Drawing a radius

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Drawing a radius

Postby MHB » Mon Jan 21, 2019 5:48 am

Could someone please explain how to draw the 1.5" radii that are located at the top of the drawing that is attached.
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Re: Drawing a radius

Postby highpockets » Mon Jan 21, 2019 5:55 am

Not to scale, but draw square corners then use the fillet drawing tool.

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Re: Drawing a radius

Postby FixitMike » Mon Jan 21, 2019 9:37 am

Assuming that the two arcs are tangent without a line between them.
From the dimensions on the drawing, the horizontal distance between the lower and upper points where the arcs are tangent to the horizontal lines is 2.5". Therefore, the two arcs will touch each other half way between or 1.25" from where they touch the horizontal lines.

1. Start by drawing 3 vertical lines 1.25 " apart. The center line is where the arcs will contact each other.
2. Draw a 1.5" radius circle with the center on the lower end of the right hand line.
3. Trim the circle to make an arc between the 2 right hand lines.
4. Draw a horizontal line from the intersection of the arc and the center line.
5. Mirror the arc about the center line.
6. Mirror the 2nd arc about the horizontal line.
The drawing shows the process.
Construction.png
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Re: Drawing a radius

Postby highpockets » Mon Jan 21, 2019 2:31 pm

Mike, good information, but way over my head :D :D :D I'd rather let the program do the work for me. :lol:

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Re: Drawing a radius

Postby 4DThinker » Mon Jan 21, 2019 3:16 pm

Highpockets,

The only mistake you've made is that based on the given dimensions the width of the S curve should be 2.5" and you've made it 3". 1.25" width for each half rather than 1.5" (a full quarter). The height of the S curve isn't 1.5" but rather 1.3424" based on what Aspire tells me after constructing the drawing.

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Re: Drawing a radius

Postby adze_cnc » Mon Jan 21, 2019 5:49 pm

MHB wrote:Could someone please explain how to draw the 1.5" radii that are located at the top of the drawing that is attached.


MHB:

One thing that is missing is the overall width of this object (i.e. 2.5 plus ?)

According to 4DThinker (and Aspire) when he posted his sample it is 2.5+1.3424 = 3.842 which seems to me to be wrong.

There appears to be 3 components to the s-curve as pictured: two sections of a 3-inch diameter circle and one short, straight, connecting line. The other solutions presented here presume that the two arcs connect directly.

I could be wrong as I haven't actually tried to draft your object.

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Re: Drawing a radius

Postby highpockets » Mon Jan 21, 2019 7:24 pm

4D,

Thanks for the correction. That's what I get for messing with this stuff before coffee :lol:
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Re: Drawing a radius

Postby TReischl » Mon Jan 21, 2019 7:31 pm

Capture.JPG


The part appears to be 4.00 tall after scaling this all up in Corel to where it made sense.

All you need to do is create a line parallel to the 2.5 surface and move it up 1.5 inches.

The location for the arc tangent to the top surface is given. So draw it. Then offset that circle by 1.5.

Where the large circle and the top line cross is the center of the radius. Then it is just a matter of trimming things up.
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Re: Drawing a radius

Postby adze_cnc » Mon Jan 21, 2019 7:54 pm

TReischl wrote:The part appears to be 4.00 tall after scaling this all up in Corel to where it made sense.

Where the large circle and the top line cross is the center of the radius. Then it is just a matter of trimming things up.


4" makes more sense than 3.842".

But! Try your method on the left side and you'll find that the circle intersects with the flat at 10.9019" and not the 11" as implied by the original drawing.
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Re: Drawing a radius

Postby MHB » Mon Jan 21, 2019 7:56 pm

The height of the object is 4" - sorry that I left this out. Thank you all for the different approaches. I had absolutely no idea on how to go about accomplishing this.
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Re: Drawing a radius

Postby TReischl » Mon Jan 21, 2019 8:31 pm

adze_cnc wrote:
TReischl wrote:The part appears to be 4.00 tall after scaling this all up in Corel to where it made sense.

Where the large circle and the top line cross is the center of the radius. Then it is just a matter of trimming things up.


4" makes more sense than 3.842".

But! Try your method on the left side and you'll find that the circle intersects with the flat at 10.9019" and not the 11" as implied by the original drawing.


I do not think there is any flat between those two arcs. What I know for certain is that whoever drew that up is definitely not a professional draftsman/engineer. I spent the early part of my career as a tool designer working on the board. I can guarantee that if I had dimensioned to where an arc is tangent to a flat I would have been looking for a new job.

If one works the drawing from the left end, with the dimensions given, it would definitely require a flat between the two arcs as you indicated.

With the way this person dimensioned the drawing I would not imply anything about it. We all know if this went to a machine shop he would be getting a call asking him what he really wanted.
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Re: Drawing a radius

Postby 4DThinker » Mon Jan 21, 2019 9:56 pm

The part can't be 4" tall if the S curve is composed of two tangent arcs 1.5" radius and 2.5" apart where they are also tangent with the top and the center flat. Even if there should be a flat between them. I drew a 3" circle, Exploded it to leave 4 separate 1/4 circle arcs. I drew a vertical centerline and offset it both side so they were 2.5" apart. I let those 2 lines chop the arcs to leave 1.5" r arcs that were 1.25" wide. Their height when combined is 1.3424" not 1.5" Add 1.3424 to 2.5 and you don't have 4". 3.8424" is the what Aspire reports.

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Re: Drawing a radius

Postby TReischl » Mon Jan 21, 2019 10:14 pm

Well, 4D, like I said above. . . . no real draftsman dimensions anything to a tangent point. For exactly the reasons we have all been discussing. Besides, it is virtually impossible to measure to a tangent point since there is no "feature" at a tangent point.

Since we have both been around the block more than a few times we also know that there is about a 1 in a trillion chance this part is supposed to be 3.8424 tall.

The flat that would be created would not result in a nice smooth transition, there would be an edge since the circles overlap when using the "dimensions" on the left side of the drawing.
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