#21
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I always thought that an oil can was stretched metal contained by a tighter perimeter.
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Ross If at first you don't succeed....skydiving is not for you. |
#22
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Or non-stretched metal surrounded by (at least at some point) by shrunk metal. It's the tighter perimeter relative to the effected area that causes the problem. That's why they are so confusing. Sometimes you shrink the oil can to 'fix' the problem and in doing so, accidentally shrink an adjoining area. Problem still exists so you shrink some more and now you're going to chase...and chase....and chase. Sometimes the problem is caused by a shrink, not a stretch.
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Kerry Pinkerton |
#23
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Quote:
but i want to ad ,shrink by heat does happen using spot sandblasters on a roof panel will result in sort of the same dents you get welding holes used for mounting chrome parts i think it starts with heat shrinking and if and when angle ,pressure, etc. are wrong it changes to stretching. in my oppinion we all agree on how the oilcan gets in our panel now we need to know how to read our panel if we have to shrink ore stretch and where. at this point i stay with my experiance to overshrink and stretch the panel back in shape, because the wheeling machine gives a better finisch then shrinking with a torch
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robert veldman |
#24
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Quote:
Just like Richard said "What makes it very hard to fix is the fact that the stretching is very uneven across the panel. Depending on how close, how long and what angle the blast nozzle was from the sheet at any given point on the panel." It really helps if you know how the damage was done. I had a '36 Cabrolet I spent a good 12 hours on with the shrinking disc and slappers. Most of the damage was done when the blaster did the inside supports. You could see the panel was raised in straight lines that match up to the body supports and braces perfectly.
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Jeff Dyce Hell, there are no rules here - we're trying to accomplish something. Thomas A. Edison |
#25
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O.K. Just going to throw this out there, so here goes. Can we use this to our advantage? Suppose I WANT to make a low crown panel (a roof insert, or door skin), and I cut my rectangular blank. I then lay out a pattern of concentric oblongs getting closer and closer until I reach the middle of my blank. I support the perimeter with a 2X4 form (maybe or maybe not partially filled with sand), I then use a sand blaster straight on at a constant distance to follow my pattern tighter and tighter until I reach the center. Will I have just formed a controlled low crown panel, or added to my scrap pile? Can we shape intentionally with the force of a sand blaster? Bob
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Bob Persson |
#26
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Bob,
I like the way you think. You should get an A just for the suggestion. I would make some room on the scrap pile and give it a try. It would be a great experiment. -Mark |
#27
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Possible idea, blast to shape. Consider using a medium that is non abrasive so as to not wear away metal. Blasting to shape consists of millions of impacts on the material's surface. This will cause work hardening. thinking of many tiny impacts it may only work harden to a limited depth. Not sure of the effect. The work hardening would yield a stronger panel. Exactly what a low crown panel needs.
Interesting to about. As Mark stated " I would make some room on the scrap pile and give it a try. It would be a great experiment."
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Richard K |
#28
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shotpeen?
Perhaps find a commercial shotpeenshop top try this out on? If I recall they have differnet size steel shot depending on the application. Air pressure can be adjusted to get the desired velocity.
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Steve ærugo nunquam dormit |
#29
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I guess I'm always trying to make lemonade (I do like lemonade)! We all pretty much have had to fix sand blasted distortion, so yes it is work hardened, but still workable. Millions of tiny hits vs. thousands of hits with a Yoder. Which would make scrap faster? I like the shotpeening, with non-abrasive media with variable air pressure to control the results. Also can experiment with patterns and density of patterns. Now to hook it up to an X-Y table (like a plasma cutter or torch) to write CNC programs to not only experiment with the patterns, but to be repeatable when you finally get good results. Save programs for Ford doors, Dodge roof inserts, trunk lids, etc. Hmmmm, even bigger scrap pile! Bob
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Bob Persson Last edited by BobPer; 03-20-2011 at 03:53 PM. |
#30
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That's an interesting idea ob.. I was thinking a female mold made from concrete or something similar.Steve
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Steve ærugo nunquam dormit |
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