Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Bend chart for 3/8" aluminum tubing  (Read 3821 times)
KD5GR
Member

Posts: 100




Ignore
« on: June 03, 2013, 07:17:21 AM »

A friend and I are building 2-meter LFA yagis and are having a hard time making the end pieces for the driven element loop.  The bends aren't coming out the right size in terms of spread; i.e. keeping the two driven elements correctly spaced.  Here is a link to the LFA loop design.  http://www.g0ksc.co.uk/making-the-lfa-loop.html   We've tried the method shown, but it doesn't work, the end piece is too short.  We've added the depth of the 3/8" slot on the bender (approx. 3/8") and the end piece is too long.  If we have to, we'll just stay with the trial and error method, but a bend charge would sure speed up the process and save material.

This is the bender we are using:  http://www.lowes.com/pd_331956-943-66575.UPP5_0__?productId=3228222&Ntt=tubing+bender&pl=1&currentURL=%3FNtt%3Dtubing%2Bbender&facetInfo=  

Does anyone know of a bend chart showing the set back for tubing this small?  I know they are available for conduit, but I can't find one on the Internet for tubing.

Thanks,
Chas.
« Last Edit: June 03, 2013, 07:40:23 AM by KD5GR » Logged
WB6BYU
Member

Posts: 13253




Ignore
« Reply #1 on: June 03, 2013, 08:48:13 AM »

Or you could bend the corners then splice them to straight lengths for the
sides of the loop, making adjustment much easier.
Logged
K2CUB
Member

Posts: 15




Ignore
« Reply #2 on: June 03, 2013, 11:51:34 AM »

Google Aircraft mechanics handbook and tube bending.  There are many resources in this arena for bending tubing and setbacks.  Also google 43.13 aircraft mechanics handbook and FAA to download a copy.  I believe they are in there also.  Hope this helps.  73
Logged
KD5GR
Member

Posts: 100




Ignore
« Reply #3 on: June 03, 2013, 01:48:42 PM »

Thanks for the help guys.

Chas.
Logged
KD5GR
Member

Posts: 100




Ignore
« Reply #4 on: June 03, 2013, 01:49:32 PM »

Or you could bend the corners then splice them to straight lengths for the
sides of the loop, making adjustment much easier.

This would be easy and it would allow us to easily adjust the spread between DE1 and DE2.

Thanks Dale,
Chas.
Logged
KW6LA
Member

Posts: 92




Ignore
« Reply #5 on: June 06, 2013, 04:30:06 PM »

I have bent more than my share of tubing and WR-xx waveguides. Bend charts are only a start and you learn how your tool reacts on different material and or radii. The speed in which you fold the bend, one to
the next can change things. You will need to over bend for spring back also. Now you go into learning mode ? Is it long or short ? Add or substract as required and use small pieces to perfect the bend with the tool
you are using. Use paper or plywood to draw up a 1:1 template to check your work. Use a pencil to mark the tube as a reference to the bender to be consistent. Never scribe lines for it will crack upon bending.
The tool you have is fine, however I build my own jigs with rollers in each corner. What happen is the tube wants to pull away from it position on the following bends. Now the chart is useless. With a little practice
you will learn the art of bending. Good Luck !
Logged
KW6LA
Member

Posts: 92




Ignore
« Reply #6 on: June 06, 2013, 04:42:03 PM »

Oh BTW.. the best of the best benders would have a difficult time folding a rectangle with a perfect match end to end. Bend it long, so you have a overlap to cut off for a match. 3/8  tubing will easily over lap
so you can hacksaw it off. The best secrets in sheet metal / bending is how to cheat ! !
Logged
KD5GR
Member

Posts: 100




Ignore
« Reply #7 on: June 07, 2013, 05:46:44 PM »

I'm convinced that Dale's suggestion is the way to go.  I'll bend the ends, then put them into a 1/2" piece and adjust for proper element spacing at the ends of DE1 and DE2.

Chas.
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!