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Crvsecretary(at)aol.com
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 Posted: Mon Apr 24, 2006 4:49 am Post subject: Rivets for Aileron bellcrank bracket |
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Hello All:
I finally caught up in reading a lot of posts that have come in over the
past two weeks and I have a concern about the A5 rivets coming loose on the
aileron bellcrank support P/N 6W6-11. I see these brackets are held to the Rear
Rib # 7 with (3) each A5 rivets. As the bracket receives force from the
control cables through the bellcrank the brackets are pulled in to the rib, but
as the bellcrank transmits that force to the aileron the brackets are
receiving shear forces and transmitting that load through the A5 rivets to the rib.
My question is: I do not understand the forces involved here to cause those
rivets to fail in this location. Are rivets by design stronger in shear than
in tension? I don't see a lot on tension force here - what am I missing?
Also, are AN bolts stronger than rivets in this situation? No, I am NOT
doubting the designer here, I'm just trying to understand this situation.
Can't you tell I am at this point in wing construction?
Thank you everyone for the suggestions, directions, and contributions made
on this list for the benefit of everyone.
Best Regards,
Tracy Smith
Naugatuck, CT
601xl N458XL (reserved)
do not archive
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nfivesl(at)yahoo.com
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larry(at)macsmachine.com
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| Posted: Mon Apr 24, 2006 6:43 am Post subject: Rivets for Aileron bellcrank bracket |
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Tracy,
If you've not tensioned the cables past 20 to 25 lbs and not created a
binding condition on the aileron crank arms,
you should not see a problem. In flight, if you horse the controls
around hard, you could conceivably have enough repeated
force to damage the mounting area of the rib or loosen the A5s.
Seriously doubt A5s would give it up without other
things going on. I don't fly heavy on the controls at any time because
of the risk of something working loose, or worse,
over-stressing things. The walking action of the aileron control rod on
the belcrank creates a tension on the A5s side to side
and does a bending action on the rib if the forces are high enough.
Yes, riveted fasteners are twice as vulnerable to tension as shear.
Larry McFarland - 601HDS at www.macsmachine.com
Crvsecretary(at)aol.com wrote:
| Quote: |
Hello All:
I finally caught up in reading a lot of posts that have come in over the
past two weeks and I have a concern about the A5 rivets coming loose on the
aileron bellcrank support P/N 6W6-11. I see these brackets are held to the Rear
Rib # 7 with (3) each A5 rivets. As the bracket receives force from the
control cables through the bellcrank the brackets are pulled in to the rib, but
as the bellcrank transmits that force to the aileron the brackets are
receiving shear forces and transmitting that load through the A5 rivets to the rib.
My question is: I do not understand the forces involved here to cause those
rivets to fail in this location. Are rivets by design stronger in shear than
in tension? I don't see a lot on tension force here - what am I missing?
Also, are AN bolts stronger than rivets in this situation? No, I am NOT
doubting the designer here, I'm just trying to understand this situation.
Can't you tell I am at this point in wing construction?
Thank you everyone for the suggestions, directions, and contributions made
on this list for the benefit of everyone.
Best Regards,
Tracy Smith
Naugatuck, CT
601xl N458XL (reserved)
do not archive
|
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dredmoody(at)cox.net
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| Posted: Mon Apr 24, 2006 8:32 am Post subject: Rivets for Aileron bellcrank bracket |
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I don't think the designer would be terribly offended nor would it be an "over the top" measure of extra safety to substitute an AN3 bolt for an A5 rivet in critical or high stress assemblies. This assumes that the bolts used are of the right grip length, acceptable number and placement of washers, etc. The small extra weight is obvious but not a deal breaker. The caveat is that the use of an AN bolt and locknut should probably only be done where inspection is possible.
Ed Moody II
Rayne, LA
601XL wings
| Quote: |
From: Crvsecretary(at)aol.com
Date: 2006/04/24 Mon AM 08:47:09 EDT
To: zenith-list(at)matronics.com
Subject: Rivets for Aileron bellcrank bracket
Hello All:
I finally caught up in reading a lot of posts that have come in over the
past two weeks and I have a concern about the A5 rivets coming loose on the
aileron bellcrank support P/N 6W6-11. I see these brackets are held to the Rear
Rib # 7 with (3) each A5 rivets. As the bracket receives force from the
control cables through the bellcrank the brackets are pulled in to the rib, but
as the bellcrank transmits that force to the aileron the brackets are
receiving shear forces and transmitting that load through the A5 rivets to the rib.
My question is: I do not understand the forces involved here to cause those
rivets to fail in this location. Are rivets by design stronger in shear than
in tension? I don't see a lot on tension force here - what am I missing?
Also, are AN bolts stronger than rivets in this situation? No, I am NOT
doubting the designer here, I'm just trying to understand this situation.
Can't you tell I am at this point in wing construction?
Thank you everyone for the suggestions, directions, and contributions made
on this list for the benefit of everyone.
Best Regards,
Tracy Smith
Naugatuck, CT
601xl N458XL (reserved)
do not archive
|
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larry(at)macsmachine.com
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| Posted: Mon Apr 24, 2006 9:57 am Post subject: Rivets for Aileron bellcrank bracket |
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Ed,
I'd recommend an AN bolt with a castellated nut safetied with a cotter
where it's used as a pivot
component.
Larry McFarland at www.macsmachine.com
do not archive
dredmoody(at)cox.net wrote:
| Quote: |
I don't think the designer would be terribly offended nor would it be an "over the top" measure of extra safety to substitute an AN3 bolt for an A5 rivet in critical or high stress assemblies. This assumes that the bolts used are of the right grip length, acceptable number and placement of washers, etc. The small extra weight is obvious but not a deal breaker. The caveat is that the use of an AN bolt and locknut should probably only be done where inspection is possible.
Ed Moody II
Rayne, LA
601XL wings
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dredmoody(at)cox.net
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| Posted: Mon Apr 24, 2006 10:16 am Post subject: Rivets for Aileron bellcrank bracket |
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I'm sort of leaning towards mounting critical stuff as in the case of the aileron bellcrank with AN bolts and castle nuts/cotter pin or Nylok with 3 threads showing. Might even use a backing plate under the stiffeners to spread load and minimize rib flexing. I promised myself I wouldn't get too OCD on this plane..... my UL is way too tricked out..... but I think this might be a place to use extra caution. Besides, I break a lot of those promises.
Ed
| Quote: | Zenith-List message posted by: LarryMcFarland <larry(at)macsmachine.com>
Ed,
I'd recommend an AN bolt with a castellated nut safetied with a cotter
where it's used as a pivot
component.
Larry McFarland at www.macsmachine.com
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PatrickW
Joined: 27 Oct 2006
Posts: 380
Location: Fort Worth, Texas
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| Posted: Mon Apr 30, 2007 8:20 am Post subject: Re: Rivets for Aileron bellcrank bracket |
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I did exactly the same thing that Scott did - used a slightly larger bracket and six A-5 rivets (instead of the smaller bracket with 3 rivets).
Patrick
XL/Corvair
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Tim Juhl
Joined: 21 Mar 2006
Posts: 488
Location: "Thumb" of Michigan
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| Posted: Mon Apr 30, 2007 2:06 pm Post subject: Re: Rivets for Aileron bellcrank bracket |
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I took a compromise route. I replaced the middle A5 rivets with AN bolts backed up by a large flat washer to distribute the load over a larger area. I have no idea whether the result is any stronger than the part would be as designed but it made me feel better 
Tim
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| Bellcrank bracket - front and back |
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Champ L16A flying
Zodiac XL - Jabiru 3300A
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TxDave
Joined: 22 Jul 2006
Posts: 168
Location: Temple, TX
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| Posted: Mon Apr 30, 2007 9:13 pm Post subject: Re: Rivets for Aileron bellcrank bracket |
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Its amazing how creative the posters on this group can be. I used solid rivets in place of the A5's. Probably overkill, but...
Dave Clay
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