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martinlaw

Too much control surface slop

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martinlaw

Hi

need some advice please, I am trying to reduce/eliminate the slop in the aileron and flaps on my Crossfire as I am getting a small amount of flutter at very high speeds.

There is some play in the gear train of the servos so I am replacing those which is easy enough but I have also noticed play in the fiberglass control horns.

these are heavy duty rds horns which will be very difficult to replace, the play is originating from the hole the clevis attaches to being too big due to wear and tear.

i have tried superglue to fill the gap which works well for a short time but the slop soon returns.

i have tried to source some clevis's with oversized pins, to no avail.

I would be very grateful for any other thoughts?

Martin.

 

 

 

 

 

 

 

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satinet

What are RDS horns? 

RDS has pockets.

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martinlaw

Perhaps they are lds?

they are located under the wipers so nothing is visible on the outside

 

martin

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satinet

Lds doesn't have clevises really. Not the metal ones you would use on a normal linkage.

 

It sounds like its just a linkage done under the skin. That's very hard to achieve without slop. LDS is a super tight normal linkage, in effect, designed to counter this problem. However it puts more strain on the servos.

 

 

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satinet

Photo?

 

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martinlaw

I am on holiday at the moment, will post some when I get back

martin

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pete beadle

Hi Martin

Can you undo the pushrods in order to access the worn PCB ends? I f you can I'd cyano one small washer shaped circular piece of PCB each side of the worn PCB horn, each circular piece drilled to be a tight fit on the clevis pin.

Locate and centre one of them in place with a pin through the centre of the hole, cyano it when centred, then push the pin through to centre the second circular piece and cyano that one in place.......works for me but I prefer to remove the horns from the airframe and work on them outside the wing, clamped in a vice or similar.......but you should end up with strong and tight horns

Good luck

Pete

BARCS1702

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martinlaw

Thanks for the advice Pete.

yes, the pushrods can be removed but not the horns without ruining the aileron or flap.

unfortunately the clevis's only just fit over the horns now due to their thickness so I am not able to add anything extra.

i suppose I could make new pushrods with thicker wire and just use a 90 degree bend but the problem is how to drill the hole in the horn larger as it is under the wiper and only 6 or 7mm of it is visible?

I am still enjoying the Race M I bought from you last year!

Martin

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pete beadle

Hi Martin

Glad you're still enjoying the RaceM, I thought your name rang a bell, but I'm just not trusting my long term memory at all these days, so,  I am now almost "mouldie free" after my selloff of the bulk of my "'spensive stuff" earlier this year.......still got two of my dear old Europhias though, so the withdrawal symptoms aren't appearing just yet......:)

The only other thing I could suggest is to try pieces of hollow tube, brass, carbon, glass or the like with an ID to suit your clevis pin OD.....drill out the horn centres to fit the tube OD's, then grind down the (probably) brass tubes so they're flush to the thickness of the horn.......not the perfect answer, I know, but doable yes?

I'm sure you've seen bellcranks fitted with brass bushes, to reduce wear, that use the same principle(?)

Best of luck

Pete

BARCS 1702

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satinet

Ultimately you probably want to replace the horns with ones that are longer. I.e stick above the wing skin.

You'll never get a really good linkage under the skin without some sort of lds system - servos frames, fixed pushrods etc.

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isoaritfirst

It's not that difficult to remove horns and replace them. 

If you have a dremel and a fine point router type bit. 

It doesn't matter if you catch the surface a little as this will be filled when you pit in the new horns. 

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isoaritfirst

Well worth dremel if out those horns and replacing with longer ones. 

longer horns not only give you fine control of the surface but also reduce the pressure on the clevises pins. 

Ptessure on the pins of course means fast wear and slop developing quickly. 

Short horns means poor positioning of control surfaces. (Less efficiency. More drag)

horns inside the wing skin gives cleaner more efficient wing. But of course all that benefit is quickly lost if you don't have control. 

Dig them out and make them longer. 

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isoaritfirst

Or fit a lds system  but again insure that all horns are positioned as heigh as possible   

See baudis installs where he removes a little of the to skin  

fit smallest possible horns on servo if using lds

 

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