The "old way" is to mount a plywood plate in the middle of the wing,
then mount the bellcrank to the plate by screwing down a bushing to
retain the bellcrank.

The "new way" is to use small plywood plates top & bottom, with an
all-thread steel rod mounting that bushing in the middle of the wing.
Because the plates are much closer to the strong points of the wing
spar, it takes less material to bring the bellcrank forces (which by the
rules get tested to ten times the weight of the plane) out to where they
need to be.

This is my "new way", just because. The big aluminum post replaces the
bushing (I hope Nylon wears well working against aluminum), the little
aluminum bushing determines the spacing of the plywood plates, and the
post rides in the plates on 1/4" pegs, which gives a lot more area to
bear on the plywood than an 8-32 all-thread rod would.

http://www.metalworking.com/dropbox/belcrank_mount.jpg

--
Tim "Over Engineered" Wescott
Control system and signal processing consulting
www.wescottdesign.com

On Jun 17, 3:52*pm, Tim Wescott wrote:
The "old way" is to mount a plywood plate in the middle of the wing,
then mount the bellcrank to the plate by screwing down a bushing to
retain the bellcrank.

The "new way" is to use small plywood plates top & bottom, with an
all-thread steel rod mounting that bushing in the middle of the wing.
Because the plates are much closer to the strong points of the wing
spar, it takes less material to bring the bellcrank forces (which by the
rules get tested to ten times the weight of the plane) out to where they
need to be.

This is my "new way", just because. *The big aluminum post replaces the
bushing (I hope Nylon wears well working against aluminum), the little
aluminum bushing determines the spacing of the plywood plates, and the
post rides in the plates on 1/4" pegs, which gives a lot more area to
bear on the plywood than an 8-32 all-thread rod would.

http://www.metalworking.com/dropbox/belcrank_mount.jpg

--
Tim "Over Engineered" Wescott
Control system and signal processing consultingwww.wescottdesign.com

Nylon LOVES to absorb water. How will this work on damp days when the
nylon swells up?

On 06/17/2010 02:01 PM, Cross-Slide wrote:
On Jun 17, 3:52 pm, Tim wrote:
The "old way" is to mount a plywood plate in the middle of the wing,
then mount the bellcrank to the plate by screwing down a bushing to
retain the bellcrank.

The "new way" is to use small plywood plates top& bottom, with an
all-thread steel rod mounting that bushing in the middle of the wing.
Because the plates are much closer to the strong points of the wing
spar, it takes less material to bring the bellcrank forces (which by the
rules get tested to ten times the weight of the plane) out to where they
need to be.

This is my "new way", just because. The big aluminum post replaces the
bushing (I hope Nylon wears well working against aluminum), the little
aluminum bushing determines the spacing of the plywood plates, and the
post rides in the plates on 1/4" pegs, which gives a lot more area to
bear on the plywood than an 8-32 all-thread rod would.

http://www.metalworking.com/dropbox/belcrank_mount.jpg

--
Tim "Over Engineered" Wescott
Control system and signal processing consultingwww.wescottdesign.com

Nylon LOVES to absorb water. How will this work on damp days when the
nylon swells up?

This is the problem with design reviews -- the information that's most
likely to make you happy (or at least not deeply unhappy) in the long
run is the information that in the short run is most likely to make you
want to point and scream "you *******!".

I think the tolerances are open enough that it won't make a difference,
although I could thin the post down a bit (as long as I do it _now_) to
make sure. If anything I'll have problems when it dries out and gets
smaller -- we're having a humid summer here in Oregon.

I am going to chuck the assembly into the freezer in a moment, to see
how it'll work at cold -- for which idea I thank you. Presumably at hot
it'll just have more slop and it'll work better, although perhaps I
should chuck it in a 150 degree (F) oven to make sure. Perhaps to make
_really_ sure I should chuck it in that oven & bake out moisture for a
while, then toss it into a sealed jar so I know that it's nice and dry
at room temperature. Or maybe I'll just go put my damn wing together --
the wood working has been waiting on this part for a while.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

On Thu, 17 Jun 2010 13:52:13 -0700, Tim Wescott
wrote:

The "old way" is to mount a plywood plate in the middle of the wing,
then mount the bellcrank to the plate by screwing down a bushing to
retain the bellcrank.

The "new way" is to use small plywood plates top & bottom, with an
all-thread steel rod mounting that bushing in the middle of the wing.
Because the plates are much closer to the strong points of the wing
spar, it takes less material to bring the bellcrank forces (which by the
rules get tested to ten times the weight of the plane) out to where they
need to be.

This is my "new way", just because. The big aluminum post replaces the
bushing (I hope Nylon wears well working against aluminum), the little
aluminum bushing determines the spacing of the plywood plates, and the
post rides in the plates on 1/4" pegs, which gives a lot more area to
bear on the plywood than an 8-32 all-thread rod would.

http://www.metalworking.com/dropbox/belcrank_mount.jpg

Looks great. Just weigh it relative to the old way to know whether
you over-engineered or not.

Pete Keillor
(locomotive jack stand weight bench guy)

On 06/17/2010 02:27 PM, Pete Keillor wrote:
On Thu, 17 Jun 2010 13:52:13 -0700, Tim
wrote:

The "old way" is to mount a plywood plate in the middle of the wing,
then mount the bellcrank to the plate by screwing down a bushing to
retain the bellcrank.

The "new way" is to use small plywood plates top& bottom, with an
all-thread steel rod mounting that bushing in the middle of the wing.
Because the plates are much closer to the strong points of the wing
spar, it takes less material to bring the bellcrank forces (which by the
rules get tested to ten times the weight of the plane) out to where they
need to be.

This is my "new way", just because. The big aluminum post replaces the
bushing (I hope Nylon wears well working against aluminum), the little
aluminum bushing determines the spacing of the plywood plates, and the
post rides in the plates on 1/4" pegs, which gives a lot more area to
bear on the plywood than an 8-32 all-thread rod would.

http://www.metalworking.com/dropbox/belcrank_mount.jpg

Looks great. Just weigh it relative to the old way to know whether
you over-engineered or not.

Seven grams, which compares favorably to #10 hardware but probably gains
a gram on #8 hardware. If it weren't going into a sport plane I'd use
1/16" plywood instead of 1/8", on the grounds that the larger bearing
surface of the aluminum vs. #8 hardware would give better local crush
resistance.

But it's a plane to learn stunt on (yes, it's dumb to be doing this much
work for that), so I think the "crush resistance" that I'm going to test
is going to be the fuselage, the wings, and the vertical stabilizer
surfaces.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

On Thu, 17 Jun 2010 14:46:11 -0700, Tim Wescott
wrote:

On 06/17/2010 02:27 PM, Pete Keillor wrote:
On Thu, 17 Jun 2010 13:52:13 -0700, Tim
wrote:

The "old way" is to mount a plywood plate in the middle of the wing,
then mount the bellcrank to the plate by screwing down a bushing to
retain the bellcrank.

The "new way" is to use small plywood plates top& bottom, with an
all-thread steel rod mounting that bushing in the middle of the wing.
Because the plates are much closer to the strong points of the wing
spar, it takes less material to bring the bellcrank forces (which by the
rules get tested to ten times the weight of the plane) out to where they
need to be.

This is my "new way", just because. The big aluminum post replaces the
bushing (I hope Nylon wears well working against aluminum), the little
aluminum bushing determines the spacing of the plywood plates, and the
post rides in the plates on 1/4" pegs, which gives a lot more area to
bear on the plywood than an 8-32 all-thread rod would.

http://www.metalworking.com/dropbox/belcrank_mount.jpg

Looks great. Just weigh it relative to the old way to know whether
you over-engineered or not.

Seven grams, which compares favorably to #10 hardware but probably gains
a gram on #8 hardware. If it weren't going into a sport plane I'd use
1/16" plywood instead of 1/8", on the grounds that the larger bearing
surface of the aluminum vs. #8 hardware would give better local crush
resistance.

But it's a plane to learn stunt on (yes, it's dumb to be doing this much
work for that), so I think the "crush resistance" that I'm going to test
is going to be the fuselage, the wings, and the vertical stabilizer
surfaces.

Yup, my second r/c plane did the figure 9 on the 1st flight. The
engine was buried 9" in clay. It still works. I also have the pilot
figure, although he's a little banged up where he flew through the
bubble canopy.

Pete Keillor

On 06/17/2010 03:18 PM, JR North wrote:
(top posting fixed)

Tim Wescott wrote:
The "old way" is to mount a plywood plate in the middle of the wing,
then mount the bellcrank to the plate by screwing down a bushing to
retain the bellcrank.

The "new way" is to use small plywood plates top & bottom, with an
all-thread steel rod mounting that bushing in the middle of the wing.
Because the plates are much closer to the strong points of the wing
spar, it takes less material to bring the bellcrank forces (which by
the rules get tested to ten times the weight of the plane) out to
where they need to be.

This is my "new way", just because. The big aluminum post replaces the
bushing (I hope Nylon wears well working against aluminum), the little
aluminum bushing determines the spacing of the plywood plates, and the
post rides in the plates on 1/4" pegs, which gives a lot more area to
bear on the plywood than an 8-32 all-thread rod would.

http://www.metalworking.com/dropbox/belcrank_mount.jpg


Speaking of control line; I just snagged a Testors .049 BD5 on Ebay.
SUPER rare. The engine mounts just behind the cockpit, with the same
shaft drive setup as the original. Super cool. About 22" wingspan.
Unfortunatly, it was displayed in an evironment of heavy cooking fumes
and prolly cigars or pipe smoke.The slime etched into the plastic, which
I am slowly fixing by careful wet sanding with 1k grit.
JR
Dweller in the cellar

If I were at all the collector type I would be absolutely green with
envy -- I didn't know they _made_ a BD5. It seems like they would have
lost their shirts on it, unless they really jacked the price up.

Kewl -- that would be one to model with an electric, with the engine
behind and the battery waaaay out in front.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

Yup - used to fly a 2-meter glider. 8 Ni-cad pack and a cobalt
motor used to drive it almost upwards. It took a while to understand
that up is down and down is up and one day as landing on a blacktop
it came in a bit hot and instead of flaring for a stall - I tipped
it into the blacktop. bent a 3/8" Stainless propeller shaft.
Ugly. got a new gearbox/shaft and worked at it for a while.
Now it is long gone. Just stuff here and there for the hobby.

Martin

Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
"Our Republic and the Press will Rise or Fall Together": Joseph Pulitzer
TSRA: Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Charter Charter Founder
IHMSA and NRA Metallic Silhouette maker & member. http://lufkinced.com/

snip

Yup, my second r/c plane did the figure 9 on the 1st flight. The
engine was buried 9" in clay. It still works. I also have the pilot
figure, although he's a little banged up where he flew through the
bubble canopy.

Pete Keillor

On Thu, 17 Jun 2010 14:26:25 -0700, Tim Wescott
wrote:

On 06/17/2010 02:01 PM, Cross-Slide wrote:
On Jun 17, 3:52 pm, Tim wrote:
The "old way" is to mount a plywood plate in the middle of the wing,
then mount the bellcrank to the plate by screwing down a bushing to
retain the bellcrank.

The "new way" is to use small plywood plates top& bottom, with an
all-thread steel rod mounting that bushing in the middle of the wing.
Because the plates are much closer to the strong points of the wing
spar, it takes less material to bring the bellcrank forces (which by the
rules get tested to ten times the weight of the plane) out to where they
need to be.

This is my "new way", just because. The big aluminum post replaces the
bushing (I hope Nylon wears well working against aluminum), the little
aluminum bushing determines the spacing of the plywood plates, and the
post rides in the plates on 1/4" pegs, which gives a lot more area to
bear on the plywood than an 8-32 all-thread rod would.

http://www.metalworking.com/dropbox/belcrank_mount.jpg

--
Tim "Over Engineered" Wescott
Control system and signal processing consultingwww.wescottdesign.com

Nylon LOVES to absorb water. How will this work on damp days when the
nylon swells up?

This is the problem with design reviews -- the information that's most
likely to make you happy (or at least not deeply unhappy) in the long
run is the information that in the short run is most likely to make you
want to point and scream "you *******!".

When you're ready to go beyond denial, consider acetyl (Delryn) or
Noryl.

On Fri, 18 Jun 2010 01:05:33 -0500, Don Foreman
wrote:

On Thu, 17 Jun 2010 14:26:25 -0700, Tim Wescott
wrote:

On 06/17/2010 02:01 PM, Cross-Slide wrote:
On Jun 17, 3:52 pm, Tim wrote:
The "old way" is to mount a plywood plate in the middle of the wing,
then mount the bellcrank to the plate by screwing down a bushing to
retain the bellcrank.

The "new way" is to use small plywood plates top& bottom, with an
all-thread steel rod mounting that bushing in the middle of the wing.
Because the plates are much closer to the strong points of the wing
spar, it takes less material to bring the bellcrank forces (which by the
rules get tested to ten times the weight of the plane) out to where they
need to be.

This is my "new way", just because. The big aluminum post replaces the
bushing (I hope Nylon wears well working against aluminum), the little
aluminum bushing determines the spacing of the plywood plates, and the
post rides in the plates on 1/4" pegs, which gives a lot more area to
bear on the plywood than an 8-32 all-thread rod would.

http://www.metalworking.com/dropbox/belcrank_mount.jpg

--
Tim "Over Engineered" Wescott
Control system and signal processing consultingwww.wescottdesign.com

Nylon LOVES to absorb water. How will this work on damp days when the
nylon swells up?

This is the problem with design reviews -- the information that's most
likely to make you happy (or at least not deeply unhappy) in the long
run is the information that in the short run is most likely to make you
want to point and scream "you *******!".

When you're ready to go beyond denial, consider acetyl (Delryn) or
Noryl.

Tim, I forgot what you were doing here when I posted. If you'd like a
bit of Delryn and glass-filled Noryl I would be happy to send you
bits. Also bronze. We're talking ****ant postage here, not worth
worrying about. Say the word and an addy. Tell me what size OD stock
would enable you.

On 06/17/2010 11:05 PM, Don Foreman wrote:
On Thu, 17 Jun 2010 14:26:25 -0700, Tim
wrote:

On 06/17/2010 02:01 PM, Cross-Slide wrote:
On Jun 17, 3:52 pm, Tim wrote:
The "old way" is to mount a plywood plate in the middle of the wing,
then mount the bellcrank to the plate by screwing down a bushing to
retain the bellcrank.

The "new way" is to use small plywood plates top& bottom, with an
all-thread steel rod mounting that bushing in the middle of the wing.
Because the plates are much closer to the strong points of the wing
spar, it takes less material to bring the bellcrank forces (which by the
rules get tested to ten times the weight of the plane) out to where they
need to be.

This is my "new way", just because. The big aluminum post replaces the
bushing (I hope Nylon wears well working against aluminum), the little
aluminum bushing determines the spacing of the plywood plates, and the
post rides in the plates on 1/4" pegs, which gives a lot more area to
bear on the plywood than an 8-32 all-thread rod would.

http://www.metalworking.com/dropbox/belcrank_mount.jpg

--
Tim "Over Engineered" Wescott
Control system and signal processing consultingwww.wescottdesign.com

Nylon LOVES to absorb water. How will this work on damp days when the
nylon swells up?

This is the problem with design reviews -- the information that's most
likely to make you happy (or at least not deeply unhappy) in the long
run is the information that in the short run is most likely to make you
want to point and scream "you *******!".

When you're ready to go beyond denial, consider acetyl (Delryn) or
Noryl.

For the pivot, or for the bellcrank?

The bellcrank is a commercial (Sig) unit -- I'm just making a new pivot
for it. I think Delrin would be way too flexible for a pivot, although
glass-filled might be OK if I didn't mind dulling all my bits.

The materials of choice for the bellcranks in really competitive circles
seems to be either aluminum alloy, linen-filled phenolic with brass
bushings, or the obligatory CF-epoxy laminate.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

On 2010-06-18, Tim Wescott wrote:
On 06/17/2010 11:05 PM, Don Foreman wrote:
On Thu, 17 Jun 2010 14:26:25 -0700, Tim
wrote:

On 06/17/2010 02:01 PM, Cross-Slide wrote:
On Jun 17, 3:52 pm, Tim wrote:
The "old way" is to mount a plywood plate in the middle of the wing,
then mount the bellcrank to the plate by screwing down a bushing to
retain the bellcrank.

The "new way" is to use small plywood plates top& bottom, with an
all-thread steel rod mounting that bushing in the middle of the wing.
Because the plates are much closer to the strong points of the wing
spar, it takes less material to bring the bellcrank forces (which by the
rules get tested to ten times the weight of the plane) out to where they
need to be.

This is my "new way", just because. The big aluminum post replaces the
bushing (I hope Nylon wears well working against aluminum), the little
aluminum bushing determines the spacing of the plywood plates, and the
post rides in the plates on 1/4" pegs, which gives a lot more area to
bear on the plywood than an 8-32 all-thread rod would.

http://www.metalworking.com/dropbox/belcrank_mount.jpg

[ ... ]

When you're ready to go beyond denial, consider acetyl (Delryn) or
Noryl.

For the pivot, or for the bellcrank?

The bellcrank *may* already be natural Acetyl (Delrin).
Whatever it is, it was molded, not machined.

Delrin is stronger and more humidity resistant (thus more
dimensionally stable) than Nylon, so it would be a better choice. It
comes in your choice of natural (looks like what you have there) or
black (more UV resistant).

The bellcrank is a commercial (Sig) unit -- I'm just making a new pivot
for it. I think Delrin would be way too flexible for a pivot,

It would certainly be more rigid than Nylon would.

I would not suggest that you make the bellcrank and the pivot of
the same material. With metals, you have the problem of galling
(pressure welding and then pulling out material from one part and
sticking to the other, making a rough surface.)

One possibility might be the body of the pivot of something low
friction like Teflon with a steel core making up perhaps half the
diameter of the pin. This would produce some savings in weight yet
retain sufficient rigidity.

although
glass-filled might be OK if I didn't mind dulling all my bits.

:-)

The materials of choice for the bellcranks in really competitive circles
seems to be either aluminum alloy, linen-filled phenolic with brass
bushings, or the obligatory CF-epoxy laminate.

O.K.

Perhaps a hard aluminum alloy for the bellcrank with lightening
holes scattered around it.

Good luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On Fri, 18 Jun 2010 13:28:44 -0700, JR North
wrote the following:

Too much. I got my BD5 for $50.

OMG! What a deal, JR!

http://www.bd5.com/My5JPics/P1020131.JPG


--
Peace of mind is that mental condition in which you have accepted the worst.
-- Lin Yutang