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xyz

Help: Problem with dimensions

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xyz

Hello,

when I draw this sketch in AutoCAD, I can't get the exactly same vertical dimensions. The original shows whole numbers for dimensions and I am getting numbers with decimals.

Am I doing something wrong or are just dimensions on the original written with whole numbers?

Tnx for help.

 

Original drawing: https://drive.google.com/file/d/0B1A8tnujmj3BNDVQMUQtM0lZTUk/view

 

My drawing in AutoCAD: https://drive.google.com/file/d/0B1A8tnujmj3BeWZ0NXpVVHBaUFU/view

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steven-g

Your drawing looks good to me, I did only check one dimension but I get 103.1579, you can set the default value for the number of decimal place shown in a drawing using the units command (the keyword is "shown" Autocad will always work to 16 decimal places)

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xyz

So is this drawing ok or not?

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steven-g

It looks to me like an exercise in constructing a drawing using circles and working out the correct radius for each point. Unfortunately like so many of these drawing exercises it is missing a few bits of info around the upper left circles, all the arcs appear to me to be tangent to each other which would be logical in such an exercise, and with those assumptions in place then then the linear dimensions are rounded to the nearest full integer and in Autocad can be shown more accurately to read as 103.15789474, 105.05681818, and 68.04485315. I would imagine that trying to draw this with the linear dimensions zero'd to 8 decimal places would result in either the radius dimensions changing or that circles would begin to overlap.

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eldon

I would say that the figure can be drawn to the exact figured dimensions. The centres of the three remote sets of circles are given by an offset from the centre line and a radius from the centrepoint. All other lines can be drawn to suit the figured dimensions. I guessed at the radii of the left top two circles and also at the fillet radius between the large radius lines.

 

If you have a dimension which is not exactly 103, then your drawing is wrong.

ExactDims.PNG

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steven-g

I stand by my comments the drawing can be drawn to the shape shown without the linear dimensions, basing everything on circular dimensions and using tangents and quadrants, using fixed measurements of 103 and 105 stops the two arcs of 95 and 220 joining tangentially (at the center of the drawing) and gives a distance of 0.22496720 between the quadrant points of those two circles. And is not the method intended to be used in the spirit of this exercise. But that information is missing from the whole story and may not even be present in the original paper. But I would put money on this being an exercice using just circles to locate further center points, and that linear dimensions were added as a mere check and have been rounded to the nearest whole figure.

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xyz
I stand by my comments the drawing can be drawn to the shape shown without the linear dimensions, basing everything on circular dimensions and using tangents and quadrants, using fixed measurements of 103 and 105 stops the two arcs of 95 and 220 joining tangentially (at the center of the drawing) and gives a distance of 0.22496720 between the quadrant points of those two circles. And is not the method intended to be used in the spirit of this exercise. But that information is missing from the whole story and may not even be present in the original paper. But I would put money on this being an exercice using just circles to locate further center points, and that linear dimensions were added as a mere check and have been rounded to the nearest whole figure.

 

Yes that's the problem if you make offsets from centerline. Then are those arcs not joining tangentially.

I also think that these linear dimensions were rounded to the nearest whole figure. If you set precision to the whole numbers is ok.

One who checks exercise is always looking for maximal precision, that's why was I confused if I drawed right or not with these linear dimensions.

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steven-g
Circles exercise.jpgBoth Dana and Eldon have valid points, I would be interested to hear what the actual result is supposed to be, but as is so often the case, with the information given it is open to interpretation.

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ReMark

I agree with eldon.

Edited by ReMark

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xyz

When I knew what was the purpose of this exercise, I will let you know.

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ReMark

The purpose was merely to further acquaint the student with the TTR option of the circle command.

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xyz

eldon was right. Important was to have exactly same dimension as on the drawing at paper.

Does anyone know where to find more mechanical 2D exercises? I know, search on google, but I wanna find some collection of those 2D exercises.

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ReMark

Any good technical drafting book (remember libraries?) would have exactly what you are looking for. I could recommend three.

 

You can always try an Internet search on "drafting problems".

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