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Elevator Control Friction

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countzero

Joined: 25 Oct 2007
Posts: 25

Posted: Tue Nov 20, 2007 5:39 am Post subject: Elevator Control Friction

UK built XLs have a mandatory modification to replace the existing fairlead on the fuselage frame with a pulley wheel mounted on fabricated brackets to reduce the friction in the elevator control circuit. 



Just a question for UK builders; can anyone tell me the thickness of the sheet I should use or you used for the brackets?



Rob

Martin Pohl

Joined: 30 Jan 2006
Posts: 118
Location: CH-8645 Jona SG, Switzerland

Posted: Tue Nov 20, 2007 1:33 pm Post subject: Re: Elevator Control Friction

Rob: I am also interested in the sheet-thickness of the bracket. For the ones who don't know the link to the modification, here it is:



http://www.pfa.org.uk/Standard%20Mods/162_SM10366.pdf



Cheers Martin

_________________
Martin Pohl
Zodiac XL QBK
8645 Jona, Switzerland
http://www.pohltec.ch/ZodiacXL/Main.html

malcolmhunt(at)mha1.fsbus
Guest

Posted: Wed Nov 21, 2007 4:11 am Post subject: Elevator Control Friction

Rob



I asked the question of PFA Engineering and they said they would endeavour 

to find out from the mod application (that was about six months ago) but 

they did say that they thought .063" would be ok!  I have made mine out of 

this material but used a  .125" bend radius, which worked for me.



I think the mod is a standard mod, not mandatory or have you found out 

otherwise?



If I can find the PFA e-mail to me I will send it direct to you.



Kind regards



Malcolm Hunt

CH601XL plans builder in England

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david_a_g_johnson(at)btin
Guest

Posted: Wed Nov 21, 2007 5:14 am Post subject: Elevator Control Friction

This is a 'standard mod' - not a mandatory one.



Details can be found on the PFA website at 

http://www.pfa.org.uk/Standard%20Mods/162_SM10366.pdf



Dave Johnson

 do not archive



---

countzero

Joined: 25 Oct 2007
Posts: 25

Posted: Wed Nov 21, 2007 5:32 am Post subject: Re: Elevator Control Friction

You are correct it is not mandatory. The TAD has a special inspection point noted about 'Elimination of undue friction in elevator controls' I don't think there's another way to do it.



Rob

swater6

Joined: 16 Dec 2006
Posts: 52
Location: Minnesota-KMIC/KANE

Posted: Wed Nov 21, 2007 7:28 am Post subject: Re: Elevator Control Friction

Gentlemen,

This mod is to replace the fairlead on the HT frame for the lower elevator cable.  Is there a mod for the larger fairlead  that is connected to the bottom of one of the bulkheads for the top cable?  

I'm building in the US but not really comfortable with two plastic fairleads here. 



Anyone else replaced fairleads with pulleys that would like to share?

Thanks

_________________
601 XL kit N596SW reserved
Tail, control surfaces and both wings complete. Now working on fuselage

www.scottwaters.com

s.c.richards(at)homecall.
Guest

Posted: Wed Nov 21, 2007 8:56 am Post subject: Elevator Control Friction

Will check Rays 601HD when at airfield Friday the Sketch he used  of  Mod no 

10366  is stronger than the current PFA Drawing it shows 11/2 inch x 11/2 

inch x 1/8th inch  & the length is 6 inches pulley 2 inch OD it is installed 

where control cable angle changes as cable will saw through a plastic 

fairlead in UK, not it seems in US .

         The PFA could not find their mod at time of rays inspection.

G CBDG 179 Hrs



Clive

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dave.thompson(at)verizon.
Guest

Posted: Thu Nov 22, 2007 3:45 pm Post subject: Elevator Control Friction

Looking for outlook and opinions…  

   

For the last year or so as I pour over my 601ZL plans, I have wondered about the nylon fairleads and control cables “bending” and rubbing through them. I’m by no means any kind of engineer. In fact, I’m not even building yet. However, it seems to me that a better way would be to use a pulley to “bend” or re-route the cables to the required positions. Any other airframe plans that I’ve studied uses pulleys rather than nylon fairleads.  

   

Guys that have some hours on their airframe:   

   

Do you see any notable wear on the nylon fairleads? Specifically, the rudder fairlead and upper elevator fairlead attached to 6B5-2 on page 6-B-23 of the plans.  

   

I have not seen the actual cables installed in an airframe so I might be looking for troubles that are not there. The link to the pulley modification on previous links looks interesting and is something like I had envisioned. Would pulleys be overkill? Am I trying to re-invent a wheel that rolls just fine?  

   

What are your opinions?  

   

Dave Thompson  

Corvair engine in parts & rudder workshop  

No money to build…Yet  

        [quote][b]

davgray(at)sbcglobal.net
Guest

Posted: Thu Nov 22, 2007 4:55 pm Post subject: Elevator Control Friction

Dave 

  

 My fairleads are very close to being in the line of  travel for the cables and I am not seeing wear.  The highest point of  friction in the control system that I experienced was at the lower nose wheel  bearing block.  Initially it had a clamping pressure that  interfered with the rudder action since the nose wheel steering  is connected to the rudder pedals.  I found that a thin shim of 0.025  between the left and right halves was needed to free up the motion.  I  can still feel it while in the air but it is not very irritating because once  centered the 601XL does not require much attention to the rudder to keep the  ball centered during normal flight.  I expect with time I will get the  extra 1/1000 inch as wear and it will then be a non issue. 

  I would suggest everybody elevate the nose  wheel and try the rudder pedal action before flight.

  

 Gary Ray 601XL  58 hours TT

  

  

 [quote]   ---

tigerrick(at)mindspring.c
Guest

Posted: Thu Nov 22, 2007 6:40 pm Post subject: Elevator Control Friction

Hi, Dave!  I, too, had my initial misgivings about the stone-simple method of routing control cables through nylon blocks, but it's turned out to be a brilliantly simple way of doing things.  Unlike Dr. Ray, I haven't had any binding issues at all with the rudder.



My airplane now has roughly 95 hours on it since it was completed, and the controls feel pretty much the same as they did during those first flights just over a year ago.



After owning quite a few airplanes with much more complex control systems, it's actually a bit of a relief to fly around in something so straightforward and basic as the 601XL with the Corvair engine.



My advice? Find something better to worry about.  



Rick Lindstrom

N42KP



--

planejim(at)bellsouth.net
Guest

Posted: Fri Nov 23, 2007 5:16 am Post subject: Elevator Control Friction

Dave & Listers,

  

 Traditionally fairleads may change the direction  of cable travel no more than 3 degrees. All cables and/or the fairleads will  eventually wear! There are many manufactured, certificated airplanes that use  fairleads with the original cables lasting many years. Look at the Piper J-3.   Pulleys will almost always be the best solution, but usually more  comlicated and more expensive!

  

 All that being said, my 601HD ( which may have  slightly different cable routing than either the 701, 801 or the 601XL ) now has  565 hours with no noticable wear yet! I used only fairleads, no  pulleys.

  

 My Midget Mustang I of many years ago called for  the elevator cable to go around a small pulley on the firewall and then pass  under the main spar center section and ( saw ) on a micarta fairlead on it's  path back to the elevator. I didn't like that then so I designed a "pushrod" to  go to just aft of the cockpit where it connected to a bellcrank ( again my  design ) and then a straight run of cables to the elevator. This worked  fine for hundreds of hours. Of course the Dave Long designed MM I was designed  as a racer with limited life not as a normal everyday use airplane.

  

 The nice thing about "Experimental" airplanes (  at least in the U.S. ) is that you can do pretty much what you want. Someone  recently mentioned using pushrods for the ailerons on a 601XL. My main concern  there would be vertical and horizontal vibration movement of the pushrods near  midspan. Someone stated that they would be about 8 feet long. Many other  airplanes have used pushrod of that length or longer with no major problems. The  pushrod material, diameter and stiffness must be calculated so that it meets all  requirements. If in doubt, you might want to seek the help of an engineer, or  some experienced person. Most homebuilders do tend to "overkill" the situation.  Be carefull!

  

 Do not archive.

  

  

 JIm Hoak - 601HD - Rotax 912UL - 565  hours

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