How do I balance blades?

[jonny5]

I am trying to balance the blades on my Twister FP. Following the instructions in the manual and given to me by my local model shop I have taken the head off and am balancing it on two glasses using the flybar.

The thing is, the whole thing won't stop rocking!!!! It looks to me as though it's rocking equally about the horizontal position, but as soon as I get near it it starts moving! Can I assume that it is balanced as it is moving equally both ways?

Cheers

Jon

[Quattro]

Why are you removing the head to balance the blades?

[jonny5]

That's what it says in the manual and what the guy in the shop said to do.

Here's what the manual says:

"If vibration of tail boom or undercarriage is noticeable, the most likely problem will be out of balance main blades. To cure this, balance the blades as follows: Remove the metal pin retaining the complete rotor head onto the main shaft. Turn the head upside down and support it on 2 glass tumblers or similar. Observe which blad falls lowest and add tape to the undersurface tip area of the higher blade. Adjust until the blades are level and re-attach rotor head."

Is that the wrong way to do it?

[G-DAVE]

No -- by doing so your balancing the complete head and blades-
Dave

you need to get a blade balancer or a set of scales like the ones for weighing grammes,you can usually find these at markets and boot sales where the stall holder sell bongs and rizlas,im sure you know the ones i mean. and add tape to the lighter one on the two blades,i have also had a twister fp and sometimes the blades go out of track after a collision,so all you do is hold the blade and twist it a bit to bend it back into shape,add a bit of tape to one blade and get the rotors turning while holding the heli and determine which blade you need to twist(its not called a twister for nothing lol )

[jonny5]

Surely just making sure the blades weigh the same does not mean they are properly set, the C of G must be at an equal radius to ensure the centrifugal force is the same?

you have to bend them back to shape not just add tape,so if you are trying to balance the complete head how do you honestly expect to get every push rod weighing the same and things like the swash plate ,surely the swash plate will be a little heavier on one side, but personally i think the shop has told you a bucket of pooh,just try the blades by twisting them back into shape.

[G-DAVE]

Surely just making sure the blades weigh the same does not mean they are properly set, the C of G must be at an equal radius to ensure the centrifugal force is the same?

Correct !!
The length wise c of g is vital but not so critical if you get it within 2 mm that will be ok
So if there is weight to be added to achieve balance it must be added on the c of g.
Dave

[Jamez]

Fixed Pitch.

I believe the best way to balance the fixed pitch blades on these little blighters is to pop of the 2 links that join the blade carrier to the see saw (with the fly bar running through it) and remove the blade carrier completely from the Hub (it should just pop of the 2 bearings) Then balance this bit with the blades still attached across you 2 glass (or what ever provided they are at equal hieght!!) on the 2 balls sticking out of the blade carrier, make sure your blades are straight and inline. Then you add your tape a bit at a time until they hang straight and level (after they have stopped rocking!!). Be careful not to distort the blade when you apply the tape. After this is done pop the head and links back on and spin the blades up to see if they track correctly, if the do not, locate the lowest blade and twist it slightly towards the trailing edge from the tip whilst holding the root where it is bolted on so you don't twist the head then re check and repeat if necessary. Thats the way I have always done it and mine flys a treat.

[Sao]

Of course you can also dynamically balance the blaes and head by adding a bit of tape to the c of g of one blade and observe if the vibrations get better or worse, if better ttry adding a bit more tape to that blade, if it made it worse swap tape to the other blade and repeat till happy.

[daveoftheclub]

thats how i do it

[kingchopper]

once youve spent almost £100 on koll blade balancer, the best and only one i use now.

what i do is find the chord wise balance first and add lead weight to the trayling egde of the light blade on the underside as close to the bolt hole as possible. i fix the correct amout of lead with expoy and allow to cure.

next i find the spanwise balance and transfer the centre of gravity of the heaviest blade to the light blade and i just use tape and apply this to the light blade until it has the same centre of gravity of the heavy blade.

both blades now have the same c of g , but are now difference weights so i put tape around the C of G of the light blade to bring it all back into balance.

the hole job takes about two hours.