In this lesson, we'll talk about creating a top down view sketch. After completing this lesson, you'll be able to create construction geometry. Let's carry on with our design by starting a new sketch on the top plane. So far we have our front shape, and we also have keep outs for our batteries. So let's go and start a new sketch. Make sure that we're on the top plane and let's start to talk about the overall shape of our design. Now this is where we're really going into more of our mass location and our overall size. So we need to consider a few things here. First thing we need to consider is symmetry. We need to make sure that the location of our motors, all four, are symmetric about the origin. Now that's not necessarily the case in all designs. But for us, it's going to be important to keep all the motors in the right location, we're going to know exactly where our flight controller needs to be to keep it centered, to make sure that we have the most stable flight possible. We're going to start with a rectangle. I'm going to make sure it's a center point rectangle from the origin, and I want to draw this out. I'm not going to give any dimensions just yet, I'm just going to place it, and I'm going to turn each of these lines into construction. Now the reason I'm doing this is because, this is going to be a square. And this square is going to dictate the location of all four motors. We're going to come in here, and we're going to take this vertical line, control select a horizontal line, and we're going to make them equal. Now this is going to mean that we have a square. Now we simply have to dimension it. Now, I've played around with this quite a bit. So I have a few numbers that I want to deal with. I'm going to be using 265 millimeters, from corner to corner. Now when you talk about quadcopters, if you're completely new to this topic, you'll see a lot of people talk about a 250 series quad, or a micro quad, or different sized quads. Well, the 250, is generally the size between the motors. When we're talking about the size of the quad that we're building, we're looking at about a 250 sized quad, a little bit bigger, because we want to incorporate two batteries, where most of these 250 size race squads are going to just have a single battery. We're sort of bumping those dimensions out a little bit. But overall, we're going to try to stick between 265 as the smallest number that we can hit, if we have to go bigger than we can. But this is going to be our starting point. So now, we've turned this into a complete construction square. We have a fully defined square because we have an equal relation between a vertical line and a horizontal line. And we have a dimension from corner to corner. Now I want to start to place a bit more information here so we can start to really visualize the overall shape. The first thing that I want to do, is I want to draw a circle in this bottom corner. And again, you can access these tools however you want. I'm going to use my quick keys on the keyboard. The letters C, and I'm going to place a circle here that is 28 millimeter diameter. Now this is going to be the outside diameter of my motor. If you remember when we talked about our design criteria and the motor numbers, we're dealing with a 22.05 motor, which is 22 millimeter diameter on the stator, and five millimeters tall on the stator. The overall size of the motor itself is 28 millimeters on the outside. This gives me a good flat, circle area that I can mount the motor knowing that it's exactly the size of my motor, and I'm not going to be obstructing the props at all. Because I don't really need this circle, I'm going to turn it into construction as well. I don't necessarily have to put this on all four corners, but visually if it helps you, you can certainly add another one to any of the corners, especially since we're dealing with two different sized batteries, that could potentially help. Because I know that the width of these two batteries is essentially the same and this one's taller, I know if it's going to clear on the side, it will clear on the side just fine. Next I'm going to place another circle, and this time, I'm going to do 127 millimeter. This is going to be the outside diameter of the prop that we're dealing with. We're going to be dealing with a five by four and a half pitch prop. This is the overall spin or the overall circle that this prop is going to be moving in. Now again, this can be construction. We don't need it to be any geometry that we're going to extrude or anything like that. But this gives me a good reference for the location of my battery, and the location of the prop. Also keep in mind that we're looking at everything in 2D right now, and that's something that's hard to get around at this stage since we don't have any geometry. This is assuming that, the thrust plane or the plane that the actual prop is spinning on, is also centered on the mass of the battery. Remember, that was sort of important. That was a topic we talked about, in terms of where the center of gravity vertically is going to be. If we move the weight down below the props, then we're going to have more stable flight but is going to be a little bit harder to change directions. If we have it completely centered on the thrust plane, then it's going to be really quick at changing directions. It's going to be really agile on the air. If we put it above, then it's going to be very easy for it to flip, and do some of those acrobatic maneuvers. But it's not going to be as stable in flight. So again, that's why you see a lot of off-the-shelf camera drones that are meant for photography or video. You see that, they'll have the props all the way at the top and all of the masses below the props. And that's because they're not necessarily meant to be agile. They're not meant to be a quick flying drone. They're meant to be very stable in the air to give you good control over the camera. Keep that in mind that the location of the mass as we're looking at it, we're only really talking about up and down, left and right in a plane. We're not talking about going vertically in 3D just yet. But assuming everything clears from this view, then we have complete control over the height of the batteries. If you're planning on putting him well below are well above then of course, we could tighten everything up a bit more. But I found that this 265 millimeter number between corners, is going to be about the extent that we can go. If you decide in your design that you want to use a much larger battery, a much longer battery, for instance the 2650 millimeter power battery that we talked about in our design criteria, then you're going to have to go a bit bigger than 265. You're going to have to push these motors out a little bit. Because you can see that this one here, is going to be fairly close. We're going to get pretty close to the prop, and that's about as close as I would feel comfortable. This one is 105 millimeters long, whereas the larger four cell battery was 137 millimeters long. Keep that in mind, that if you decide throughout your design that you want to use a bigger battery, you want to fly this thing for as long as possible, then you're going to have to make the overall size a little bit bigger. One thing that we haven't talked about in the design criteria and that could potentially be important to you is the actual production of the body. Assuming that you have access to a 3D printer wherever you are, the type of printer that you have access to, as well as the size that it can print is going to be important to you. A lot of printers, for instance, 3D printer that's a desktop unit like a MakerBot Replicator, which is on the higher scale end of a desktop unit. That's going to have about a 12 by 12 inch print table. Keep in mind that, if you're designing for a specific printer, then you want to keep that in mind as well in terms of the size. We're doing everything as if this body is one piece. Of course, you could make it multiple pieces and bolt it together whatever the case might be. We're assuming that it's all one piece and we're going for a SLS nylon print. So, one big 3D print for our design. But that might change depending on what you're designing for as well. So now that we have a single prop and a single motor in the location, I want to start to lay out what the shape of this thing is going to look like. So I need to add a few more lines. And the first couple lines I'm going to add are construction. I'm going to turn on construction, use my marking menu, start the line tool. And I'm going to be coming out collinear here. I'm not going to add any dimensions just yet. And hit the okay. I'm going to go from the origin out to the right, again, not adding any dimensions just yet. And I'm going to say, okay there. And then I'm going to add a vertical line, and I'm going to add it off to the right for right now, and I'm going to say okay. Then I'm going to have to escape. Now this vertical line, I'm going to select, control, select the origin, and I want to place a midpoint constraint. I'm going to hit escape. And that way, this line is constrained to the origin at its midpoint. So I can move it up and down, make sure everything is symmetric front to back. I also have this horizontal line, which is going to be the location of the mirror, from left to right, or front to back depending on how you're looking at it. And I'm going to go ahead. I'm going to turn off the Keep Out. I'm going to turn off the Front Profile. I don't need to see any of those right now especially the Front Profile, it's not doing anything for me. But now what we've done is we've laid out some symmetry lines for left to right because we're only going to be sketching everything on the right hand side, and front to back or top to bottom again depending on how you're looking at it and visualizing it. So let's get started again with the line tool. I'm going to start sketching out to the right. And notice that, it's still construction because I didn't turn that construction off. So that's something that you want to make sure you do go back again and turn that construction off before you start sketching. We're going to come out to the right. We're going to come over here. We're going to draw a line. And I'm going to make sure that I'm not creating any constraints. I'm going to hold down the control key. Holding down that control key will override any persistent constraints. I'm going to let it go and snapped to this point. And this is going to be all that I need to sketch so far. I want to take this line out right here, and I'm going to control select this line, and I'm going to add a midpoint. I then want to make sure that I add a perpendicular constraint. Might have to zoom in, between these two. So now I have a perpendicular constraint between this line and this line. It's midpoint. In this line is collinear with that X, that cross that's going directly through my origin. Now I just need to add a few dimensions. So the first thing that I want to do, is press D on the keyboard, and I'm going to add a 50 millimeter dimension here. Now this may look kind of funny right now but once we start to add a bit more dimensions, it'll make sense. Again, we're going to place another dimension. And this time instead of placing something here, I'm going to click on this 50 and hit enter. What this does is it makes that number equal to this 50 millimeters. So that way if I decide to come back and change this 50 to a 75, it's going to update both of them. Now while that works out great in this instance, it may or may not work out great in other instances. So just keep that in mind that, creating this equation, this reference on the fly, can be very helpful especially when you're dealing with symmetry and you're dealing with an instance like this where you're trying to keep everything as symmetric and uniform as possible. I'm going to add a few more dimensions in here. I want a 105 degrees on this angle here. And this line, I'm going to make 100 millimeters. So the last thing that really needs a dimension, is going to be this line right here, and I'm going to make this 30 millimeters. So again, you might wonder where these numbers came from. Well, as we're looking at this, the prop is five inches and it's spinning all the way out past where we drew. Now this doesn't necessarily mean that our prop is going to extend past our body. But, the overall shape that we drew from the front, is going to be the overall shape at the top of this quadcopter. That doesn't include anything that goes around the blades to protect him or anything like that. So this is why I wanted to stop short, so that I can really focus on the design of the area that goes around the prop and protects it. So I'm stopping there at 50 millimeters within the five inch prop circle. The 30 millimeters up here, is going to stop short of that five inch prop. And I could make it coincident with here and it would be pretty close to 30 millimeters. But essentially, this is going to give me a vertical line and I can actually draw that vertical line here if I want to. That's going to allow me to keep an area for my components, things like my camera, my flight controller, and all that, and allow me to keep that squared off. And that way, I can have solid geometry here if I need it, that's not obstructing the flow of the prop. And so, we've got a good bit drawn in, but now we need to start to add some mirror and some symmetry. So let's go ahead and stop the sketch right now, and let's go ahead and save our design so that way we can come back to this sketch and make edits without losing any of our work.
