The Murphy Builders Site

Posted: **Fri Feb 17, 2012 4:20 pm**

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From: "Charles Skorupa" <chucks@gte.net>
To: "Murphy Rebel" <murphy-rebel@dcsol.com>
Subject: Fw: EDGE DISTANCE; TORQUE ARM
Date: Sun, 29 Mar 1998 08:39:58 -0800
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-----Original Message-----
From: MMoreho699 <MMoreho699@aol.com>
To: CaptVictor@aol.com <CaptVictor@aol.com>; cbrd@zeuter.com
<cbrd@zeuter.com>; ccrawfor@linknet.kitsap.lib.wa.us
<ccrawfor@linknet.kitsap.lib.wa.us>; cdenny@mindspring.com
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<MMoreho699@aol.com>
Date: Sunday, March 29, 1998 12:21 AM
Subject: EDGE DISTANCE; TORQUE ARM

Hello!

In building my torque arm I am asked to drill a #11 hole through a 2.25"
sleeve, the torque tube and the end plug (EL-31). I am asked to space this
1/2" from the end of the tube. The plug extents 13/16" into the tube from

it's

collar to the end of the plug. So this places the hole 5/16" from the end

and

1/2" from the collar.
But the #11 hole is .191" with edge distance of .382". Since 5/16" = .3125

I

can't safely do this.

Calculation for edge distance with a #11 hole: going rootward I would have
.382 and .382 tipward, or .764" for minimum length. 13/16 = .8125 That's
cutting it pretty tight in my book. Are my calculations correct?

I also may need some control horns or fabricate them. What are their specs?

I

have some ones that the holes were drilled too close to the edge, using
similar numbers as above. I could just trace them out of stock aluminum.

Also my clearance between the control horn going through the bottom of the
wing to the skin is 1/16". Is this enough?

Concerning the push-pull tube to flaperon control horns connection: my

push-

pull tube looks different than figure 79 of 7/27/94 Rebel manual. In the
manual, it looks like the flaperon horns are nearly flush with the Rod End
Bearings (HM-4M). I have a 1/8" gap between the outsides of the rod end
bearing and the flaperon horns. Problem?

Thanks,
Dan
R280

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Posted: **Fri Feb 17, 2012 4:20 pm**

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From: "Charles Skorupa" <chucks@gte.net>
To: "Murphy Rebel" <murphy-rebel@dcsol.com>
Subject: Re: EDGE DISTANCE; TORQUE ARM
Date: Sun, 29 Mar 1998 09:47:23 -0800
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Hi Dan,
My 2 cents worth! I think that the parts you are referring to are not
loaded axially, and therefore the edge distance is not as big an issue. The
arm is used to apply torque only to the torque tube, although some small
axial load component might be generated due to misalignment over the entire
stroke. So what's all that mean? It means that I probably wouldn't worry
about the smaller edge distance in this particular application. There is no
load condition that is trying to pull the end cap out of the tube. In
addition you have a circular component inside another circular component and
"hoops" behave differently than straight sections. There is a
circumfirential load applied when the arm rotates the tube, or the
ailerons/flaps apply air load that is resisted by the stick. However, that
could be conceivably reacted by notches or cogs which have NO edge distance.
I wouldn't be surprised if some folding wing aircraft do just that to avoid
disconnecting something during wingfold. I suspect one of the main reasons
Murphy went to the larger rivet sizes here was to increase the bearing area,
thus reducing the stress and increasing the fatigue life.

Once again, this is only a seat of the pants opinion based on whatever
popped into my head at the moment. To do it right, a complete set of loads
is needed for all normal and non-normal conditions. Only Murphy has that
info, and they are very good about answering questions. As always, they
have the final word. I wouldn't scrap anything until I talked to them.

Good Luck,

- Chuck Skorupa -
Rebel Elite Taildragger S/N #500
-----Original Message-----
From: Charles Skorupa <chucks@gte.net>
To: Murphy Rebel <murphy-rebel@dcsol.com>
Date: Sunday, March 29, 1998 8:55 AM
Subject: Fw: EDGE DISTANCE; TORQUE ARM

-----Original Message-----
From: MMoreho699 <MMoreho699@aol.com>
To: CaptVictor@aol.com <CaptVictor@aol.com>; cbrd@zeuter.com
<cbrd@zeuter.com>; ccrawfor@linknet.kitsap.lib.wa.us
<ccrawfor@linknet.kitsap.lib.wa.us>; cdenny@mindspring.com
<cdenny@mindspring.com>; chucks@gte.net <chucks@gte.net>; cimaut@ven.net
<cimaut@ven.net>; Clarapegg@aol.com <Clarapegg@aol.com>;

croft@islandnet.com

<croft@islandnet.com>; CWS1932@aol.com <CWS1932@aol.com>;

MMoreho699@aol.com

<MMoreho699@aol.com>
Date: Sunday, March 29, 1998 12:21 AM
Subject: EDGE DISTANCE; TORQUE ARM

Hello!

In building my torque arm I am asked to drill a #11 hole through a 2.25"
sleeve, the torque tube and the end plug (EL-31). I am asked to space this
1/2" from the end of the tube. The plug extents 13/16" into the tube from
it's
collar to the end of the plug. So this places the hole 5/16" from the end
and
1/2" from the collar.
But the #11 hole is .191" with edge distance of .382". Since 5/16" = .3125
I
can't safely do this.

Calculation for edge distance with a #11 hole: going rootward I would

have

.382 and .382 tipward, or .764" for minimum length. 13/16 = .8125 That's
cutting it pretty tight in my book. Are my calculations correct?

I also may need some control horns or fabricate them. What are their

specs?

I
have some ones that the holes were drilled too close to the edge, using
similar numbers as above. I could just trace them out of stock aluminum.

Also my clearance between the control horn going through the bottom of the
wing to the skin is 1/16". Is this enough?

Concerning the push-pull tube to flaperon control horns connection: my
push-
pull tube looks different than figure 79 of 7/27/94 Rebel manual. In the
manual, it looks like the flaperon horns are nearly flush with the Rod End
Bearings (HM-4M). I have a 1/8" gap between the outsides of the rod end
bearing and the flaperon horns. Problem?

Thanks,
Dan
R280

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