TurboCAD Forums

The Ultimate Resource for TurboCAD Knowledge

Register
 
All posts discussing pricing or where to buy TurboCAD will be deleted.

Obtaining accurate measurement from drawing
Read 17292 times
* January 02, 2010, 01:28:30 PM
This is probably more a math question than a TC question, but I'll ask it anyway in the hopes that there is some way to do it.  In the attached drawing, I am trying to determine the exact length of the legs of what looks like a sawhorse.  It is actually a stand for a small metal lathe which I am going to build.  As can be seen in the drawing, the dimensions of the legs differ in the "front" and "side" view, as would be expected since the angles are different.  Obviously, neither dimension is correct, since neither view takes into account both angles that affect the length of the part.  Is there a way to figure this without doing too many mental gymnastics?  I have exactly zero experience with 3D as of yet, so it is not really a simple matter to draw it up in 3D, though eventually I hope to be able to do that.  Even if I could, would that get me the dimension I seek?

Eric

[attachment deleted by admin]

Logged
Eric


* January 02, 2010, 02:45:45 PM
#1
This is probably more a math question than a TC question, but I'll ask it anyway in the hopes that there is some way to do it.  In the attached drawing, I am trying to determine the exact length of the legs of what looks like a sawhorse.  It is actually a stand for a small metal lathe which I am going to build.  As can be seen in the drawing, the dimensions of the legs differ in the "front" and "side" view, as would be expected since the angles are different.  Obviously, neither dimension is correct, since neither view takes into account both angles that affect the length of the part.  Is there a way to figure this without doing too many mental gymnastics?  I have exactly zero experience with 3D as of yet, so it is not really a simple matter to draw it up in 3D, though eventually I hope to be able to do that.  Even if I could, would that get me the dimension I seek?

Eric

It's fairly simple to draw this in 3D Eric -- in fact, I'd call it an excellent exercise. And doing so will give you all the dimensions of all the pieces. The drawing doesn't contain quite enough dimensions to do the job accurately, however, because there's no way to determine the thickness of the legs except by scaling the drawing. Without this info the result cannot be precise. When using the given dimensions and scaling the side view, the legs work out to be 3.059" × 4.075" × 30.016".

Henry H

Logged


* January 02, 2010, 04:25:17 PM
#2
Ah, OK.  I forgot to dimension the legs; the material I decided on is 4" x 3" angle iron with wall thickness of 0.375".  As you came up with dimensions very close to that, I'd say the number you came up with is close enough.  The whole frame will be made of this material, all welded together.  There will be another piece as well, a chip pan, which will sit atop the frame in the drawing.  I don't have that piece sketched yet, but it isn't complicated at all. 

Henry, if you're willing to give me a clue how to get started I'll try to draw it in 3D.  I'd like to learn how; I plan to purchase the 3D training cd since I've gotten so much out of the 2D version (Ken Doyle's training cd's).




Logged
Eric


* January 02, 2010, 06:44:30 PM
#3
Ah, OK.  I forgot to dimension the legs; the material I decided on is 4" x 3" angle iron with wall thickness of 0.375".  As you came up with dimensions very close to that, I'd say the number you came up with is close enough.  The whole frame will be made of this material, all welded together.  There will be another piece as well, a chip pan, which will sit atop the frame in the drawing.  I don't have that piece sketched yet, but it isn't complicated at all. 

Henry, if you're willing to give me a clue how to get started I'll try to draw it in 3D.  I'd like to learn how; I plan to purchase the 3D training cd since I've gotten so much out of the 2D version (Ken Doyle's training cd's).

The two attached screenshots illustrate how to make a leg. Mirror-copy it to make its neighbor, then mirror-copy the pair to make the second pair.

Henry H

[attachment deleted by admin]

Logged


* January 02, 2010, 07:17:07 PM
#4
Thanks, Henry!  I am about to turn in now, I'll start on this tmorrow morning, and let you know how I do.

Eric

Logged
Eric


* January 03, 2010, 10:36:53 AM
#5
Henry,
I created a 3D image of the angle iron by extruding, but I'm having trouble figuring out how to rotate it a specific amount on a specific axis.  I'm sure it's in the book someplace, but I can't seem to find it.  I also did this in the same drawing, and I'm not sure if that was a good ideaor if I should have started with a clean sheet, so to speak.

[attachment deleted by admin]

Logged
Eric


* January 03, 2010, 10:39:45 AM
#6
Thanks, Henry!  I am about to turn in now, I'll start on this tmorrow morning, and let you know how I do.

Eric

Be aware, Eric, that the flanges of the legs will not precisely align with the edges of the top. This is a consequence of rotating them about both the X and Y axes, and it cannot be prevented. But whether they misalign along the 3" sides or along the 4" sides depends upon whether you rotate them about the Y axis first or the X axis first. If you rotate them first about the Y axis, as shown in the pics I posted earlier, the misalignment will occur along the 3" sides, where I suppose it will be less noticeable. Attached screenshot shows a plan view of the top of the two left-hand legs.

Henry H

[attachment deleted by admin]

Logged


* January 03, 2010, 10:54:33 AM
#7
Henry,
I created a 3D image of the angle iron by extruding, but I'm having trouble figuring out how to rotate it a specific amount on a specific axis.  I'm sure it's in the book someplace, but I can't seem to find it.  I also did this in the same drawing, and I'm not sure if that was a good ideaor if I should have started with a clean sheet, so to speak.

Eric, for starters I'd suggest that you "float" your Inspector Bar to make its various options more easily accessible. To do so, place your mouse cursor on the IBar's extreme upper left corner, then press and hold the left button while dragging the IBar up and into the field of the drawing. Reshape/resize it with the cursor. If the Rot X, Rot Y and Rot Z fields are not visible when you have selected an object, then right-click an empty spot on the IBar to open a list of the available fields and buttons, and place a check in front of each Rot. (I keep ALL available fields and buttons visible; and I've assigned the F8 key to toggle the IBar's visibility On/Off, so I can quickly access it or get it out of the way.)

To rotate a selected object about a specific axis, TAB to the appropriate Rot field, type the number of degrees of rotation required, and press Enter.

Doesn't really matter whether you start with a clean sheet, but doing so would make your drawing less cluttered.

Henry H

Logged


* January 03, 2010, 12:03:47 PM
#8
Henry,
Please excuse me for being thick:  First of all, I started over in a new drawing for several reasons.  First of all, so I had a "clean sheet", and the drawing would be less cluttered, as you suggested.  Second, I drew the part initially with the long leg of the angle "pointing" "north", or in degrees, 90*.  It should have been pointing west, or 180* in order to view it correctly if it were "stood up" on end.  Third reason:  I tried to rotate the camera around in order to view the thing more like how it would be positioned "in situ", so to speak, and while I got the part positioned close to where I thought I wanted it I thought when I started trying to actually rotate it the prescribed amount its "home" position would be all screwed up.  So now I have the thing drawn in 2D again, extruded to a height of 32" in the z plane, and am ready to try again.  Do I first need to change the camera view so I'm looking at the part from the front in stead of the top?  If so, how do I do that? 
Attached is my starting point, if you need to see it.

I hope you knew you were volunteering for a remedial 3D lesson here...

Eric

[attachment deleted by admin]

Logged
Eric


* January 03, 2010, 01:12:51 PM
#9
Henry,
Please excuse me for being thick:  First of all, I started over in a new drawing for several reasons.  First of all, so I had a "clean sheet", and the drawing would be less cluttered, as you suggested.  Second, I drew the part initially with the long leg of the angle "pointing" "north", or in degrees, 90*.  It should have been pointing west, or 180* in order to view it correctly if it were "stood up" on end.  Third reason:  I tried to rotate the camera around in order to view the thing more like how it would be positioned "in situ", so to speak, and while I got the part positioned close to where I thought I wanted it I thought when I started trying to actually rotate it the prescribed amount its "home" position would be all screwed up.  So now I have the thing drawn in 2D again, extruded to a height of 32" in the z plane, and am ready to try again.  Do I first need to change the camera view so I'm looking at the part from the front in stead of the top?  If so, how do I do that? 
Attached is my starting point, if you need to see it.

I hope you knew you were volunteering for a remedial 3D lesson here...

Eric

Your drawing is fine, Eric, and you're ready to go. Work in an Isometric view so you can see what's happening. I did take the liberty of correcting the profile for the extrusion, rounding the toes of the legs and filleting the reentrant corner. Modified file is attached herewith; work with it if you want a more realistic result.

Henry H

[attachment deleted by admin]

Logged


* January 03, 2010, 03:24:46 PM
#10
Henry, I can't open the file.  I'm going to guess that you have a newer version of TC than I do; I'm using v12 Deluxe.  Could you try saving it as an older version and reposting it?  I always seem to forget to specify the version when I post.

Eric

Logged
Eric


* January 03, 2010, 04:40:14 PM
#11
Henry, I can't open the file.  I'm going to guess that you have a newer version of TC than I do; I'm using v12 Deluxe.  Could you try saving it as an older version and reposting it?  I always seem to forget to specify the version when I post.

Eric

Here ya go, Eric. This version opens in 12.5 Deluxe and I guess it'll open in earlier v12 "point" versions.

Henry H

[attachment deleted by admin]

Logged


* January 03, 2010, 05:46:35 PM
#12
Thanks, Henry, that one works for me.  So far, I have rotated the part on the y and then the x axes, as you instructed.  Actually, I did so in both my drawing and yours, though I will keep working with yours since it is, as you pointed out, more accurate.  But happily, I was able to do it in the one I started from scratch, so at least I know it works.  Anyhow, attached it the leg rotated.  Currently trying to figure out how to change the view by the path Workapce/Workplane/By View.  The book isn't very clear on this.  It states that the workplane is turned to that it is parallel to th eview plane.  In the example in the book, the z axis becomes perpendicular to the drawing screen.  I want the y axis to become perpendicular to the drawing screen.  I think I got it, will post results.

Attached is the result, with the lines added to "cut" the leg to length.  It doesn't look exactly right to me, I think the 3" side of the leg is currently on the "front", though it shouldn't be according to what I did with it.

[attachment deleted by admin]

Logged
Eric


* January 03, 2010, 05:50:46 PM
#13
Wrong file above.  This is the correct one, sorry.

Eric

[attachment deleted by admin]

Logged
Eric


* January 03, 2010, 05:52:58 PM
#14

Attached is the result, with the lines added to "cut" the leg to length.  It doesn't look exactly right to me, I think the 3" side of the leg is currently on the "front", though it shouldn't be according to what I did with it.

Are you sure you attached the right file, Eric?

Henry H

Logged


* January 03, 2010, 06:02:27 PM
#15
It was the wrong file.  I reposted with the correct one attached.

Eric

Logged
Eric


* January 03, 2010, 06:15:07 PM
#16
Ok, I realize that the view I have of the leg is not the correct view.  I can't seem to get it right; I know I need to be looking squarely at the 4" side of the angle, but can't figure how to get the blasted thing turned the right way!

Eric

Logged
Eric


* January 03, 2010, 07:08:08 PM
#17
Ok, I realize that the view I have of the leg is not the correct view.  I can't seem to get it right; I know I need to be looking squarely at the 4" side of the angle, but can't figure how to get the blasted thing turned the right way!

Eric

If all you want to do is rotate the part, it doesn't matter how you look at it -- although I recommend an Isometric view so you can see better what's happening. Just select the part and enter values in the Inspector Bar as I outlined in an earlier message. If you haven't done so already, I strongly recommend that you make the "Standard Views" Toolbar visible: Open the View menu, click "Toolbars," scroll down the list, and place a checkmark by "Standard Views," click "OK." Drag the new toolbar to the side or top of your screen and it should attach itself there. One mouse click on the appropriate icon in that toolbar will switch you instantly to that view.

Henry H

Logged


* January 03, 2010, 07:25:38 PM
#18
Ok, I realize that the view I have of the leg is not the correct view.  I can't seem to get it right; I know I need to be looking squarely at the 4" side of the angle, but can't figure how to get the blasted thing turned the right way!

Eric

The object in your drawing wasn't rotated correctly, Eric. Not sure where you went astray, but I fixed it. Updated drawing is attached herewith. (It'll open in SE Isometric view. Switch to Front view, then go to Workplane by View and slice along the blue lines.)

Henry H

[attachment deleted by admin]

Logged


* January 04, 2010, 05:51:58 AM
#19
Ok, I realize that the view I have of the leg is not the correct view.  I can't seem to get it right; I know I need to be looking squarely at the 4" side of the angle, but can't figure how to get the blasted thing turned the right way!

Eric

Do you have Entity CS switched on in Selector 3D Properties?
I changed the orientation of the leg and hopefully set it at the correct angles. When the leg is selected the angles will show in ROT - X - Y fields.
The .tcw file is from v.12 Pro, I hope it opens for you.

d

[attachment deleted by admin]

Logged


* January 04, 2010, 10:42:38 AM
#20
Henry,
Been doing some tinkering with this, and in the original 2-D drawing, I came up with -6.12º for the Y rotation angle, instead of -3.88.  What did I do differently?

Logged
D Fishback


* January 04, 2010, 11:30:39 AM
#21
Don,

Unfortunately, I can't open the drawing.  Without Pro, the "ASICS solid" is disregarded, so all that shows up are the two "slice" lines and the dimension 28".

As for coordinate system, Entity CS was not turned on, World CS was.

Henry,

AH!  Standard Views Toolbar!  Ok, now I think I have it.  Oh, and there is "Front View" right in the selcetion menu that drops down from "View".  Geez, if it had teeth it would've bit me.

And now I get what "By View" does when selected in Workspace.  Ok, it's all becoming clear as mud now...

So here is what I have at this point. The one titled "... another try" is the one I have done from scratch.  Please tell me if this one and yours match up, Henry.

Don't ask why I didn't delete the "cut offs" yet; my scrap bucket in the basement is full of such small pieces "just in case I need one" .  Ridiculous, I know.

Eric



[attachment deleted by admin]

Logged
Eric


* January 04, 2010, 11:38:03 AM
#22
Henry,
Been doing some tinkering with this, and in the original 2-D drawing, I came up with -6.12º for the Y rotation angle, instead of -3.88.  What did I do differently?

Minus 6.12 degrees is correct, Eric. It was I who said -3.88, not you. Sorry about that :-(

Henry H

Logged


* January 04, 2010, 11:54:47 AM
#23
That was me you replied to, Henry.  One more example of why so many of us still dislike this site's flat type of format.  ;-) 

Thanks for clarifying. Thought that detail might be important to Eric.

Don Fishback

Logged
D Fishback


* January 04, 2010, 12:16:03 PM
#24
Thanks for clarifying. Thought that detail might be important to Eric.


It's gotta be important. Hope he sees it before going too far.

Henry H

Logged


* January 05, 2010, 07:00:59 AM
#25
Gentlemen,  I see the issue of rotation on the y axis.  I'm guessing that if I rotate it another -2.24 degrees that should resolve the issue.  Of course, then the leg will need to be sliced again, as that will change the angle of the "cut" on each end.  I'll see what I can do about making that happen.

Logged
Eric


* January 05, 2010, 07:44:28 AM
#26
I think I have corrected the rotation issue.  This will be determined for certain sure once the leg has been "mirror copied" and the resulting dimension from the outer edges of the legs can be determined.  If the result is 20", then it must be correct.

Attached is my progress so far.  I have used "Mirror Copy" to get all four legs in place, as you suggested, Henry.  Using the right side view, I measured the base at its "feet", and came up with 20", so the correction of the "y" axis must have worked. 

The next step is going to be making the top.  For this I assume I can use the original 2D "section" of the angle iron and simple extrude it again in order to get the longer pieces made for the top, then move them into place?  Does that sound about right?

Eric

[attachment deleted by admin]

Logged
Eric


* January 05, 2010, 08:48:24 AM
#27
If I may intrude again, Eric -

Rotating farther on the Y axis after slicing wouldn't change the 20" base measurement, but should have made the legs slightly too short to reach bottom to top (the 28"), and would make the front base length both base lengths slightly longer. However, somehow these look right, lengthwise.

The only problem I see now is the base measurement across the "front" in this drawing is now 56 1/8". Easy to fix.
« Last Edit: January 05, 2010, 09:57:31 AM by Don F »

Logged
D Fishback


* January 05, 2010, 10:04:47 AM
#28
I think I have corrected the rotation issue.  This will be determined for certain sure once the leg has been "mirror copied" and the resulting dimension from the outer edges of the legs can be determined.  If the result is 20", then it must be correct.

Attached is my progress so far.  I have used "Mirror Copy" to get all four legs in place, as you suggested, Henry.  Using the right side view, I measured the base at its "feet", and came up with 20", so the correction of the "y" axis must have worked. 

The next step is going to be making the top.  For this I assume I can use the original 2D "section" of the angle iron and simple extrude it again in order to get the longer pieces made for the top, then move them into place?  Does that sound about right?

Eric

Looking good, Eric (except for the 8-1/8" discrepancy Don F mentions), but you're starting to run into trouble as a result of not using a high enough Precision. I see errors and mismatches on the order of 1/16 inch and 1/10 degree -- well within fabrication tolerances, of course, but small errors can easily cause more serious discrepancies as the drawing progresses. TurboCAD has no trouble at all maintaining much tighter accuracy. Go to Options|Space Units and increase the Precision there. Many users like to use 6; I use 10 myself, and am not aware of any drawbacks to doing so. Use a higher value for the Precision of Angles, too, by visiting Options|Angle. Considering all the practice you've been getting lately, it should take only a few minutes to redraw the whole thing, saving only the 2D extrusion profile.

... And yes, your proposed method for making the top is exactly the way I'd do it. (One method of accurately positioning a 3D object is to move its Reference Point to some specific vertex, then drag the object to its new home and Snap that vertex to a chosen destination vertex. Or use one of the "Assemble" tools available on the 3D Modify toolbar.)

Henry H

Logged


* January 05, 2010, 05:33:03 PM
#29
Thank you for pointing out the incorrect dimension on the front of the stand.  I really don't know how that happened, I thought I placed a vertical construction line 21" from the vertex of the "outside top" of the right hand leg and used it to mirror copy the other side.  not sure what happened there.  Maybe I typed 2' 1" inadvertently?  Don't really know, but I'll have to fix it.  Thanks for pointing it out or I wouldn't have discovered it until I went to fit the top on. 

Been busy with work today and haven't had much time to devote to this, and tomorrow looks like it's going to be the same.  I may get some time in the afternoon, but we'll see. 
anyway, thanks for all the help so far and I'll post my progress as I make some, along with whatever questions I have. 

Thanks for all the help so far, especially Henry, you've been extrememly helpful and not just with this project.  Your patience astounds me.

Eric

Logged
Eric