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Old 09-05-2018, 12:12 PM
topher5150 topher5150 is offline
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Default reverse engineering sheetmetal parts

rocker boxes.jpgAs part of my training at my new job, and I do this because I must, not because I want to, the boss wants me to design and make some parts out of sheet metal. Well i have some car parts that i need help with on getting a couple of measurements. I got all of the overall dimensions but i'm having trouble trying to determine the large radius to the right of the parts. Any input would be appreciated.
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Old 09-05-2018, 12:20 PM
Mike Rouse Mike Rouse is offline
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Do you want to know the radius in inches?

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Old 09-05-2018, 01:51 PM
topher5150 topher5150 is offline
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yes in inches
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Old 09-05-2018, 02:39 PM
Jaroslav Jaroslav is online now
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Default Geometry 4 elementary school. x = r

Radius graficky..jpgGeometry 4 elementary school. x = r .
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Old 09-05-2018, 03:32 PM
Gareth Davies Gareth Davies is offline
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Here ya go.

https://www.mathopenref.com/arcradius.html

Sit a straight edge of a known length over the longest part of the radius you can and then measure the gap between straight edge and part then put the 2 figures into the formula in the link. Piece of cake.
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Old 09-05-2018, 03:51 PM
cliffrod cliffrod is offline
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Jaroslav's sketch is somewhat similar to how I would figure it.

Hard to tell from pics but it probably combination of radii, not just one. When I have to figure a specific curve and can trace an accurate duplicate pattern onto paper (like a sweeping arch in a initial 2D rendering that is simply drawn, not accurately laid out), it allows me to fold the paper pattern back on itself to see where a specific radius is present as well as its centerpoint. As long as they line up perfectly, it's the same radius. When it doesn't line up, it helps define the points where a radius changes value, so provides information about transition. Draw your chord between those endpoints and start measuring. Not scientific but quick and easy without excess math.

One of these books here has formula for determining the radius given the height of arch and distance between end points of chord from which height is measured. There's probably lots of CAD and computer ways to figure it, as well as measuring it with patterns or sweeps if you have access to them.

The above is how I do it in studio, especially for one-off stuff before making a pattern(s) to add to the collection.

Good luck.
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Old 09-05-2018, 05:35 PM
billfunk29 billfunk29 is offline
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Default Radius calculation

This may be easier for big arcs.
chord.JPG
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Old 09-06-2018, 12:11 PM
topher5150 topher5150 is offline
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Quote:
Originally Posted by Jaroslav View Post
Geometry 4 elementary school. x = r .
I was to busy drawing cars in class that day
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Old 09-06-2018, 02:13 PM
dwmh dwmh is offline
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Bill I think the denominator should be 8Xh NOT 8Xh squared.

But it is a very useful formula.
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Old 09-06-2018, 03:18 PM
rewdco rewdco is offline
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Quote:
Originally Posted by dwmh View Post
Bill I think the denominator should be 8Xh NOT 8Xh squared.

But it is a very useful formula.
Indeed David, absolutely correct.
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