Tail & Control System
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02/11/02 TORQUE TUBE ELEVATOR STOPS
12/02/01 PUSHRODS, FISHMOUTHS, AN490HT ROD ENDS, REMOVE CAD PLATING
12/01/01 SHORTER TRIM RODS, TRIM ROD, SAFETY WASHERS
12/01/01 PUSHROD ENDS
11/09/01 FITTING TRIM TABS TO ELEVATORS
11/09/01 PLANS VS. HP ELEVATORS
10/24/01 TRIM HORN AND ARMS ALIGNMENT IN STAB
10/22/01 ELEVATOR HORN BLOCK
10/03/01 WELDING STAB RIB 310-10
09/14/01 TAIL HINGE FREE PLAY, RINGS
06/28/01 TAIL STRAP HINGES, DR-109
06/28/01 BEARING CAGES, STIFF CONTROLS, ASSEMBLY PLUGS
02/06/01 TAIL TUBES
01/24/01 HINGES, STRAPS, HINGE RESTS
12/21/00 HINGE BUSHINGS
12/20/00 RUDDER PEDAL, BRAKE PEDAL
11/29/00 FUSELAGE MODIFICATIONS, CONTROL SYSTEM, IDLER, TAILWHEEL LOCK
11/11/00 FUSELAGE MODIFICATIONS, TORQUE TUBE, REAR STICK, BEARINGS, IDLER
11/05/00 RUDDER PEDAL JIGS
08/28/00 TUBE BENDING, TUBE ROLLER
04/30/00 TAIL RIB BENDING
03/22/02 SUBSTITUTING AURORA ROD ENDS FOR FAFNIR
I was wondering why, instead of the Fafnir rod ends specified in the plans I couldn't use another brand with
the same dimensions. I am talking about the ones for the push-pull tubes in the elevator and aileron control
systems. I was looking through the latest edition of my 'Chassis Shop' catalog (they sell race car equipment)
and noticed they had Aurora brand 4130 rod ends rated at 5260 lbs radial load for $14.96 each in
quantity (10+). The equivalent Fafnir from ACS cost $50. Personally I don't see how I could ever come close
to exceeding the load they are rated for. Brad
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Here is an image showing information from the Aurora and Fafnir bearing
catalogs:
Fafnir vs. Aurora Rod Ends
The question was about substituting an Aurora AM series rod ends for
designer-specified Fafnir REP series. Without a bearing catalog to look at, you had
little information, mostly just price and a load rating. Might there be more?
As it turns out, the Fafnir REP series and the Aurora AM series are very
different bearings. Different doesn't necessarily mean "can't substitute",
but it's best to do so in an informed manner.
The major difference is that the REP is a ball bearing rod end, while
the AM is a simple PTFE coated race (no rolling elements). That explains the
difference in cost, and the lower load rating for the Fafnir. If I
understand the tech pages correctly, the Fafnir rating is based on the lower
of two different methods, the load that dents the rolling element parts, or
66% of the load that ruptures the outer casing. Aurora doesn't tell you
much in their catalog. Apparently it's rupture strength less "appropriate
safety factors". Point is that you gotta read the tech pages to find out how
they came up with that load rating. In any case, the Aurora plane bearing
will have a higher static load rating just because the only moving part (the
big ball) has much more contact area than the little bearing balls in the
Fafnir.
Ok, the Aurora is stronger. Here's the downside. Given a proper
clamped installation in double shear, it will have more friction, perhaps a
LOT more. I suspect the designer specified the Fafnir for a reason, that
being control feel (frictionless) and better hands-off return-to-center
performance after a control input away from trim speed. We all value buttery
smooth, frictionless, low-breakout control forces in a sports biplane. So
what are you willing to pay for it? When considering the overall cost of the
airplane, most people opt for the Fafnir.
There is another important detail. Note the allowable misalignment
angles. The Fafnir allows 20 degrees total. The Aurora is 16 degrees. This
is often an issue on elevator control systems, usually at the aft end of the
control stick mechanism. If you use the Aurora, you much check carefully to
be sure you have enough angle without hitting the limits at full control
deflection. Dan
02/11/02 TORQUE TUBE ELEVATOR STOPS
Kevin, what hardware (bolts/nuts) do you use for the elevator stops on the torque tube?
Do I need to grind flat or round the end of the bolt for hitting the stick lower 510-14 plates?
See Front Stick Picture
Also I just discovered that I put the -14 plates a little too high about .15 -.20. When I look
through the stop hole, it doesn't appear to hit the stick lower much, maybe just the edge. Same
in the back. Should I just cut a couple little pieces from some sheet and weld them in for the stops to hit?
It looks like even if I had put them right at the 3.20 dimension from bearing C/L, there still wouldn't
be much there for the stop bolt to hit. Just exactly how much of the -14 plate on the stick lower is the
stop bolt supposed to hit? Darin
----------
We use 5/16-24 2" long stainless steel bolts that we thread full length for the elevator stop bolts.
If the nuts welded to the torque tube are positioned such that the bolt is as high in the thru hole as
possible and the stick is welded up correctly, you should have full bolt contact to the stick face but a
2/3rds minimum bolt dia hitting the stick face is OK. Keep in mind that the stick positioning and travel
affect the contact point. Normally, there is quite a bit of bolt sticking into the box area (over an inch).
Sounds like you built the sticks with the end plates too high. A simple fix would be to move the nuts that
are welded to the torque tube up as needed to give you full bolt contact on the sticks. KK
----------
I ended up moving the nuts higher on the torque tube. Also, after ruining a die trying to cut threads
to the bottom of a stainless bolt, I cut a length of SS threaded rod and welded a nut on top to
accomplish the same result.
See My Elevator Stop Bolt...Darin
12/02/01 PUSHRODS, FISHMOUTHS, AN490HT ROD ENDS, REMOVE CAD PLATING
How do you prepare the AN490HT threaded rod ends and the pushrod tubes for welding?
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All push-pull rods are fishmouthed. Aileron, elev, trim etc. The 2 fuse idlers are not as there is not
a large enough load pulling the end out of the tube. The proper angle for a fishmouth joint on a
tube is 30 degrees. You can get that in 2 ways. A single angled cut or a V style cut.
The V style is shorter overall and is the one that will work with AN490HT ends. The 30deg angle is from
centerline of tube in 2 directions so the included angle of the cut should be 60 degrees. On a 3/4
tube, this usually leaves about a 1/4" wide flat on the end of the tube in 2 places so that your cut does not fall
off the end of the AN490 insert. The weld is to be 360 deg around tube in the V's and the 1/4" flats. All welded.
On the trim rods, this is V cut is done as well but is small and by the time it is all welded and painted, it
is hard to see.
One additional note on AN490 HT ends. If you get them from most of the vendors rather than direct from
the manufacturer, thay will be CAD and Irridite plated like an AN bolt giving them a gold color,
which is clear/silver CAD like the old days plus a coat of gold irridite. CAD plating does not
weld very well and causes lots of snapping popping, gas smoke etc. So, remove the plating. Get some
Muriatic Acid (swimming pool acid) and and plasitc container and put the ends in the acid. It will
quickly eat the Cad off and leave the parts bare steel for welding. Wash them with water to neutralize
the acid then quickly rust lick them to prevent rust. Welding will be much nicer. KK
12/01/01 SHORTER TRIM RODS, TRIM ROD ENDS, SAFETY WASHERS
Regarding our earlier discussion about your HP elevators being slightly shorter chord than plans,
what length should I make the trim tab push rods, shorter or plan length?
Regarding the hardware, from the pics I have of N360KC
Front End of N360KC Trim Rod
Aft End of N360KC Trim Rod
To verify the hardware used: I know you substitute F34-14M rod ends for the trim rods, and use
AN3-10a bolts and AN310-3 castle nuts, but what are those BIG washers? It looks like they're
there to keep the rod end on if the bearing fails.
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Darin, you are right on target. Shorten the trim rods so that with the elevator and trim tabs in
neutral the trim arms that hang out the bottom of the stab are in a vertical position, approx 1"shorter.
Regarding the rod ends, a large area safety washer is required on all bearings that are installed in single shear,
where there is structure only on one side. That way if the bearing fails the washer will keep the rod end
from coming off entirely. If the bearing is sandwiched in the structure like the elev
push rods no washer is required. These trim rods, aileron slave struts at the bottom, torque tube hanger KP4 bearings
in the fuselage, etc are places to use a safety washer. An AN970-3 is the one to use.
KK
12/01/01 PUSHROD ENDS
Whats the basic method to making the pushrod ends shown at
See Picture?
Does the tube just get flattened then welded to the two channels, or is part of the tube cut away?
Is any welding done vertical inbetween the two channels?
----------
Making the elevator pushrods is not that difficult. The trick is that you want to end up with a 1/2"
gap between the 2 channels so that after paint, etc. the rod end will still slip between the channels.
To flatten the end, mark the tube at the point where the flat spot ends(don't have the dimension in
front of me at the moment), stick a piece of 3/8" thick flat stock inside the tube deeper than the
line just drawn. This 3/8" thick piece needs to be as wide as you can fit in the tube and can be made
of alum, hard plywood etc. Take this set up to the vise and crank the tube flat down to the 3/8" piece
inside. We use our hyd press with a set of flattening plates we have but vice will work. The tube will
spring open a bit leaving the 3/8" piece loose in the tube. That is about right.
We have a fixture to weld the channels to the tube but you can bolt them together with a 1/2" spacer
between them. Line up the angle bend to the line on the tube and tack in place. Form angle tab to match
slope of tube and tack. The channels shou ld be welded along the length both sides and around the angled
tab but should NOT be welded inside across the end of the tube.
Keep in mind that you have a special fuselage. Plans length pushrods will not fit your airplane. This
will require that you install the sticks, torque tube, stab, elevators, make and install the elev idlers
and then make the pushrods to fit. KK
----------
See Picture of Jig I made Darin
11/09/01 FITTING TRIM TABS TO ELEVATORS
Any tips or tricks on how to assemble the trim tab hinge rib in there when building the elevators?
Does it get laid out at the 4.5 & 3.0 dimensions from the trailing edge? Darin
---------------------
Yes, the trim tab is the same size as the plans. You can make slight adjustments to the hinge
to get proper trailing edge alignment to the tabs. But an easy way to have the trim tabs line
up to the elevator is to make or buy the tabs first, screw the attach former to it, align it
to the trailing edge of the elev, then tack weld the strip.KK
---------------------
I already have the trim tabs I got from you on one of my Orlando layovers. It sounds like my
next mission is to find a 120 degree countersink and a cherry rivet puller. Darin
---------------------
You do not need to rivet the nutplates on now. It is better to rivet them on after you sandblast
and powdercoat the elevators. So, for now, simply use 3 screws and 3 nuts to hold the trim
tab to the strip. This way you can tack the elevator together, then remove the tab, weld,
sandblast, powdercoat, then rivet the nutplates in place.KK
---------------------
I put the 3 screws in, but the channel seems to be much lower than the tab. Is it supposed to
be that way? Should I replace half the piano hinge and re-drill it to put them closer together?
Heres a picture of
what I'm talking about. Darin
---------------------
Darin, I have looked at the pic you posted. Try something for me. Put a .040 to.050 shim
between the hinge and the strip. See how the tab aligns then. Look for the tab skin to match
the rail not the hinge bulb. Also, check and see if the strip is at the correct bend angles.
Sometimes we have to tweak them a bit opengin up the lower bend and closing the top bend.
If this needs to be done, the hings will lay down more.
If one or both of these gets things lined up for you, good. If not, see how much you need to
move the holes in the hinge. If it is less than 1/4" hole, simply elongate them in the
direction needed. If over 1/4 hole (I don't think it is), replace the hinge.
Oh yeah, you might be wonderin' what the shim is for...Fabric, dope and paint have measureable
thickness. Especially when you end up with 3 to 5 layers of it in a trim attach strip area.
When the strip is angled like the model 12, that thickness pushes the tab down as much as aft
.....He He, He.....BTW, don't weld the rail into the elevator with the shim in place and
align the tab to the elev trailing edge. If you do, the fabric build up on the trailing edge
will make the tab look as though it is too far forward. KK
---------------------
I think those suggestions will take care of it. One more question about the tabs: When I fit
the trim tabs in the elevator there seems to be a large gap on each side of the tab.
I'm pretty sure I laid out the elevator right, it matches the stab. Do you add some sort
of wingtip to the tab, or is the gap supposed to be there?
Trim Tab Gaps
---------------------
Darin, Glad you got the tab lined up. The gap is normal. There will be 4 to 6 layers of
fabric wrapped around the elev rib by the time it is covered and taped. Add to that
some dope and paint and the gap will tighten up a bit. The gap is about the same as
the 1/4" to 5/16" gap called out on the ailerons. It just looks big on the smaller tab.
KK
11/09/01 PLANS VS. HP ELEVATORS
Kevin, I was doing the layout of my elevators today, and the pre-bent HP elevator ribs I got
from you don't match the plans, it appears the ribs are almost 1" shorter than plans dimensions,
resulting in less elevator area. For example the 320-8 rib in the plans is supposed to go 20"
back from C/L of the elevator spar, but mine is only 19".
This discovery is correct I hope. How did you come to change it? I guess I'll just layout the
trailing edge to hit all the ribs. Thanks, Darin
---------------------
Darin, You look too close at everything, man!! We have solds lots of the fuse/tail metal sets
and you are the first one to see the difference in the elevator chord length. Most builders simply
clamp the spar tube to the table with rib locations marked, put the ribs in place and then stuff
the trailing edge up against it. But, if you draw out the elevators to the plans dimensions, you
will see the difference as you found.
Basically, it comes down to area. Curtis spec'd the elev area and stock planform. We changed
the tip shape to a sharper corner. To correct the area back, we trimmed the chord of the elevator
a bit. This allowed us to maintain the spec'd elevator area. Now, if you Cad draw the stock elevator
and cad draw our HP elev, you will see an additional slight error in area. This error is very
slight, I don't recall the amount but I thin it is lees that 1 square inch. That is, the area of
the HP elevator is almost the same as the area of the stock plans elevator but not exactly the
same. This small error in area is due to slight differences between the orignial area spec we developed
the HP tail from and the final form of the elevator after Mid America did the Cad drawings.
The error was small enough that there was no need to bother adjusting the plans.
So, square corner elevator=less chord.
Round corner elevator = 1" more chord.
KK
10/24/01 TRIM HORN AND ARMS ALIGNMENT IN STAB
Regarding the 510-31 stab trim horn and the two 310-22 stab trim arms, are they aligned with each other and
perendicular to the stab centerline when rigged properly with the elevators and trim tabs faired?
----------
Yes they are Aligned
As Shown Here KK
10/22/01 CONTROL TRAVEL
What is Aileron, Elevator & Rudder travel, and does it vary between plans and HP versions?
---------------------
Travel is 25 deg up and down ailerons, 25 up and down elevator, and 30 left and right for rudder.
Plans and HP are same.KK
10/22/01 ELEVATOR HORN BLOCK
Regarding the elevator horn block, what is it's material and dimensions?
---------------------
The elevator spacer block is basically like the one in all pitts. It is a piece of 1/2"
square alum 6061 bar that is as long as it can be and beveled on the front 2 corners
as needed to clear the pushrod end and the stab tab. KK
Elevator Spacer Drawing
10/03/01 WELDING STAB RIB 310-10
I'm wondering how you guys weld the little rib inside the big rib
shown at: StabRib310-10.jpg
I know I can get to part of it easy enough,
but is that enough? Darin
-------------------
Yep, just weld the 3/8" long easy edge. the sides are not to be welded. KK
09/14/01 TAIL HINGE FREE PLAY, RINGS
Kevin, I just looked at the pictures of your rudder hinges AFTER tacking mine in
place. I noticed my hinges are only free to slide about
1/8" in the spar tube, while yours seem to have about
1/4". Am I ok since I will be setting my
fin/rudder/fuselage together at once instead of batch
production like you do?
Picture of Yours
Picture of Mine
Hopefully its no big deal, but now I'm
wondering since you do everything for a reason.
Also, do you use the 1/4" wide rings or the 1/8" rings? Darin
-------------------
Darin, we use the 1/4" rings and set the
hinges up with 1/16" gap on each side of the hinge. So, with a hinge slid over tight to
one ring, the total gap or side play is 1/8". So your 1/8" is ok. The
reason for the gap is to prevent binding at the hinge as it rubs
on the rings. The reason we use 1/16" gap on each side
is because that is what Curtis Pitts says to do. We just
say, "Yes Sir" KK
06/28/01 TAIL STRAP HINGES, DR-109
The DR-109 uses 3 strap hinges per side PLUS the center pitts style double KP4 bearing center
mount. This is WAY past over kill unless you plan on 100-150 mph backwards...........
The pitts style set up with one strap hinge per side plus the center bearing mount works great and
is exactly what we have on the model 12. Some super abusive acro guys add on extra strap
hinge per elevator very near the tip for a total of 2 per elevator plus the center mount. If you don't
understand the center mount, get a look as some S1S plans or model 12 plans, or superstinker
plans. The reason for the added hinge outboard is that the end of the elevator can get bent in tail
sides. Usually a minor bend that is not noticed until sometime later. So the extra hinge. Many
people that add a hinge let it kinda float in the reduce binding. It can contain the elevator spar
from bending while being allowed to float fore and aft a bit. The strap style hinge goes way back
to the late 20's. It is a good, strong way to get the job done. KK
-----------
Also as I recall, the DR109 copies the tail hinge design of the Eagle II with a slight modification.
The Eagle II uses a 3 piece hinge assembly. The strap and 2 bronze halve sleeves with a
shoulder. Kind of a slip bushing. These are installed after the elevator is welded between the 2
1/4" wide rings. The DR109 does basically the same thing but with nylon or delrin instead of
bronze. When people have added a tip hinge to the elevator of existing pitts, they use the split
eagle hinge assy.
The advantages are that you don't have the hinge in the way to cover the part, can polish the
bearings surface after all the wetsanding etc. then install the hinge. The disadvantages are you
have more pieces to deal with, the support piece on the tab needs to fit the bushing better to
support the 2 piece bushing more, and you don't have the actual hinge in place to jig the 1/4"
rings in place during welding. Basically, it is a slick way to do it but not needed. To quote my
Dad......"It's a lot of sugar for a nickel" KK
06/28/01 BEARING CAGES, STIFF CONTROLS, ASSEMBLY PLUGS
I remember at SNF we looked at a biplane that had
very stiff controls, and I can't remember what you said caused it, but I
remember it was something to do with the bearings or cages. I want to make sure
my bearings work smoothly without inappropriate stress on the bearings. Since I
am getting close to making some bearing cages (I cut a bunch of tube on the
lathe yesterday) could you tell me:
1) What is the basic method to building them? Any techniques, tricks, or things
to avoid would be appreciated.
2) Which dimensions have to be spot on, and which dimensions are not critical
for it to work smoothly?
3) What made the controls stiff on the one we talked
about? Thanks, Darin
-------------------------------
Darin, that airplane at SNF had stiff
controls due to poor workmanship of assembly. Here are some answers to
your questions:
1) Cut the tubes to the specified lengths and deburr. Drill rosette holes
in outer tube only. Cut some assembly plugs for each end from 1"
solid bar and machine them to have 1/4" of 1" OD and a section turned
down to 0.901 that is the exact length of the bearing position in the cage.
Make 2 of these one for each end so it centers the inner tube precisely in
the outer one. I don't have that dimension at this computer, sorry but you
can do the math for it. Drill a 1/4" hole in the center of each and
use a 1/4" bolt to hold the entire package together while you rosette weld
it. Also use these plugs to keep the tube round while welding on the
various arms etc. Use anti seize compound on it too (lesson learned here).
2) The length of the inner tube must be dead on to get the proper bearing
spacing. Also the 3/8x058 spacer needs to be dead on length too. The
bearing cages should be cleaned out with a paper roll on a die grinder so that
the bearing slips in by hand. DO NOT PRESS IT IN!!! This is the big
screw up in that other airplane. They did not clean the powdercoating out
of the cages and the forced the bearings in. This deforms the outer race
of the bearings making them stiff and ratchet as the rotate.
3) See above. They screwed up. I am quite sure that the bearings in
the wings are OK. It is all in the fuse. This wings were built here
in FL by a friend of mine. The fuse was done in a real hurry in MO.
All the stiffness could be in the cages on the fuse that the TT hangs
from, the sticks themselves, and the idlers for the elev rods.
I just finished the control riggin on the blk/pur 12 here. They move soooo
sweetly. The difference between sweet movement and the super stiff
situation in that airplane is approx 1 or 2 hrs work. Lets see, that's
about 0.08% extra time in the project......KK
-----------------------------
For a drawing / pictures of the Bearing Cages see
BearingCages.gif
CagePartsWithPlugs.jpg
PlugWeld.jpg
BearingCageAssembled.jpg
-----------------------------
Here's the method I devised to get my bearings fitting perfectly in their
cages...Darin BearingCageReamer
02/06/01 TAIL TUBES
Kevin, I just discovered that in the set
of bent tail tubes you sent, the two 310-2 are .875 x .035 tube, while the
plans call for .049. Same with the 210-4 LE. Is this another
Kimball optimization? Darin
------------------------------------
The original plans by curtis call for .035 on the stab LE and TE tubes.
This is what we use in ours and build all our stabs with as we begain
doing so prior to Mid America reworking the drawings in CAD. So, you are
good to go with them as they are.
As for making a dwg change, I don't think it is required. Those plans
building can bend .049 to the same curves as the .035. There are about a
dozen tubes in the airframe that are larger or heavier than Curtis originally
specified. Our Yellow 12 has tubes sizes like curtis spec'd. as does the
black prototype. All the fuseframes we build has tube sizes like the
plans show so that a customer who buys a frame from us doesn't think he got
short changed. None of the Mid America changes were needed. KK
01/24/01 HINGES, STRAPS, HINGE RESTS
I recommend that on your next trip to Orlando to
see Kevin, take along the materials to make all the empennage hinges. Jim
showed me a simple jig they use to center the strap around the tubing. This is
sort of hard to get exact without it, and I bet they wouldn't mind letting you
use the jig. If they are off at all, then getting them aligned with the
bushings is difficult. All you need to do to prep the straps is to drill the
rosette holes before you bend them. This is one of the things that make
the empennage difficult to build. If you do that, and drill the bushing
holes straight, it won't be as difficult.
Also, and you probably already know this, Kevin doesn't make the hinge
rests/brackets the same as the plans call for. His are like Pitts.
They are the 4 pieces of about 1 X 1.25 inch metal.
Elev & Rudder Hinges.JPG Hinge
with arrow.jpg Hinge
Brackets on Weldment Sheet.jpg -Bud Clark
------------------------------------
My hinges are already bent from Kimball's, do I still need a
jig? Darin's
Hinges.jpg -Darin
------------------------------------
Maybe a jig won't be needed. Mine weren't pre-bent like yours. They
came in the flat sheet , and I had to figure out how to center and bend them.
Just make sure that the arms are equal length on each side of the hinge
when you are through. You might want to tack them at the rosette, slide
them all on a tube and see that they all line up.
Again, make sure the bushings that they attach to are straight and aligned with
the tubes they go through. I'm sure there is a good way to do that, but I
haven't found it. After doing it manually, I bought a tool to help
alignment things one plane (see pic), but it still takes some setup and
eyeballing in the other. Give it some thought. Maybe your friend
with the milling machine has a good way to do it.
The rests aren't quite as big a deal since you will have to adjust them when you
assemble things. You want the rests to bottom out as well as touch the
sides of the hinges. Remember that the tubes on the vertical stabilizer
are a different size from the top to the bottom. The bottom is the 1 inch
tube that is part of the fusleage, and the top is smaller to fit down inside it.
At first I was thinking I needed to put a something under the top one, but
you don't. The key is the hinges are all the same length, and you alter
how far they standoff from the tubes with the rests. By the way, it would
be better to not powder coat the fuselage until you have finished and fitted the
empennage in case you need to bend or file things a bit. I didn't and now
will have to touch up afterward. Have fun, Bud
------------------------------------
Kevin, some time back you sent me a drawing for setting up the tail
hinges. I've noticed in my laser cut metal that you use a different piece to act
as a spacer instead of the plans combination of 310-18 & 310-20.
Before I start to build a jig to put the hinges together, I want to verify that
the spacer in my laser cut set works to the same dimensions as the plans.
HingeJig1.gif
HingeJig2.jpg
------------------------------------
The plans way is a change that Randle did when drawing up the plans. This is
actually a more difficult way of building a hinge support.
We use the original way that Curtis Pitts designed the support which is the
1" wide "V" shaped piece of 4130. It works perfectly.KK
12/21/00 HINGE BUSHINGS
Here is a tip you might need later on. You have to drill some 3/8" holes for bushings in the horizontal stabilizer and vertical stabilizer spars. They need to be perpendicular to the stabilizer spar tubes when you are through, and it is hard to free hand the holes exactly as they should be. What I did was drill the holes as best I could freehand. You then put the bushing in place, and then run a piece of 1/4" X 36" threaded rod throught it. The long rod allows you to see if they are in fact straight. If not, some file work will let you alongate the holes so the bushing can be positioned exactly, and then spot welded. I use threaded rod because sometimes you want to run some nuts up to keep it in place. Bud Clark
12/20/00 RUDDER PEDAL, BRAKE PEDAL
Regarding how to attach the 510-60 outer tube to
the 510-59 inner tube on the brake pedal: Does it just get edge welded on the
outer side away from the rudder pedal tube 510-54?
---------------
YEP! KK
11/29/00 FUSELAGE MODIFICATIONS, CONTROL SYSTEM, IDLER, TAILWHEEL LOCK
I had a long layover in Hawaii with my laptop and spent about 4 hours figuring out how long to make Idler 510-41, don't think I'm completely nuts, I did get a little beach time. I'm pretty sure it needs to be 0.7" shorter, does that sound about right? I know the width of the pushrod is 1.188 but I used 1.4 to give me a little cushion up there. I also plan on leaving the idler mounts set at the same 48 degree angle, is there any reason to tweak that? Maybe you can tell me why they don't align with the 210-14 tubes to begin with. Also, what's up with the tailwheel lock shown on the idler in the plans? Does it engage the lock with full up elevator? I don't recall seeing it in any pictures, do you even install it? Darin
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That sounds about right. I don't recall the final length of the rear idler. I do recall that I had a length that was shorter and that I thought would work but had to shorten it a slight bit more when the airplane actually got built. I maintained the 48 deg angle of the mounts. The prototype 12 had a one of a kind locking tailwheel on it. It was elevator control system operated. With the stick at full down, the tail wheel was unlocked. Just a bit off the down stop relaxed the cable attached to that rear idler arm and lock the tail wheel for straight ahead only. So, if you wanted to taxi and steer, you had to do it with full forward stick which is spooky with all that power. That is why we don't have that tab on the rear idler. KK
11/11/00 FUSELAGE MODIFICATIONS, TORQUE TUBE, REAR STICK, BEARINGS, IDLER
Darin, Here's a hint
for you on the controls......Keep the torque tube the same length as stock and
adjust rear seat to clear curved stick. A short TT won't work out. I
tried it too. KK
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Thanks for the advice. As I was drawing it I realized that any length adjustment
would only be made to the rear stick mount location. Let me guess, the short TT
probably is probably limited in down elevator travel by hitting the front seat
up higher where the added recline isn't a factor.....
I ordered a few pieces of hardware like the rod end bearings, and rod ends so I
could measure them for my drawing and analysis of the idlers. I'm basically
going to figure out the "plans" geometry, then adjust my idler
radiuses to keep the pushrods in the same angles as the plans version. After I
ordered them from AC Spruce I remembered that you guys sell them too. How's your
pricing on the bearings, rod ends etc compare?
Its really cool to draw the fuselage stuff and see how it all fits together, its
like getting building experience without touching metal. Plus it keeps me out of
the bars on my layovers. I never would have known about the very slight
interference fit of the TT in between the bearing cages otherwise. Also I
discovered how close the elevator horn comes to rubbing on the stab rear spar,
it must just kiss it.
Darin
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Yep. The rear stick down travel is the issue on the TT. Keep smilin.
Sounds like you are having fun KK
11/05/00 RUDDER PEDAL JIGS
Darin, I finally stumbled onto a good box for the jigs. They are boxed up, and I will mail them tomorrow. You probably know this, but remember to just tack them while on the jig, and then remove them for final welding. If you don't, you'll end up welding the pedals to the fixtures. On the brake pedals, you will have to make sure the toe portion is straight after tacking as the tube is able to move slightly on the jig if your not careful. The brake jig is such that you will add the tube that goes inside the rudder pedal after it is off the jig. Add it before you final weld the pedal or you will have to have a hard time reaming it out before the tube will slide in. If you don't already have one, you might as well go ahead and get a .510 inch straight fluted reamer as you are going to need it. You can get a good carbide tipped one from MSC Supply They are pricey. Later, Bud
08/28/00 TUBE BENDING, TUBE ROLLER
The radius of bend that
Curtis uses in his tail feather designs was determined by him
experimentally. In otherwords, Curtis took some 3/4 4130 and kept bending
it until he got as tight a turn as possible with out kinking. That is
where the 9.5 to 10 inch radius on the stab leading edges comes from. Here
is how he and now we do it.
Take a piece of 3/4 thick hard wood, ply will work for 1 or 2 times. Cut
it in about a 8.5" radius and put a strap on it to hold the end of the tub
against it. Clamp it in a vise and pull the tube down and around
it. It will spring back to about 10" radius. Recut the radius
as needed to get the final shape you want. Put a mark on the board to tell
you where to stop the bend.
For the stab tubes we make here
for the model 12, the tube flattens approx .015 but the flattened protion is in
an area of the stab, the tip, where it does not matter. This method is
fast too.
For many other tubes, round and square, in the Model 12 like sticks, I
strut tubes, canopy frames, engine mount rings etc, we use our powered tube
roller. We have roller wheels for it to roll tubes from 3/8" dia up
to 1.25" dia. Max wall thickness for 4130 we can roll is about
.095. Mild steel .190. This device works great and can produce any
desired raduis of bend from infinite to as small as 7" in 1x.095 tube as an
example using the same wheels rather than having to have a set of dies for each
radius. We use this tool to create the airfoil curved square tubes on the
top and bottom of our I struts.
I do agree that the tools you refer to as well as the one I have mentioned can
produce parts to a greater level of accuracy. But, in the case of the
original posters Super Stinker, the tolerances are lax enough to allow for
flattened tubes, heated bends etc and still have a high quality part. It
was designed that way, Curtis built it that way. Heck most homebuilders
don't even have the tools to measure .010 squish in a tube. KK
04/30/00 TAIL RIB BENDING
Darin, Tail rib bending can be bent on a common brake with some extra mallet work after. You bend the hug up edges, then the 90 degree bends, but stop short on the 90's and then use a mallet and bench to finish. We have a special brake for bending the tail ribs and a few other parts. KK