+++ #153
Subject: Re: my latest press die
From: Lee H. Erb

A "reliable source" for normalized or annealed 4130 at room temperature
gives the following bend radii:

Thickness               Radius
.012 to .018    .03
.020 to .032    .06
.036 to .045    .09
.050 to 063             .13

If you have used a smaller bend radius and there are no cracks on the
outside of the bend, you can stress relieve by normalizing again the
finished part.  If you are going to have fatigue loads, small cracks in
the outside of the bend can cause failure.

+++ #154
Subject: Re: my latest press die
From: Float-by Shooter

> A "reliable source"...

Using that data would seem to make my bends of insufficient radius in
*all* of the 4130 fittings I have bent so far and causes me some
concern.

<drives to shop to get AS&S catalog which I used as my source.>

Under "Bending of 4130 Steel" on p.62, "...Condition N materials shall
be bent around a diameter three times the thickness of the material..."
This translates to a 1.5T minimum bend radius and is what I used.  Like
I said, I could have sworn I saw a tighter radius allowed elsewhere but
I was not about to commit something out of my highly suspect memory to
metal.  I don't know why the difference, but my thoughts are along the
lines of 'if I can't trust the outfit I am buying the material from
(Aircraft Spruce in this case) to provide safe data for the use of their
product, what *can* be trusted?'

> If you have used a smaller bend radius and there are no cracks...

No cracks that I can detect with the naked eye.  If my bends *are* too
sharp, and I try to normalize them with the torch, I'm not entirely
convinced that I won't make matters worse with my inevitably uneven
heating of the parts.  I bet it would also do nice things to my match
drilled/reamed pivot holes.

Thoughts?

P.S.  I just added a couple pictures showing the resulting radius in
better detail to my project pictures page.

+++ #155
Subject: Re: Bend radius in steel a definitive answer!!!
From: Kevin Deutscher (bearhwk27-)

Drum roll............... for 4130 normalized under .125 thick the bend
radius minimum should be equal to material thickness.

Note 3 sources have same info........ A&P training manual, Mr.Bingelis
book and last but not least......... Northrop - Aircraft Maintenance and
Repair Manual.

Now for the clincher.... Remember the bend radius is from the neutral
axis of the material, not the inside or outside radius of the finished
bend.  So if you had .090 material bent at 1x thickness for 90 Deg the
inside bend radius to inspect your work would be......090 -.045 = .045
Inside radius. So just lay an .093 drill inside your part and see how it
fits.

The above assumes that your fitting is 90 deg and that you did not
excessively work the material to get it to the finished state.  Clean
the bend, use a 10x or greater magnifier, or spray dye pen or magniflux
for inspection if your not sure as to material condition.

+++ #156
Subject: Re: Bend radius in steel a definitive answer!!!
From: Lee H. Erb

Kevin, I don't want to start a controversy, but was you information for
hot forming?

All the aircraft companies I have worked at use the inside radius as the
bend radius. This radius made it easy for the shop to select the correct
radius on the die.  Admittedly the values I gave were standard values of
bending dies in the shop.

The normalizing only needs to be on the bend. I doubt if you get any
distortion but may get a little change in the bend which can be restored
mechanically. Obviously, try a scrap piece and keep the torch moving.

+++ #159
Subject: Re: Controversy ?
From: bearhwk27-

Bend radius forming 1x min cold.

The reason for the controversy is that in the olden days the
weight,stress,metalurgists and engineers analyzed bends to death and
came out with a scientifically derived bend radius. Hence the use of the
neutral axis. In the olden days just like today, the above individuals
never built anything, so why should they care are if tooling does not
exist ? ( Actually, they never knew that fabrication required tools. )
:>)

+++ #302
Subject: "oops" (more homebrew metal brakes)
From: Float-by Shooter

More on the recurring topic of brakes:

Awhile back when we were discussing homebrewed metal benders, somebody
suggested a book called "The Racer's Guide to Fabricating Shop
Equipment" because it contains instructions for building a sheetmetal
brake (and a lot of other neat tools).  I happened to have this book
sitting by my desk (I built the hydraulic press detailed in it) and had
looked at the brake in question.  I posted that it didn't look like it
would work for the materials we would be forming due to the way the toe
was set up, it didn't appear to have allowance for springback.

Anyway I've been researching brakes with an eye to purchasing a 4 footer
lately, and happened to pick up the book and take another look at the
brake instructions.  Turns out I wasn't looking at it carefully enough I
guess, and the way the angle steel toe is positioned it seems that there
actually is enough allowance for a fair amount of springback.  Part of
the problem is the way the book is illustrated, no drawings and poor
quality photographs, but if anybody actually listened to me before and
didn't look into the brake as a result, I am sorry.

According to the book, it is capable of bending 5 foot lengths of 14
guage mild steel, 16 guage stainless steel, and .120" aluminum.  Page 68
of the '98-99 Aircraft Spruce catalog has a chart to translate guage
measurements into more useful thickness units; I don't see why people
have to use such a stupid unit of measurement.  Then again everybody on
the list living outside of the US is probably snickering at me now.

Also, in my continuing quest to do things the hard way, I have found the
following URL which tells how to make a small brake plus a lot of other
neat things, go to: http://www.loganact.com/mwn/mf.html

I still dunno if I will go to the trouble of making another brake.  The
project qeue is undeniably full which is why I was looking into
purchasing a manufactured brake, for doing the .032 4130 parts, fuel
tanks, and such.  But who am I kidding, making my own tools so I can
make my own airplane is half of the fun.  right?  right??  I am
beginning to think that by the time it flies (if ever) I will have one
of the better equipped workshops around.  8^P

+++ #321
Subject: wing ribs
From: Russ Erb

[ re: Al grain and bending ]

We've discussed grain orientation before. It is preferable to bend
across the grain (grain roughly perpindicular to bend line), but you can
bend with the grain with sufficient bend radius. With the tip ribs, you
can't avoid bending with the grain because they're longer than 4 feet
and the sheet is only 4 feet wide. With 1/8" bend radius (not diameter)
I had no problem.  Point: By making the partial ribs, you can cut them
out such that the flange bend goes across the grain, thus giving
yourself better peace of mind.

However you do it, doing it right will require time and effort. Probably
more than you'd wish it would. Get used to it. This isn't a weekend
project.

+++ #1137
Subject: Metal breaks
From: budd davisson

Charlie Vogelson sells plans for a home made pan break that works really
well but takes some time to build.

For long stuff, like spars, I used to make up long shims from stacks of
varying thicknesses of cold roll that would be slipped over the nose of
a pan brake to give the right bend radius, then I'd take my aluminum and
shims down to my local heating contractor and have them bend them.

For small stuff, I made up a vertical blade-break where a longish block
with a groove milled in it was forced up against the stationary pointed
edge by a 12 ton bottle jack (less than $20). Here again, shims gave the
bend radius. I made the whole mess out of scrap 2" angle iron in an
afternoon. It was blacksmith crude but it worked. That's where having a
little cheap arc buzz box comes in handy, although a Mig is probably
better.

+++ #1173
Subject: built up spar
From: stephan pelgar

you guys were also talking about a brake for bending the spar web.i saw
that you said you know of a set of plans to make a brake.please let me
know of the ones that you have and where can get a copy of them.i was
also thinking of making a press brake for this.i saw a set of plans for
a 6 ft back at home and thinking of just streching it 2 more feet.

+++ #1174
Subject: Re built up spar
From: budd davisson

> i saw that you said you know of a set of plans to make a brake.please
> let me know of the ones that you have and where can get a copy of
> them.

charlie Vogelsong at Dillsburg sells plans, or at least he used to.

+++ #1457
Subject: Small Brake
From: J.T.Newbegin

I made 3 brakes (gave 2 away) from plans at www.loganact.com/mwn/mf.html
I followed the plans, but they could be changed to thicker mat'l for
4130 or lenthened for alumimum. The three brakes cost 24.00 for mat'l.

+++ #1909
From: Tim Anderson  <fuzzet@h...> 
Subject: [Bearhawk] 4130 bending/fabrication 

A general question on fabricating parts with 4130 sheet. If a part is
made from somewhat thick material (dig my technical terms), and out
little homegrown metal brakes can't bend the part, is heating the metal
an acceptable method, or does that damage the strength? I saw in the
newletter, of someone that had built a jig to bend the flap/ailiron
brakets, it looked like it was done with cold metal, not heated.

We heat 4130 when welding, so I would think that heating prior to
bending is OK, as long as the bend radius is not too small.

+++ #1910
From: budd davisson  <budd@g...> 
Subject: [Bearhawk] Re: 4130 bending/fabrication 

Bending sheet stock hot is okay, just make sure you don't get it so hot
it looses it's color. A dull red will bend okay. Also, if you're bending
a small piece in a vice (with a shim to establish the bend radius) use a
normal torch tip, not a rose bud or it heats up too wide of an area.

Heating it up to bend in a break might be tough because it'll cool off
so fast. Anyone else tried that? I haven't.

+++ #2343
From: William & Delinda Johnson  <wjohnson@f...> 
Subject: RE: [Bearhawk] Updated Pictures 

Just make a really nice 3/4 inch wide block about 7 inches long.
Sand/file or mill a 3/32 radius on both corners.  Do not heat 4130
when bending, just use a BIG ball peen hammer and bend slowly down
the length of the piece so you don't strecth the steel.  It works
great.  Centering the piece on the block is the only challenge.  I
center the piece, bend one side, turn it over, bend the other.  Put
a wood block between the vise bottm and the block so it won't slip
down when bending.

Pictures worth a thousand words so here ya go.  Hope it helps.
http://home.fuse.net/wjohnson/wcbendblock.jpg
http://home.fuse.net/wjohnson/wcbendblock1.jpg
Sorry for the bad focus but you probably get the idea.

+++ #2348
From: William & Delinda Johnson  <wjohnson@f...> 
Subject: RE: [Bearhawk] Updated Pictures 

> Thanks for the pictures, but I have to ask...
> 
> How come your 4130 is all shiny like a piece of AL?  My 4130 is a dark
dull
> color,  are you polishing it first?
> 
> Just Curious.

The bending block is just mild steel cut from a BIG valve cover.  I
milled both sides and edges to form the bending block.  It creates a
very nice shinny finish.

The 4130 parts are as you describe; however, sometimes the flash
makes the parts look shinny or I sand a scratch which also adds some
shine . . .

+++ #2361
Bruce A. Frank  <BAFRANK@w...> 
Subject: [Bearhawk] Rust Prevention 

> I was wondering the exact same thing! I always thought it made
> more sense to leave the oil on the tubes (except for the weld
> area, of course!). The humidity around here dictates the practice.
>
> You can clean it off if you want to, and polish everthing nice and
> pretty, then sit back and watch it rust before your eyes. Not
> fun. My guess is Bill's steel came that way (or close to it) and
> he has a thin film of preservative on there you're not seeing in
> the image. Discard all of this if you're in Arizona in August.

Even here in CA after the tube is welded, if left as is, it will
rust. It takes longer than it did in PA, but it still rusts. As soon
as the weld cools I hit everything with WD-40. It prevents
rust. Stops rust. And it is easily cleaned off to do additional
welding if necessary.

+++ #2874
From: budd davisson  <budd@g...>
Subject: Re: [Bearhawk]brakes and stuff

Any body know of a good outlet for surplus big tools? I'm looking for an
8' shear and 8' brake. Or any good outlets for new ones?

+++ #2891
From:   <lcarlstrom@w...>
Subject: Re: [Bearhawk]brakes and stuff

I don,t have a good source for shears or breaks but I was wondering what
size of such tools I can get away with building a bearhawk? I have a
friend with a 3 foot shear is that big enough?

+++ #2892
From: Bob Romanko  <romanko@v...>
Subject: RE: [Bearhawk]brakes and stuff

The only two big ticket tools you need to build a Bearhawk are an 8'
brake and a small metal lathe.  You need the brake for the spar webs,
and you need the lathe if you plan on making your own gear struts.  My
cousin, an ace machinist, is building my struts, and I just happened
across an 8' brake.  The only reason I bought one that large is I was
planning on spending about $400 for a smaller one, and just stumbled
upon an 8' brake, used, that needed some TLC that was right next to my
brother's house in PA.  I am still probably going to buy a smaller 3in1
tool from Harbor Freight or Northern Tool.

What you buy really boils down to how fast you want the plane, and how
many times you can milk the project to load up your shop without the
wife complaining.  In spite of my joy of collecting tools, I still like
doing things the old-fashioned way.  It's my nostalgic nature.

Hope this helps.

+++ #2893
From: Float-By Shooter  <packrat@c...>
Subject: Re: [Bearhawk]brakes and stuff

> I don,t have a good source for shears or breaks but I was wondering
> what size of such tools I can get away with building a bearhawk? I
> have a friend with a 3 foot shear is that big enough?

It won't be able to do everything, but the 3' shear will be extremely
handy when you begin to make the rib stiffeners and attach angles.  I
was able to borrow a 3' squaring shear from an IA friend, and it saved
me an incalculable amount of time making those parts.  They require a
large number of repetitive cuts to be made as straight as possible.  For
most other cuts, its been easier to just make them with my hand snips.
The only disadvantage of the 3' shear is that it won't accept a full
sheet width of aluminum so you have to cut it to a smaller size by
another method before using the shear, which will result in some waste,
but it was well worth the time saved.

+++ #2894
From: Tim Anderson  <fuzzet@h...>
Subject: Re: [Bearhawk]brakes and stuff

I have found that the real big decision (at least on sheet metal equip)
is whether or not to buy or to use someone elses/have someone do it for
you.  Spending the money on even a 4 ft brake when one doesn't have But
a few hours of work for it may not be a good investment.  I found a
welding shop with an old 8 ft brake out back, gave the guy $10, and made
my spars in about 3 hours.  The money I saved will buy a lot of metal
(I'm not an alum grower).

Unfortunately, we can't always find those opportunities.

+++ #2895
From: Bob Romanko  <romanko@v...>
Subject: RE: [Bearhawk]brakes and stuff

Ah, Tim.  IF, however, you can buy a used piece of equipment for below
market value, it's safe to say that you can probably use it for five
years and sell it at a profit.  I don't buy anything used that I can't
sell down the road for more than I paid for it.  At least that's the
justification I use with my wife.  An 8' brake for $400 that's 50 years
old is worth $500 five years from now.  Someday I may actually sell
something, but that would be a first (grin).

Good point from Del on the shear.  I'm buying a 3in1 shortly just for
the attach angles and stiffeners.  My right hand's already twice the
size of my left from all the snipping, and that's just from cutting out
the ribs. All those straight, parallel cuts for those angles and
stiffeners just BEG to be sheared.  The way I see it, God invented the
shear for a reason, and I'm not one to question Him.

+++ #2896
From: Float-By Shooter  <packrat@c...>
Subject: RE: [Bearhawk]brakes and stuff

> cutting out the ribs. All those straight, parallel cuts for those
> angles and stiffeners just BEG to be sheared. The way I see it, God
> invented the shear for a reason, and I'm not one to question Him.

One thing I did that saved me some time, was not using the ruler that
was built into the shear to get the right size strips for the angles.
Instead, I went into CAD and drew a series of parallel lines the right
distance apart to account for bend allowance and setback. Plotted it
out, and used clear contact paper to stick it to the top of the shear
(just be sure it is parallel to the blades). Then I used the lines as a
guide for shearing each strip in rapid succession. Note that you will
have to make 2 different sheets, one for .025 and one for .032 due to
the slight difference in setback. Or you could make them all the longer
length and live with the excess, but with CAD it was easy to make the 2
sheets and make them all perfect. You could almost as easily do the same
thing with pen and paper.

+++ #2898
From: Float-By Shooter  <packrat@c...>
Subject: Re: [Bearhawk]brakes and stuff

Another thing to think about in addition to the cost, is the space all
this equipment is going to occupy. I could probably find the money for a
good used 8' brake without too much difficulty, but I'm not so sure I'd
want to store it when I'm not using it. If I found a good deal on one
I'd probably go ahead and buy it, but my ideal solution would be to find
one that I can use, and then buy a nice 4' pan and box brake for the
other 98% of bends I need to make, that wouldn't take up as much space
in my shop.  (the unused space could then hold a shear or a lathe or...)

+++ #2899
From: Tim Anderson  <fuzzet@h...>
Subject: RE: [Bearhawk]brakes and stuff

I made all my angles by hand (bad, but do-able).  If I had to do it
over, I would increase the size of the strip used.  The stiffener angles
aren't that critical, but the attachment angles could have been wider.
I made mine from about 1 1/16 strips, but ended up with a much larger
bend radius then planned.  With both side needing to be riveted, it
doesn't leave much room for rivet/side clearance.

+++ #2900
From: Float-By Shooter  <packrat@c...>
Subject: RE: [Bearhawk]brakes and stuff

> I made all my angles by hand (bad, but do-able). If I had to do it
> over, I would increase the size of the strip used. The stiffener
> angles aren't that critical, but the attachment angles could have been
> wider. I made mine from about 1 1/16 strips, but ended up with a much
> larger bend radius then planned. With both side needing to be riveted,
> it doesn't leave much room for rivet/side clearance.

I thought about that too, but the nice thing about using a shear, is
that if I have to remake some of the attach angles, it won't be a big
deal.  Now if I had cut those little buggers all out by hand, I might be
a bit annoyed.

+++ #2905
From: Russ Erb  <erbman@c...>
Subject: RE: [Bearhawk]brakes and stuff

> One thing I did that saved me some time, was not using the ruler that
> was built into the shear to get the right size strips for the angles.
> Instead, I went into CAD and drew a series of parallel lines the right
> distance apart to account for bend allowance and setback.

Gee, Del, I feel so low tech. As best I can remember from ancient
history: I figured out the width I needed. Used a decimal tape measure
to make a mark at each edge of the sheets. Using a calculator, added the
width again, made two more marks. Repeat as required. Stick sheet in
shear, line up blade with marks. Stomp on pedal. Repeat as required.

+++ #2907
From: Float-By Shooter  <packrat@c...>
Subject: RE: [Bearhawk]brakes and stuff

> Gee, Del, I feel so low tech.  As best I can remember from ancient
> history: I figured out the width I needed.  Used a decimal tape
> measure to make a mark at each edge of the sheets.  Using a
> calculator, added the width again, made two more marks.  Repeat as
> required.  Stick sheet in shear, line up blade with marks.  Stomp on
> pedal.  Repeat as required.

I tried that, but the lighting in the hangar containing the shear was so
miserable, that I couldn't look down between the blade and the guard and
SEE my marks on the aluminum.  But I could see the marks on the paper
pretty easily.  The disadvantage of my method, was that I had to shear
the sheets into small enough lengths to fit on the 11x17 size paper onto
which I had plotted my guide marks.

+++  #2951
From:   <pfflyerz@c...>
Subject: Re: [Bearhawk] back to work

Well then, let me tell you about THAT 3-in-1.  I mentioned earlier that
I had been having trouble making the the 1/8 bend on the T-25 channel
pieces for the tail-feathers on my friends brake, besides being a hassle
to drive over there whenever I needed to do something.  I also
considered the tool you are looking at and snuck into Harbor Freight
with a 6 or 8 inch piece of .032 4130. I tried bending it the long way
but there wasn't enough clamping pressure.  I then tried to shear it,
but felt that jumping up and down on the handle for leverage would draw
too much attention my way.  Needless to say, I went home without the
machine.

I purchased a book about fabricating shop equipment and have all the
parts cut up to assemble a brake, but haven't put it together yet, so
don't know how it will function.  I'ld still rather dirve over to use
the guy's brake as he also has a very nice shear which REALLY makes the
job easier.

+++ #2973
From: Tim Anderson  <fuzzet@h...>
Subject: Re: [Bearhawk] back to work

I built a 3 ft brake of simular design to the one in the book. ("The
Racers Guide To Fabricating Shop >Equipment", by John Block.)  It works
OK for real small parts up to 025, but had a devel of a time on 032.  It
is almost a boat anchor.

+++ #3056
Subject: Re: [Bearhawk] Re: tongue brake
From: Donald Schindler  <t18skyguy@h...>

Hi Benton, It is really a hydraulic press brake. I called it a
tongue brake cause the part that does the bending is called the
tongue. Ill quote how the author describes it. " A close fitting
blade is brought into a matching slot with the work piece between
them. The work will yield to the blade/slot and bend. The dimensions
of the blade and slot determine the bend radius, and maximum bend
degree that can be accomodated. This particular design is made to
bend .032 aluminum sheet at a .100 inch radius" The plans are
6-eleven by seventeen pages and very well done. In general, it is an
8 foot by 2 foot rectangle made of I beam. Inside the rectangle, the
slot is welded to the bottom and the tongue welded to an upper beam
which rides up and down inside the frame. Power is supplied to the
upper beam with four hydraulic jacks actuated with a common handle.

I have had the plans some years and the original ad for them is no
longer in print. The only identifying marks on the plans themselves
are DJJ-1995.  Maybe some of you out there might know who it
is. Anyway, if anyone is seriously interested and we cannot locate
the author I would consider reproducing them for Bearhawker's and if
the author steps forward I will gladly pay him, but lets see how
much interest there is.

+++ #3123
Subject: Press Brake
From: Donald Schindler  <t18skyguy@h...>

For those of you interested in the press brake plans read on. I will
make the plans available for the next 30 days for a cost of
$2.50. Please understand that these plans are not mine, that I have
had them some years, and that there is no meaningful I.D. on the
plans or envelope they came in.  The ad that advertized the plans
seems to be long gone or at least not running currently. If the
author steps forward, or one of us can locate the ad, then that will
negate this offer and any checks sent will be destroyed.  I will
collect orders for 30 days, make one trip to do the photocopying on
Sept. 10th, and will send all the plans out on the same day on
Sept. 11th.  So you are sure of what you are getting; this is an 8
foot, hydraulic press brake designed to bend .032 Aluminum at a .100
inch radius. In other words, it's perfect for the bearhawk spar, can
bend other thickness to varying degree's, but the RADIUS IS
FIXED. This is a one shot deal and any checks that arrive after the
10th get torn up as I am only going to make one trip for the
copying. If interested, send check for $2.50 to Donald Schindler
2443 35th St., Springfield, OR. 97477. Please include your address
and email. Email for me is T18skyguy@h...

+++ #3142
Subject: 8 foot brake
From: Tom & Michelle Brant  <tmbrant@u...>

After purchasing the materials for the fuselage, I have started
reading up on the construction procedures for working with the
tubing.  In the Jan. 97' issue of Beartracks it is mentioned to
start on the tail group first.  In this article it says you will
need "A GOOD 8' or larger brake (for the force required to bend the
steel).  After reviewing the plans, I haven't found anywhere where
anything over about 4'-0" would be bent out of .032 (Sta. G-N on
drawing 18) which is actually 2 shorter bends...  Other than that,
all I have found is the top former channel on drawing 16.  I have
access to an old 8' apron brake and a 6'-0" 45 ton press brake.  Is
the apron brake going to have enough force for the long piece (top
former channel) or will I need to use a press brake?  To me .032
seems like it would be pretty easy to bend.

+++ #3290
Subject: Re: [Bearhawk] CAD file
From: mailstuff  <theferdons@m...>

Be careful of bend radius. I know of a machinist who is building a
bearhawk, and his bend radius on his spar is too tight for my
liking. His CNC cut ribs and lightening holes are better than Cessna
though. Most machine shops don't bend much aluminum. Most heating
and air-conditioning installers have an 8 foot brake to fabricate
ducting. The bend radius will be too tight, but you can use a set of
radius gages to determine what it is.  Cut some 8 foot long strips
(6 inches wide) of thin (.020) aluminum and bend them lengthwise in
the brake until the thickness is the right bend radius.  (stack them
as necessary) Cut some short trial pieces to practice the spar bends
on. Once you have the location where the bends have to be, and
verified that the bend radius on the test piece is correct, bending
the spar blank will be easy. Some high school and junior colleges
have eight foot brakes. The shop teachers usually love to do a
project like this. Don't be afraid to ask. Most people are more than
willing to help. Show them some picture of the Bearhawk and the
plans. Then they will know you are serious.  Most tradesmen will
look at the plans and say, "Hey, I can build one of these!" They
will fall over when they here how cheap it is. Most are used to the
prices of muscle cars, drag cars, or circle track cars. I have been
amazed at the cross-industry interest that the Bearhawk
draws. E-mail me if you have any questions. I don't like to respond
to the group since I am pissing off some super-internet techno
someone about not using some kind of format. Hope you can find a
brake and get the satisfaction of bending the spars yourself!

+++ #4767
From:  "Donald Schindler" <t18skyguy@h...>
Subject:  Apron brake plans review

I just received plans for the 8 foot apron brake as featured in
the November issue of the Experimenter. For those that are
interested, these plans are 40 pages, CAD drawn, numerous
closeup photo's and very good descriptive text to go along with
it. The plans are $35.00 dollars and they get a big thumbs up.
Available from Larry McFarland 4706 5th St., East Moline, Il
61244. You can reach him by e-mail at larrymc@qconline.com

+++ #4794
From: Bob Thomasson  bobthomasson@c...
Subject:  8 Foot Brake

I uploaded the 8 Foot Brake photo page from the November 2000
EAA Experimenter on to the egroups Bearhawk "files" page.  There
are several small photo's on it, so I saved the file as about
800kb in hopes that it would show the detail.  I think it did,
but at the price of taking forever to download. If the file is
too large, I will be glad to delete it and repost it with lower
resolution.  I experimented with zipping it, but the difference
in file size didn't seem worth it.  Also, it's a .tif file,
which is I guess what the default on my software was set at.  If
it would be better to have it as a .jpg like most of the other
files, let me know.

The plans are $35 from Larry C. McFarland, 4706 5th Street, East
Moline, IL 161244.  His e-mail is larrymc@q...

+++ #4797
From:  "Tim Anderson" <fuzzet@h...>
Subject:  Re: [Bearhawk] Apron brake plans review

Any guess as to the cost of materials for the brake?  Does it
appear to be as strong as commercial 8 ft brakes?

+++ #4799
From:  "Donald Schindler" <t18skyguy@h...>
Subject:  Re: [Bearhawk] Apron brake plans review

He estimates the cost of materials at $600.00. It is a minimum
size, 8 foot, all steel,compact sheet brake that will bend .040
AL 6061-T6 at full width. It will also bend .060 at shorter
length. Designed as such, it is on casters for easy moving. Mr
McFarland is a professional equipment designer by trade and also
a homebuilder(Zodiac). The brake weighs 600 pounds and he built
it in 6 weeks, evenings and weekends. This brake really looks to
be the real deal.  Don 068

+++ #4816
From:  Russ Erb <erbman@c...>
Subject:  One-upsmanship...

Here is the text for the bending brake pictures.  I OCRed it
quickly and have not proofread it, so if there is something
confusing, say so and I'll check the original.

  AN EIGHT-FOOT AIRCRAFT BENDING BRAKE
  by Larry C. McFarland

  Upon renewing my pilot's certificate after a 25-year pause in
  flying, my best friend, Ed Hale, and I flew to Zenith Aircraft
  Company, in Mexico, Missouri, in a Cessna 150. Zenith gave me a
  flight-evaluation ride in a really neat all-aluminum Zodiac
  601. 1 was really impressed with the beautiful view through the
  large bubble canopy and with the way the airplane flew. I went
  home with a set of plans, a rivet gun, and a metric tape. Within
  two months I was making wooden forms and cutting aluminum. I'm a
  scratch builder, like many of you, because I just like making
  parts. In the process, I soon cut a rudder spar that needed two
  long bends. The Zodiac requires good 1/8-inch bends in most of
  its construction.  I took the spar to a heating contractor's
  sheet metal shop that had an eight-foot bend brake. The owner
  wasn't experienced with bend radii, and our first effort had no
  bend radius. The spar was ruined. I made another blank, but the
  bend would just have to wait till I could simply acquire my own
  brake.

  Curiously, no eight-foot brakes were available anywhere at
  reasonable prices. I soon found out that the commercial
  eight-foot manually operated sheet brake is a heavy piece,
  usually 1,500 pounds to a ton at a cost of over $3,500, new. You
  could presumably buy one and sell it when done, but a used bend
  brake doesn't offer a reasonable percentage of resale value.
  Buying one also presents the problem of positioning and
  use. Seldom do you have the space or the kind of floor that
  tolerates moving 1,500-plus pounds around a shop when only
  occasionally you must bend metal.  I checked the Internet and
  found nothing less than a century old for $3,000 and one in
  Louisiana for $800 plus freight that weighed 2,500 pounds. No
  plans were available. Stretching a 48-inch model isn't good. An
  Internet friend in Toronto who's building a 601 had a stretched
  brake, but he complained of it having too much "give." He was
  getting twisted and bowed parts because of the tool's inability
  to grip the sheet along its entire length. I was confronted with
  a "bend brake design necessity."  With frustration, from
  November to midDecember 1999, 1 researched the numbers and
  designed a minimum-size, all-steel, "compact," eight-foot sheet
  brake that would bend 0.040 aluminum 6061-T6 at full width. I
  found supporting the beams inboard of the ends reduced span
  deflection. Stresses get well beyond the short four-foot and
  six-foot types in a hurry. Limiting stresses to what must be
  bent reduced the problem more. Heavier materials, up to
  0.060-inch thick, of considerably shorter length (12 inches) are
  easily bent, but nothing heavier than 0.060 would be wise here.
  In choosing standard-section steels that are personally
  weight-limited to 85 pounds each, I decided quickly what is
  available and reasonable. There are no special expensive
  materials, cold-rolled steel, super alloys, nor special hardware
  requirements beyond using grade 5 bolts at main connections. In
  fact, the hot-rolled steel was all obtained from a reseller's
  junkyard and sorted for straightness and minimal rust.  I must
  caution and encourage anyone building this size brake to use all
  safe lifting and handling measures during the build
  process. Common sense goes a long way. I loaded my trailer with
  a 112 x 6inch plate, 2 x 6 10-pound channels, and some light 4 x
  4 steel tubing. Construction from mid-December to January seemed
  a long way down a crooked road to build an airplane.

  I enjoy the flavor of building more than design as I design
  equipment for a living. But at age 60, this would become a test
  of fitness as well as enabling my aircraft construction.  This
  brake, like any other project, is just making one piece at a
  time. I knew that if I got bogged down, it would only be for
  muscle. I did require my wife's assistance once while lifting
  the 165-pound clamp weldment in place. Everything else remained
  at or near the original 85 pounds per part.  This is not a
  project that can be done without some machinery, owned,
  borrowed, or rented. I have the minimum items-a metal cutoff
  band saw, a drill press, an oxyacetylene torch, an arc welder,
  and two 8inch C-clamps.  You should have some access to any
  reasonably sized horizontal or vertical milling machine and a
  small lathe with a 9-inch swing. There are ways to get past the
  need for a lathe and even the mill, but eight feet requires too
  much handwork to try to avoid them. Someone in an EAA Chapter
  always has these.

  Processes seem to get awkward when trying to weld and machine
  elements that will just stay straight. I spent an inordinate
  amount of time recalculating joint construction that reduced
  welding distortion to zero, and I made a complete record of what
  worked best.  This sheet brake weighs in at less than 600 pounds
  on casters and is compact enough to be rolled to a wall when not
  in use. I was surprised that I'd only spent six weeks, evenings
  and weekends, in the build process. The brake turned out to be
  an investment of less than $600 in materials. The brake has
  since provided me accurate bends with a consistently good
  1/8-inch radius.

  Since then, I've finished my rudder, stabilizer, elevator, and
  wing spars.  I'm now completing the skeletal construct of the
  center section of the Zodiac 601. It's been just one year since
  the open house at Zenith 1999.  That said, I'm very pleased with
  the convenience of bending the long and short parts easily when
  I need them. The "pain of heavy work" is gone, and its cost has
  proved to be more than worth the effort.  I've assembled the
  information on building this bending brake into a three-part,
  39-page manual. It consists of drawings, photos, a
  billof-materials, process methods, and sequences that simply
  describe the project from start to finish. This package is
  offered to EAA aircraft builders as of this issue. If you're
  interested, send a $35 check or money order (to cover cost of
  copying, shipping, handling, and mailing) to Larry C. McFarland,
  4706 5th Street, East Moline, IL 61244. E-mail inquiries may be
  made to larrymc@q...

>>> 2mar02 #7686-9153
+++ #8037
From: "Montee, Dan L." <dlmontee@s...>
Subject: Spars (Help!)

Well, in every project there's at least one mountain with a
shear cliff to climb and I've come up against my first one.
Bending up the spars has become a show stopper.  I have been
unable to locate an 8' brake that I can use personally.  The
only 8' brakes I can locate in the area are owned by sheet metal
fabricators and liability being what it is today no one is real
keen on me using their shop.  I decided to hire it out.  I was
told the right guy for the job was the guy who bends up spars
for a local company, American Champion.  After two attempts we
(we being spars times 2, Dan Neuman, plans #219, and mine. Dan
will be using my form blocks), still do not have usable spar
material.  After spending an hour going over the drawings in
every detail the first attempt failed because he missed the fact
that the flanges were different sizes.

Attempt number two produced dimensionally correct c channels but
he forgot about the .100 radius, which he had managed to get
right on the first attempt. We now have more scrap ( I supplied
the materials, another lesson).  Needless to say I will never so
much as taxi an American Champion aircraft.  This whole fiasco
has consumed three months and lots of $.  I'm continuing to look
for a local firm that can and is willing to bend up our spars.

My question is: in the event I am unsuccessful is there anyone
within a resonable distance of Milwaukee that knows someone that
is capable of doing the job or has a brake we can use?  Dan &
Dan

+++ #8038
From: "Bruce A. Frank" <bafrank@w...>
Subject: Re: Spars (Help!)

How far off were the flanges?

You are telling us that after he screwed up your material twice
he didn't buy the material himself to make a correctly formed
third attempt? I certainly hope you did not pay him for wasting
your material.

Bruce A. Frank

+++ #8039
From: "Derrick Howard" <derrickhoward@h...>
Subject: Re: Spars (Help!)

Why didn't he use scraps to practice with first ???

+++ #8040
From: Russ and Penny Erb <erbman@p...>
Subject: RE: Spars (Help!)

Dan^2--if you're having that much trouble, put some spar blanks
in UPS to me and I'll go bend them on my friends brake, then
ship them back.  They're under 8 feet so UPS should ship them.
Be sure to figure bend allowance when calculating the width of
the blank.  The bend radius will be .125 on his brake.  If you
don't know how to do that, tell me exactly how tall you want the
spar and I'll do the calculation for you.  Don't forget the rear
spars, too.  I'd recommend including some of the excess material
cut to the same width for practice pieces.  I got mine right on
the first try.  It's not that tough for someone willing to learn
how it's done.

Not the best solution, but if you can't find someone closer,
it's better than nothing.

You can always cut up the scrapped spars for rib angles and
other smaller parts.  That's what I did with a skin I
mis-drilled.

If you wish to try my solution, contact me off-list at
erbman@p...

Russ Erb

+++ #8041
From: "lbhensley" <lbhensley@a...>
Subject: Re: Spars (Help!)

Sorry to hear about your bad luck.  If you are anywhere near
Tampa/Brooksville area, your are more than welcome to use my new
10 foot brake that already has the radius machined on the
bending edge.  Again, bummer!!!

Larry

+++ #8042
From: "Montee, Dan L." <dlmontee@s...>
Subject: RE: Spars (Help!)

> How far off were the flanges?
> 
> You are telling us that after he screwed up your material
> twice he didn't buy the material himself to make a correctly
> formed third attempt? I certainly hope you did not pay him for
> wasting your material.

He started off with the flap and aileron spars and used the same
flange dimension on the main, rear, and false spar.  He has
offered to try again but my confidence is gone. I think I would
always have that "what did he screw up that I didn't catch?"
doubt nagging at me forever.  It's time to cut the loses and
move on.

On the positive side, the fuel tanks are air tight and all that
is left is to attach the filler necks.  The tanks are per "the
Bob" right down to the cap.

All ribs, stiffeners, and attach angles are painted and ready
for assembly.  Nose rib stiffeners are attached. The bar stock
for spars is on the rack and the misc. .125 spar plate fittings
are fabricated and waiting spar webs.  All wing steel is
fabricated and painted.

Thanks to all for the support.
Dan Montee # 415 

+++ #8060
From: Jimmy Mathis <tallow_98@y...>
Subject: Re: Spars (Help!)

You should have a sheet metal union local up ther some
where. contact them and ask if there is a union training
facility clos by. They will bend for reasonable fee.

Jimmy 501

+++ #8741
From: "Del Rawlins" <del@netpackrat.com>
Subject: Brake attachment for EAA ch. 1000 worktables

Thanks to this discussion and some others in the past I think I
now know how I am going to build my sheetmetal brake, combining
several ideas that Bearhawk list members have come up with over
the years.  Building a decent brake wouldn't be difficult at all
except for machining the correct angle and radius on the toe,
which requires a milling machine and has stopped most of us who
are otherwise decent steel fabricators in our tracks.  Of course
it is a piece of cake to machine the angle and radius in a chunk
of wood, just run it once over the tablesaw (which is a lot more
common than a milling machine) and then hit it with a router (or
hand rasp) to give the correct bend radius.  You can then clamp
your workpiece between the resultant form block and a backup
block, and hammer away (or use a seamer, or whatever) to form
the bend.  I submit that this is a low class method of spar
forming and could be improved on with some more materials and
effort.

What I am proposing is essentially a quick and dirty sheetmetal
brake which sets up fairly quickly but can stow neatly out of
the way when you are not using it.  It will be cheap to build
and makes use of something many of us already have built for our
shops- The EAA Chapter 1000 Standardized General Purpose
Worktable.  These tables are stiff and dimensionally stable
thanks to the screw and glue construction technique, and should
provide an acceptable basis on which to build the brake and thus
avoid a bunch more steel fabrication.  Now you may be thinking
that the tables are 5 feet long and you need an 8 foot brake,
but just because the tables are standardized it doesn't mean you
have to build them that way.  Rod has a couple of 8 footers in
his shop in Wasilla and they seem to work very well and make
best use of the 3/4" plywood tabletops.

What I want to do, is get a piece of heavy steel angle iron (at
least 2"x1/8") the length of my table and drill a hole (say 3/8"
or so) 3/4" from each end.  The radiused form block that was
made on the table saw gets placed on the edge of the tabletop,
with the radius lined up directly over the edge.  On top of
this, set the piece of angle iron and clamp it down well.  The
holes you drilled should be against the radius block and the
vertical part of the angle iron needs to be on the side opposite
the radius, so it won't limit the bend angle possible.  Using
the holes as a drill guide, drill down through the radius block
and the tabletop.  You don't have to drill all the way through
the table, since you'll be drilling into the 2x4 on each end.
Drop a bolt (or piece of rod) into each hole.  These will serve
as alingment pins so you don't have to realign the toe every
time it is used.  It's also probably a good idea to screw the
angle iron down into the radius block along its length so that
it won't warp or flex.  If it still bows upward in use, it may
be necessary to add a triangulated brace like a "real" brake
uses.  In use, you'll hold down with a large C clamp on each
end.

Once the toe is in place, all that is needed is some means of
uniformly bending the workpiece over it.  Get a piece of lumber
(I would use at least 2x8 to give some leverage) and attach it
to the 2x4 on the edge of the table using door hinges.  Space
them closely and bolt them all the way through the table so it
won't flex out in use.  The top edge of the 2x8 should be
perfectly aligned with the top of the table.  You may need more
than once person doing the bending in case the 2x8 flexes.

I think that about covers it.  The toe can be stored under the
table when not in use, and the 2x8 can just be left where it is
without hindering you.  For my next project, I will design a
metal lathe that can be built for $50 with simple hand tools....

Del Rawlins

+++ #8742
From: "Kent White" <kent@t...>
Subject: RE: Spar Formblock? Stretch/Shrink?

Spar Formblock? Stretching and shrinking both occur at the point
of bend, as compression at the inside radius of the metal occurs
right alongside the tension at the outside radius.

It may not be much, but with the tightest radius bends, it does
occur. To the degree that both compression and tension balance
each other, the bend will be straight along the length. Other
factors also contribute to achieving a straight or curved bend,
such as the die condition and alignment and strength of the
machine (flex).

It is possible to shrink 2024 T3 with hand hammers, as it is
also obviously possible to stretch. Those of you making the ribs
might have seen some compression of the wrinkles, at some ideal
spot.

Using the form blocks may be the ticket, If...  The clamping and
the forms are groinked down tight and solid...  The legs are
worked consistently and gradually, avoiding any sudden departure
of contour.

And if the striking surface is contoured to avoid marks or
sudden departures when striking the metal.

Flow forming may have the advantage, as many sudden whacks are
better than fewer big sluggish ones, and the tooling (whacker)
is more easily adjusted for the metal contour and thickness.

Thanks to kind contributions by Kevin Deutscher, Benton
Holzwarth, and Russ Erb-onomic the wingrib article is due to
appear in Sp Av in a few days.  There is mention of the flow
forming method in this article, and the tooling and images of
the work possible is now up on our website.

Kent White
www.tinmantech.com

+++ #8745
From: "Greco, Bob" <bob.greco@h...>
Subject: RE: Brake attachment for EAA ch. 1000 worktables

When several of us built Mustang IIs which have spars similar to
the Bearhawk. we made a real simple press brake which worked
easily and gave very straight flanges.  We used a 4 inch angle
iron as the receiver or lower part of the brake, inside of the
angle iron we glued and screwed a maple wedge that ran the full
length of the angle iron on each side to close the 90 degree
angle enough to correct for the springback of the aluminum.  We
then mounted the angle iron on some 2x4s on top of the
workbench.  These do not have to be attached to the bench but
are just there to provide working clearance and to position the
angle iron.  Then we made a blade to push the aluminum sheet
into the v formed by the angle iron and maple wedges. This blade
was a 2x4 maple board cut into a v and with the bend radius on
the edge.

To use this we placed the aluminum sheet on top of the angle
iron then pushed it into the v using the blade which we powered
by "C" clamps located about every 6 inches along the length of
the brake.  Screwing the clamps closed we were able to easily
watch the bend as it developed and to adjust our pressure as
needed.  We made a few sample tries using short pieces of
aluminum to practice and to verify our setback allowance.  We
successfully made every spar we attempted and were able to
control the flange angle to less than 1/2 degree.  As I remember
this whole thing came for the cost of a couple of maple 2x4s
since we already had the angle and the clamps.  We used maple
because of its hardness and strength.  It looked almost unused
after forming four sets of spars (two main and two aft and one
center aft, four elevator, two vertical fin, two aileron, two
elevator one rudder per aircraft)as well as several fuselage
frames and other parts.

+++ #8746
From: Budd Davisson <buddairbum@h...>
Subject: Re: Spar Formblock?

FYI, breaking spars.

Even with a hot dog 8 foot brake like ours at the plant, it took
a lot of futzing around with it to get an even radius from one
end to the other because even a big break as a minute amount of
flexing in the middle. And then there was the enormous amount of
set up time getting the bends in the right place and making the
angles repeatable.

There's more to it than just taking it down to your local
airconditioning shop and saying "here, make four of these."

bd

+++ #8747
From: Bob Romanko <romanko@v...>
Subject: RE: Spar Formblock?

My point EXACTLY!!!  Budd, this is the very reason I think it
would be BETTER to form them by hand with the lightening holes
securely pinned to a form block.  On a brake, you're at the
mercy of the silly thing evenly clamping that narrow 'ol hunk of
allooominium over that big 'ol length!

If one were to use my suggested method and simply pin the entire
thing along the lightening holes to a form block NO SLIPPAGE!
The only factor to worry about would be whether or not one could
hand-form the flange within specs.  Using the form block method,
there is very little stress on the piece, as one would work his
way up and down the thing evenly, not trying to form the flange
all at once as in a brake and risking the whole mess flexing.

Now, if you could pin the thing on a brake and not be at the
mercy of the clamping of the foot, you'd be fat city.  Most
brakes Joe Builder will run across would probably not be up to
snuff 'nuf to handle the job on the first (or maybe second)
shot.

+++ #8753
From: Jim Ash <ashcan@m...>
Subject: RE: Spar Formblock?

I'm kinda with Russ here. Aluminum sheet has constant stresses
rolled into it. The top and bottom edges of the spar are under
both compression or tension depending on the the phases of
flight and are dependent on the strength of the material to some
degree. The only way to bend them over without effecting the
constant strength of the material would be to put the required
bend in the metal without any other incidental bends, i.e. using
a brake.

If you're going to hand-form it, then Kent's suggestion is the
way to go, with lots of small hits, so the whole edge somewhat
goes over at the same time anyhow, with no waves.

Jim Ash

+++ #8756
From: Budd Davisson <buddairbum@h...>
Subject: Re: Spar Formblock?

Speaking as an engineer: I can't imagine that bending the
material over a form block versus a break is going to have
measurable effect on the strength of the finished item. As long
as you don't go willy nilly with a ball peen hammer and
introduce secondary stresses by violently hammering it over, I
don't think it makes any difference how it makes it around the
radius. The radius is what's important.

The minor amount of straightening done after bending, using duck
bill pliers, won't even be noticed by the material.

The only place a wavy flange would be a problem would be if we
were depending on the flange to carry a load in compression,
which we're not.

Also, although it's important that the flanges be as straight as
possible, in reality, it doesn't make much difference
structurally. The flanges are just there to give a convenient
place to attach the skin and transfer the distributed flight
loads to the spars. The strengh of the spar is driven by the
thickness, height and distance the spar caps are from the
neutral axis (center of the spar web). As long as there are no
sharp bends, nicks or other sharp discontinuities in the flange,
you'd be surprised how crude the actual flange itself can be and
still be structurally sound.

It's desirable the flanges be parallel to the local skin line
(correct bend angle) to make it easier to rivet it. However,
even if the flange was wavy and, before bucking each rivet, you
tucked the skin next to the rivet up tight to the skin and then
bucked the rivet, the qualit of the joint wouldn't suffer much.

In lousy craftsmanship, items like scratches and tight bend
radii are more harmful than wavy flanges (assuming tight fits,
skin to skin, at each rivet).

Damn! It's too late to philosophize.

bd

+++ #8759
From: Timothy Neil <beanman@a...>
Subject: Re: Spar Formblock?

As to forming the spars : I followed the intructions in the
newsletter and had no problem whatever. Once everything was
marked it took about 20 minutes at the brake to bend all 4. The
trick is to get access to a GOOD brake that is not worn out!
                                                         Tim Neil

+++ #8762
From: Jim Ash <ashcan@m...>
Subject: Re: Spar Formblock?

The top side of the spar outboard from the strut isn't under
compression?  I'm confused. It's been 20 years since I've done
statics, but I thought this was the basic I-beam thing.

For those paying attention to this thread, please excuse my
inquiry. I'm not trying to scare anybody; I'm just trying to
understand what's going on.

Jim Ash

+++ #8765
From: Budd Davisson <buddairbum@h...>
Subject: Re: Spar Formblock?

I apparently didn't make the point clear. The point was we
aren't depending on the flange to carry either compression OR
tension loads. That's what spar caps are for. In this
application the flange could be viewed as a clip that is
transferring skin loads to the spars. Yes the local volume of
the skin does add a little to the effect of the spar caps, but
that's not its intended function.

bd

+++ #8767
From: "gjvf" <mvfco@k...>
Subject: Re: Spar Formblock?

A friend of mine has a friend with a heating business who has an
8' break and a 10' shear.  My friend, who is a DER at Parker
(they make fuel and hydraulic pumps for aircraft), came along to
help.  I thought we would knock out all the spars in a couple of
hours but after 4-1/2 hrs we only had the main spars done.  We
made about 4-6" test pieces like Bob says and from these got the
measurements required.  The rest of the time was spent shearing
the spar blanks and carefully measuring and marking them.  A lot
of time was spent trying to figure out where to stop the break
to get the correct flange angle.  We found that the short test
pieces bent differently than the full length spar - for the same
break angle the shorter pieces bent more than the full length
spars. It takes two people to position the blank in the break -
one at each end.  Both our arms were sore the next day from
pulling down on the locking levers many, many times trying to
get the blanks positioned "just right".  We ended up with "good
enough" spars (they were off by +0.01") and no scraped
aluminum. Anyway, it takes a lot of force to bend the full
length 0.032" stock - I don't think any wooden break will be
strong enough to do the job.  A form block would work but it
would take several tries to get the correct spar dimensions.
Also, if the flange is wavy it seems to me that the stiffer
0.032" material would make the 0.025" skin wavy.  I recommend
making friends with some HVAC guys!
Jim Van Fossen #411 Grafton, OH

>>> 20may03 #11298-18250
+++ #11798
From: Benton Holzwarth <bcgh@a...>
Subject: Formblock for Spars

I tried making a formblock to bend spars over.

Routed an edge into a 8' 2x4, and screwed some steel strap onto it,
then radiused it to the 0.1" callout on the plans.  Total invested,
including eight bar-clamps to hold the metal in place -- about $25.

Tried running a first test this evening -- putting a flange on a 2'6"
piece of scrap 0.025 Al.  I think it did a decent job on the first 80
deg (90 deg less springback) but when I tried to whack the edge over
the rest of the way 'freehand', to the slightly closed angle to match
the flap rib, I think there was a little stretching, so that over the
length there is about a 1/8" rise (bow) towards the flange.

I'm guessing flutes on the spar flanges would be a bad thing, so I'll
try some more to perfect the technique.  Failing that, I'll look again
for a brake.

  Benton

+++ #12535
From: "kb8rnu" <kb8rnu@y...>
Subject: Greetings from new builder, and a question....

I ran across the group while researching the Bearhawk. I ordered my
plans yesterday and am looking forward to getting started.

One question (and I apologize if it has been covered - did not find it
in the unofficial FAQ):

I have been looking for a sheet metal brake for my shop. I have
occasional access to an 8 foot brake for the spars, but would like to
be able to do the majority of the bends at home to save time.

I've seen reference in the FAQ to small 30" brakes from Harbor Freight
for around $50:

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=41311

Would this be adequate, or should I go with the beefier 40" version for $130:

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=46508

Is the increased size of the 40" going to allow me to do the majority
of the bending, or would the 30" suffice?

Any advice would be appreciated.

Sincerely, 

Jason Bowling

+++ #12536
From: petz187@a...
Subject: Re: Greetings from new builder, and a question....

Jason, for what it's worth, I would look for a 4 foot brake, and get
sheet metal shop to cut @ bend to your spare's.
 HAL # 355

+++ #12537
From: Del Rawlins <del@r...>
Subject: Re: Greetings from new builder, and a question....

The small harbor freight version is suitable AFTER MODIFICATION for
bending the rib stiffeners and attach angles.  For details on the
modifications required, see
http://www.rawlinsbrothers.org/planes/bhtools.html I don't think it
would be any good for most of the other bends, and I wouldn't spend
any extra money on the 30" (I bought the 18" version) brake because it
would be even more prone to flexing than the 18" brake, and you'd have
to file down another 12" of radius on the toe of the brake to use the
full width.

> Is the increased size of the 40" going to allow me to do the
> majority of the bending, or would the 30" suffice?

IF it is actually beefy enough to make the bends without flexing out
of shape, then it is just barely wide enough to do the bends for the
fuel tanks (which are 39-3/4" wide).  Personally I would feel a lot
more comfortable spending the money on a small brake from Williams
Lowbuck tools, since they are not an imported item; the proprietor
actually makes them in his own shop as far as I know.  I don't have
any personal experience with his stuff but check out
http://www.lowbucktools.com/

> Any advice would be appreciated.

Good luck.

+++ #12540
From: Tony Dean <tdean@d...>
Subject: Re: Greetings from new builder, and a question....

>I have been looking for a sheet metal brake for my shop.
>
> Anyone make one of these?
>  
> http://groups.yahoo.com/group/Bearhawk/files/brake%205.JPG
> 
> Someone remember the address for the plans?

Does anyone know what issue of Experimenter this came out of?

+++ #12542
From: "kb8rnu" <kb8rnu@y...>
Subject: Re: Greetings from new builder, and a question....

Thank you all.

I'll probably go with the heavier one at Harbor Freight - you've
definately talked me out of the cheaper one. I think the heavier one
will probably be ok - while the shipping weight on the small/cheap 30"
one is 30 lbs, the 40" one is 115 lbs. Should be substantially
tougher.

Jason

+++ #12543
From: Del Rawlins <del@r...>
Subject: Re: Greetings from new builder, and a question....

Let us know how it works out.  I've done a lot of shopping around for
metal brakes online, and the impression I get is that you buy them by
the pound.

-- Del Rawlins

+++ #12552
From: nov222pa@c...>
Subject: Re: , and a question....8ft brake

> Does anyone know what issue of Experimenter this came out of?

I just received plans for the 8 foot apron brake as featured in the
November issue of the Experimenter. For those that are interested,
these plans are 40 pages, CAD drawn, numerous closeup photo's and very
good descriptive text to go along with it. The plans are $35.00
dollars and they get a big thumbs up.  Available from Larry McFarland
4706 5th St., East Moline, Il 61244. You can reach him by e-mail at
larrymc@qconline.com

+++ #12879
From: "kb8rnu" <kb8rnu@y...>
Subject: 40" bending brake from Harbor Frieght comments

A while back I asked for opinions on the 40" brake Harbor Frieght
sells. It was relatively inexpensive ($130) and very heavy (115 lbs).

The brake arrived a couple days ago. Although it took almost three
weeks to get here, shipping was o$5 since I orderd from their web
site.

The brake appears to be very solidly made - it is 1/4" steel plate all
around. I doubt seriously it would need any reinforcement. I just need
to figure out the best way to radius the edge to allow for bending
aluminum.

Picture at my web site at:

http://wright.cs.uakron.edu/bearhawk/tools/bending_brake.jpg

Jason

+++ #12880
From: Russ and Penny Erb <erbman@p...>
Subject: RE: 40" bending brake from Harbor Frieght comments

Jason--two options on getting a bend radius--

1.  (Destructive) Get out the file/grinder/belt sander and go at it.
2.  (Non-destructive) Get a thin piece of steel sheet and bend it over
the sharp edge.  Steel can take a much sharper radius than aluminum.
Leave this steel sheet over the edge when bending aluminum to provide
the bend radius.  The radius you get will depend on the thickness of
the steel sheet.  In the Spring 1995 Bear-Tracks (yes, I have them
all--also on the CD) The Bob recommends using a 18 gauge soft sheet
steel foot cover.

Russ Erb

+++ #12883
From: "Bruce A. Frank" <bafrank@w...>
Subject: RE: 40" bending brake from Harbor Frieght comments

I agree with Russ on the second method. I would not permanently change
the hold down radius. Also, though I am not familiar with that brake,
does it not have an adjustment to move the hold down back from the
edge? This would allow a less sharp radius.

I have a small 18" wide brake, that was intended for light material
(20-22 gage), on which I needed to bend .065 4130. The movable jaw
would flex preventing me from obtaining a clean uniform bend (this is
a high dollar unit using high strength steel so flexed parts would
spring back to proper position). The hinge pins are (relatively)
massive able to handle several times the force one is able to generate
on this brake, but I needed to make the movable jaw more rigid. I
obtained a piece of angle that was 1.5" X 1.5" X 1/2" thick and 18"
long. I drilled holes through the angle every 2 inches along its
length. I used it as a template to mark the movable jaw, then drilled
and taped holes in the movable jaw. I then bolted the angle to the
jaw, as shown in the rough drawing attached to this email, using grade
5, 1/2" X 13 thread bolts using flat and lock washers to adjust the
length so there was no protrusion on the working side of the jaw. I
torqued the bolts to their recommended maximum. I now regularly bend
1/8" and 1/4" aluminum and 1/8" mild steel with no problem at all (as
limited by my strength, I do not mean that I can make a full width
bend on such heavy metal). Sixteen gage and .100" 4130 brackets
present absolutely no problem. If you notice any belly developing in
the movable jaw from ever so slight abuse, you should consider
modifying your unit as I did.

Bruce A. Frank

+++ #13310
From: Benton Holzwarth <bcgh@a...>
Subject: re: A humble Aluminum Bending Question?

> Some time ago someone bent some spars without a bending break. Well,
> I have a similar bending delima. I need to bend a 30 degree angle on
> two sides of a piece of aluminum that is 8 ft long and three inches
> wide with about 1/2 inch flanges along each side after bending. The
> material is 2024T3.
> 
> It is a reinforcemnt part so it goes up against two straight
> parts. Any ideas on getting long and rather straight bends into this?

(Oh, good!  Something ON TOPIC to reply to.)

That might have been me.  I bent my flap spars over an 8' formblock,
built up from a 2x4 with an inset steel strap rounded to form the
radius.

It worked.  The second spar did get just a little more stretching in
the flange, so it bows towards the flange about a 1/4".  Not so much
that it doesn't pull back straight with about an ounce of pressure.

On the one hand, I can say I stand my 'brake' up in the corner when
I'm not using it, something few other people can claim.  On the other
hand, I'm thinking I'll find a shop with an 8' brake to use, if I can
find one at a decent price -- doing it on the formblock was a *lot* of
work.  Both making the block and then forming the metal.

I took a few pictures.  When I have time, I'll write it up pretty.
Else, if you're really curious, drop me a note and I'll fire off
something, quick 'n dirty.

  Benton

+++ #13372
From: "egenz" <egenz@y...>
Subject: Bend Radius

... So, I might as well get my feet wet and ask my first question.
Can someone give me a short class on the "bend radius" measurement.
How is it defined and how do you measure it?  I have an idea in my
head but I just want to confirm.

Eric Genzlinger #595

+++ #13376
From: "Lee H. Erb" <leeerb@c...>
Subject: Bend Radius

> Can someone give me a short class on the "bend radius" measurement.

There are two definitions that float around every so often, The
practical one that industry uses and a theortical used in some
analyses.

The only one to use is the one published in aircraft design manuals:
The inside of the bend. If you wrap a sheet around a 1/8 inch diameter
rod, without springback you have a 1/16 inch radius.

If you go to a Minimum Bend Radius Table, remember that it is Minimum
radius. Minimum Radius seldom needs to be used except when needing to
stack parts.

Lee H. Erb

+++ #13841
From: "yah67890" <yah67890@y...>
Subject: Bend Calculator  uploaded

Bend Calculator uploaded in the files folder .  Click on the html file
or jpeg to see what its about.

Also when is the 2 seater babybear going to be ready , is it tandem
,what hp will it require , sorry if this has already been done to
death.  Thanks Yah

+++ #17277
From: Budd Davisson <buddairbum@c...>
Subject: Re: big brake question

> Assuming I can make the bend radius work, is there any problem
> bending spars with a 10' portable siding brake or is that job best
> done with a big shop brake/shear?

I'm certain everyone will send in answers on this, but this is mine:

Trying to get an even radius and bend the full length of the spars is
a pretty good trick even with a really heavy pan break. A siding break
is meant to bend super light material so probably isn't close to being
stiff enough. Although, without actually seeing the unit, I'm making
some assumptions.

bd

+++ #17281
From: "larpnwt" <penner@a...>
Subject: Bending Brakes

> Assuming I can make the bend radius work, is there any problem
> bending spars with a 10' portable siding brake or is that job best
> done with a big shop brake/shear?

I've been using a siding brake for some of the small jobs like rib
stiffeners/attach angles. But trying to bend a piece of .032 2024 over
more than about 2ft. is too much for this type of brake and you'll
probably just bend or break the brake. The clamping system (foot) just
can't hold it and the work piece slides out as you try to bend which
makes a mess of the work. I am going to try to bend my Ail/Flap
trailing edges with it but I suspect I'll end up using the big shop
brake. I think you'll find bending an 8 ft spar blank with a real
brake challenging enough without worrying about the brake doing its
job properly.

Larry BH562 

+++ #17946
From: Russ and Penny Erb <erbman@p...>
Subject: RE: Formblock radius: how much is too much?

With regards to "minimum" and "normal" bend radii...

Minimum bend radius is typically the tightest bend you can make and
have a reasonable chance of not cracking the part.

Normal bend radius is sufficient for most applications and should not
crack, even when bending "with the grain" (oh, heck, let's not start
that thread again...).

You can look at various bend radius tables and get differing answers
based on material and thickness.  I've found for .020, .025, and .032
thick 2024-T3 that 1/8" (0.125, or 4T for .032) is an excellent
compromise.  Yes, you could bend the thinner sheets tighter, but I
haven't found a need to.
 I've used 1/8" as a bend radius for everything I can remember.

Your quoted 3T number is only .032 less than 1/8".  You'd be hard
pressed to bend it so accurately that it would be an issue.

I've also found that 2024-T3 is hard enough to bend to a "normal"
radius--it would be very difficult to bend to a "minimum" radius
without doing some sort of hammering.

By the way, 1T is usually sufficient for thin 4130 sheets.  You can
hammer the steel over a sharp ("unrounded") edge and generally get
away with it.

Russ Erb

+++ 

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