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Vario Bell 230 trying to blow apart...

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Vario Bell 230 trying to blow apart...

Old 06-06-2007, 12:40 PM
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jetnuno
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Default Vario Bell 230 trying to blow apart...

Hi

I have a Bell 230 helicopter with a Sky Fox mechanics and a Rossi .67 engine. Herewith you will find a photo. .

Nevertheless, I am writing this because I am quite desperate with a reincident issue that as broken my heli twice, and that I try to decribe:

1- My heli is built-up exclusively with Vario recomended equipment, mechanics, blades, pilots, etc., etc.

2-I have finished my heli in October 2006 and after tunning tracking and running in the engine, I was trying to match thrtle and pitch curves when suddenly, the heli starts to shake so much that destroyed the upper covers and broke the tail. I guess this was due to over revving in the main rotor, so after I rebuild the heli, with an incredible hand work and patience effort, I have decided that I had to change something.

3- After the rebuild I installed a Futaba governor to maitain revolutions in the 1150rpm range. I also reinforce the fuselage structure with plywood. Made several flights and then set it at 1170rpm. I am using ord.423 - 1780 mm main blades that you recommend a 1270 rpm maximun.

4-Last sunday I was flying and at about 4 m height, the model started to shake in the same manner as it did previously the governor installation, and it is broke again.

I do not know what to do anymore, so I ask for help regarding this issue. What could have been the cause? I have been thinking and can not find an explanation. Perhaps the fuselage is too big to the mechanics? Perhaps the blades need to be tightened strongly? The blades are a bit broken, so I will replace these. Do you find another ones to be a better choice?
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Old 06-06-2007, 02:11 PM
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jez33
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Default RE: Vario Bell 230 trying to blow apart...

hi mate.
i have vario scale helis and have had a similar problem in the past too. the heli was/is an airwolf from vario.
im assuming you have enough knowledge to have set the heli and tracking/ballancing ect properly so ill skip the obvious.


in my case at least i can say the problem was the tuned pipe vibrating inside the fuselage..it took me a few flights to find this out. meaning i would try it then the problem would show its self and i would take it home ,work on it then fly it then take it home to try another alteration, then i knowticed the exhaust pipe could wobble at the end if i pushed it even though it was already quite stiff becuase of the nylon manerfold joiner which holds it already .when though i made the exhaust even more secure i haven't had this problem.

so to cure this problem i secured the end of the exhaust pipe so that it could not wobble. without the pipe secured it would fly fine until i descended the heli reasonably fast and this would make the heli to vibrate so bad that it really looked like it would blowup or shake itself violently to pieces.it was very scary.

Old 06-06-2007, 02:23 PM
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heli_Rod
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Default RE: Vario Bell 230 trying to blow apart...

Both of my scale helis vibrate and shake if the head speed is operated in certain ranges. They have a resonate frequency that enhances the shaking and vibration and can get quite extreme if left unchecked. You might try running the head speed faster or slower to see if there is any improvements. Just a thought.

Rod
Old 06-07-2007, 06:30 AM
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jetnuno
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Default RE: Vario Bell 230 trying to blow apart...

Hi

Thanks. I assume this is a problem related to head speed rotation. That is why I have installed a governator. Manufacturer states that maximun head speed is 1270rpm. I was running at 1170 rpm. The muffler is well fixed and if it was not it the muffler vibration it self would not had enough power to shake the heli that way. I think that as something to do with tightening torque of the blades and rotation itself, because if you do nor ight it enough and headspeed not proper the blade will come back and unballance head rotor. Nevertheless I am not sure about that and worse I do´not have a solution

Regards
Old 06-07-2007, 05:19 PM
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jez33
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Default RE: Vario Bell 230 trying to blow apart...


ORIGINAL: jetnuno

The muffler is well fixed and if it was not it the muffler vibration it self would not had enough power to shake the heli that way
hi again,

if your muffler is secure then it must be something else ofcause,
but if its not secure at the end then dont discount the muffler it realy can shake i very violently. if your mulfer hasnt got something on or near the end of the pipe then what i think was happening in my case was the nylon would get hot and soften up, plus the engine exhaust pulses and resonance from the main blades ect would make the pipe on my heli vibrate very violently and this made the body of the heli vibrate very violently too.it was very scary, it looked like it would blow up... ouch,,lol

i could some times fly for a few minutes without any problem ( no vibration) but once it started to shake violently there wasn't any thing i could do to stop it except land. once i found out the muffler could be the cause and repaired it i havent had the problem since..it was aprox a year ago and i have flown it many hours since ..

sadly i cannt tell you for sure that the problem you have is the same as mine . if it was in front of me im sure i could diagnose the problem with your heli within a short time..

im afraid i didnt understand your comments about the blades. make sure obviously both blades are balanced ( even if they are carbon blades still double check ) make sure the blades are the same tightness, ( my blades are fairly tight but not over stiff.. i would also check if the paddles are balanced on the heli( dont take them off but ballance them on the rotor head ).

also perhaps keep an eye on the engine. you might get some vibrations from the clutch and also make sure your engine isnt running week or to rich as sometimes in exstrem cases this can cause vibration but i doubt it would cause such a violent shaking that you are having on your heli..

what blades are you flying with ????
Old 06-08-2007, 06:31 AM
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heli_Rod
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Default RE: Vario Bell 230 trying to blow apart...

It's difficult to diagnose problems without seeing them. I think at this point, I would remove the complete rotor head and main shaft assembly and check the static balance of the entire assembly as one piece. That would eliminate any possibility that it could be a balance problem. Check the dimensions between rotor head parts to be sure that everything is assembled correctly.

You haven't mentioned what blades and paddles you are using. Are they rigid? It could be possible that one may have internal damage and is flexing at speed, causing flutter. Try twisting the blades by hand to see if they are rigid and there are no de-laminations occuring.

Also check the tail rotor balance as an assembly. The drive line could cause a vibration if the clutch and flywheel aren't lined up correctly, but I've never seen one cause that much vibration.

That's just some thoughts that you might look at. I hope it helps. Keep us posted.

Rod

Old 06-08-2007, 05:53 PM
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jetnuno
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Default RE: Vario Bell 230 trying to blow apart...


ORIGINAL: jez33


ORIGINAL: jetnuno

The muffler is well fixed and if it was not it the muffler vibration it self would not had enough power to shake the heli that way
hi again,

if your muffler is secure then it must be something else ofcause,
but if its not secure at the end then dont discount the muffler it realy can shake i very violently. if your mulfer hasnt got something on or near the end of the pipe then what i think was happening in my case was the nylon would get hot and soften up, plus the engine exhaust pulses and resonance from the main blades ect would make the pipe on my heli vibrate very violently and this made the body of the heli vibrate very violently too.it was very scary, it looked like it would blow up... ouch,,lol

i could some times fly for a few minutes without any problem ( no vibration) but once it started to shake violently there wasn't any thing i could do to stop it except land. once i found out the muffler could be the cause and repaired it i havent had the problem since..it was aprox a year ago and i have flown it many hours since ..

sadly i cannt tell you for sure that the problem you have is the same as mine . if it was in front of me im sure i could diagnose the problem with your heli within a short time..

im afraid i didnt understand your comments about the blades. make sure obviously both blades are balanced ( even if they are carbon blades still double check ) make sure the blades are the same tightness, ( my blades are fairly tight but not over stiff.. i would also check if the paddles are balanced on the heli( dont take them off but ballance them on the rotor head ).

also perhaps keep an eye on the engine. you might get some vibrations from the clutch and also make sure your engine isnt running week or to rich as sometimes in exstrem cases this can cause vibration but i doubt it would cause such a violent shaking that you are having on your heli..

what blades are you flying with ????
Hi

As stated in the first quotes iam using vario ord.423 fiberglass blades for a total rotor diameter of 1780mm. The blades are very stiff and have a leading edge with lead inside. These are well balanced both as a rotor and cg of each one. The muffler is supported in 2 points (at the end and at arround 3/4 of the end)beside the teflon tube itself. My guess and agin to try to explain myself in a better way, is that i think i did not tighten the blades strong enough, at least as i used to, and coincidence or not, this horrible shaking happened. When you have a constant speed head rotor there is no problem but with a slight variation in rotor speed, aceleration or deceleration, one of the blades might come back turning some degrees in its pivot and causing a terrible unbalance in rotor head causing the rattle and shake down
Old 06-10-2007, 01:36 PM
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jez33
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Default RE: Vario Bell 230 trying to blow apart...

i cannt think of any thing extra then what heli rod has said already..

sorry if it sounded like i was repeating my self earlier , i wasnt sure if both of us had unerstood each other corectly..lol
Old 07-19-2007, 03:59 AM
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Default RE: Vario Bell 230 trying to blow apart...

Regardless of problems, that heli is just stunning.

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