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  #21  
Old 06-14-2011, 11:12 AM
Jerry Cochran's Avatar
Jerry Cochran Jerry Cochran is offline
 
Join Date: Jan 2005
Location: Sherwood, Oregon
Posts: 981
Default Indignation or Sarcasm? You decide...

Easy sometimes on these forums to mistake sarcasm ( like Jon's comment about loose wings) for indignation... Pretty funny I thought.
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Jerry Cochran
Sherwood, Oregon

RV-7a 707DD Bot from David Domeier 12/01/11
Lycoming IO-360 Catto 3 blade Panel upgrade in progress

RV6a 18XP 1st flite 03/21/07 sold to Dale Walter 10/22/2011
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"Suppose you were an idiot, and suppose you were a member of Congress; but I repeat myself."

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  #22  
Old 09-29-2011, 11:33 AM
jdiehl jdiehl is offline
 
Join Date: Jan 2011
Location: Williamsport, Pa
Posts: 159
Default If only I could get the wing bolts in!

A few days ago I installed the wings on my 7A for hopefully the last time. I temporarily used some slightly undersized bolts to mount the wings. Well, yesterday I spent 6 hours replacing the temp. bolts with the close tolerance bolts. After a full day in the cockpit with a rachet and open end wrenches, I managed to get the top bolts (two big/two small) on each wing. I used a small amount of grease and racheted them in with a fair amount of effort.
The bottom bolts are in place but have a long way to go. With less space to work, I'm open for suggestions on how to get these installed. I was thinking about simultaneously using my rivet gun and an open end wrench to 'assist' in getting them in the hole.

Jim Diehl
7A
Lock Haven Airport, Pa.
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  #23  
Old 09-29-2011, 11:51 AM
pvalovich pvalovich is offline
 
Join Date: Dec 2005
Location: Ridgecrest, CA
Posts: 395
Default Wing Bolts

I used a rivet gun - but be sure to pad the tip to avoid mushing the bolt heads and preventing a wrench to fit.
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  #24  
Old 09-29-2011, 11:54 AM
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Noah Noah is offline
 
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Location: Rhode Island
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Default

Jim, just did these on my 7A a couple of weeks ago, so the pain is still fresh in my mind. A couple of things I noted when doing mine:
1. Start from the outboard bolts and work inboards. Fully tighten each nut before moving to the next one. If you don't do this, you will not be able to get your wrench on the previous nut that you left loose.
2. It is not possible to torque most of these nuts with a torque wrench because of access and the fact that you can only rotate the bolt. And the prevailing torque of the bolt in its hole is very high, meaning the you are not torquing the nut to the required value. Just torque it until the prevailing torque spikes up which indicates that it is bottomed and squeezing, then turn another quarter turn.
3. I used crows foot wrenches with a 3/8" drive universal attached, then a 6" extension for all of the nuts. This was the ONLY combination which worked to hold the nuts out of many ways attempted. Note that you cannot TURN the nuts at all, the best you can do is KEEP THEM FROM TURNING while you rotate the bolt on the aft side. Some people use a flat screwdriver blade wedged against the nut to keep it from rotating, but I was able to use the crows foot wrench which is a little less ghetto I guess.
4. Several people reported using liquid nitrogen to cool and shrink the bolts. I found this to be unnecessary. A small hammer worked fine to tap the lubricated bolt shanks in without ridiculous effort.
5. When driving the bolts in, drive them slowly/carefully so that only 2 threads show on the fwd end. Then start the nut, drive a little more, torque a little, drive a little, then tighten completely. If you drive the bolt too far, you will not be able to get the nut on because of interference with the gear weldments.
6. After each bolt is in, get out of the airplane and take a walk. Shake off the cramps and start again on the next bolt. It took me all of 8 or 10 hours to get these bolts in and tight!
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Last edited by Noah : 09-29-2011 at 12:00 PM.
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  #25  
Old 09-29-2011, 12:16 PM
alpinelakespilot2000 alpinelakespilot2000 is offline
 
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Posts: 3,489
Default

Jim-
Trying to ratchet them in probably won't work. A rubber mallet and/or some taps with a hammer or the rivet gun that others have noted will probably be required. FWIW, my oiled bolts went in fairly easily a couple days ago, chasing out the drift pins one at a time. The rubber mallet sufficed for those and is consistent with AC43.13-1b where it discusses inserting close tolerance bolts. Only with one bolt did I need to use some stronger taps with the hammer. Could have used the rivet gun there, but same difference. As Noah mentioned, do pay attention to see if your wrenches will fit with all four bolts in at once. I didn't do that, but hadn't thought about it until now. I'll maybe have to grind a wrench down. Good luck.
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Last edited by alpinelakespilot2000 : 09-29-2011 at 12:25 PM.
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  #26  
Old 09-29-2011, 03:46 PM
Finley Atherton Finley Atherton is offline
 
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Location: AUSTRALIA
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Jim,

Possibly too late for this but before installing my wing bolts I measured the diameter of each bolt with a micrometer over the length of the bolt and found some were slightly bigger in the area where the shank meets the threaded part. I carefully filed away this area to remove the bulge. From memory this mostly amounted to removing the cad plating locally. After this my bolts went in relatively easily. Obviously I would have preferred not to remove the cad plating but I think you would find that some cad plating is removed in this area anyway by all the turning, tapping etc when attempting to install the tight bolts. I also liberally coated them with the lubricant/corrosion inhibitor recommended by my local LAME (A & P).

Using the smaller MS21042 nuts on the lower bolts is an option, see my posts #16 and #18 http://www.vansairforce.com/communit...ad.php?t=34728

Fin
9A

Last edited by Finley Atherton : 09-29-2011 at 03:57 PM.
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  #27  
Old 09-29-2011, 08:45 PM
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GAHco GAHco is offline
 
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Location: Paso Robles, CA
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Exclamation Long Thread......

I might have missed it in this thread, but my understanding is that the final torque is the sum of friction torque of the Locknut/fastener combination and the specified torque range of the normal free running nut. That is what I recall.
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  #28  
Old 09-30-2011, 09:11 AM
Captain Avgas Captain Avgas is offline
 
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Location: Melbourne, Australia
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Quote:
Originally Posted by Bavafa View Post
Also, these bolts are vastly on sheer force and no tension on the nut, so unless it is sloppy lose, how important is it to get them all right?
It is always important that bolts in shear are fully torqued up to their proper value for a couple of reasons:

1. The nuts are less likely to back-off if the bolt is properly prestressed.

2. Engineering analysis assumes that a certain percentage of the shear forces at the connection are picked up as frictional forces between the mating surfaces rather than purely by the shank of the bolt. But if the bolt is not properly torqued then there is insufficient frictional forces developed between the mating surfaces....that then reduces the safety margin of the bolt.

If it wasn't important for bolts in shear to have a torque value then they wouldn't have one.
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  #29  
Old 09-30-2011, 02:26 PM
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Bob Kuykendall Bob Kuykendall is offline
 
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Quote:
Originally Posted by Captain Avgas View Post
...Engineering analysis assumes that a certain percentage of the shear forces at the connection are picked up as frictional forces between the mating surfaces...
That may be the case sometimes, but it is an unconservative approach and one that is far from universal.

Thanks, Bob K.
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  #30  
Old 09-30-2011, 10:12 PM
Captain Avgas Captain Avgas is offline
 
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Quote:
Originally Posted by Bob Kuykendall View Post
That may be the case sometimes, but it is an unconservative approach and one that is far from universal.

Thanks, Bob K.
On the contrary, using the proper torque values on bolts in shear is always the most CONSERVATIVE approach for a number of reasons (regardless of whether the design engineer assumes frictional forces at the connection or not).

I don't know that it's a good idea to be encouraging backyard aircraft builders to either undertorque or overtorque their fasteners and fittings.

The aim of my original post was to ensure that RV builders on this forum (very few of whom have any engineering background) do not make dangerous assumptions regarding the need (or lack of need) to apply the proper specified torque on all fasteners and fittings. It's just not an area that lends itself to "intuitive" decision making by laymen.
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