Matronics Email Lists :: View topic - Aircraft Control Cable (to stretch or not)

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Aircraft Control Cable (to stretch or not)

Matronics Email Lists Forum Index -> Zenith-List

View previous topic :: View next topic

Author Message

Ron Lendon

Joined: 10 Jan 2006
Posts: 685
Location: Clinton Twp., MI

Posted: Sat Nov 29, 2008 2:44 pm Post subject: Aircraft Control Cable (to stretch or not)

FYI



Today I called my mentor and asked about stretch in the cables.  After much listening I came away with the realization that I won't be conducting a pre-stretch because that has already happened in the manufacturing process.



He did however maintain that checking the tension periodically is necessary.  The major factors effecting the tension are temperature variation from the last check and wear of the fair leads/pulleys.



Comparing the expansion coefficients of both:



Aluminum  	12.3

Steel                 7.3



You can see Aluminum expands and contracts 5 times that of Steel.  So if you tension your cables on an 80 degree day you can bet they will need it again on a 0 degree day in the winter.  Just some thoughts.



I checked the cable I got from ACS and it is  MIL-DTL-83420 with a red and gold filament.

 	  Quote: 	
		  There are two easy identification methods that may help you identify aircraft control cable:



(1) All MIL-DTL-83420 contains a two-color tracer filament embeded within the cable that identifies the manufacturer,

(2) All MIL-DTL-83420 cable sold on a shipping real must contain the identification number of the manufacturing reel. (All MIL-DTL-83420 cable is lubricated with a corrosion inhibiter.)

	




So Gig, Don't wait for me to set up a test.  Keep building.

_________________
Ron Lendon
WW Corvair with Roy's Garage 5th bearing
CH 601 XLB
N601LT - Flying
http://www.mykitlog.com/rlendon
Corvair Engine Prints:
https://sites.google.com/site/corvairenginedata/

JohnDRead(at)aol.com
Guest

Posted: Sat Nov 29, 2008 6:25 pm Post subject: Aircraft Control Cable (to stretch or not)

Hi, You are not wrong but you did not include the fact that aluminum  expands approximately three time the amount that steel does for the same  temperature rise. So what will happen is that increases in temp will increase  the tension in a cable not decrease it.

  

 John  Read



Phone: 303-648-3261

Fax: 303-648-3262

Cell: 719-494-4567   

  In a message dated 11/29/2008 5:11:54 P.M. Mountain Standard Time,  chicago2paris(at)msn.com writes:

  	  Quote: 	
		  -->    Zenith-List message posted by: "Sabrina"    <chicago2paris(at)msn.com>



Correct me if I am wrongâ€¦



10â€™    of Galvanized Steel Cable will expand 4/64" during a rise of 80F.



10â€™    of Stainless Steel Cable will expand 6/64" during a rise of 80F



10â€™    of 6061 T6 will expand  10/64â€ during a rise of 80F.



Mil Spec SS    has lubricant too.   MIL-C-18375 can have red and gold filaments    too.



I loose 700 (240 for 83420) pounds of ultimate strength but my    tensions donâ€™t vary as much and the SS cables running past the Dynon compass    in the tail are not going to be magnetized, even though a moving cable does    create some current.





Read this topic online    here:



http://forums.matronics.com/viewtopic.php?p=216921#216921



	






Finally, one site has it all: your friends, your email, your favorty&ncid=emlcntaolcom00000006">Try The NEW AOL.com.

  [quote][b]

Ron Lendon

Joined: 10 Jan 2006
Posts: 685
Location: Clinton Twp., MI

Posted: Sat Nov 29, 2008 6:34 pm Post subject: Re: Aircraft Control Cable (to stretch or not)

Sabrina,



I seriously doubt that you are wrong.  The two color filament is the manufactures designation.  Guess they make stainless cable also.  



The point about the variance relates to the aluminum body of the aircraft and the steel composition of the cables.  The fuselage could shrink 0.1565" but the cable would shrink only 0.0625" over the 10' you state. 



0.0937 slop would be introduced in the hot to cold example. The reverse would be true if the temperatures are reversed cold to hot.  That would not be a very good thing because the cables are very strong and as the aluminum grows it could tension the cables above spec or perhaps damage the airframe.

Brady

Joined: 26 May 2008
Posts: 182
Location: Poulsbo, WA

Posted: Sun Nov 30, 2008 3:05 am Post subject: Re: Aircraft Control Cable (to stretch or not)

Sabrina,



The Length differences in your turnbuckle question is called the lead and will depend on the thread type & pitch. If you had a Machinery Hand book you could look up the thread pitch & lead for any thread type.



For example: 

A 1/4 x 24 thread has the pitch of about 0.04167"

1" divided by 24 = 0.041666667" (rounded to 0.04167")

so for every complete revolution the mating pieces would move one pitch (lead).

On a turn buckle this is doubled so the lead would be 0.08334"

There are 3 classes of threads and the tolerances are different for each class. so there will be some variance depending on the manufacturer and class. 



Lead = Pitch x Starts (starts is the number of threads (single, double,etc.))



So imagine we had a turnbuckle that was 5/16 x 32 and was a double thread?



what is the lead now?

_________________
Brady McCormick
Poulsbo, WA
www.magnificentmachine.com

jaybannist(at)cs.com
Guest

Posted: Sun Nov 30, 2008 7:02 am Post subject: Aircraft Control Cable (to stretch or not)

Sabrina,

 

 For an AN155-22 turnbuckle with AN161-22 fork end, the threads are 1/4" - 28.  Therefore the take-up per 360 deg turn would be 0.071428" or about 5/64".  For 180 deg, it would be half that. So to get your 4/64" and 6/64", you would turn the turnbuckle barrel about a quarter turn each way.

 

 Jay in Dallas

 

   

 

   

 

 --

Brady

Joined: 26 May 2008
Posts: 182
Location: Poulsbo, WA

Posted: Sun Nov 30, 2008 8:19 am Post subject: Re: Aircraft Control Cable (to stretch or not)

Jay,



I think you may have misunderstood her question. 

I looked to me as though she was asking what the adjustments would net in tension.



For example:

If you started with a cable tensioned to 30lbs then tightened it 4-6/64Th's what would the tension be? (31lbs?)



My guess is that it would be insignificant.

The aileron spec is 30lbs +/- 5lbs.

I doubt you would see a difference of 1 pound either way.

I could be wrong, it's happened before 



Sabrina,



there is a formula for that but I haven't found it yet.

Still looking 



I am sure the tension to turnbuckle lead is not linear.

The cable will continue to stretch until you reach the yield strength and so the ratio is a "parabolic" curve. (if I'm using that right?)

The Curve will depend on material, diameter and class (construction; IE 6x19, 6x25, 6x32 etc.) of the wire rope.

also the length of the cable will have a lot to do with it.

The stretch is a percentage so a shorter cable will stretch less total distance than a longer one will.



If you decide to take on that experiment and take it to cable failure, be very careful!

I have seen cables break before and they store an amazing amount of energy!

_________________
Brady McCormick
Poulsbo, WA
www.magnificentmachine.com

jaybannist(at)cs.com
Guest

Posted: Sun Nov 30, 2008 8:46 am Post subject: Aircraft Control Cable (to stretch or not)

Brady,

 

 No, I didn't misunderstand her main question.  I just didn't know the answer to it. (:>) 

 

 What I answered was her secondary question about take-up measurements when turning the turnbuckle.

 

 Jay in Dallas

 

   

 

   

 

 --

Brady

Joined: 26 May 2008
Posts: 182
Location: Poulsbo, WA

Posted: Sun Nov 30, 2008 9:34 am Post subject: Re: Aircraft Control Cable (to stretch or not)

Oh, gotcha,

_________________
Brady McCormick
Poulsbo, WA
www.magnificentmachine.com

psm(at)att.net
Guest

Posted: Sun Nov 30, 2008 10:02 am Post subject: Aircraft Control Cable (to stretch or not)

Hi Sabrina,



I am not willing to play the game your way, but I can supply a 

slightly different point of view that might be helpful.



The question I can answer, sort of, is how much cable tension can you 

generate by turning the turnbuckle by hand.  The answer is something 

around 25 pounds of tension.  You can get this through a long 

tortuous set of calculations on the cable and thread along with the 

diameter of the turnbuckle barrel, or you can measure the tension 

achieved by hand after the new tensiometer arrives from Aircraft 

Spruce.  Guess which method I used . . .



Paul

XL getting close

At 09:34 AM 11/30/2008, you wrote:

 	  Quote: 	
		  Thanks guys--your explanation seems so obvious, sorry I missed it, 

it must be all the turkey (tryptophan.)



So it is Ron's turn  )



It seems my guess as to tension change is too great.



Any others willing to post before Ron does his experiment?



The winner gets a Christmas card containing an invite to the launch 

of N5887Q in June of 2018 (fall back dates 2020 & 2035.)



Ron gets an invite for just doing the experiment.

psm(at)att.net
Guest

Posted: Sun Nov 30, 2008 11:01 am Post subject: Aircraft Control Cable (to stretch or not)

Hi Sabrina,



I'm really not sure.  I hooked up the elevator and rudder cables and 

safety wired them before getting the tensiometer.  I intend to take 

them all apart and redo the tension to the new specs some day.



As I recall the process, the tension really didn't build until the 

last turn or so on the turnbuckle.  This would be the case if there 

was very little stretch in the whole system.  My best guess now is 

backing off a half turn on the turnbuckle would remove all the 

tension in the cable.



My point in making my post was not clear so let me try to make it 

clearer.  It is a lot easier to figure mechanical advantage and work 

from force (applied to the turnbuckle) to force (tension on the 

cable) than to go about analyzing the impact of the thread on the 

cable.  Indeed, I am not at all sure the cable is the most 

interesting part of this whole system.  It may be that the aluminum 

sheets, plastic fairleads, and other exotic things like play in the 

control surface hinges play bigger roles than stretching the 

cable.  This is just as true after some time has passed as it is when 

first applying tension to the cables.



After half a lifetime working as an electrical engineer, I am a firm 

believer in "Closed Loop Control Systems".  In this case, it means 

taking measurements of cable tension and adjusting the turnbuckle to 

get the tension you want rather than trying to predict the tension 

achieved from a certain amount of turns.  The second choice is an 

"Open loop" system since there is no feedback of results.



Sorry about the lecture . . .



Paul

XL getting close





At 10:39 AM 11/30/2008, you wrote:

 	  Quote: 	
		  



Dear Paul,



So, when you back off the tension 1/2 turn what happens?



A full turn?



The other way?



How many degrees of rotation per 5 pounds of tension change each way?



If you use those turnbuckle safety clips rather than safety wire, 

how much rotation can you get with those installed?  (We are talking 

about the Zenith supplied turnbuckles)



Thanks,



Sabrina

Ron Lendon

Joined: 10 Jan 2006
Posts: 685
Location: Clinton Twp., MI

Posted: Sun Nov 30, 2008 3:01 pm Post subject: Re: Aircraft Control Cable (to stretch or not)

Sabrina,



I accept the launch invitation, but decline on the test fixture challenge for cable tension.



I'm back at the school KISS and will probably make a Larry Mac tension gauge and be done with it.



Read my initial post and I believe I conveyed this position in my note to Gig.

planes_by_ken(at)bellsout
Guest

Posted: Sun Nov 30, 2008 3:04 pm Post subject: Aircraft Control Cable (to stretch or not)

With an installed cable you are tensioning a sorta stretchable cable 

against a very springy airframe.  1 turn on the turnbuckle on one 

aircraft may change the tension twice as much as on another.  As a side 

note, Beech uses springs in the LG retract system with pushrod 

tensions.  Bonanza series.  Cessna uses the airframe as the "spring".  

300 - 400 series.

Ken Lilja



Zenith-List message posted by: "Sabrina" <chicago2paris(at)msn.com>



Dear Paul,



So, when you back off the tension 1/2 turn what happens?



A full turn?



The other way?



How many degrees of rotation per 5 pounds of tension change each way?



If you use those turnbuckle safety clips rather than safety wire, how 

much rotation can you get with those installed?  (We are talking about 

the Zenith supplied turnbuckles)



Thanks,



Sabrina

jshep00(at)centurytel.net
Guest

Posted: Mon Dec 01, 2008 7:22 pm Post subject: Aircraft Control Cable (to stretch or not)

I have a scary story to tell about control cables:

I used a very expensive nicropress tool to do my cables for my 701, used the 

gauge and thought all was well.

One day before my first flight, I had my shoulders up in the access hole in 

the bottom of the airplane, stressed one of the cables for the elevator and 

it let loose!!!!---Needless to say I was really dumbfounded and worried as 

to what had happened.  I later found out after I had built some test cables 

and placed them under a load of 1500#  , that I had used the wrong gauge . I 

would recommend that everyone who makes up cables test and verify their 

process. May the angels watch over you as they did me. I am quite certain 

that a 701 is very difficult to fly with only elevator trim for control. 

Jerry Shepard.Original Message ----- 

From: "Ron Lendon" <rlendon(at)comcast.net>

To: <zenith-list(at)matronics.com>

Sent: Saturday, November 29, 2008 4:44 PM

Subject: Aircraft Control Cable (to stretch or not)

 	  Quote: 	
		   



 FYI



 Today I called my mentor and asked about stretch in the cables.  After 

 much listening I came away with the realization that I won't be conducting 

 a pre-stretch because that has already happened in the manufacturing 

 process.



 He did however maintain that checking the tension periodically is 

 necessary.  The major factors effecting the tension are temperature 

 variation from the last check and wear of the fair leads/pulleys.



 Comparing the expansion coefficients of both:



 Aluminum  12.3

 Steel                 7.3



 You can see Aluminum expands and contracts 5 times that of Steel.  So if 

 you tension your cables on an 80 degree day you can bet they will need it 

 again on a 0 degree day in the winter.  Just some thoughts.



 I checked the cable I got from ACS and it is  MIL-DTL-83420 with a red and 

 gold filament.



> There are two easy identification methods that may help you identify 

> aircraft control cable:

>

> (1) All MIL-DTL-83420 contains a two-color tracer filament embeded within 

> the cable that identifies the manufacturer,

> (2) All MIL-DTL-83420 cable sold on a shipping real must contain the 

> identification number of the manufacturing reel. (All MIL-DTL-83420 cable 

> is lubricated with a corrosion inhibiter.)

>

 So Gig, Don't wait for me to set up a test.  Keep building.



 --------

 Ron Lendon, Clinton Township, MI

 WW Corvair with Roy's Garage 5th bearing

 Zodiac XL, ScrapBuilder 

 http://www.mykitlog.com/rlendon





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 16912#216912

psm(at)att.net
Guest

Posted: Mon Dec 01, 2008 7:32 pm Post subject: Aircraft Control Cable (to stretch or not)

How about the pilot who actually landed a DC-10 with no controls at 

all except throttles.  It was a crash caused by loss of the rear door 

which took out all the hydraulics that ended up somewhere in Iowa (I 

think).  There was some loss of life but lots of survivors.



Paul

XL getting close

do not archive



At 07:21 PM 12/1/2008, you wrote:

 	  Quote: 	
		  I am quite certain that a 701 is very difficult to fly with only 

elevator trim for control. Jerry Shepard.Original Message ----- 

From: "Ron Lendon" <rlendon(at)comcast.net>

ggower_99(at)yahoo.com
Guest

Posted: Tue Dec 02, 2008 9:26 am Post subject: Aircraft Control Cable (to stretch or not)

Hello Jerry,

 That IS a good story about how serious is to build an aircraft project.   

 For all of us is very important to double check everything.  Also something that has work in our area,  is to have a day every month (first Thursday) of the month to visit a building project, we all check the airplane around and tell the builder about any detail we find.   Has worked great, we hads found several scary details that were rebuilt or repaired.   Sometimes we go over some serious details without notice, because we did them and see them every day, without watching them.

 Thank you very much for your post.

 Saludos

 Gary Gower.

--- On Mon, 12/1/08, jerry Shepaed <jshep00(at)centurytel.net> wrote:

  	  Quote: 	
		  From: jerry Shepaed <jshep00(at)centurytel.net>

Subject: Re: Aircraft Control Cable (to stretch or not)

To: zenith-list(at)matronics.com

Date: Monday, December 1, 2008, 10:21 PM

 	  Quote: 	
		  --> Zenith-List message posted by: "jerry Shepaed"

<jshep00(at)centurytel.net>

I have a scary story to tell about control cables:

I used a very expensive nicropress tool to do my cables for my 701, used the

gauge and thought all was well.

One day before my first flight, I had my shoulders up in the access hole in the

bottom of the airplane, stressed one of the cables for the elevator and it let

loose!!!!---Needless to say I was really dumbfounded and worried as to what had

happened.  I later found out after I had built some test cables and placed them

under a load of 1500#  , that I had used the wrong gauge . I would recommend

that everyone who makes up cables test and verify their process. May the angels

watch over you as they did me. I am quite certain that a 701 is very difficult

to fly with only elevator trim for control. Jerry Shepard.Original Message -----

From: "Ron Lendon" <rlendon(at)comcast.net>

To: <zenith-list(at)matronics.com>

Sent: Saturday, November 29, 2008 4:44 PM

Subject: Aircraft Control Cable (to stretch or not)

 	  Quote: 	
		   --> Zenith-List message posted by: "Ron Lendon"

<rlendon(at)comcast.net>

 	  Quote: 	

 FYI

 Today I called my mentor and asked about stretch in the cables.  After

much listening I came away with the realization that I won't be conducting a

pre-stretch because that has already happened in the manufacturing process.

 	  Quote: 	

 He did however maintain that checking the tension periodically is

necessary.  The major factors effecting the tension are temperature variation

from the last check and wear of the fair leads/pulleys.

 	  Quote: 	

 Comparing the expansion coefficients of both:

 Aluminum  12.3

 Steel                 7.3

 You can see Aluminum expands and contracts 5 times that of Steel.  So if

you tension your cables on an 80 degree day you can bet they will need it again

on a 0 degree day in the winter.  Just some thoughts.

 	  Quote: 	

 I checked the cable I got from ACS and it is  MIL-DTL-83420 with a red and

gold filament.

 	  Quote: 	

> There are two easy identification methods that may help you identify

aircraft control cable:

 	  Quote: 	
		  > 

> (1) All MIL-DTL-83420 contains a two-color tracer filament embeded

within the cable that identifies the manufacturer,

 	  Quote: 	
		  > (2) All MIL-DTL-83420 cable sold on a shipping real must contain the

identification number of the manufacturing reel. (All MIL-DTL-83420 cable is

lubricated with a corrosion inhibiter.)

 	  Quote: 	
		  > 

 So Gig, Don't wait for me to set up a test.  Keep building.

 --------

 Ron Lendon, Clinton Township, MI

 WW Corvair with Roy's Garage 5th bearing

 Zodiac XL, ScrapBuilder 

 http://www.mykitlog.com/rlendon

 Read this topic online here:

 http://forums.matronics.com/viewtopic.php?p 16912#216912

         [quote][b]

Display posts from previous:

	Matronics Email Lists Forum Index -> Zenith-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum