Join Dave Schultze for an in-depth discussion in this video Making a chain drive for gears, part of Rhino: Tips, Tricks & Techniques.
- In this third and final gear demo, we create a chain drive. We're going to solve this in a couple simple steps. First, we have a curve used for a path. Then we use some link parts, already made, and array them along this curve. Let's review the scene here in Perspective. We've got a couple existing gears we did previously, and we've added one extra. You might notice that curve path is a little bit deformed and bent. This happens a lot when you have complicated geometry or just a busy scene.
When things are being drawn, they sometimes snap to the wrong spot. But it's very easy to fix, as long as it looks correct from one of the views. Here in the front, it looks perfectly fine. So we're going to use a command called Project to the construction plane, and flatten that out so it's perfectly flat and aligned to the gears and the links. So that's under Transform, we Project to CPlane, which is short for Construction Plane. Hopefully you knew that. We're going to select the objects, which is just the one deformed curve, right-click to accept.
You do have to say we want to delete the inputs, we only want the output which is corrected. So I'm going to say yes. Soon as I do that, boom. That thing flattens out. So if you have trouble drawing something accurately with too much geometry, go ahead and draw it. Just flatten it back out as your final step. Okay, I'm going to go ahead and move the two parts of the link, I'm going to zoom in here from the front view. I do need some extra O snaps and settings here adjusted. I want to keep this link perfectly centered on the construction plane, along with the curve.
Since we're already there, I want to make sure they don't move away, which can easily happen when you move and rotate. That's going to be our next two steps. To help keep it from moving in and out, I'm going to go ahead and put on this Project. That'll keep it locked to wherever it is currently. I also want to add a couple more O snaps here. Let's go with Perpendicular and Center. Centers are very important because we're going to now move this link, starting from a center point of one of these openings.
So we'll just grab the whole assembly there, it's actually just two parts. We're going to use the formal Rhino Move command. I call it formal because a lot of times, people just drag stuff around, or they use the arrow keys to nudge, which is great, this is just far more accurate. Go ahead and start the Move command. I do want to make sure I snap on the center. You'll notice things jump around a bit, so you may have to zoom in. There's the center. Okay, want to just come out here just a little bit, and I want to land on this line. Now sometimes I'll turn on Near, but that can make things a little bit harder to do, because Near is always finding stuff.
It can be hard to get that center like we did. So I've got Perpendicular on, that'll work fine, it doesn't really matter where we're going, we just want to make sure we hit that line. And the second part of getting this in position is rotating. So kind of the same general idea, we got both still selected. We're going to rotate 2D. We need to give it a reference, which is the object itself. Just right there, horizontally, we're going to reference that. And then rotate it to the inclined curve. So let's find that center again. We need to find another point perfectly over there.
That will work. Then we come down, looks like it found an intersection. Perfect. So what I want to point out here is I don't know what that angle is. But also, I don't care. It snapped perfectly. From before to after, should match and be right in perfect alignment with it. So now let's talk about two different ways to array these two link parts around the curve. Pretty straightforward. It all depends on how accurate you want to be and how much time you got. Let's start with the most accurate method first.
I call this the math method. We do need to make two quick measurements, so let's select the curve here. I want to know how long it is. We can go up to Analyze, select Length, boom, there you go. 2,000, roughly, 20 millimeters. So that would be your path length, and then you'd divide it by the distance here from, again, center to center. We can do that pretty easily with a drafting command here on the toolbar. I'm going to use the Align Dimension. Most people are probably familiar with the horizontal and vertical.
Align's really nice if it's at a weird angle, which we are. Just want to zoom in here. Hopefully all these snaps will work. I want to make sure I get the center again. You do have to move around, let it find it. There's a lot of geometry here. There's the center. Okay. There's the other center, and I'm going to come up. So with two centers, we have an Align Dimension from center to center, or end point to end point, of about 57.96. So, you can do the math. You can figure out how many multiples will fit. You can make the link grouping smaller, bigger, or change the curve.
Whatever you need to do to get it to fit perfectly if that's what you want to do. Let's go ahead and just delete that. Now we're going to do the method I probably use way more often. I call this just the trial and error guessing method. So, you have to have a little more patience here. But, if you guess pretty close, it goes fairly fast. Alright, so I'm going to grab these two guys, just select them, draw a little box there. Go to Transform, Array, and Along a curve. So check in the command line here, it's asking for the path curve.
That's just the only curve we have in the scene. And now comes the guessing game. I'm going to try out maybe 20. What's really cool is it gives you the distance between items. So if you're interested in being more accurate, that might be helpful. I've totally forgotten what the overall measurement was, so let's just see what happens. By default, this should be freeform, that's kind of important, 'cause it'll rotate things going around corners. Let's hit OK. And in perspective, we can see that was not enough. We've got some gaps there.
That chain is definitely not going to work. Okay, so, I said this was trial and error. Control-Z. And we can come up here and repeat all of the prior commands. I'll pick the same one again, Array along a curve. Same question. Path curve. Now I've actually practiced this a little bit, so I know that 33 should get me really close. Let's go ahead and hit OK. And that does look pretty good. So again, this is not super precise engineering, but as a designer, if you want to make something look fairly realistic and presentable, this definitely will do that job.
If we maximize Perspective, the array along a path is a very powerful command. But can be a little challenging when you're using multiple pieces of geometry. So you can use the accurate measurement method, or just be patient. If you choose the trial and error guessing method.
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Skill Level Intermediate
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