Helicopter › Effects of tight dampening at low head speeds

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Home › Scale › Aircraft › Helicopter › Scale Model RC Helicopters › Effects of tight dampening at low head speeds

04-28-2018 12:01 PM 3 months ago

Post 1

tgalo

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USA

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Got a weird violent shake only when spooling down on a 800 size Bell47. I was wondering if I should try softer dampers since it only at 1300 RPM. Smooth and solid except for spool down motor off. Thanks, T

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04-28-2018 01:13 PM 3 months ago

Post 2

ICUR1-2

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Ottawa, Ontario

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If it wobbles in flight at low HS then I would go with softer dampners. If it's only on spool down tighten up your blades and see if it's better.

spending time, paying attention

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04-29-2018 02:52 AM 3 months ago

Post 3

Chris Bergen

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cassopolis, MI USA

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How much negative pitch are you using? I agree with trying changing your blade tightness, but keeping you pitch near 0 or slightly below, vs a full -8 to -10 on spool down may help as well.

Chris D. Bergen

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04-29-2018 12:19 PM 3 months ago

Post 4

tgalo

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I didn't mention that it did have a aileron wobble at 1200 rpm. went away at 1300. Flew fine at that speed till I landed and the spool down shake came. I personally thought the blades were pretty tight but maybe I'll try a bit tighter. Since this was a test I only had about 1 degree of negative. I ordered some softer dampers and will retest. Thanks, T

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04-29-2018 07:24 PM 3 months ago

Post 5

dgoss999

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Why tighter??
DG.

"Believe none of what you hear, and only half of what you see." • Benjamin Franklin

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04-30-2018 01:14 AM 3 months ago

Post 6

ICUR1-2

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Ottawa, Ontario

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dgoss999
Why tighter??
DG.
if the blades were too loose, because the drivetrain would act as a braking force on spool down the blade tips would advance throwing off the balance.

spending time, paying attention

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04-30-2018 07:31 AM 3 months ago

Post 7

dgoss999

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Don't you have an auto rotation hub between your drive train and main rotor? Besides, I am not thinking the blades so loose they fold back when you power up!! If the blades are dynamically balanced as the should be, they should not shift in the blade holders other than for some lead lag movement in flight.. DG.

"Believe none of what you hear, and only half of what you see." • Benjamin Franklin

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04-30-2018 11:48 AM 3 months ago

Post 8

steph

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Hampshire England

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If one of the blades is tighter than the other it can on spool up or spool down cause this wobble you are getting

The world is round you can run but you will always end up where you started from

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05-01-2018 12:30 AM 3 months ago

Post 9

ICUR1-2

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You're right the one way should allow the head to free spin

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05-01-2018 03:15 AM 3 months ago

Post 10

Chris Bergen

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cassopolis, MI USA

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Agreed, as long as you're not pulling mass negative pitch. Which the OP has clarified he is NOT doing, so carry on!

Chris D. Bergen

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Got a weird violent shake only when spooling down on a 800 size Bell47. I was wondering if I should try softer dampers since it only at 1300 RPM. Smooth and solid except for spool down motor off. Thanks, T

Gravity's a bitch ant it?

If it wobbles in flight at low HS then I would go with softer dampners. If it's only on spool down tighten up your blades and see if it's better.

spending time, paying attention

How much negative pitch are you using? I agree with trying changing your blade tightness, but keeping you pitch near 0 or slightly below, vs a full -8 to -10 on spool down may help as well.

Chris D. Bergen

Gravity's a bitch ant it?

Why tighter??DG.

"Believe none of what you hear, and only half of what you see." • Benjamin Franklin

dgoss999Why tighter??DG.if the blades were too loose, because the drivetrain would act as a braking force on spool down the blade tips would advance throwing off the balance.

spending time, paying attention

"Believe none of what you hear, and only half of what you see." • Benjamin Franklin

If one of the blades is tighter than the other it can on spool up or spool down cause this wobble you are getting

The world is round you can run but you will always end up where you started from

You're right the one way should allow the head to free spin

spending time, paying attention

Agreed, as long as you're not pulling mass negative pitch. Which the OP has clarified he is NOT doing, so carry on!

Chris D. Bergen

Why tighter??
DG.

dgoss999
Why tighter??
DG.
if the blades were too loose, because the drivetrain would act as a braking force on spool down the blade tips would advance throwing off the balance.