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07-24-2016, 03:03 PM
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Join Date: Oct 2013
Location: SoCal
Posts: 83
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Torqueing AN818 nuts for vent and fuel lines?
I'm working on installing the vent tube in the RV-7 fuel tank but I'm puzzled on how to torque the AN818 nut.
The tank vent tube is 1/4" 3003 AL and takes a AN818-4D nut. AC43.13 says to torque the nut to 40-65 in-lbs. I have a 1/4" drive torque wrench (20-150 in-lbs). I need a 9/16" crowfoot in a 1/4" drive, which I cannot find. It seems most crowfoot wrenches are 3/8" drive, but virtually all 3/8" drive torque wrenches can barely get down 65 in-lbs (5.4 ft-lbs).
Also I've seen people tighten the nut so many flats. How many turns is needed for a AN818-4D nut on a 3003 tube?
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Into the blue again, after the money's gone
RV-7A
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Wings kit in progress.
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07-24-2016, 03:17 PM
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Join Date: Jan 2005
Location: Hopkinsville, KY
Posts: 957
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3/8 - 1/4 adapter
Why can't you use a 3/8 to 1/4 adapter for the crowsfoot? Extensions do not change the torque. Just turn the crowsfoot 90? to the Tq wrench.
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Bobby Hester - Builder/Pilot/A&P
Surfing the web from Hopkinsville, KY
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07-24-2016, 06:48 PM
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Join Date: Mar 2013
Location: Flathead Lake Montana - 8S1
Posts: 334
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I'd just "tighten" it... but if you wish to torque it simply use your 9/16" open/box combo wrench and measure the distance from the nut CL to the center of the box. Do the math and hang the requisite weight from the box end.
For example, if your combo wrench had a 12" arm you'd hang a 4# weight from the box end and Bob's your Uncle.
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07-24-2016, 07:47 PM
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Join Date: Oct 2013
Location: SoCal
Posts: 83
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I got a 3/8 to 1/4 adapter and a 3/8 crows foot set, installed the crowfoot at 90 deg to the torque wrench and torqued a couple of test fittings to 65 in-lbs. Here's the first one after I torqued it, removed it, torqued again, then sectioned.
I turned the nut until it just started to interfere, marked with a sharpie, then torqued. Both times, the wrench clicked at 1/2 flat of additional turn. Again, this is with 3003 1/4" tubing provided by Vans for the tank vent lines.
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Into the blue again, after the money's gone
RV-7A
Empennage complete minus glass work.
Wings kit in progress.
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07-24-2016, 08:27 PM
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Join Date: Sep 2007
Location: Central IL
Posts: 5,516
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Good Research Work
You did your homework. Tested and verified. I did the same thing. Keep it up and you will have a well built plane.
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Bill
RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
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07-24-2016, 08:28 PM
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Join Date: Mar 2008
Location: Dublin, CA
Posts: 1,261
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I measured my crowsfoot wrenches and made a spreadsheet with the corrected values. I think the calculation is in AC43.13. I know a lot of people do the 90 degree thing but I don't think its technically correct. It may be close and good enough though.
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Ray Tonks
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07-25-2016, 05:57 AM
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Join Date: Apr 2014
Location: Underwood, WA
Posts: 413
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Check on Amazon. I was able to find a set of 1/4" drive crow's foot. If I recall, the set wasn't that expensive.
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Eric Rushing
RV-10
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Molalla, OR
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07-25-2016, 07:45 AM
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Join Date: Jul 2013
Location: US
Posts: 2,251
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Quote:
Originally Posted by rapid_ascent
I measured my crowsfoot wrenches and made a spreadsheet with the corrected values. I think the calculation is in AC43.13. I know a lot of people do the 90 degree thing but I don't think its technically correct. It may be close and good enough though.
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It IS correct. At 90 degrees, the correct torque is unchanged from the specified value.
http://www.dmctools.com/Products/tor...on_charts.html
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07-25-2016, 08:20 AM
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Join Date: Oct 2009
Location: Victoria, BC, Canada
Posts: 3,932
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Quote:
Originally Posted by spaceflightmeow
I got a 3/8 to 1/4 adapter and a 3/8 crows foot set, installed the crowfoot at 90 deg to the torque wrench...

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Just in case anyone misinterprets... This photo does *not* show the crows foot at 90 degrees to the wrench.
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Rob Prior
1996 RV-6 "Tweety" C-FRBP (formerly N196RV)
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07-25-2016, 11:26 PM
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Join Date: Oct 2013
Location: SoCal
Posts: 83
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Quote:
Originally Posted by Snowflake
Just in case anyone misinterprets... This photo does *not* show the crows foot at 90 degrees to the wrench.
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I'm embarassed to admit that I thought the orientation shown in the picture is 90 degrees. Then again I didn't look too closely, since there was a bit of wobble to the wrench thanks to the 1/4" to 3/8" adapter.
__________________
Into the blue again, after the money's gone
RV-7A
Empennage complete minus glass work.
Wings kit in progress.
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