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HelicopterHIROBOOther › Vibration and smoke
11-27-2007 12:51 AM  9 years agoPost 1
wild1957

rrApprentice

Malaysia

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I own the Hirobo Freya with OS 90 engine, I use this for AP recently I found I had some vibration whilst shooting video so I decided to try to isolate this.

So far I stripped down the whole heli to just the frame, engine and fan. My direction will be to look at each item individually to try to solve the imbalance. Last night I started the engine in the frame with only the fan attached and straight away vibration can be felt it is not smooth. Although it is not shaking around the vibration is very fine but very high frequency that after a while it makes your hand feel numb. Is this normal? Should I be able to run the engine alone with fan and not feel anything?

I am replacing the main shaft and the tail rotor shaft and then checking the balance before fitting back into the frame. I will also recheck the cg and weight of the main blades before reassembly.

Is there anything else I should look at to try to solve this vibration whilst the m/c is in pieces?

On another note my heli seems to be kicking out huge clouds of smoke much much more than my EVO 50 no matter what I do to the mixture settings. The fuel is Cool power 30% heli fuel. How can I reduce this? I am aware I need to have some smoke but as you can see from the pics this is quite a lot. Have you any suggestions? Will a new engine solve this problem?

Stephen

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11-27-2007 02:41 AM  9 years agoPost 2
rhazbun

rrApprentice

Miami, FL

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To reduce the smoke, you can use the coolpower heli 30% LS. (Low smoke) It works great with a lot less smoke.

Try checking the runout on the fan and clutch. If the tail is not moving up and down or side to side and the fuel in the tank is not foaming, this is most likely your source of the high freq vibes.

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11-27-2007 06:42 PM  9 years agoPost 3
Dr.Ben

rrMaster

Richmond, VA, USA

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Which OS "90"? What cylinder head?

The vibration from an engine at or around idle is not a reliable indicator of its smoothness at normally flying rpm. Indeed, it is virtually impossible to make a single cylinder engine run equally smooth at all rpms. Dynamic balancing is an art, and I can tell you for a fact that one of the ways that OS R&D's their engines for smoothness is with plain old flight testing and watching sensitive indicators such as the fuel in the tank with the engine at flying rpm. That set up which ought to be smooth on paper may be a different animal in the air. But I digress...

My Evo resonates a fair amount at idle, but immediately settles into a smooth drones upon acceleration.

If you want to exhaustive about your process, you need to balance your rotor head alone with grips both horizontal and vertical, do the same for the t/r, CG correct and mass match both the main and tail blades, double check the flybar and paddle balance, and balance the engine fan and dial it on the engine to under 1/2 thou. Then dial the clutch to the same spec.

If the engine in this model is an OS SZ, do not expect the model to be glass smooth. The SZ simply is not as smooth an engine as the C-Spec, YS ST, or YS SR.

Ben Minor

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