All MetalShaping

Go Back   All MetalShaping > General Metal Shaping Discussion > Basic questions and answers
  Today's Posts Posts for Last 7 Days Posts for Last 14 Days  

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 08-02-2021, 03:21 PM
tjratz tjratz is offline
Member
 
Join Date: Jun 2014
Location: Liberal Kansas
Posts: 40
Default linear/ radial stretching

Now while I know the difference between linear and radial stretching (at least I think I do). How does one know when to use either one? What are the clues that a piece needs to be stretch either radially or linearly?
__________________
TJ Ratzlaff
Reply With Quote
  #2  
Old 08-02-2021, 03:30 PM
Jaroslav Jaroslav is offline
MetalShaper of the Month April 2020, September 2021, November 2022
 
Join Date: Dec 2012
Location: Czech Republic
Posts: 2,594
Default

TJ. Don't look for science and names. Learn to make paper templates. They will show you all directions. Paper is the basis. It will show you the direction.
__________________
Jaroslav
Reply With Quote
  #3  
Old 08-02-2021, 05:52 PM
Steve Hamilton's Avatar
Steve Hamilton Steve Hamilton is offline
ADMINISTRATOR MetalShaper of the Month Dec. '09 & May '11
 
Join Date: May 2009
Location: Fond du Lac WI.
Posts: 2,404
Default

Quote:
Originally Posted by tjratz View Post
Now while I know the difference between linear and radial stretching (at least I think I do). How does one know when to use either one? What are the clues that a piece needs to be stretch either radially or linearly?
Hi TJ
if you wanted to make half of a beach ball, (hemisphere) where the crown is the same in all directions you would use radial stretch. Starting with a metal disk, the most stretch in the middle and gradually less as you move outward. A round tool is used to cause this kind of stretch. The metal will increase in surface area north to south and east to west. Most shapes are created with a blend of shrink and stretch to keep a more uniform metal thickness. In this case the outer portion would be shrunk.

An example of linear stretch would be if you wanted the hemisphere to have a flange around the outside so that you could fasten it to a flat surface. This would require that the flange be the same circumference as the sphere at the bend line but would need to be longer at the outer edge. the stretch zone needs to be like the shape of a piece of pie. very little stretch at the point and a lot more out at the crust. this could be done with stretch dies in a mechanical stretcher or by thinning the metal with a rounded chisel or chisel end of a body hammer into a shot bag or a firm rubber pad. you could also stretch into a void cut out of stump.

Steve
__________________
Steve Hamilton
Hamilton Classics
Auto Restoration & Metalshaping
Reply With Quote
  #4  
Old 08-02-2021, 06:17 PM
Charlie Myres Charlie Myres is offline
Member
 
Join Date: Jun 2013
Location: Narrogin, Western Australia
Posts: 579
Default

Well said Jaro!

Read the paper pattern and find the answers there,

Cheers Charlie
__________________
Why does dust stick to everything, but nothing sticks to dust?
Reply With Quote
  #5  
Old 08-03-2021, 03:42 PM
crystallographic crystallographic is offline
MetalShaper of the Month October '14 , April '16, July 2020, Jan 2023
 
Join Date: Dec 2010
Location: Western Sierra Nevadas, Badger Hill, CA
Posts: 4,385
Default

Long narrow shapes like channels and angles that need to be curved (outwards) are shaped with linear stretch techniques.
P1060856 c.jpg
On this part, above, the stretch dies leave marks showing their distinct imprint (track). This circle started out as a straight 90 flange. One edge was stretched back and forth very evenly and the curve eventually formed into a circle. Even though the marks now radiate from the center of the circle, the stretching was done using linear dies and only moving in a linear direction whilst keeping the shape 90deg to the flange, at each point of die contact.

Large areas (lily pads/reverse shapes/saddles/flips) which need curved surface areas lifted up are stretched with radial methods.

W_R finger pattern c.jpg
The "paper pattern," which has been previously mentioned here, shows how the shape does radiate up and out. In metal, this will become a radial shape that is also reversed/flipped.

P1010070 c.jpg
Resulting radial shape.
See radiating lines of stretch marks, coming from center of panel and radiating out to the shaped, lifted edge.
A modified linear stretch die was used - in a radial method.
If you simply shape "back and forth" on a panel like this you will discover that "bunching" happens at the ends of your passes. See the little one on the right end?
Using radial shaping techniques, consciously, makes for even radial shapes - with no bunching.

and etcetera :
One finger fit, wingroot fairing copy.jpg
H1 tail panel done, R copy.jpg
P1010202 copy.jpg
gearleg fairing, Waco c.jpg
P1020859 copy.jpg
P1040246 copy.jpg
P1050830 c.jpg
P1030887 copy.jpg
P1090190 copy.jpg
P1000225 copy.jpg

For myself, I have only begun to discover the shapes I really want to make, so my understanding is yet incomplete.
__________________
Kent

http://www.tinmantech.com

"All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919.

Last edited by crystallographic; 08-03-2021 at 04:52 PM.
Reply With Quote
  #6  
Old 08-04-2021, 02:46 PM
tjratz tjratz is offline
Member
 
Join Date: Jun 2014
Location: Liberal Kansas
Posts: 40
Default

All very useful and helpful insight and knowledge. Thank you everyone for clearing it up for me. I greatly appreciate it!
__________________
TJ Ratzlaff
Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 On

Forum Jump

All times are GMT -5. The time now is 05:20 AM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.