE + (x2)Shuttle ZXX w/os46FXx + Eslayer wing + Raptor 90SE+ Futaba 9ch H
08-18-2008 07:57 PM
 
 
storman1969
Senior Heliman
Location: Timmins,Ontario

I had the same thing happen to my OS70, fan got loose and I can see rubbing on back cover. I caught it in time because there is no damage and when I tried to start it the clutch would stay engaged..Pushing inside the bell.

Well Happy that I loctited that fan and retaining nut now.

Are you sending it in to OS???

Keep your eyes in the sky I might be Flying Yeeeeeh!!!!
08-18-2008 09:32 PM
 
 
iher
Heliman
Location: mexico

well....
If the fan comming loose is the reason, then it is not really a faulty engine.
Dont you think?

I will send them the pictures, and see what they have to say about it.

Blade CX + Trex SE + (x2)Shuttle ZXX w/os46FXx + Eslayer wing + Raptor 90SE+ Futaba 9ch H
08-18-2008 09:40 PM
 
 
storman1969
Senior Heliman
Location: Timmins,Ontario

Yup that's right!!!

Good Luck!

Keep your eyes in the sky I might be Flying Yeeeeeh!!!!
08-19-2008 12:01 AM
 
 
Dino Spadaccini
Key Veteran
Location: USA

why

There are a lot of reasons why that could happen the most common is running the motor to lean. I takes a lot of heat to brake the bushing out, the other thing is how old is the motor what fuel are you using what head speed are you running what gear ratio are you using this could happen to a brand new motor or one that has hundreds of flights, I had con rods go after 50 flights for no reason that’s why there is a warranty Dino

Team Thunder Tiger
Team Futaba
CY Enterprises
Morgan fuel
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TEAM MAPTERGY
08-19-2008 02:39 AM
HOMEPAGE  
 
 
iher
Heliman
Location: mexico

Maybe it all started with a crack (see the picture) on the connecting arm, once the engine cooled, might allowed the bushing to move outside the arm and striking the back plate...and the rest is history.

If so ....what caused the crack. A bushing too large, that cracked the arm when pressed in, and with the extra heat?

or fatigue from the forces exerted in the motor by compression , dilating and contracting due to temperature, added to an inadequate metallurgy or tolerances?



Blade CX + Trex SE + (x2)Shuttle ZXX w/os46FXx + Eslayer wing + Raptor 90SE+ Futaba 9ch H
08-19-2008 08:33 PM
 
 
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Thunder Tiger Raptors 30-90 - Imperio > RAPTOR 90 what caused this? OS 91SZ blew a bushing!
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