Google SketchUp 8 Tutorial - Drawing a Gear

I set out at around 5 PM today to draw a gear in Google SketchUp 8. How hard could it be? I said. It's only a couple of circles, I said. Five and a half hours later, I finally have this to show for myself:

Are you proud? I'm proud.

I spent an awfully long time looking for the tools I needed to make this, so I thought I'd put a tutorial out there about how I finally managed it. I'm going to assume that you have a basic working knowledge of SketchUp - what the premise is, how to use the more basic of the tools, etc. - but no more. So, in approximately 18 easy steps, here we go!

Step 0. One of the things I've really gotten used to in other graphics programs (namely, Illustrator and Photoshop) is the ease of using keyboard shortcuts. I'm so used to them that it's irritating that my favorites (Ctrl to switch to the last tool you used, anybody?) aren't here in SketchUp, but there are a fair number of easy-to-remember shortcuts that I used in drawing this. I'll list them where I think they're useful. I'd highly recommend getting used to using them, especially if you're using a touchpad instead of a mouse.

Step 1. Open Google SketchUp (I have version 8), and use the circle tool (keyboard shortcut "C") to draw a circle on the x-y plane. Here, I'm using red as x and green as y.

I made my gear with exact dimensions, so that's how I'll write the directions, but there's no need to be so precise. You can make most of the dimensions to be whatever you want. That said, there's an easy way to make your shapes with exact measurements. Here, I made a circle with a 2 cm radius. Using the circle tool, click anywhere, move the mouse a little distance away (don't click!), type "2cm", and press enter. You should have this:

Little floating circle. You're viewing it at an angle, so it doesn't look perfectly round.

Step 2. Using the line tool (L), draw a 15 cm line from the center of the circle out parallel to the x (red) axis This will be a guide line, so don't worry if it doesn't look like a gear. 

A couple of useful pointers here. To find the center of the circle quickly, once you've picked up the line tool, hover over the edge of your circle for 2 seconds, then move your cursor slowly toward the circle's center. A light blue dot labeled "center" should pop up. Your mouse should snap right to it. 

Although the line doesn't need to be drawn in any particular direction, I like orienting to the axes if only so I'm positive I haven't suddenly drawn a line in the z direction (out of the plane). When you're moving in the x direction, the line trailing from the line tool will turn red, and a popup box next to your mouse will tell you what direction you're going. You should have this after you've drawn your line: 

Step 3. Before I did the next step, I orbited (O) so that I had a top-down view of my figure. That makes it a little easier to draw the next bit. Using the line tool (L again), you're going to draw three sides of a square at the end of your guideline. Click on the endpoint of the guide, draw a 1 cm line in the same direction, turn right to draw a 1 cm line in the green direction, and right again to draw one last 1 cm line in the red direction. This will be your first gear tooth. 

Ignore the blue line. I just spun the view around a bit. 

Step 4. Use the eraser tool (E) to erase the very first line you drew.

First tooth! It's so cute.

Step 5. Select the gear tooth by pressing the spacebar and click-dragging over all three lines. (Side note: there is a difference between dragging right-to-left and left-to-right. The Google SketchUp video tutorials explain this very well, so I won't.)

Step 6. This step can be finicky, but I'll try and break it down as best I can. First, choose the rotate tool. Find the center of the circle again and click once. Move your mouse along the red axis and click again - it really doesn't matter how far along you go. Now, before you do anything else, press Ctrl (Option on a Mac) once. A small plus sign should appear next to your cursor. This means that SketchUp is not only going to rotate our tooth, it's going to be duplicated as well. 

Step 6a. Move your mouse clockwise a small distance. Type "360" and press Enter. 

Creating the first duplicate. You can do this by hand - just move the duplicate tooth in a full circle so that it overlaps the original, then click. I had trouble with this, though - as soon as I overlapped the first tooth, the counter at the bottom right would click back over from 359.9 to 0.0, and that would mean that you're not rotating through any degrees. Easier to just type in 360.

Step 7.  Before you do anything else, type "/50" and press Enter again. What you just did was tell SketchUp to rotate the tooth through 360 degrees, then duplicate it evenly 50 times through the whole circle.

Starting to look gear-like!

Now, 50 was a semi-arbitrary number that I chose. It just happened to make a regular-looking gear. If I were modeling this for physical production, I'd be much more careful in how I sized the teeth. At this point, any number that makes the gaps nearly the same size as the teeth will do. 

Step 8. This is the tedious bit. Take the line tool again and connect the bases of all the teeth together. 

Connect the teeth bases endpoint-to-endpoint. Takes a while, but it's gotta be done.

Step 9. When you connect the last one, the shape you made should turn gray, meaning that it's no longer a line - it's a face!

Ok, that wasn't really a step. I just added it in because I mis-numbered my screenshots and I needed an extra one to make them line up with my notes.

Step 10.  Now we have to set some guidelines so that we can form the spokes of our gear. This is another slightly finicky process, so be methodical and take it step by step. 

Choose the protractor tool (Tools menu > Protractor) and click in the center of the small circle. Now, move your mouse along the red axis (again, any direction in the same plane is fine, but the red axis is convenient). Click anywhere on the line you chose. Move your mouse clockwise slightly. Type "72" and press enter. A dotted guideline should appear 72 degrees clockwise from the red axis. 

Now, do the same thing again, except this time, instead of moving your mouse along the red axis, move and click along the guideline you just made. You should have two guidelines now. 

Repeat those steps three more times, each time clicking first in the center of the circle, then along the newest guideline before moving the mouse clockwise and typing in "72". 

You should have something like this:

Gear pizza.

I did one more thing to make my life easier later on. We're only going to be using half of those guidelines, so I used the rectangle tool to mark every other one.

Step 11. Use the push-pull tool to pull your gear up 1 cm vertically.

Step 12. Before you start this step, orbit (O) to the bottom of the figure. This will make your guidelines easier to work with.  Using the offset tool (F), offset the center circle first by 12 cm, then by 3 cm. 

 Step 13. Choose the line tool. Using the marked guidelines, connect the two circles you just drew. Make sure that when you draw them, the "intersect" symbol pops up as a red cross when you hover over the points where the guidelines and the circles meet. I thought I had a picture of this step, but I don't.

To make your figure look like the next picture, use the eraser tool to remove the guides. Then, using the offset tool on each of the slices you just made, offset them inwards by 0.5 cm.

Sorry, that's a lot of steps with very few pictures. To clarify: this picture shows five "spokes" alternating with five curved pieces. The thin spokes are the lines that you draw to connect the outer and middle circles. The curved pieces are what you get when you offset the shapes from the first step by 0.5 cm inwards. 

Step 14. Use the eraser to remove the thin spokes, leaving only the curved slices behind. 

Step 15. Use the push-pull tool to push the fat arcs through the gear to make windows. I found that I had the best luck with this when I entered "1cm" manually after clicking on each shape with the push-pull tool. Otherwise I had a tendency to just push them all the way through to the other side.

Step 16. Orbit to the other side again. Using the offset tool, offset the rim of the inner circle 0.25 cm outwards. (This is another one I wish I had taken a screenshot of, but didn't. Essentially, what you want to do is widen the center hole so that you can easily erase the surface that's in the middle.)

You should have a very very thin sliver of a hollow cylinder surrounding the center circle. Push that sliver through the gear 1cm, so that you have a thin window. Now, select the gray face that's left over and delete it.

Note: If you turn the gear back over, you'll note that it looks hollow. This is easily fixable by using the scale tool to shrink the middle edge of the gear in to meet the center hole. Press Ctrl (Option on a Mac) to highlight the center of the circle, then pull one of the corner handles in until the edge of the gear and the edge of the hole overlap. 

Step 17. Now, all that's left to do is color it! I modified the stock corrugated metal skin to look more like brass, but you can do whatever you want with it. 

And there you have it! I know there's some stuff here that is a little roundabout and could probably use some tweaking. Do you have an easier way to make a gear? Let me know in the comments!