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Esprit Model . Thunder Power RC . Mikado Modellhubschrauber

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CAD - Engineering - Technical > Dampening for flapping heads
 
 
soupisgoodfood
Senior Heliman
Location: New Zealand

Hi. I'm designing a small, 3-blade flapping head for a scale project. I've seen a couple of flapping heads on 50 size RC helis, and they feel as if they have little or no dampening compared to a teeter.

How much, if any, dampening is needed? How will the level of dampening affect the flight characterisics? Are their any good threads on desiging flapping heads for small RC helis (yes, I have searched). Anything else I should know?

Thanks.
06-02-2006 Over year old.
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ziptone
Heliman
Location: Arlington,Texas

Dampening is Spring Force

Be advised R/C helo "dampening" is spring force, not true dampening. The "dampening" o-rings affect the amount of body roll and pitch response to cyclic input. More spring for 3D, less for scale flight. Most multi-blade R/C helos use a gimbaled rotor head. On full scale birds it is the lead/lag hinge that is heavily damped. On the flapping axis the blade's centripetal force should help to "tame" the amount of flapping, however some spring force is probably a good idea.

The simplest way I have seen to implement flapping is using a spring steel plate to connect the blades to the hub. This puts a lot of fatigue on the metal, so be very careful. A safer way is to just use hinges with some kind of rubber force "dampeners". Be aware that any ACTUAL dampening applied to the flapping axis from blade mass or hydraulics or any other source will change the phasing angle (delay of cyclic control from swash plate to rotor disk) from the ninety degrees assumed.

The offset between the flapping hinge and the rotor head will also provide "dampening force". Search for "Colin Mill w3mh" for some articles on "practical theories".

ziptone
09-09-2006 Over year old.
 
 
busted blade
Senior Heliman
Location: orlando,florida

when the blade hits the boom that too much. or this-http://www.helihobby.com/videos/InflightRefueling.mpg

bling bling, cha ching......... but honey
10-11-2006 Over year old.
 
 
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GrandRC . CanoMod . Futaba-RC

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CAD - Engineering - Technical > Dampening for flapping heads
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