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Bolt Torque Specs
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randy(at)shadycreekoutlaw
Guest

Posted: Mon Jun 12, 2006 6:11 am Post subject: Bolt Torque Specs

I am finishing up the center spar for my 601  XL.  There are 6, AN4-15A bolts that go through the center  spar.  Are there torque specifications on these bolts that I need  to follow?

  

 Thanks in advance,

  

 Randy

 XL Wings - Plans Only

 http://www.n344rb.com

larry(at)macsmachine.com
Guest

Posted: Mon Jun 12, 2006 7:05 am Post subject: Bolt Torque Specs

Randy,

Most bolts in structural applications will have a torque value for the 

place they are used.

The AN4-15A bolt is a high strength fine thread bolt with 50-70 inch 

pounds standard type nuts.

You need the Standard Aircraft Handbook 6th ed or later.  Most of this 

kind of information is

in this handbook.  Your plans have the final word on fasteners, 

dimensions etc.



Larry McFarland - 601HDS at www.macsmachine.com

do not archive



Randy Bryant wrote:



 	  Quote: 	
		   I am finishing up the center spar for my 601 XL.  There are 6, AN4-15A 

 bolts that go through the center spar.  Are there torque 

 specifications on these bolts that I need to follow?

  

 Thanks in advance,

  

 Randy

 XL Wings - Plans Only

 http://www.n344rb.com

randy(at)shadycreekoutlaw
Guest

Posted: Mon Jun 12, 2006 11:59 am Post subject: Bolt Torque Specs

Thanks Larry,



My plans don't say what to torque these bolts to...  Since most are kit 

builders and don't have to actually build this part, since it comes from the 

factory already assembled, I guess that the torque value for these 6 center 

spar bolts is not 'common knowledge'...  I guess my best bet is to call ZAC 

and see what they can tell me...



Thanks much,



Randy

XL Wings - Plans Only

http://www.n344rb.com



Do Not Archive

---

normskiroo@ukonl

Joined: 10 Jan 2006
Posts: 7

Posted: Tue Jun 13, 2006 6:56 am Post subject: Bolt Torque Specs

Hello Randy,

  

 According to CZAW the recommended torque for the  AN4 bolts are 50 to 70 in. lb. (5.6 to 7.9  Nm) the limit being 11.3 Nm.

 Hope this helps.

  

 Norman

 601 XL G-DONT 40 hrs  U.K.

frank.hinde(at)hp.com
Guest

Posted: Tue Jun 13, 2006 7:25 am Post subject: Bolt Torque Specs

Actually the real limit is when you strip the threads! You  cannot cause a bolt to fail in service due to over torquing. They will break (if  subjected to vibrational tension changes that cuse fatigue) if you UNDER torque  them.

  

 Bottom line (and I can't wait to get flamed on  this......) the listed torques specs really are on the very bottom limit for  comfort and I assume are primarilly for fasteners in shear rather than tensile  applications.

  

 You would never find a cylinder head or tensile faster with  so little torque, but they have been shown to work in practice . Mine are all a  little tighter than this though.

  

 Frank

  

 Do not archive



   From: owner-zenith-list-server(at)matronics.com  [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of  norman

Sent: Tuesday, June 13, 2006 7:54 AM

To:  zenith-list(at)matronics.com

Subject: Re: Bolt Torque  Specs

 

 Hello Randy,

  

 According to CZAW the recommended torque for the  AN4 bolts are 50 to 70 in. lb. (5.6 to 7.9  Nm) the limit being 11.3 Nm.

 Hope this helps.

  

 Norman

 601 XL G-DONT 40 hrs  U.K.

randy(at)shadycreekoutlaw
Guest

Posted: Tue Jun 13, 2006 8:10 am Post subject: Bolt Torque Specs

I thought that the reason for torquing bolts was to  achieve the proper 'stretch' in the bolt...  I know in an engine, you  torque rod bolts, they stretch and apply tension to the rod caps and this helps  hold the cap on...  If you over torque, you 'stretch' the bolt past its  elasticity and loose this extra holding capacity...

  

 Maybe I'm wrong...??  I just hate having to  tighten something as far as it will go then 1/4 turn more as the torque  specs...

  

 Thanks!

  

 Randy

  

 Do Not Archive

  

 [quote]   ---

randy(at)shadycreekoutlaw
Guest

Posted: Tue Jun 13, 2006 8:48 am Post subject: Bolt Torque Specs

Thanks Frank,

  

 It looks like I'm gonna agree with you after  all...  I just got a response back from ZAC about the torque of these bolts  and here's what they said:

  

 "For proper bolt selection and installation,  please refer to the FAA

publication, Acceptable Methods Techniques, and  Practices: AIRCRAFT

INSPECTION AND REPAIR AC 43.13-1B"

  

 We all know what that says, 50-70 inch  pounds...  Its a crying shame that a go-kart manufacturer can tell you  specifically to torque certain bolts, used in certain applications, to an exact  spec, and aircraft manufacturers can't... (I guess they're too busy  keeping their rivets exactly 8mm from the edge)  Even the auto makers  do this...  They'll tell you specifically how many foot/pounds or  inch/pounds to tighten certain bolts, not some broad range of 50-70 inch  pounds...

  

 I guess I'll just tighten em' as tight as they'll  go, then go about 1/4 turn more... that should do it..

  

 Thanks,

  

 Randy

  

 [quote]   ---

Carlos Sa

Joined: 13 Jan 2006
Posts: 96

Posted: Tue Jun 13, 2006 10:00 am Post subject: Bolt Torque Specs

Randy, I think you are quite right.

The more torque you apply, the closer the material gets to "plastic" (as opposed to "elastic").



There is a lot of good reading material out there. I found this one to be interesting:

http://www.auf.asn.au/scratchbuilder/hardware.html



Cheers



Carlos

CH601-HD, plans

Building aeroplanes (one) since 1999. A tradition in the making.



---

_________________
CH601-HD, plans
Montreal, Canada

frank.hinde(at)hp.com
Guest

Posted: Tue Jun 13, 2006 10:02 am Post subject: Bolt Torque Specs

There is no way on Earth you will stretch AN bolts with  the miniscule listed torque specs. The AN4 is listed at about 6 ft  lbs...On a cylinder head this would be  more like 15lbs and it still won't stretch.

  

 Frank



   From: owner-zenith-list-server(at)matronics.com  [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of Randy  Bryant

Sent: Tuesday, June 13, 2006 9:08 AM

To:  zenith-list(at)matronics.com

Subject: Re: Bolt Torque  Specs

 

 I thought that the reason for torquing bolts was to  achieve the proper 'stretch' in the bolt...  I know in an engine, you  torque rod bolts, they stretch and apply tension to the rod caps and this helps  hold the cap on...  If you over torque, you 'stretch' the bolt past its  elasticity and loose this extra holding capacity...

  

 Maybe I'm wrong...??  I just hate having to  tighten something as far as it will go then 1/4 turn more as the torque  specs...

  

 Thanks!

  

 Randy

  

 Do Not Archive

  

 [quote]   ---

moorecomp(at)yahoo.com
Guest

Posted: Tue Jun 13, 2006 10:15 am Post subject: Bolt Torque Specs

Randy,



Remember that the torque is to be added to the running

torque of the nut. If you are using self locking nuts,

then you need to measure the amount of torque required

to turn the nut and add it to the 50 - 70 in. lbs.  If

you really want to get educated on threaded fastener

torque, go here and look at MIL-HDBK-60. 



http://www.combatindex.com/mil_docs/mil_hdbk_index_01.html



This is a great link and all should bookmark it. Lots

of info here.



BTW - At the end of the handbook, it shows a chart

that looks like the AN4 bolt, which is a 125ksi

tensile material, would require approx. 100 in. lbs.

of torque, the max value given in the 43.13.



Small flame for Frank, 

Excessive torque can be a bad thing too, especially if

you exceed the elastic limit of the bolt. Over time,

with cyclic loading and vibration, the preload on the

fastener will be gone, resulting in a situation you

described - undertorque. As another lister noted, bolt

stretch is commonly used as a method of checking for

proper preload. But, the value is within the elastic

limits. All of this is the reason that we go back and

retorque fasteners after a certain time. Also, in the

type of joint we are talking about, the use of many

bolts is because the majority of the shear loads are

transferred through friction of the joint components,

and the load is spread over a large area and not just

taken up by the bolt shanks. Lose the preload, and you

cause stresses to be concentrated at the bolts, thats

were elongated holes come from.



Ducking,



Craig Moore A&P

701 builder wannabe



--- Randy Bryant <randy(at)shadycreekoutlaws.com> wrote:



[quote] Thanks Frank,

 

 It looks like I'm gonna agree with you after all... 

 I just got a response back from ZAC about the torque

 of these bolts and here's what they said:

 

 "For proper bolt selection and installation, please

 refer to the FAA

 publication, Acceptable Methods Techniques, and

 Practices: AIRCRAFT

 INSPECTION AND REPAIR AC 43.13-1B"

 

 We all know what that says, 50-70 inch pounds... 

 Its a crying shame that a go-kart manufacturer can

 tell you specifically to torque certain bolts, used

 in certain applications, to an exact spec, and

 aircraft manufacturers can't... (I guess they're too

 busy keeping their rivets exactly 8mm from the edge)

  Even the auto makers do this...  They'll tell you

 specifically how many foot/pounds or inch/pounds to

 tighten certain bolts, not some broad range of 50-70

 inch pounds...

 

 I guess I'll just tighten em' as tight as they'll

 go, then go about 1/4 turn more... that should do

 it..

 

 Thanks,

 

 Randy

 

   ---

frank.hinde(at)hp.com
Guest

Posted: Tue Jun 13, 2006 10:44 am Post subject: Bolt Torque Specs

No need to duck Craig...



Good point but...the point about "stretching" the bolt is basically

taking the fastener up to the top of its elastic limit...In fact most

cyl head bolts today cannot be reused so this presumably means the have

been torqued INTO their plastic range.



I am am not talking about going anywhere near that point....10 foot

pounds say will still be well within the elsatic range of a 1/4" 125kpsi

bolt.



But I agree...You can't just keep tightening the thing at will...



Frank

Do not archive



 



--

randy(at)shadycreekoutlaw
Guest

Posted: Tue Jun 13, 2006 10:59 am Post subject: Bolt Torque Specs

Thanks Craig,



This is good info... This really helps...  My fear was I wouldn't tighten 

them enough and have to worry about that from now on after my plane is 

flying, or be in fear that they are too tight and loose the preload...yet 

another thing to worry about...



One more quick question for you:

Would a certain bolt such as an AN4 require the same torque regardless of 

it's application (where it's being used on the plane) ?



Thanks much,



Randy



Do Not Archive

---

moorecomp(at)yahoo.com
Guest

Posted: Tue Jun 13, 2006 12:13 pm Post subject: Bolt Torque Specs

Randy,



I assume you looked at the MIL-HDBK-60. Paragraph 4.2

gives the two type of shear loaded joints. One is like

your wing attach bolts. No sliding, with shear loads

transmitted by friction. Think of the other as like a

rod end or fork fitting. This type obviously does not

use friction to transmitt the load from one fitting to

the other, it goes through the bolt. In this case, the

torque is only to hold the joint together so that

bending loads do not occur on the bolt. A castle nut,

finger tight, then tight to line up the cotter pin

hole would suffice. On a high tensile load like an

engine mount to firewall, then the clamping force of

the rated torque would be used to keep the joint

together and prevent bending. Good luck building. I'll

be there one day.



Best regards,



Craig Moore A&P

701 builder wannabe 



--- Randy Bryant <randy(at)shadycreekoutlaws.com> wrote:



 	  Quote: 	
		   

 <randy(at)shadycreekoutlaws.com>

 

 Thanks Craig,

 

 This is good info... This really helps...  My fear

 was I wouldn't tighten 

 them enough and have to worry about that from now on

 after my plane is 

 flying, or be in fear that they are too tight and

 loose the preload...yet 

 another thing to worry about...

 

 One more quick question for you:

 Would a certain bolt such as an AN4 require the same

 torque regardless of 

 it's application (where it's being used on the

 plane) ?

 

 Thanks much,

 

 Randy

 

 Do Not Archive

 

snip
	




__________________________________________________

noelloveys(at)yahoo.ca
Guest

Posted: Tue Jun 13, 2006 2:01 pm Post subject: Bolt Torque Specs

 

 I usually go with the lower end  of the range...50 - 70 In.Lb.  Use 50 In. Lb. on the first use... if the  nut is removed and used again then I'll use 60"Lb. The second time it's removed  may as well replace it if it is in an area of any stress.

  

 One other thing I always  turn/torque the nut....  never the bolt.

  

  

 

Noel [quote]   

   --

zodierocket(at)hsfx.ca
Guest

Posted: Tue Jun 13, 2006 2:33 pm Post subject: Bolt Torque Specs

Randy not to dampen your expectations but “you are” the manufacturer, not the kit provider. It is your responsibility to ensure compliance to FAA regulations.  Zenith sells and supports kits that will someday fly. If you want an exact torque you could try AMD which manufacturers Zodiacs for the LSA market, but I doubt they will respond. ZAC’s response was correct and expected. It is up to you as to what torque you are comfortable with.   

     

cdngoose  

www.ch601.org / www.ch701.com/ www.Osprey2.com  

do not archive  

  

-----Original Message-----

      

Thanks Frank,  

    

   

    

It looks like I'm gonna agree with you after all...  I just got a response back from ZAC about the torque of these bolts and here's what they said:  

    

   

    

[i]"For proper bolt selection and installation, please refer to the FAA[/i]

 [i][i]publication, Acceptable Methods Techniques, and Practices: AIRCRAFT[/i]

 [i]INSPECTION AND REPAIR AC 43.13-1B"[/i][/i]  

    

   

    

We all know what that says, 50-70 inch pounds...  Its a crying shame that a go-kart manufacturer can tell you specifically to torque certain bolts, used in certain applications, to an exact spec, and aircraft manufacturers can't... [i](I guess they're too busy keeping their rivets exactly 8mm from the edge)[/i]  Even the auto makers do this...  They'll tell you specifically how many foot/pounds or inch/pounds to tighten certain bolts, not some broad range of 50-70 inch pounds...  

    

   

    

I guess I'll just tighten em' as tight as they'll go, then go about 1/4 turn more... that should do it..  

    

   

    

Thanks,  

    

   

    

Randy

daberti(at)sbcglobal.net
Guest

Posted: Tue Jun 13, 2006 3:29 pm Post subject: Bolt Torque Specs

50 to  70 is NOT "some broad range"  in fact + or - 10 inch lbs Is a rather  standard torque tolerance.  Certificated (calibrated) torque wrenches are  only good to 2 percent of the total range of the wrench so if you have a 0  to 150 in lbs wrench it's accurate to  3 inch lbs from what you set it  to.  Sounds like a pretty tight specification to me, and I shoot for the  mean plus the drag of the nylon stop nut.

  

  

Dave 601-HD 912ULS 

  	  Quote: 	
		     [i]"For proper bolt    selection and installation, please refer to the    FAA[/i]

[i][i]publication, Acceptable Methods    Techniques, and Practices: AIRCRAFT[/i]

[i]INSPECTION AND REPAIR AC    43.13-1B"[/i][/i]

         

 

      

We all know what that says, 50-70    inch pounds...  Its a crying shame that a go-kart manufacturer can    tell you specifically to torque certain bolts, used in certain applications,    to an exact spec, and aircraft manufacturers can't... [i](I guess they're too busy keeping    their rivets exactly 8mm from the edge)[/i]  Even the    auto makers do this...  They'll tell you specifically how many    foot/pounds or inch/pounds to tighten certain bolts, not some broad range of    50-70 inch pounds...

noelloveys(at)yahoo.ca
Guest

Posted: Tue Jun 13, 2006 9:15 pm Post subject: Bolt Torque Specs

I only use the drag of the  fibre lock nut (AKA friction torque) when it is specified.  Wearing of the  fibres in the locknuts is the main reason I dump them after they have been  tightened three times.  In the overall scheme of things they are cheap  enough to use relatively new.

  

 As for the torque wrench I tend  to check mine out with a known weight every couple of months.  Right now  for 200"Lb. I set for 187"LB.  checking it is easy as suspending a known  weight on the handle at a specific distance from the centre of the stud and then  adjusting the wrench to just click at that torque.

 e.g. 16.6Lb. suspended at 12"  from the centre of the stud = 200"Lb.  When calibrated this way the torque  wrench should be less than 1% out.  you can also put the same weight at 6"  top check the calibration of 100"Lb.

  

 In Canada torque wrenches used  on certified A/C have to have a certificate of calibration in effect before the  wrench is used.

  

  

 

Noel [quote]   

   --

normskiroo@ukonl

Joined: 10 Jan 2006
Posts: 7

Posted: Tue Jun 13, 2006 10:38 pm Post subject: Re: Bolt Torque Specs

Randy,



A word of caution here, I have this morning checked my CZAW drawings and they specify the bolts that attach the wings on my XL are AN5 15A not AN4 15A.

The torque for these bolts according to the data CZAW gave me is - 

100 to 140 in. lb. recommended 11.3 to 15.8 Nm with a limit of 25.4 Nm.



I shall, next time a am down at the aircraft use a vernier gauge to confirm the size.

During a wings off/back on operation some time ago I managed to strip the threads of one of the bolts /nuts by over tightening and I was only using a ratchet socket handle six inches long!

Needless to say the drilling of the bolt head took a while to get the whole thing out!



Regards,

Norman 601 XL G-DONT 40 hours, UK

p.mulwitz(at)worldnet.att
Guest

Posted: Wed Jun 14, 2006 3:28 am Post subject: Bolt Torque Specs

 	  Quote: 	
		  16.6Lb. suspended at 12" from the centre of the stud = 200"Lb.  When 

calibrated this way the torque wrench should be less than 1% out.


	




This estimate assumes the measurement of 12 inches and 16.6 pounds 

have a combined error of less than 1%.  I find this conclusion very 

unlikely.  Still, the procedure will assure a reasonably accurate 

torque from the wrench.



Paul

XL wings

do not archive

p.mulwitz(at)worldnet.att
Guest

Posted: Wed Jun 14, 2006 3:31 am Post subject: Bolt Torque Specs

 	  Quote: 	
		  CZAW drawings and they specify the bolts that attach the wings on my 

XL are AN5 15A not AN4 15A.


	




ZAC drawings for the XL also call for AN5 -15A attach bolts on the 

wings.  I decided to change to AN5-14A since the originals seemed a 

little too long to me.



Paul

XL wings

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