The Biplane Forum > Biplane Builder's Forums > Acrosport > Fittings bending
Reply
 
Thread Tools Display Modes
Old 08-12-2017, 06:44 PM   #1
chiru
Registered Users
 
chiru's Avatar
 
Join Date: Oct 2008
Location: Geneva
Posts: 50
Default Fittings bending

Hi all,
I gave my fittings for bending to a specialized company but they used a too small radius. For me that's a No Go for 0.090 thickness.
Do you think there is a way to repair the fittings ? For example by welding the corners or adding some external or internal reinforcement ?
Thank you for your opinion.


IMG_5836.jpg   IMG_5837.jpg   IMG_5838.jpg   IMG_5839.jpg  
__________________
http://acrosport.chiru.ch/
chiru is offline  
 
Reply With Quote
Old 08-12-2017, 08:06 PM   #2
crankyklingon
 
crankyklingon's Avatar
 
Join Date: Mar 2010
Location: Springfield Ga
Posts: 1,545
Liked 612 Times on 401 Posts
Likes Given: 2

Default

Well that sucks.
No.
Also, since they used a dead sharp radius if the flat pattern was per plans the hole locations will be off.
Sometimes it's better to make the holes after bending. I know, I know in this world of lasers and water jet cutting those words are herasy, but that approach avoids this sort of discomfort.


__________________
Rob
crankyklingon is offline  
Jean-luc Likes This 
Reply With Quote
Old 08-12-2017, 08:23 PM   #3
Kiwi
Registered Users
 
Join Date: May 2010
Location: New Zealand
Posts: 326
Liked 84 Times on 55 Posts
Likes Given: 473

Default

Are they cracked? Usually they crack at the ends, especially as you did not polish the edges prior to bending, or crack on the outside of the bend somewhere along the length.

By chance is the material 4130A (annealed). There is a bit of that floating around.

Do some research on minimum bend radii for 4130. You may find the material to be more malleable than what is intuitive and the bend radii you have there to be OK.

I'm reluctant to advocate for using them, but I think those fittings may get welded along the bend line anyway upon being attached to the fuselage, so does the bend radius matter that much?

On a personal / human factors note, I find if I put stuff-ups like this aside for a week or more and then pull them out after a cooling off period, the path forward becomes a lot clearer. i.e. no big deal or there's no way I'm putting those on my plane!

Andrew.
Kiwi is offline  
 
Reply With Quote
Old 08-12-2017, 08:41 PM   #4
TFF1
Registered Users
 
Join Date: Apr 2010
Location: Memphis,TN
Posts: 2,523
Liked 399 Times on 307 Posts

Default

They are already bent, weld the corners and see. If the outside is welded, it's not going to matter. If they are bolt on I would be more concerned.
TFF1 is offline  
 
Reply With Quote
Old 08-12-2017, 09:07 PM   #5
crankyklingon
 
crankyklingon's Avatar
 
Join Date: Mar 2010
Location: Springfield Ga
Posts: 1,545
Liked 612 Times on 401 Posts
Likes Given: 2

Default

As an observation I'd like to point out the legs are not equal.
The top picture, the legs are supposed to be the same length.
They bent them wrong.
Put a bolt in it and check if the bolt is parallel with the flat part of the bracket. Shud be. Bettin it ain't.
__________________
Rob
crankyklingon is offline  
 
Reply With Quote
Old 08-12-2017, 10:28 PM   #6
garyg
BiP_LIFETIMESUPPORTER.png
 
Join Date: Nov 2011
Location: cedar rapids, ia
Posts: 380
Liked 33 Times on 29 Posts
Likes Given: 36

Send a message via MSN to garyg
Default

Not just put a bolt thru it, put on the spar and then put the bolt thru it.

I vote start over. Not that I know that much but those look some hard bends waiting to crack. I would assume they would bend new ones on the house.
garyg is offline  
 
Reply With Quote
Old 08-12-2017, 10:33 PM   #7
chiru
Registered Users
 
chiru's Avatar
 
Join Date: Oct 2008
Location: Geneva
Posts: 50
Default

This version is the first with holes done before bending. As I didn't like the result I cut them again and asked for another bending with a larger radius. But they did it wrong again ...
The symmetry oh holes is not a problem as I have one version with no holes.
My concern is about the potential cracks. The radius is below the tolerance, from what I read in several documents. The weld won't go along all corners, that's why I try to find an alternative solution to creating them from scratch third time.
It's the wings and landing gear attachment. I don't want to play with that. If you think the reinforcement welding I suggested doesn't help, I will create them again.
IMG_5852.PNG  
__________________
http://acrosport.chiru.ch/
chiru is offline  
 
Reply With Quote
Old 08-12-2017, 10:44 PM   #8
cwilliamrose
BiP_LIFETIMESUPPORTER.png
 
cwilliamrose's Avatar
 
Join Date: Nov 2009
Location: SW Florida
Posts: 6,500
Liked 1276 Times on 964 Posts
Likes Given: 9

Default

The 'official' reason for the lower rear spar fitting AD on the Pitts is that the parts were incorrectly bent and I suspect that means the radius was too small. To my mind there's no point to saving those parts, in the long run it will only be a source of concern for you.
__________________
...........Bill

Project:Stretched Pitts S-1SS

cwilliamrose is offline  
biplanebob Likes This 
Reply With Quote
Old 08-12-2017, 10:45 PM   #9
garyg
BiP_LIFETIMESUPPORTER.png
 
Join Date: Nov 2011
Location: cedar rapids, ia
Posts: 380
Liked 33 Times on 29 Posts
Likes Given: 36

Send a message via MSN to garyg
Default

I think if you try to do a weld on the inside corner, I am sure the spar will not fit correctly. There is not a lot of extra room on the inside.
garyg is offline  
 
Reply With Quote
Old 08-12-2017, 10:55 PM   #10
chiru
Registered Users
 
chiru's Avatar
 
Join Date: Oct 2008
Location: Geneva
Posts: 50
Default

Ok, thank you for your advices. I will do them again. It's just a mess for bending correctly a 0.090 4130 but there is always a solution.
__________________
http://acrosport.chiru.ch/
chiru is offline  
 
Reply With Quote
Old 08-12-2017, 11:02 PM   #11
Neil
BiP_LIFETIMESUPPORTER.png
 
Neil's Avatar
 
Join Date: Nov 2006
Location: Monroe, LA Work at F89 Winnsboro, LA
Posts: 5,780
Liked 738 Times on 562 Posts
Likes Given: 250

Default

That part is suppose to have a 1/4" radius in the bend.
Scan.jpg  
__________________
OOPS you can fix with a paper towel. UH OH is going to require more money.
Building Acro Sport II NX11ND
Plans #425
Neil is offline  
 
Reply With Quote
Old 08-12-2017, 11:19 PM   #12
Neil
BiP_LIFETIMESUPPORTER.png
 
Neil's Avatar
 
Join Date: Nov 2006
Location: Monroe, LA Work at F89 Winnsboro, LA
Posts: 5,780
Liked 738 Times on 562 Posts
Likes Given: 250

Default

It is possible to make a punch and die that will form the bend from hardwood. The punch will need to be the thickness of the spar plus the spar plates and the wing spar attach straps. You will also need a block that has a cutout in it the width of the punch plus the metal thickness. (Two times the metal thickness in this case.) The bottom of the die can be square cornered. The punch should have the desired radius on the corners and the die will need to have a radius at the top to allow the metal to be drawn down into it without too much starting force. The die will have to be deep enough to hold the finished part to get good form and you should be able to provide enough force with a good bench vise but an arbor press would be better.

This is a bending die I made to form the aileron hinge parts but the idea is the same.

__________________
OOPS you can fix with a paper towel. UH OH is going to require more money.
Building Acro Sport II NX11ND
Plans #425

Last edited by Neil; 08-12-2017 at 11:22 PM.
Neil is offline  
 
Reply With Quote
Old 08-12-2017, 11:57 PM   #13
taff
Senior Member
BiP_SUPPORTER.png
 
taff's Avatar
 
Join Date: Apr 2007
Location: Georgia. USA
Posts: 2,970
Liked 684 Times on 507 Posts
Likes Given: 1290

Default

one of the pix right side up
IMG_5836[1].jpg  
__________________
Greetings. Eric.
Skybolt under construction. not expert but aspiring + builder
taff is offline  
 
Reply With Quote
Old 08-13-2017, 12:59 AM   #14
crankyklingon
 
crankyklingon's Avatar
 
Join Date: Mar 2010
Location: Springfield Ga
Posts: 1,545
Liked 612 Times on 401 Posts
Likes Given: 2

Default

Don't be discouraged. You've got a good looking project and you are getting to the most rewarding part.
It can be expensive, frustrating and time consuming trying to get non aviation folks to understand our standards and why we must adhere to them.
You can bend metals tighter than the recommended bend radius...sometimes without cracks. But their physical properties (strength, fatigue life) will be diminished.
You can't trust your life to something like that or compromise your project by using it.
I bent all of my steel in a simple break with the correct bend radius and performed the final trim and drilling after.
__________________
Rob
crankyklingon is offline  
 
Reply With Quote
Old 08-13-2017, 01:23 AM   #15
death trap
Registered Users
 
Join Date: Sep 2009
Location: palm coast fl
Posts: 368
Liked 64 Times on 48 Posts
Likes Given: 37

Send a message via MSN to death trap
Default Bent parts

Looks like they used the wrong punch ( male die on a press brake ) . Did you give them specs for the bends ? On the holes matching after bending , I'd opt for 1 hole then drill the other after its bent .
death trap is offline  
 
Reply With Quote
Old 08-13-2017, 01:49 AM   #16
biplanebob
Member
BiP_SUPPORTER.png
 
biplanebob's Avatar
 
Join Date: Aug 2006
Location: Pennsylvania,United States
Posts: 744
Liked 247 Times on 185 Posts
Likes Given: 1504

Default

It is much easier to make new fittings now than after they are welded on and you decide you are not happy with them or are worried about their airworthiness !

Bob
__________________
biplanebob,

Built and flying a Willie II Biplane
biplanebob is offline  
3
People Like This 
Reply With Quote
Old 08-14-2017, 01:44 AM   #17
Dennis Flamini
BiP_SUPPORTER.png
 
Dennis Flamini's Avatar
 
Join Date: Sep 2007
Location: Near Chicago Acrosport 2 Pitts S-1S
Posts: 1,863
Liked 623 Times on 385 Posts
Likes Given: 852

Default

Christian,
It takes so long to build these biplanes i forget how i bent the fittings but here is a post where i tack welded the fittings in assembly with the wings rigged.
http://www.biplaneforum.com/showpost...57&postcount=8


__________________
Dennis near Chicago
How can you not be romantic about biplanes.
If your Father is poor it's fate, if your Father-in-law is poor it's stupidity
Wilbur Wright said he "did not have time for both a wife and an airplane."
Which is the better portion -- bondage bought with a ring,
Or a harem of dusky beauties, fifty tied in a string?
Dennis Flamini is offline  
 
Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Bending 4130 rawlin27 Pitts Fuselage & Empennage 2 10-27-2016 09:46 PM
Bending Handles wandersen Skybolt Fuselage & Empennage 26 09-20-2014 09:11 PM
Tube Bending Oldernut Handy Resources 15 10-18-2009 08:46 PM
bending longerons zevans Steen Skybolt 2 06-25-2009 08:05 PM
Heating fittings before bending ? Jerry Hangar Talk 7 03-25-2008 10:15 AM