#21
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Bill I agree that the Indy car panel does not need any shrinking in the center. If he is worried about the edge getting to thin he could cut the blank a few inches long on that end. Use that extra metal to help create the reverse by stretching then cut that thin excess metal off.
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Dave Bradbury |
#22
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"Shrinking" on a "reverse, saddle, or flip."
From the bit of metalworking I have done, "shrinking" does not help to make a "reverse, saddle, or flip" .... (As Mr. Bradbury is so gently pointing out.)
.... BUT - shrinking helps correct the mistaken shaping strokes that have taken the reverse too far or in the wrong direction. Mostly, anyway.... Once, on a very rare occasion .... I used shrinking to shape a reverse : I had a big aeroplane re-skin job come into the shop which needed a large shaped reverse. 5feet long and 3feet across and only .032" thick, 2024 .... T3 ... and on a "one-off" experimental modification for a jet ..... I was greatly reluctant to stretch a big reverse into such an odd and thin panel. But stretching is the way to do this in production - 99.9% of the time.... But the shape can be shrunk into a panel ... for sophisticated application, and on large panels ... (not just for small shop demos of also can do thusly ...) P1120519 copy.jpg Good thing I had a pneu. shrinker with an 18in throat on hand .... Hulk, proto, copy 2.jpg .... so I carefully shrank the center over the long distance needed ... P1120522 copy.jpg and then just planished the whole panel to fit nice and tight. It worked! (Very critical inspections were done on this job - micro-photo inspections, x-ray flaw-checks, laser contour measuring, hardness specs .... sheesh! ... no rejects, tho ... )
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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; 02-14-2022 at 03:08 PM. |
#23
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Kent. Yes, know how and when to use the right way.
I think shrinkage is the right way for this part. The tapes that hold the shape for inspection are also quite important. Large panels with a small bend are "panels from hell". They look simple, but if they are to be accurate, they will not forgive the wrong move. I admire parts for planes. I would be afraid of cracks ....
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Jaroslav |
#24
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Kent,
You do some amazing work. When I asked my question in post #18 as to if there was any shrinking in the panel I mentioned, I already knew there was not. I was trying to point out to Denny G. that stretching would be the easiest way to do his panel. I figured conformation from someone of your experience and ability would help get my point across.
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Dave Bradbury |
#25
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Dave, there's a problem with thinning material on the plane.
You can stretch material for design things. However, the central fiber must remain at its original length or shrink as Kent demonstrated. But that's a different level ..... Or you can do smaller things my way ... again, not touch the center thread. https://www.allmetalshaping.com/showthread.php?t=20460 https://www.allmetalshaping.com/showthread.php?t=18968 According to the zero reaction, no one in EW tried it ... That's a mistake on your part. Hammer and sack is the highest science.
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Jaroslav |
#26
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Hi Dave, Thank you. Yes, I understand ... and was supporting your line of reasoning with the follow-on posting. I'll add a thread pertinent to this topic ... thanks for the kind nudge.
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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. |
#27
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Hi Mr. Graham, What sort of "air hammer" do you have? I might be able to help you modify that air whacker - so that it makes your "teaching errors" happen a whole lot faster - so you can arrive at yer accurate completion much quicker ... ..... (learn from others' mistakes b'cuz ain't 'nuff time ter make 'em all y'sef.)
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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. |
#28
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Kent, I think once Denny G. starts to get the idea that his panel is created by controlled stretching and some practice on some scrap that he will begin to get some where.
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Dave Bradbury |
#29
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Jaro, Yes I see airplane parts need special treatment. I always block out any shape I am having problems with. The hammer and stump or hammer and sandbag help me understand what the panel needs to get the shape I am going for It does make the arm tired though
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Dave Bradbury |
#30
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Dave, while studying shaping, I started shaping with a machine - a very old Eckold with a very bad tool. Later, I made one of my own bombing tools that worked very well. Later, I equipped myself with other machines and tools. Later I welded EW from some old transport truck. Later I made EW from a band saw. At the saw, I already knew exactly what I wanted and what I expected it to do. Only then did I buy the first mallet. I use the mallet as an additional tool. That's the huge difference in thinking and shaping.
Using paper, I understood what fibers I should adjust and where. It doesn't matter which method is used. I try to combine all the ways. I remember a sentence from Peter Tomashini. The plate must always be soft. If you hurt him with a hammer, you've reached the end of shaping. It's hard and you're done. Sometimes it's good to bend the sheet metal on the table or over the knee and you see places where you need to pull or stretch the fibers, but that's about experience. Everything needs its time and peace for thoughts, to break a lot of metal, to try, to try and to try. Don't be afraid of stupid experiments and the fact that someone is better. He also started.
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Jaroslav |
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