WEBVTT 00:00:01.056 --> 00:00:03.246 A:middle >> This is a short video with hints 00:00:03.746 --> 00:00:08.626 A:middle for doing homework number three and lab number three. 00:00:08.726 --> 00:00:10.476 A:middle Let's start with homework number three. 00:00:11.396 --> 00:00:14.476 A:middle Okay, first part of it is doing a linear sweep. 00:00:15.606 --> 00:00:17.756 A:middle This problem here, we are given a series 00:00:17.756 --> 00:00:22.016 A:middle of three dimensional profiles that are constructed on the X, 00:00:22.016 --> 00:00:26.336 A:middle Y. So for this one here, we're supposed to do a linear sweep, 00:00:27.606 --> 00:00:29.296 A:middle okay, in the positive Z axis two units. 00:00:29.496 --> 00:00:34.376 A:middle So what we need to do is move this profile here, 00:00:34.376 --> 00:00:38.856 A:middle make a copy of it two units forward in positive Z direction 00:00:39.426 --> 00:00:42.296 A:middle and then connect them with lines. 00:00:42.366 --> 00:00:44.956 A:middle The original profile and then your profile created. 00:00:45.496 --> 00:00:46.666 A:middle Now, how does that work? 00:00:46.936 --> 00:00:48.946 A:middle You're supposed to do that on paper and pencil. 00:00:49.416 --> 00:00:51.146 A:middle But how does that work on auto tab? 00:00:51.226 --> 00:00:52.246 A:middle Use that illustration. 00:00:52.796 --> 00:00:55.986 A:middle I'm going to do it for the second one, okay? 00:00:56.146 --> 00:00:59.766 A:middle For the second one here, it's the original profile. 00:00:59.876 --> 00:01:04.196 A:middle Let's change our point of view so that we see X, 00:01:04.296 --> 00:01:07.596 A:middle Y and Z. I'm going to be working on the one on the left. 00:01:07.596 --> 00:01:10.426 A:middle So I'm going to do what's called an extrude. 00:01:11.616 --> 00:01:13.926 A:middle This whole profile here, I'm going to extrude it 00:01:13.926 --> 00:01:17.366 A:middle in the positive Z direction to give it depth. 00:01:17.886 --> 00:01:18.676 A:middle And that becomes a solid. 00:01:18.676 --> 00:01:23.966 A:middle So that's one we are creating 3D objects from 2D objects, okay? 00:01:24.646 --> 00:01:24.856 A:middle That's called linear sweep. 00:01:24.856 --> 00:01:26.756 A:middle And you're going to do it right 00:01:26.756 --> 00:01:29.176 A:middle on the paper that's provided right on the profile. 00:01:30.436 --> 00:01:33.966 A:middle Now, the second part, we do what's called a circular sweep. 00:01:34.386 --> 00:01:37.146 A:middle So this profile here of B, 00:01:37.146 --> 00:01:40.466 A:middle we go to the Y axis becomes number five. 00:01:40.466 --> 00:01:43.026 A:middle So it's multiple choice or matching. 00:01:43.026 --> 00:01:48.756 A:middle So if you look at A and again the one above the Y axis, 00:01:48.756 --> 00:01:50.336 A:middle it becomes number eight. 00:01:51.226 --> 00:01:52.756 A:middle That's a circular sweep. 00:01:53.206 --> 00:01:57.276 A:middle Now, let me illustrate circular sweep again, 4.3, 00:01:57.276 --> 00:02:02.946 A:middle focusing on this profile, the second profile B. I'm going 00:02:04.156 --> 00:02:06.136 A:middle to illustrate how that works. 00:02:07.096 --> 00:02:11.836 A:middle When you rotate it about the Y axis at 360 degrees. 00:02:12.586 --> 00:02:14.226 A:middle So going back to AutoCAD, 00:02:15.476 --> 00:02:18.606 A:middle looking at the same profile here, this time on the right, 00:02:19.106 --> 00:02:23.216 A:middle okay, I'm going to revolve this, rotate this, do a circular sweep 00:02:24.046 --> 00:02:28.786 A:middle of this profile about this line to this end point 00:02:29.046 --> 00:02:32.636 A:middle and this end point and at an angle of 360 degrees. 00:02:33.316 --> 00:02:36.336 A:middle So this is a resulting solid, it's a solid revolution 00:02:37.466 --> 00:02:40.736 A:middle by revolving the original profile here 00:02:41.276 --> 00:02:44.806 A:middle about the vertical axis of the Y. So what you need 00:02:44.806 --> 00:02:49.816 A:middle to do is catch the resulting circular sweep. 00:02:50.206 --> 00:02:56.126 A:middle Now, the last part of this homework is you're given three 00:02:56.126 --> 00:02:59.736 A:middle solids, the cylinder and two boxes. 00:03:00.236 --> 00:03:02.116 A:middle You're supposed to position the boxes, 00:03:02.116 --> 00:03:04.036 A:middle relative to the cylinder shown here, 00:03:04.486 --> 00:03:07.066 A:middle and then to this Boolean operation, 00:03:07.066 --> 00:03:09.776 A:middle I'll subtract A minus B minus C, 00:03:10.086 --> 00:03:11.486 A:middle and then the resulting profile, solid sketched in the isometric space. 00:03:12.136 --> 00:03:18.556 A:middle Illustrate it in AutoCAD again. 00:03:19.146 --> 00:03:23.916 A:middle Here are the three cylinder horizontal box 00:03:23.916 --> 00:03:24.776 A:middle in the vertical box. 00:03:24.776 --> 00:03:27.606 A:middle The first thing I do is move the horizontal box 00:03:27.606 --> 00:03:30.146 A:middle from its current location so that the midpoint 00:03:30.526 --> 00:03:33.406 A:middle on that edge is going to then over the center 00:03:33.406 --> 00:03:35.676 A:middle of a circular box for the cylinder. 00:03:35.676 --> 00:03:39.586 A:middle And then repeat the move command this time 00:03:39.586 --> 00:03:45.706 A:middle for the skinny vertical box by taking the midpoint again 00:03:45.706 --> 00:03:49.546 A:middle to the same location here in the center of the circle on top. 00:03:49.846 --> 00:03:52.416 A:middle And then I'm going to do the boolean operation 00:03:52.416 --> 00:03:54.706 A:middle of subtract, okay? 00:03:56.336 --> 00:04:00.436 A:middle Object to subtract from over the cylinder, press enter, 00:04:01.756 --> 00:04:06.246 A:middle objects to subtract are the two boxes and then press enter. 00:04:06.676 --> 00:04:10.426 A:middle This is what is the resulting 3D object. 00:04:10.426 --> 00:04:13.246 A:middle And you're going to sketch that 3D object 00:04:13.246 --> 00:04:19.156 A:middle in this isometric space that's provided. 00:04:19.156 --> 00:04:24.246 A:middle Finally, the last part of this tutorial is related 00:04:24.326 --> 00:04:26.336 A:middle to lab three. 00:04:26.426 --> 00:04:30.076 A:middle Lab three, you're going to use concepts of internally tangent 00:04:30.076 --> 00:04:31.506 A:middle and externally tangent circles. 00:04:32.266 --> 00:04:36.006 A:middle These circles are externally tangent, such as this one here 00:04:36.006 --> 00:04:37.966 A:middle in the middle and this one on the right. 00:04:38.546 --> 00:04:40.156 A:middle They are tangent to each other. 00:04:40.316 --> 00:04:42.366 A:middle And the smaller one is outside. 00:04:42.936 --> 00:04:44.966 A:middle Here is another pair of externally tangent. 00:04:44.966 --> 00:04:48.456 A:middle The biggest one is 3.5 and externally tangent. 00:04:48.896 --> 00:04:52.526 A:middle Internally tangent example is the 3.5, the big one 00:04:52.526 --> 00:04:57.376 A:middle and the tiny one already is 1.5 because the small one is inside. 00:04:57.786 --> 00:05:01.786 A:middle Now, the relationship between externally tangent is the 00:05:02.406 --> 00:05:07.356 A:middle difference between the centers, okay, 5, is equal to the sum 00:05:07.356 --> 00:05:11.256 A:middle of the radii, 3 and 2, when they are externally tangent. 00:05:11.886 --> 00:05:15.316 A:middle Another illustration is let's see the pair, 00:05:15.716 --> 00:05:18.676 A:middle externally tangent is two biggest ones, okay? 00:05:18.936 --> 00:05:22.526 A:middle If we look at the distance between the centers of the two, 00:05:23.466 --> 00:05:26.966 A:middle center of the big one and center three, the distance 00:05:26.966 --> 00:05:32.526 A:middle between them is 6.5 because the sum of the radii is 3.5 less 3. 00:05:33.126 --> 00:05:36.046 A:middle On the other hand, for the externally tangent, okay, 00:05:38.046 --> 00:05:39.676 A:middle the distance between the two, 00:05:39.946 --> 00:05:43.146 A:middle the center for the two is two units 00:05:43.146 --> 00:05:45.206 A:middle because it's the difference between the radius 00:05:45.256 --> 00:05:48.596 A:middle of the bigger one, 3.5, minus the smaller one.