Hinges under stress - mechanical engineering type question

Thinking about a hinge like this (end view): ____(O)____ where "___"
is the plate, "( )" is the barrel, and "O" is the hinge pin. It would
be bolted through the plates to the surface below. The barrel sits
"on top" of the plates. Hope that makes sense.

It's in tension and/or compression (some torsion also), so obviously
the hinge pin needs to have a lot of shear strength. Clevis pins are
designed for this application, so it's a matter of doing the sums and
selecting a properly-sized one from the catalog.

But the *barrels* of the hinge are a weak point. A plain rolled
piano-type hinge would obviously just pull apart if the barrels aren't
connected back to the plate. What's the best way to prevent this?

Weld the barrels back to the plate so they are closed and can't pull
open? Makes sense - but how sure can you be of the tensile strength
of that weld? Build a test article and test it to destruction?

Or perhaps you could make the hinge by folding a strap around the
clevis pin, and back over itself. Then you have a double-thick plate
- extra weight. And tension would tend to pull the barrel out of
round and make the clevis want to center between the straps:
=====O==== rather than "on top": ____(O)____. Also, you'd have a
sharp reflex bend - potential crack site - where the barrel comes down
around the pin and then flattens out as the top layer of the two-layer
plate: __(

Ideas? I know somebody has to have already solved this. btw - assume
that the issues of properly bolting the hinge to the material below,
and properly heat -treating the assembly, have been solved. We're
just looking at the mechanics of the hinge barrel, unless I'm missing
something.

(Rich, yes, you know why I'm asking... ;-) )

Corrie "alllllways thinkin'..." B.

Most suppliers have the extruded piano hings that will not pull apart before
failure. I know Aircraft Spruce has them in 6 Ft lengths aluminum or
stainless steel.

"Corrie" wrote in message
om...
Thinking about a hinge like this (end view): ____(O)____ where "___"
is the plate, "( )" is the barrel, and "O" is the hinge pin. It would
be bolted through the plates to the surface below. The barrel sits
"on top" of the plates. Hope that makes sense.

It's in tension and/or compression (some torsion also), so obviously
the hinge pin needs to have a lot of shear strength. Clevis pins are
designed for this application, so it's a matter of doing the sums and
selecting a properly-sized one from the catalog.

But the *barrels* of the hinge are a weak point. A plain rolled
piano-type hinge would obviously just pull apart if the barrels aren't
connected back to the plate. What's the best way to prevent this?

Weld the barrels back to the plate so they are closed and can't pull
open? Makes sense - but how sure can you be of the tensile strength
of that weld? Build a test article and test it to destruction?

Or perhaps you could make the hinge by folding a strap around the
clevis pin, and back over itself. Then you have a double-thick plate
- extra weight. And tension would tend to pull the barrel out of
round and make the clevis want to center between the straps:
=====O==== rather than "on top": ____(O)____. Also, you'd have a
sharp reflex bend - potential crack site - where the barrel comes down
around the pin and then flattens out as the top layer of the two-layer
plate: __(

Ideas? I know somebody has to have already solved this. btw - assume
that the issues of properly bolting the hinge to the material below,
and properly heat -treating the assembly, have been solved. We're
just looking at the mechanics of the hinge barrel, unless I'm missing
something.

(Rich, yes, you know why I'm asking... ;-) )

Corrie "alllllways thinkin'..." B.

john wrote in message . ..
On 30 Jul 2003 16:56:37 -0700, (Corrie) wrote:

"MS20001P aluminum hinge is extruded. The closed hinge loops cannot be
pulled apart. Furnished with hinge pin. Anodized finish."

Thanks. How much stress can it take, though? That's the question.
Probably the hinge pin or the rivets holding the plates would be the
first to fail at a few hundred pounds, but still... musing I
suppose one could order some and find out.... If the specific alloy
were known, it could be looked up.
http://ourworld.compuserve.com/homep...orhis/T003.htm shows
yield and tensile strengths for a number of allows. They tend to be
around 30kpsi. The catalog doesn't give the thickness of the flange.
Assume it's .1", and the hinge is 6" long, that's .6 sq. in, at
30kpsi.. 18,000 lbs? But some alloys are as low as 5kpsi - that's
3,000 lbs. Impressive for a small hinge, but would it suffice for the
application? Marginal at best, I think.

The largest hinge at AS&S is just 2" wide, and they all seem to have
the same size pin - .089 stainless. That's .006 sq. in. area. I
can't find a reference for shear strength for stainless, but taking an
optimistic SWAG at 200kpsi (the highest yield strength for drawn ss
referenced at http://ourworld.compuserve.com/homep...orhis/T006.htm),
that's 200,000 x .006 = 1200 lbs. Not nearly good enough. /musing


My guess is that if it's not specifically rated and labeled, it's
unknown. Not something to put in a critical area. So, then, back to
the original question. Assuming you don't have the ability to extrude
a larger piece of aluminum (in order to use a larger pin), how *do*
you solve the problem?

Corrie

Just think out of the box.

Go to hardware store and buy some farm gate hinges with the 1/2 inch
bolt in them. They may be over engineered for your proposed use but
they are hell for stout and would probably do the job ok without a lot
of paper engineering..

Big John

On 31 Jul 2003 12:46:24 -0700, (Corrie) wrote:

john wrote in message . ..
On 30 Jul 2003 16:56:37 -0700, (Corrie) wrote:

"MS20001P aluminum hinge is extruded. The closed hinge loops cannot be
pulled apart. Furnished with hinge pin. Anodized finish."

Thanks. How much stress can it take, though? That's the question.
Probably the hinge pin or the rivets holding the plates would be the
first to fail at a few hundred pounds, but still... musing I
suppose one could order some and find out.... If the specific alloy
were known, it could be looked up.
http://ourworld.compuserve.com/homep...orhis/T003.htm shows
yield and tensile strengths for a number of allows. They tend to be
around 30kpsi. The catalog doesn't give the thickness of the flange.
Assume it's .1", and the hinge is 6" long, that's .6 sq. in, at
30kpsi.. 18,000 lbs? But some alloys are as low as 5kpsi - that's
3,000 lbs. Impressive for a small hinge, but would it suffice for the
application? Marginal at best, I think.

The largest hinge at AS&S is just 2" wide, and they all seem to have
the same size pin - .089 stainless. That's .006 sq. in. area. I
can't find a reference for shear strength for stainless, but taking an
optimistic SWAG at 200kpsi (the highest yield strength for drawn ss
referenced at http://ourworld.compuserve.com/homep...orhis/T006.htm),
that's 200,000 x .006 = 1200 lbs. Not nearly good enough. /musing


My guess is that if it's not specifically rated and labeled, it's
unknown. Not something to put in a critical area. So, then, back to
the original question. Assuming you don't have the ability to extrude
a larger piece of aluminum (in order to use a larger pin), how *do*
you solve the problem?

"Corrie" wrote in message
om...
john wrote in message
. ..
On 30 Jul 2003 16:56:37 -0700, (Corrie) wrote:

"MS20001P aluminum hinge is extruded. The closed hinge loops cannot be
pulled apart. Furnished with hinge pin. Anodized finish."

Thanks. How much stress can it take, though? That's the question.
Probably the hinge pin or the rivets holding the plates would be the
first to fail at a few hundred pounds, but still... musing I
suppose one could order some and find out.... If the specific alloy
were known, it could be looked up.
http://ourworld.compuserve.com/homep...orhis/T003.htm shows
yield and tensile strengths for a number of allows. They tend to be
around 30kpsi. The catalog doesn't give the thickness of the flange.
Assume it's .1", and the hinge is 6" long, that's .6 sq. in, at
30kpsi.. 18,000 lbs? But some alloys are as low as 5kpsi - that's
3,000 lbs. Impressive for a small hinge, but would it suffice for the
application? Marginal at best, I think.

The largest hinge at AS&S is just 2" wide, and they all seem to have
the same size pin - .089 stainless. That's .006 sq. in. area. I
can't find a reference for shear strength for stainless, but taking an
optimistic SWAG at 200kpsi (the highest yield strength for drawn ss
referenced at
http://ourworld.compuserve.com/homep...orhis/T006.htm),
that's 200,000 x .006 = 1200 lbs. Not nearly good enough. /musing


My guess is that if it's not specifically rated and labeled, it's
unknown. Not something to put in a critical area. So, then, back to
the original question. Assuming you don't have the ability to extrude
a larger piece of aluminum (in order to use a larger pin), how *do*
you solve the problem?

Like this:

http://www.zenithair.com/kit-data/ht-aileron.html

Rick Pellicciotti

Corrie wrote:

The largest hinge at AS&S is just 2" wide, and they all seem to have
the same size pin - .089 stainless. That's .006 sq. in. area. I
can't find a reference for shear strength for stainless, but taking an
optimistic SWAG at 200kpsi (the highest yield strength for drawn ss
referenced at http://ourworld.compuserve.com/homep...orhis/T006.htm),
that's 200,000 x .006 = 1200 lbs. Not nearly good enough. /musing



That's 1200 lbs at each hingepoint, that is every place that you could
slip a feeler guage down and touch the pin. That's about every 1/2" or
so on most of these strips.
--
----Because I can----
http://www.ernest.isa-geek.org/
------------------------

Corrie wrote:

john wrote in message . ..
On 30 Jul 2003 16:56:37 -0700, (Corrie) wrote:

"MS20001P aluminum hinge is extruded. The closed hinge loops cannot be
pulled apart. Furnished with hinge pin. Anodized finish."

Thanks. How much stress can it take, though? That's the question.
Probably the hinge pin or the rivets holding the plates would be the
first to fail at a few hundred pounds, but still... musing I
suppose one could order some and find out.... If the specific alloy
were known, it could be looked up.
http://ourworld.compuserve.com/homep...orhis/T003.htm shows
yield and tensile strengths for a number of allows. They tend to be
around 30kpsi. The catalog doesn't give the thickness of the flange.
Assume it's .1", and the hinge is 6" long, that's .6 sq. in, at
30kpsi.. 18,000 lbs? But some alloys are as low as 5kpsi - that's
3,000 lbs. Impressive for a small hinge, but would it suffice for the
application? Marginal at best, I think.

The largest hinge at AS&S is just 2" wide, and they all seem to have
the same size pin - .089 stainless. That's .006 sq. in. area. I
can't find a reference for shear strength for stainless, but taking an
optimistic SWAG at 200kpsi (the highest yield strength for drawn ss
referenced at http://ourworld.compuserve.com/homep...orhis/T006.htm),
that's 200,000 x .006 = 1200 lbs. Not nearly good enough. /musing

My guess is that if it's not specifically rated and labeled, it's
unknown. Not something to put in a critical area. So, then, back to
the original question. Assuming you don't have the ability to extrude
a larger piece of aluminum (in order to use a larger pin), how *do*
you solve the problem?


I really feel like a big dummy, because I may have missed the obvious,
and I know that I may have nothing usefull to add after all ... but ...

What are these hinges supposed to hold???
pressurized canopy?
undercarriage trunion?
control surface?
some kind of single hinge application?

Peter

"Peter Dohm" wrote in message
...
Corrie wrote:

I really feel like a big dummy, because I may have missed the obvious,
and I know that I may have nothing usefull to add after all ... but ...

What are these hinges supposed to hold???
pressurized canopy?
undercarriage trunion?
control surface?
some kind of single hinge application?

Peter

Well, the Sisu 1A sailplane used aircraft grade piano hinges in instead of
spar root fittings. The right and left wings were joined to each other with
1/16" piano wire inserted through hinges riveted to the upper and lower wing
skins. The fuselage was hung from the joined wings.

See: http://www.nasm.si.edu/nasm/aero/aircraft/arlington.htm

Bill Daniels

For the people that didn't visit the Zenith link, thats a sheet metal
hinge, no moving parts, just flexing sheet. I've seen this up close
and its pretty slick. One of those "Why didn't I think of that!" kind
of moments.

Regards

"Rick Pellicciotti" wrote in message news:3f298016$1@ham...

Like this:

http://www.zenithair.com/kit-data/ht-aileron.html

Rick Pellicciotti

Peter Dohm asked, quite reasonably
What are these hinges supposed to hold???

The spar. I'm thinking about the possibility of considering the
feasibility of investigating a folding wing. The spar would have a
hinge installed top and bottom. To fold the wing you remove the
bottom pin. GW of the aircraft in mind is ~1500lb. It would need to
be able to take 6 g's, hence my concern about strength.

The sailplane may have used standard piano hinges, but it was about
500 lbs, and probably not stressed for more than 3 g's.