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  #11  
Old 03-12-2018, 03:50 AM
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ekdave1962 ekdave1962 is offline
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per metalman sweden sells those adjustable contour gauges as well
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  #12  
Old 03-12-2018, 06:33 PM
Payupv8 Payupv8 is online now
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Here's a side view of the radius Iam trying to figure out where it starts

IMG_1635.jpg

IMG_1636.jpg
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Last edited by Steve Hamilton; 03-12-2018 at 11:49 PM.
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  #13  
Old 03-12-2018, 07:19 PM
Ken Hosford Ken Hosford is offline
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You might get your self a piece of poster board as big as possible .
Make or buy a beam compass that is easily adjusted . and start with a piont and start drawing arcs in 1/8" increments till you find on that matches by laying the template on it and you will see when it starts leaving the arc .
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  #14  
Old 03-12-2018, 08:02 PM
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Create a chord as long as possible (staying within the area you are sure is the radius), measure the sagitta, (refer to link I posted) enter your two values in the radius calculator, and you will have your radius to make a concave pattern from. Slide it slowly around the curve, center-left to the point that the pattern is only making contact on the ends, mark, then repeat by doing the same center-right, You now have your arc located.
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Last edited by Secant; 03-13-2018 at 02:24 AM. Reason: Punctuation & spelling
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  #15  
Old 03-12-2018, 09:00 PM
bobadame bobadame is offline
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I'm working on a simple device that will measure chord height at a fixed chord length of 3". It's simply a dial indicator that is centered between 3 legs that have rounded ends. The tool is initially zeroed on a flat surface. When it's placed against a curved surface the dial indicator will read some distance from zero. That is the chord height. 3" is the chord length. With these 2 values the radius can be easily calculated. Also, the dial indicator will show the point at which the radius begins to change as it's slid along a surface. I'll try to have it finished by tomorrow. A picture is worth lots of words.
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  #16  
Old 03-13-2018, 03:05 AM
metal manny metal manny is offline
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Or... you could build this gauge for yourself for only a few dollars from readily available hardware.

The flexible strip is scrap 4mm pvc sheet, but other flexible materials can be used. The slotted brackets are common drawer stays found in the cabinetry fittings section.

DSCF8675.JPG

DSCF8676.JPG

DSCF8677.JPG
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Last edited by Steve Hamilton; 03-13-2018 at 08:54 AM.
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  #17  
Old 03-13-2018, 11:32 AM
sru_tx sru_tx is offline
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I use the chord/height measurement a lot when I'm bending tubes on my ring roller. I use a 48" metal ruler as my chord with a small 12" rule at the 24" mark. Very accurate and fast and can do it while on the bender.

Keep in mind as the chord gets smaller the height accuracy needs to be higher.

Don't let the math scare you. With that online calculator it's fast easy and accurate.

tube_bending.jpg
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  #18  
Old 03-13-2018, 04:20 PM
Turbo57 Turbo57 is offline
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Just for fun, i build this today, some 2,4 mm welding rod 250 mm long between 2 soft rubberband with glue, i will have use for them soon

DSC06203.jpg

DSC06204.jpg
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  #19  
Old 03-13-2018, 07:20 PM
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Lots of good ideas to determine the radius. Once you know what the radius is, what do you do with that information.
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  #20  
Old 03-13-2018, 07:45 PM
Payupv8 Payupv8 is online now
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Lots of great ideas! That's why I like this forum! I need to determine where it starts and stops so I can duplicate it other wise it won't be accurate. Also when I know where it starts and stops so I can record the information on my flexible shape pattern.
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