Stick shake

Sv.grainne

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I helped install a new set of Rotor blades on a Tango2 yesterday. Strung them twice to be sure and then repeatedly adjusted spacing on the teeter bar (right term?). Still lots of stick shake. The rotor was test flown on another Tango2 before shipping and no reported shake.

Where would be a good place to start looking?
 

JETLAG03

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First thing I would suggest is a system or registering and recording the amplitude and frequency of the vibrations. Rotor vibrations are discussed at length elsewhere on this forum, enter Mike G in the search above.

I can recommend this programme with Iphone recommended by Mike G.

This is my iphone support, the red rings in the second photo are where I passed the cable ties to strap in the iphone ensuring no secondary vibrations from the mounting.

ipad mount 2.JPGipad mount 2a.jpg

You need to be able to record the vibrations to confirm any changes you make actually change the vibrations, personal perception is not reliable.

phil
 

JETLAG03

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Is it 2 per rev or 1 per rev or both.
Maybe the other people that tested the rotor have a different opinion on acceptable?

wolfy
That is the benefit of the programme, one can define the difference between 1st and 2nd and by frequency if the rotor or prop vibrate ... or both nd it gives a number not personal opinion. One can quantify and confirm numbers

phil
 

dbgross

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I'm in Ann Arbor Michigan and if I could hire someone to come help me resolve stick shake I would be very happy and willing to pay! I have a Sportcopter 2. I also have an issue where my plane will not hold trim once I go above about 70 knots. I think trim cylinders are leaking when stress increases but have not figured out the solution.
 

Resasi

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Great job!!!
 

Eric S

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After talking with Denis at GyroTechnic and looking at his method for adjusting blade tracking we were able to resolve the issue. Manually shimmed one side of the hub bar and at .006" shake gone.

What did you use for shims? I have heard "beer can" washers work well for small increments.
 

Sv.grainne

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Is it 2 per rev or 1 per rev or both.
Maybe the other people that tested the rotor have a different opinion on acceptable?

wolfy
Think it was 1 per rev, pretty severe cabin and stick shake. My first time training in 4 months so it was concerning, especially noticeable on banking....
 

wolfy

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I believe using stainless steel from a feeler gauge set is a no go as you have dis-similar metals and will cause corrosion.
Aluminium cans are of course aluminium but also they have a coating on them to prevent corrosion all built in.

wolfy
 

Mike G

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If tracking with shims resolved your problem then it was 1/rev, no doubt about it.

AutoGyro use stainless steel shims for tracking, I use plastic shims, they're colour coded so that later I can see what thickness is there without having to take them out and measuring them.
 

wolfy

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That's a very good idea using the plastic shims, never thought of that.
Modern plastic shim material is as strong or stronger than brass (used as a shim) obviously won't cause corrosion and comes in a huge range of thickness.

wolfy
 

Georgi

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If tracking with shims resolved your problem then it was 1/rev, no doubt about it.

AutoGyro use stainless steel shims for tracking, I use plastic shims, they're colour coded so that later I can see what thickness is there without having to take them out and measuring them.
Mike, sorry for a stupid question ( I've never needed to do it in over 20 years): where exactly do you put shims? Do you just move the bar on a J-Bolt? Can you show a picture of it?
Thanks. Georgi.
 

Sv.grainne

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Insert shim along either side of the joint between the teeter block and hub bar, fore and aft on either side along the side of the teeter tower. Pick a side, it will either get better or worse, move to the other side if you make it worse. I would go in increments of .002 at a time.

Bobby
2021-06-28_18-39-26.jpg
 
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