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02-16-2013, 08:44 PM
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Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,145
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I've been working with 3/16", 1/4", and 5/16" bolts for about 25 years now, and the torque values on these seem ridiculously low. A couple of times I've been able to get them almost to "book value" by fingers alone without a wrench. That just ain't right. I've personally done a couple "torque to failure" tests on AN hardware myself - I recommend it, it's educational.
3/8" bolts and larger, the torque values approach something I consider reasonable. I will admit I tend to run close to book values on "critical" fasteners.
__________________
Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid 
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
Last edited by airguy : 02-16-2013 at 08:46 PM.
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02-16-2013, 08:57 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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Put me down as someone who used a torque wrench on every bolt.
I also used torque seal after each bolt was torqued. How else are you going to know that each bolt is tight?
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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02-16-2013, 11:51 PM
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Join Date: Dec 2010
Location: SLC UT
Posts: 68
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My first Torquing (sp????) experience was on the 4 bolts on the rear HS spar- I borrowed the local A&P's torque wrench and tightened it to spec- drag torque and all! I then asked the guy to check my work- and he said it was too loose and cranked it down another turn or so!!!!!!!!
The guy was pretty experienced in RVs and said if I needed to replace those bolts down the road it would make for an unsightly repair. All being said I will be torquing all my nuts to spec by myself from here on out!
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02-17-2013, 12:00 AM
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Join Date: Jan 2011
Location: adelaide, south australia
Posts: 171
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Slightly off topic, but...
I found a copy of Carroll Smith's "Nuts, Bolts, Fasteners and Plumbing Handbook" a very useful addition to my technical bookshelf. Though the author is a race car builder, he covers the topic comprehensively, and he is certainly aircraft friendly. It helped my non engineer mind get a better grasp of what is really going on at a bolted connection. Lots of info on rivets and aircraft type plumbing
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02-17-2013, 01:41 AM
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Join Date: Aug 2009
Location: Southern California
Posts: 882
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Quote:
Originally Posted by daveyator
I found a copy of Carroll Smith's "Nuts, Bolts, Fasteners and Plumbing Handbook" a very useful addition to my technical bookshelf. Though the author is a race car builder, he covers the topic comprehensively, and he is certainly aircraft friendly. It helped my non engineer mind get a better grasp of what is really going on at a bolted connection. Lots of info on rivets and aircraft type plumbing
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RIP Carroll Smith.
I once knew Carroll's son through a mutual friend (granddaughter of Earl Fouts, founder of Earl's Peformance Plumbing). I have all of his books. Great reading material, even for an engineer.
Skylor
Last edited by skylor : 02-17-2013 at 01:51 AM.
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02-17-2013, 08:56 AM
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Join Date: Jan 2007
Location: Battleground
Posts: 4,348
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Quote:
Originally Posted by bret
I wonder if any one has lost a control surface in flight, due to improper Tq, that would be my biggest concern with these tiny fasteners.
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Bret - I have not heard of any specific instances. It is extremely unlikely that an under torqued nylok would back itself all the way off of the bolt. I guess one could over torque it and stretch the bolt weakening it and it could lead to a fatigue failure but again, never heard of that happening in the RV fleet.
A rule of thumb i use for the control surface AN3's is the nut should be tight enough that the bolt does not turn. If this introduces friction you need to find the cause not just loosen the nut. I know I have it torqued where I want it when the bolt does not turn with movement of the surface but I can still turn it with a wrench.
I guess this falls in the category of torque by hand.
__________________
Smart People do Stupid things all the time. I know, I've seen me do'em.
RV6 - Builder/Flying
Bucker Jungmann
Fiat G.46 -(restoration in progress, if I have enough life left in me)
RV1 - Proud Pilot.
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02-17-2013, 09:51 AM
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Join Date: Dec 2011
Location: Edinburg, TX
Posts: 617
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Torque or not what does it matter
On some things it really matters - Here is a little story:
I once bought a sport biplane from an elderly builder. It was well built and passed a detailed pre-buy without question, however it was never flown. The wings were removed and the airplane was trucked to me, the wings were reassembled and rigged. A thorough condition inspection was performed, paper work put in order and we began flying off the time. After 6 hours flight time I took off one afternoon and after climb out I went to level out and nothing happened. The stick would not operate the elevator. The only vertical control I had was power as there was no trim system in this design. The end result was a destroyed airplane and a damaged pilot. In examining the wreckage it was apparent that the An3 bolt connecting the elevator horn to the heim joint broke at the last thread and fell out. It was obviously over torqued and fractured. Perhaps the builder thought "this needs to be tight so it doesn't come loose" I will never know. What I do know is I do not reuse hardware in critical locations, I torque fasteners on control surfaces and other important connections whenever possible, and I don't fly airplanes without trim systems. So "Torque or not what does it matter" well it could matter greatly. Your choice - calibrated hand or calibrated wrench?
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RV-3 Rebuilding
RV-9 Flying and having fun, experimenting and having fun, did I mention flying and having fun?
RV-6A SOLD
Maule M5-235C SOLD
C-172G SOLD
Stinson L5 SOLD
Grumman AA1A SOLD
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02-17-2013, 10:08 AM
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Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,686
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Quote:
Originally Posted by JonJay
A rule of thumb i use for the control surface AN3's is the nut should be tight enough that the bolt does not turn. If this introduces friction you need to find the cause not just loosen the nut. I know I have it torqued where I want it when the bolt does not turn with movement of the surface but I can still turn it with a wrench.
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To add a bit to this, the bolts that capture rod end beariings must be tight in order to lock the inner bearing race to the mount.
The way you suggest above means the bearing may still be rotating around the bolt shaft.
You should not be able to rotate the bolt (easily) if it is tightened down properly. If you can rotate the bolt easily then it is not applying the proper clamping force to the bearing.
__________________
Walt Aronow, DFW, TX (52F)
EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
Last edited by Walt : 02-17-2013 at 03:21 PM.
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02-17-2013, 02:51 PM
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Join Date: Jan 2007
Location: Orem, UT
Posts: 213
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Quote:
Originally Posted by airguy
I will admit I tend to run close to book values on "critical" fasteners.
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I wonder which fasteners are "non critical". I suppose the critical fasteners are those that if they come loose or break then you are in trouble. So far in by build, I haven't come to any nuts where I said to myself, "this doesn't seem critical; I don't care if it comes loose or breaks during flight".
On a similar subject, I wonder about screws into platenuts. I imagine there is an optimal tightness, but I'm not aware of there being a specification to tell me what it is.
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Finishing -12 tail cone
-9A Empennage done, in storage
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02-17-2013, 03:27 PM
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Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,686
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A "critical" fastener is one that if it were to fail would jeopardize the safe operation of the aircraft, ie: flight controls, engine mounts/controls, fuel systems.
__________________
Walt Aronow, DFW, TX (52F)
EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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