|
-
POSTING RULES

-
Donate yearly (please).
-
Advertise in here!
-
Today's Posts
|
Insert Pics
|

08-01-2008, 11:04 PM
|
|
|
|
Join Date: May 2006
Location: Sammamish, WA
Posts: 654
|
|
Multiple washers on a bolt...
I was installing the counter-weights on my elevators today and I have to counter-sink the bolt hole a little more so that the bolt head would not protrude and bind on the stabilizer. Countersinking the head a little more made it so that there was not enough thread left to fully tighten the nut. The plans called for 1 washer under the nut. Can I put 2 washers under the nut, or do I have to get a different bolt?
__________________
Michael Burbidge
Sammamish, WA
RV-14A Empennage
RV-9A Flying?340 hours!
Last Donation: December 2019
|

08-01-2008, 11:26 PM
|
 |
|
|
Join Date: Dec 2005
Location: Hamilton, New Zealand
Posts: 632
|
|
No problem, as long as...
...there are still enough threads engaged through the nut. Can't remember the exact number and I'm sure someone here will chime in, but I think it is two threads exposed (though I read just now in another post from Gil the new specs state one thread).
|

08-01-2008, 11:34 PM
|
 |
|
|
Join Date: Feb 2006
Location: South Carolina
Posts: 659
|
|
Quote:
Originally Posted by AntiGravity
...there are still enough threads engaged through the nut.
|
If I understand your question correctly, you are having to use an extra washer or two to keep the nut from bottoming out on the non-threaded part on the bolt shank. This is very acceptable provided there are enough threads showing after the nut, especially since this is not a "structural" application of the bolt, nut or washers. Van's uses more than one washer in a few places in the fuselage (that I know of) and I'm jus getting started in the Fuse (RV-9). They even mention it in the instructions to add extra washers if needed.
__________________
"Pilots: Looking down on people since 1903"
(author unknown)
RV-9, N556RM, O-320, Dual PMags, Catto 3 blade.
FLYING since 2018
Mosquito XEL ready for flight
|

08-02-2008, 05:37 AM
|
 |
|
|
Join Date: Dec 2007
Location: Flagstaff, AZ
Posts: 2,653
|
|
IIRC, it is acceptable to use up to three washers on a bolt. I've never had to use more than two. When I do, I try to put one washer under the bolt head and the other under the nut. Another fun washer trick: there's usually a 'flat' side and a 'rounded' side (though the latest washers I'm getting from ACS are manufactured differently and both sides look flat). The flat side goes toward the parts you are bolting together. I got that from the folk at Superior though I don't know how critical it is. In any case, it's not hard to put into practice.
__________________
Patrick Kelley - Flagstaff, AZ
RV-6A N156PK - Flying too much to paint
RV-10 14MX(reserved) - Fuselage on gear
http://www.mykitlog.com/flion/
EAA Technical Counselor #5357
|

08-02-2008, 05:45 AM
|
 |
|
|
Join Date: Jan 2005
Location: Louisville, Ga
Posts: 7,840
|
|
It's normal.....
......to see most washers with a rounded inside edge and a sharper opposite edge, since they're stamped out by the thousands. The sharper edge can cut into the underside of the bolt head, causing a stress riser. This is the reason you should put the rounded edge under the bolt head.
Regards,
__________________
Pierre Smith
RV-10, 510 TT
RV6A (Sojourner) 180 HP, Catto 3 Bl (502Hrs), gone...and already missed
Air Tractor AT 502B PT 6-15 Sold
Air Tractor 402 PT-6-20 Sold
EAA Flight Advisor/CFI/Tech Counselor
Louisville, Ga
It's never skill or craftsmanship that completes airplanes, it's the will to do so,
Patrick Kenny, EAA 275132
Dues gladly paid!
|

08-02-2008, 06:37 AM
|
 |
|
|
Join Date: Mar 2005
Location: Dallas area
Posts: 10,768
|
|
It is acceptable practice to use up to 3 washers. If you need more than 3, you should go to the next size bolt.
__________________
Mel Asberry, DAR since the last century.
EAA Flight Advisor/Tech Counselor, Friend of the RV-1
Recipient of Tony Bingelis Award and Wright Brothers Master Pilot Award
USAF Vet, High School E-LSA Project Mentor.
RV-6 Flying since 1993 (sold)
<rvmel(at)icloud.com>
|

08-02-2008, 09:56 AM
|
 |
|
|
Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
|
|
Washer direction....
Quote:
Originally Posted by pierre smith
......to see most washers with a rounded inside edge and a sharper opposite edge, since they're stamped out by the thousands. The sharper edge can cut into the underside of the bolt head, causing a stress riser. This is the reason you should put the rounded edge under the bolt head.
Regards,
|
Pierre,
...but if you do this, doesn't the sharp side of the washer then bite into the airframe or engine part?
I would much rather a replaceable bolt head get marked with a permanent "ring indent" than my airframe of engine parts....
A circular stress riser at the periphery of a bolt head would probably be less harmful than one in your structural part. Worse case is that the hex flats of the bolt head would fall off....
Also, in most of our cases, we have steel washers and alumuminum parts, the aluminum will get a much deeper "ring indent" than the steel bolt head.
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
Last edited by az_gila : 08-02-2008 at 09:58 AM.
Reason: added sentence
|

08-02-2008, 10:00 AM
|
 |
|
|
Join Date: Mar 2005
Location: Dallas area
Posts: 10,768
|
|
I have to go along with Gil. I always place the "rounded" edge against the airframe/part.
__________________
Mel Asberry, DAR since the last century.
EAA Flight Advisor/Tech Counselor, Friend of the RV-1
Recipient of Tony Bingelis Award and Wright Brothers Master Pilot Award
USAF Vet, High School E-LSA Project Mentor.
RV-6 Flying since 1993 (sold)
<rvmel(at)icloud.com>
|

08-02-2008, 10:23 AM
|
 |
|
|
Join Date: May 2005
Posts: 28
|
|
Washer stress risers
When putting the sharp side of the washer against the bolt head there is only one sharp edge contacting the bolt head. All of the bolt tension is applied to this one edge. When putting the sharp side of the washer against the part to be fastened there are two edges contacting the part, one near the hole and one at the OD of the washer. Also, the washer will deform slightly upon tightening the bolt and the load will be distributed across the whole washer face.
In all honesty it probably doesn't matter. The number of load cycles that most homebuilts go through is small and Van's designs enough factor of safety in so that the fasteners and parts fatigue slowly.
But, I always place the rounded side of the washer to the bolt head. If you are really all that concerned, the arguement could be made that both ways are bad and you should deburr your washers.
(added) Also, if the clearance between the washer ID and the bolt shaft is not enough the sharp edge of the washer might contact the small radius where the bolt shaft meets the head. This would be bad. AN fasteners usually don't have this issue. At least the ones that I buy.
Last edited by jetblackaircraft : 08-02-2008 at 11:22 AM.
|

08-04-2008, 08:09 AM
|
|
|
|
Join Date: Nov 2007
Location: Cary, N.C.
Posts: 1,216
|
|
In my Aviation Mechanic Handbook (ASA-M-HB2), page 180, section on Bolt Installation, talks about our AN bolts having "a round, smooth, washer-like bearing surface just below the head"...and it continues with the reason why.
Further on..."always place a washer under the nut to provide a good bearing surface and prevent damage to the component as the nut is tightened."
It seems that our task is to use the fasteners in a manner that prevents damaging the underlying surfaces. If washers are used, use them in a manner that does not damage the joined materials.
|
| Thread Tools |
Search this Thread |
|
|
|
| Display Modes |
Linear Mode
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
All times are GMT -6. The time now is 06:26 AM.
|