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HomeAircraftHelicopterKasama Srimok 90 › Vibrations #2 UPDATE 26/1/2010
01-15-2010 08:50 PM  8 years agoPost 81
SJo1

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Finland

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I checked balance of the tail rotor as whole and w/o blades.
Measured weight of blades (Radix 105mm were differing only 0.015 gram)
Tailrotor without blades atleast was out of balance.
I fixed this by filing heavy side tailblade M3 bolt until tail was in balance.
Then I added blades to tail rotor hevier blade to lighter grip and they were out of balance, afew pushes with fine file from blade tip made them in balance. (epoxy seam residue removal)

I have now hard mounted Flybar Srimok and adjustable mounts were installed to Flybarless Srimok.

Tomorrow I will go for test flight, let see how much there is snow and - degrees in Celsius.

-Samppa

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01-16-2010 01:09 AM  8 years agoPost 82
bathmagic

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Berwick,Victoria, Australia

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Samppa

im VERY interested in your results

please post them ASAP

Dale

ENV - Still laying it down !….Ohhh yeh !!!

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01-16-2010 08:36 AM  8 years agoPost 83
hookmaker

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Copenhagen, Denmark

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Samppa, I did exactly the same to my Vibe 50 - which had a terrible tail imbalance out of the box. It worked 100%. I now check this (and do if necessary) on all my helicopters when building.

I use the blade bolts to regulate minor imbalances.

/Henrik

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01-26-2010 03:06 AM  8 years agoPost 84
bathmagic

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Berwick,Victoria, Australia

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Guys i checked the balance of my whole tail assembly and it was fine

i went for another fly today and tried out plastic tail blades, ones off an Vibe, tail blades were new and unused.

Absolutly NO difference in vibration whatsoever.

anyone else having sucess with eliminating the vibes ??

anyone tried the new engine mounts out yet ??

Dale

ENV - Still laying it down !….Ohhh yeh !!!

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01-26-2010 06:46 AM  8 years agoPost 85
SJo1

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Finland

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Hi,

I have an idea about repositioning of dog bone in another end of Torque tube.

This is already mentioned in HF or RR months ago.
To similar as MA have in Stratus.

In Kasama it's same place in both ends and MA has them positioned in around 25 degree difference.

Ofcourse there is a difference in material, MA have beefed up CF tube and KSM have Easton arrow.

I have just build MA Stratus HR kit and there is quite much similarities in drive drain.

Maybe it's worth to try it or not.

-Samppa

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01-26-2010 06:52 AM  8 years agoPost 86
bathmagic

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Berwick,Victoria, Australia

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Sam,

I am aware of this with the MA machiens and its probably worth a try.

But im just getting a little sick of trying to source this vibration..............

Dale

ENV - Still laying it down !….Ohhh yeh !!!

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01-26-2010 07:16 AM  8 years agoPost 87
SJo1

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Finland

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Dale,

I understand Your feeling.

I would like to test this too, but I don't have time for it just now

-Samppa

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03-03-2010 08:40 PM  8 years agoPost 88
independentbear

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Lichfield , Staffs, UK

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Hi All
I have been trying to solve the vibration issue for about a month - since I built the heli. I am using a YS 91 on 20% nitro with an Hatori pipe.

I have fitted the new dampers and the new starter shaft (which is a big improvement on the original).

Prior to fitting the new dampers I had vibration through the boom, tail, tail boom supports and a foaming tank. All this at 1500 head speed! I have changed both main and tail rotor blades.Increasing head speed made matters worse.

It is still the same with the new dampers. I have tried them on soft, medium and hard settings.
The machine is vibrating excessively at tickover! I also have an Align 600 with the new YS 56. No vibration issues whatsoever!

My next move is to change the fuel to 30% nitro. I have been told that the engine was designed around this level of nitro and vibration should be significantly reduced.

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03-03-2010 09:37 PM  8 years agoPost 89
hookmaker

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Copenhagen, Denmark

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1500 headspeed is way too low for a head as stiff as the Kasama head, I would expect a severe wobbling vibration from the head. Raise your head speed in 50 increments to try to solve it.

I run 30% nitro on my YS, never tried it on 20%, but my YS 50 cerainly does not like 20%.

/Henrik

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03-04-2010 12:55 AM  8 years agoPost 90
independentbear

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Lichfield , Staffs, UK

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Hi Henrik
I will do as you suggest, starting with the 30%.
Thanks
John

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03-05-2010 03:58 PM  8 years agoPost 91
independentbear

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Lichfield , Staffs, UK

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Now on 30% nitro. Rebalanced tail - to check this was ok.
Increased head speed , and at 1600 vibes decreased very significantly - hardly any. Set dampers to hard.

At 1700 it went into a severe wobble . I turned down sensitivity on the GY611 (had put it up because of tail drifting) and wobble ceased. I could see the tail servo banging back and forth!

At 1800 the wobble is back, though not so severe, but so is the tank foaming. I have stopped at this point. Any views?
I presume I should keep going to see if it goes through this stage - aiming at 1950?

John

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03-05-2010 04:33 PM  8 years agoPost 92
independentbear

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Lichfield , Staffs, UK

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Wow!
Gone to 1950. No wobble , tail steady, bit of foaming, - but what a machine - massive, incredible, awesome!

YS has huge power. Now got to iron out the small amount of foaming. May change damper settings. Might try 2000. More testing tomorrow.
John

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03-06-2010 08:07 AM  8 years agoPost 93
hookmaker

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Copenhagen, Denmark

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John, - well seems you're on the right path there. It's always hard to give 100% feedback since what you see is maybe not what I read. For instance, by wobble I think a low pitch head vibration (top of heli). By tail wag, I think tail wagging sideways, etc.

Experience here, is that most Kasama head fitted helis, have a range of HS where it will wobble inside - due to head stiffness.

Depending on how tight your tank is fitted you may have some foaming in the end, because some engine vibration (high freq) will go more mor less straight tot the fuel depending on how tight the tank is fitted. Mine still has some faming, but I don't care anymore - it flies great!

/Henrik

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HomeAircraftHelicopterKasama Srimok 90 › Vibrations #2 UPDATE 26/1/2010
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