Rod ends in single shear

[Steve S.]

Folks:

First let me say that I know well that everything is supposed to be in
double shear. Lord knows I have busted my butt to make sure
everything is in double shear.

But.

I have a portion of my aileron circuit that has a fork fitting to
provide the requisite double shear. However the bolt hole in the
crank is seeing some misalignment and is starting to wallow the hole.
I really, really should replace the fork fitting with a rod end (i.e.
it never should have been a fork fitting to begin with, it was a spur-
of-the-moment fix that was really just a band-aid). But the crank
being driven by the fork is going to be impossible to replace with a
two-armed crank that can nest a rod end.

So, I am faced with the possibility of using a rod end in single
shear. I know that this is viewed as being undesirable, as the
bearing can be popped out of the eye under certain conditions. I also
know that the traditional trick to compensate for this is to use a 970
washer (large area washer) on the outer end of the bolt holding the
rod end, such that if the bearing leaves the eye the washer prevents
the rod from departing the scene.

Now, with all of that said, here's my question: How bad is it really
to have the rod end in single shear if I do the washer trick? It's an
aileron rod, I do not think it sees much load at all--certainly far,
far short of it's rated load. I have seen several planes out there
with rod ends in single shear, so it can't be complete suicide . . .
right? No?

Thank you for your thoughts.

Steve.

[Ed Sullivan]

On Tue, 25 Sep 2007 21:58:46 -0700, "Steve S."
> wrote:

>Folks:
>
>First let me say that I know well that everything is supposed to be in
>double shear. Lord knows I have busted my butt to make sure
>everything is in double shear.
>
>But.
>
>I have a portion of my aileron circuit that has a fork fitting to
>provide the requisite double shear. However the bolt hole in the
>crank is seeing some misalignment and is starting to wallow the hole.
>I really, really should replace the fork fitting with a rod end (i.e.
>it never should have been a fork fitting to begin with, it was a spur-
>of-the-moment fix that was really just a band-aid). But the crank
>being driven by the fork is going to be impossible to replace with a
>two-armed crank that can nest a rod end.

>Now, with all of that said, here's my question: How bad is it really
>to have the rod end in single shear if I do the washer trick? It's an
>aileron rod, I do not think it sees much load at all--certainly far,
>far short of it's rated load. I have seen several planes out there
>with rod ends in single shear, so it can't be complete suicide . . .
>right? No?
>
>Thank you for your thoughts.

I have a number of them that have been in service for over 20 years,
all with the large washer. Works for me.

Ed Sullivan, Jungster II

[cavelamb himself[_4_]]

Ed Sullivan wrote:
> On Tue, 25 Sep 2007 21:58:46 -0700, "Steve S."
> > wrote:
>
>
>>Folks:
>>
>>First let me say that I know well that everything is supposed to be in
>>double shear. Lord knows I have busted my butt to make sure
>>everything is in double shear.
>>
>>But.
>>
>>I have a portion of my aileron circuit that has a fork fitting to
>>provide the requisite double shear. However the bolt hole in the
>>crank is seeing some misalignment and is starting to wallow the hole.
>>I really, really should replace the fork fitting with a rod end (i.e.
>>it never should have been a fork fitting to begin with, it was a spur-
>>of-the-moment fix that was really just a band-aid). But the crank
>>being driven by the fork is going to be impossible to replace with a
>>two-armed crank that can nest a rod end.
>
>
>>Now, with all of that said, here's my question: How bad is it really
>>to have the rod end in single shear if I do the washer trick? It's an
>>aileron rod, I do not think it sees much load at all--certainly far,
>>far short of it's rated load. I have seen several planes out there
>>with rod ends in single shear, so it can't be complete suicide . . .
>>right? No?
>>
>>Thank you for your thoughts.
>
>
> I have a number of them that have been in service for over 20 years,
> all with the large washer. Works for me.
>
> Ed Sullivan, Jungster II

Long as teh arm and bolt are stiff enough not to deform - who cares...

[[email protected]]

On Sep 26, 12:34 am, cavelamb himself > wrote:
> Ed Sullivan wrote:
> > On Tue, 25 Sep 2007 21:58:46 -0700, "Steve S."
> > > wrote:
>
> >>Folks:
>
> >>First let me say that I know well that everything is supposed to be in
> >>double shear. Lord knows I have busted my butt to make sure
> >>everything is in double shear.
>
> >>But.
>
> >>I have a portion of my aileron circuit that has a fork fitting to
> >>provide the requisite double shear. However the bolt hole in the
> >>crank is seeing some misalignment and is starting to wallow the hole.
> >>I really, really should replace the fork fitting with a rod end (i.e.
> >>it never should have been a fork fitting to begin with, it was a spur-
> >>of-the-moment fix that was really just a band-aid). But the crank
> >>being driven by the fork is going to be impossible to replace with a
> >>two-armed crank that can nest a rod end.
>
> >>Now, with all of that said, here's my question: How bad is it really
> >>to have the rod end in single shear if I do the washer trick? It's an
> >>aileron rod, I do not think it sees much load at all--certainly far,
> >>far short of it's rated load. I have seen several planes out there
> >>with rod ends in single shear, so it can't be complete suicide . . .
> >>right? No?
>
> >>Thank you for your thoughts.
>
> > I have a number of them that have been in service for over 20 years,
> > all with the large washer. Works for me.
>
> > Ed Sullivan, Jungster II
>
> Long as teh arm and bolt are stiff enough not to deform - who cares...

The single arm may not have the resistance to twisting that
the two arms do together. You'd want to compare single-arm setups with
what you have. An arm that allows twisting will eventually fail or
might allow enough aileron play to start flutter. Both are bad news.

Dan

[Ed Sullivan]

On Wed, 26 Sep 2007 20:33:05 -0700, wrote:


>> >>aileron rod, I do not think it sees much load at all--certainly far,
>> >>far short of it's rated load. I have seen several planes out there
>> >>with rod ends in single shear, so it can't be complete suicide . . .
>> >>right? No?
>>
>> >>Thank you for your thoughts.
>>
>> > I have a number of them that have been in service for over 20 years,
>> > all with the large washer. Works for me.
>>
>> > Ed Sullivan, Jungster II
>>
>> Long as teh arm and bolt are stiff enough not to deform - who cares...
>
> The single arm may not have the resistance to twisting that
>the two arms do together. You'd want to compare single-arm setups with
>what you have. An arm that allows twisting will eventually fail or
>might allow enough aileron play to start flutter. Both are bad news.
>
> Dan

As long as the uiball is tight against the bell crank or horn there
will be no play.

:Ed

[cavelamb himself[_4_]]

Ed Sullivan wrote:
> On Wed, 26 Sep 2007 20:33:05 -0700, wrote:
>
>
>
>>>>>aileron rod, I do not think it sees much load at all--certainly far,
>>>>>far short of it's rated load. I have seen several planes out there
>>>>>with rod ends in single shear, so it can't be complete suicide . . .
>>>>>right? No?
>>>
>>>>>Thank you for your thoughts.
>>>
>>>>I have a number of them that have been in service for over 20 years,
>>>>all with the large washer. Works for me.
>>>
>>>>Ed Sullivan, Jungster II
>>>
>>>Long as teh arm and bolt are stiff enough not to deform - who cares...
>>
>> The single arm may not have the resistance to twisting that
>>the two arms do together. You'd want to compare single-arm setups with
>>what you have. An arm that allows twisting will eventually fail or
>>might allow enough aileron play to start flutter. Both are bad news.
>>
>> Dan
>
>
> As long as the uiball is tight against the bell crank or horn there
> will be no play.
>
> :Ed

True, nut not necessarily the whole story, Ed.

Because there is a small moment due to the off-axis pushrod, the
arm itself could flex.

If the arm is really thin metal (as possible if a sheet steel part
were used) it MIGHT be possible to excite the aileron system -
ie: cause flutter.

Richard

[Ed Sullivan]

On Thu, 27 Sep 2007 01:45:50 -0500, cavelamb himself
> wrote:


>> As long as the uiball is tight against the bell crank or horn there
>> will be no play.
>>
>> :Ed
>
>True, nut not necessarily the whole story, Ed.
>
>Because there is a small moment due to the off-axis pushrod, the
>arm itself could flex.
>
>If the arm is really thin metal (as possible if a sheet steel part
>were used) it MIGHT be possible to excite the aileron system -
>ie: cause flutter.
>
>Richard
>
>
That could be true, however I only attached rod end bearings to 4130
tubing.

Ed

[cavelamb himself[_4_]]

Ed Sullivan wrote:
> On Thu, 27 Sep 2007 01:45:50 -0500, cavelamb himself
> > wrote:
>
>
>
>>>As long as the uiball is tight against the bell crank or horn there
>>>will be no play.
>>>
>>>:Ed
>>
>>True, nut not necessarily the whole story, Ed.
>>
>>Because there is a small moment due to the off-axis pushrod, the
>>arm itself could flex.
>>
>>If the arm is really thin metal (as possible if a sheet steel part
>>were used) it MIGHT be possible to excite the aileron system -
>>ie: cause flutter.
>>
>>Richard
>>
>>
>
> That could be true, however I only attached rod end bearings to 4130
> tubing.
>
> Ed
>

One end, maybe.

But tube arms???

[Ed Sullivan]

On Thu, 27 Sep 2007 14:12:43 -0500, cavelamb himself
> wrote:


>>
>> That could be true, however I only attached rod end bearings to 4130
>> tubing.
>>
>> Ed
>>
>
>One end, maybe.
>
>But tube arms???

I'm really not sure I understand where you're coming from, but by arms
if you are referring to bellcranks or horns, I would certainly not
skimp on thickness.

[Ed Sullivan]

On Thu, 27 Sep 2007 21:18:38 -0400, Ernest Christley
> wrote:


>
>
>The horns on the Dyke Delta are .100 4130. The prototype had flown for
>over 40 years. If the horn was thin enough to deform from the rod end
>being in single shear, it will bend just as much in double shear. There
>is room for twist in the rod end even with both sides captured.

That may be so, but it has not been my experience. My horns and bell
cranks are a bit heavier however.

Anyway I'm too old to care

Ed

[Ed Sullivan]

On Fri, 28 Sep 2007 05:18:45 GMT, Ed Sullivan >
wrote:

>On Thu, 27 Sep 2007 21:18:38 -0400, Ernest Christley
> wrote:
>
>
>>
>>
>>The horns on the Dyke Delta are .100 4130. The prototype had flown for
>>over 40 years. If the horn was thin enough to deform from the rod end
>>being in single shear, it will bend just as much in double shear. There
>>is room for twist in the rod end even with both sides captured.
>
>That may be so, but it has not been my experience. My horns and bell
>cranks are a bit heavier however.
>
>Anyway I'm too old to care
>
>Ed

Seems to me I have seen bell cranks on both Pitts
Specials and Christen Eagles. They appeared to be no thicker than
..0625 and were in double shear as you describe. They must have held up
pretty good considering the stresses imposed on them in unllimited
aerobatics.

[Dan[_2_]]

Ed Sullivan wrote:
> On Fri, 28 Sep 2007 05:18:45 GMT, Ed Sullivan >
> wrote:
>
>> On Thu, 27 Sep 2007 21:18:38 -0400, Ernest Christley
>> > wrote:
>>
>>
>>>
>>> The horns on the Dyke Delta are .100 4130. The prototype had flown for
>>> over 40 years. If the horn was thin enough to deform from the rod end
>>> being in single shear, it will bend just as much in double shear. There
>>> is room for twist in the rod end even with both sides captured.
>> That may be so, but it has not been my experience. My horns and bell
>> cranks are a bit heavier however.
>>
>> Anyway I'm too old to care
>>
>> Ed
>
> Seems to me I have seen bell cranks on both Pitts
> Specials and Christen Eagles. They appeared to be no thicker than
> .0625 and were in double shear as you describe. They must have held up
> pretty good considering the stresses imposed on them in unllimited
> aerobatics.

One thing I haven't seen mentioned is the length of the bell crank
arm or horns. I would assume a longer throw would require thicker
material assuming similar material.

Dan, U.S. Air Force, retired