384 | Cómo modelar conjuntos de suspensión en CAD
Resumen
Modelar conjuntos en CAD nos permite simular el movimiento y la interacción de las piezas. En este seminario web, veremos cómo podemos lograr esto con nuestros componentes de suspensión y cómo utilizarlo para analizar y optimizar el diseño.
00:00 | Hey team, Conor here from HPA, welcome to another one of our webinars. |
00:04 | This week, we're going to be talking about one of the projects that I most like doing in CAD and that's modeling suspension assemblies. |
00:11 | So, we're going to have a look at two different types of suspension assemblies that I have some pretty basic models for, one being a double wishbone and another just being a McPherson strut. |
00:22 | And we're going to look at how you basically set them up with all the joints between the components, some kind of best practices there to help you if you're ever doing that. |
00:34 | And then how we can take measurements from the assembly that we've set up to be able to analyze the suspension, as well as some extra software packages that we can use with those measurements we've taken out of our CAD software to be able to optimize our suspension as well. |
00:53 | But a few different approaches to show you how to do that. |
00:55 | So, if we jump straight onto my computer screen here, I have Fusion open and I just want to really quickly just make that visible again. |
01:07 | So, ignore the colors, they're really just to make it a little bit easier to see all the different components in here as we go through and discuss it all. |
01:18 | But this is actually, I'll hide this, the engine base scan here. |
01:24 | This is a model of our CRX here with our chromoly subframe that we fabricated and designed as a worked example project in our CAD modeling course. |
01:39 | So, that's got the chromoly subframe in there and then the rest of the suspension as well. |
01:45 | So, what you'll notice here is that we have some parts that are 3D scans like the upright here. |
01:52 | And if I just hide the wheel, we'd be able to see that a little bit better. |
01:57 | So, ignore the endless kind of caliper thing over there, but this is a 3D scan. |
02:04 | The top arm here is a 3D scan as well. |
02:07 | And those scans have some kind of solid bodies that we've modeled into them just to help us to be able to reference the scans and work with the mesh files and assemble them to our other components, which you'll see as we kind of get going here in a minute. |
02:26 | We also have some solid general kind of CAD modeling stuff with our subframe here and some sheet metal as well of this lower control arm. |
02:38 | Keep in mind that this design is probably going to be revised in the coming months hopefully. |
02:45 | As well as, so that's kind of accurate stuff that matches what we really have. |
02:49 | And then there is also just some kind of reference parts here as well. |
02:55 | So, I didn't have the actual coilover on hand all the time to model an accurate one. |
03:00 | So, what I've done is just taken some basic measurements of the length of the coilover and the parts of it and then the travel it has and created a very basic model that will allow us to kind of just run the part through its travel and see how that all interacts with each other. |
03:20 | And the same kind of thing goes for the stand rack here where the tie rod end is just an extruded cylinder in this case. |
03:30 | But we can use that perfectly fine to be able to work with these relationships and so on. |
03:35 | So, it's just basically showing that we've got scans here, we've got some accurate models and we've got some just really basic models using for reference as well. |
03:45 | And I've got this all set up so I can basically click and drag it and run that through the suspension cycle at the moment. |
04:01 | I've got the steering rack locked out so that can't move but I have the full kind of articulation in the suspension. |
04:10 | So, what I want to start with is just a few kind of best practices around creating an assembly like this if you should ever want to do so. |
04:20 | Because essentially what the suspension system is is basically just a big mechanical linkage. |
04:27 | If you've ever done any work with linkages or anything before, that's essentially what we're working with. |
04:33 | So, an important part of this is something that I kind of try to apply to all the projects I'm working on with assemblies and that is that every component in the real world should be represented as an individual component in our CAD software as well. |
04:53 | So, I say that, for example, in Fusion we can have our design file and then we can just have a whole bunch of bodies under here. |
05:05 | In this case, these bodies are for the subframe and that's kind of fine because the subframe doesn't move. |
05:13 | But more typically we'd have the subframe as a component, we'd have our chassis like our 3D scans as a component, steering rack as a component, everything separately as an individual component down here. |
05:26 | And what that allows us to do is control the relationships and the positioning and movement relationships between all those components more accurately. |
05:37 | What we're trying to do is represent what the real life situation is. |
05:41 | So, having them all as individual components allows us to do that. |
05:46 | So,me of the components as well might be broken up into kind of lower levels as well. |
05:53 | So, I might have multiple components that represent just the steering rack, for example, or the coil over here, I might have this kind of top section of the coil over and then the bottom body of the coil over as well, just so I can break that up and define the relationship of that coil over movement with the sliding joint as it moves through its travel. |
06:16 | Same thing for the steering rack, since the steering rack kind of moves, I might have just the body of the steering rack, then I might have the internal rack, and then I might also have the tie rod ends as a separate one, just so I can kind of control the relationship or the movement of those three components within that one kind of larger component or relative to each other. |
06:44 | So, we'll just get into a little bit of an example here of a few different ways that we can set up the joints between these components. |
06:54 | And if we're working in another type of CAD software, for example, SOLIDWORKS, it's all exactly the same ideas. |
07:02 | SOLIDWORKS are just called mates, and the way we set them up is very slightly different. |
07:07 | Whereas in Fusion, we set it up and that'll lock down three degrees of freedom, and then we kind of change the joint type to ball joint or slider or something like that to remove degrees of freedom or open up degrees of freedom. |
07:27 | Whereas in SOLIDWORKS, it's kind of the opposite way where we lock down individual degrees of freedom with using the mates. |
07:35 | So, we'd lock down movement in one direction and then basically create our joints like that. |
07:42 | But the point I'm trying to make is it's all the same idea. |
07:46 | Doesn't matter what CAD software you're working with. |
07:52 | So, if we're setting up joints in this and we have something like our lower control arm here, which has these spherical bearings in here or spherical joints, since they are included in a component, it would be possible to, inside that component, also set up those joints just inside that individual component. |
08:21 | And then they would be able to be referenced within the overall assembly. |
08:27 | But I try to avoid that. |
08:29 | I try to have all of the relationships and joints under the tab in the overall assembly, I guess. |
08:39 | I find if we have relationships inside each component as well, and then, for example, the ball moving in the race for this bearing inside that component, and then we come in and then we constrain the inside of that ball to the bolt that goes through it with a revolute joint or something like that. |
09:00 | It is possible. |
09:01 | It does work, but it gets quite messy. |
09:03 | And I find that all of my errors kind of creep in when that starts happening. |
09:08 | So, the way I prefer to do it is just basically set up. |
09:14 | If I jump into that lower control arm, give me a minute to find it. |
09:20 | So, driver side lower control arm here. |
09:23 | And if I jump inside that, you'll see under this relationships tab, everything is just set up rigid. |
09:33 | So, I actually have a rigid group here with those bearings in it. |
09:39 | And then those are set up in this case with rigid joints to the control arm itself as well, like the sheet metal parts. |
09:49 | And I could do that rather just by coming up here, going to assemble, creating a rigid group, and then just selecting that entire part. |
10:00 | So, every component within that component is just basically welded together at that point. |
10:09 | So, that's one example of kind of like rigid groups and where we'd use them. |
10:15 | And then what I prefer to do is come back into our main assembly. |
10:20 | And then from there, I will just set up a ball joint, for example, here. |
10:27 | So, this ball joint here is set up. |
10:29 | If I just will edit that ball joint, we can see that that is set up between the race, like the ball in this case, and the bolt for the lower control arm. |
10:46 | So, that's not exactly 100% accurate of representation of how it works in the real world. |
10:52 | But it does kind of work better for how this assembly would essentially work. |
11:00 | And fusion anyway, just to kind of remove any errors. |
11:05 | So, there you can see if I click and drag, if we're just watching, try to zoom in a bit more so we can see my click and drag and move that there. |
11:19 | It's a little bit tricky with everything off the screen. |
11:22 | We can see how that ball joint kind of moves. |
11:25 | And in that case, it will just represent the movement. |
11:29 | It will at least represent how it moves in real life. |
11:34 | So,mething's happened a bit weird with our coilover there, but we'll just kind of ignore that for now. |
11:39 | So, we have like a ball joint here, ball joint out here. |
11:43 | We have ball joint up the top as well. |
11:45 | We also have this slider joint here for our coilover and a pin joint, I think, here for the upper controller. |
12:02 | So, we'll just jump over to a little bit more of a simple example here being the tie rod end, which again is just some reference geometry, just an extruded cylinder in this case or extruded circle to make a cylinder. |
12:21 | And if I can just find that part in my timeline, over to the other side, I'll find the ball joint at the end here. |
12:43 | Yeah, so that's highlighted that joint here. |
12:45 | I'm just going to roll back to that and show you how I created that joint. |
12:53 | So, there, we'll just delete it. |
13:01 | And then I'm just going to set up that joint. |
13:04 | So, basically, I click the joint tool here. |
13:08 | And then what's important is what component we select as component one and component two, because one moves relative to the other. |
13:20 | So, if we did select, say, for example, the end of this, and then just if we hover over this body and I hold command, then it will keep those options open. |
13:34 | I can snap to the center point of that circle. |
13:36 | And then you can see it kind of flips us around for now. |
13:42 | And in this case, the... Oh, that's set up rigid. |
13:45 | We'll change that to ball for the motion. |
13:51 | The tie rod end is moving relative to the steering knuckle in this case. |
13:58 | And if I go back to the position, I can drag the distance of the steering knuckle relative to that. |
14:06 | So, where it attaches to the knuckle, the height. |
14:10 | So, this is quite a powerful tool for when it comes time to analyzing the bumps there. |
14:18 | But if I come back here and I've dragged this kind of off center, and then I hit play, you can see that it's now rotating at a point 10 millimeters, 15 millimeters up the tie rod end, whereas I wanted that to rotate at a point 15 millimeters from the knuckle. |
14:39 | So, that's why it's important which one we select for component one and two. |
14:44 | So, if I go back and delete those two, rather, if I select for component one, the knuckle, and then I select component two being the end of the tie rod end, then I can just drag them. |
15:02 | So, it'll be negative 15 millimeters down there. |
15:10 | And we can see that now the upright's moving around the knuckle. |
15:14 | But if we hit OK there, we can see now that the end of the tie rod end is actually spaced just down off the bottom of the knuckle. |
15:22 | So, now I can control the height of where the tie rod end attaches to the knuckle like we would on a car to be able to adjust the bump steer and so on. |
15:33 | Just a little side note on setting up these tie rod ends just as reference geometry like this. |
15:40 | Of course, we could model an accurate tie rod end. |
15:44 | But in a case like that, we know that we have a lot of adjustment in the tie rod ends. |
15:49 | They're designed to be adjusted. |
15:51 | And so really creating an accurate model like that is kind of diminishing returns. |
15:57 | It doesn't do too much for us. |
15:59 | And I find this kind of method works fine. |
16:02 | And then I just change the length of this extrude, which is here. |
16:06 | And what I do is I take a measurement from the surface of the hub here. |
16:13 | And then I just show the origin. |
16:15 | Granted that you've got everything aligned to your coordinate system. |
16:19 | And then I can see I have an angle in this case of 0.117 degrees. |
16:26 | So, that is my toe essentially. |
16:29 | And probably when I start off, I'll have an angle of 10 degrees or something. |
16:34 | And I'll just shorten or lengthen the extrude to change the length of the tie rod end to basically aim for zero toe just while I'm analyzing the suspension like this. |
16:43 | But that's my kind of thinking. |
16:45 | And I found that that works quite good for me. |
16:47 | And then that'll just get me in a good ballpark in terms of the setup to be able to take measurements of everything else from that. |
16:57 | So, let me just check my notes and then we'll move on. |
17:01 | Another thing that I wanted to... |
17:03 | So, that's a way of just using a joint between this component here and controlling the position of the ball joint where it rotates. |
17:13 | And I've just done essentially the same thing as well for all these. |
17:16 | So, this joint here, this lower ball joint, if I select that, I've clicked the bottom of the upright here as my first snap point. |
17:30 | And then the center of the ball joint here because that's where it's going to be rotating about. |
17:37 | And then I've just dragged that down about 18 millimeters in this case. |
17:42 | But we could control that with using spaces and so on to be able to set like the roll center and things like that. |
17:51 | So, that gives you a little bit of an idea of how that one works. |
17:54 | But it's essentially just the same thing, same type of ball joint that I've set up in all these locations like that. |
18:03 | Cool. |
18:03 | We also have a ball joint here. |
18:06 | This is a fixed rigid connection here with the caster arm. |
18:10 | And like I discussed before, the other type of joint that I wanted to discuss is what's called an as-built joint in Fusion. |
18:20 | And it's a really easy way of doing it. |
18:23 | So, if I just drag it along a bit, I actually could have stayed where I was. |
18:29 | If we create an internal component, so we have internal components and external components in Fusion. |
18:36 | An internal component would be one that we've modeled within this assembly file. |
18:42 | So, an internal component in this case is this tie rod end, where an external component would be like this upright scan. |
18:52 | So, I've bought this scan or this component into the assembly, whereas I've created this internal component for the tie rod end in the assembly. |
19:02 | And if we've modeled an internal component in the position it needs to be, so for example, we just created a sketch here in the center of the steering rack. |
19:19 | Oh, that one doesn't look like it quite is, but it's worked out anyway. |
19:23 | So, we created and modeled this tie rod end, representative tie rod end in the position that we wanted it to be in. |
19:32 | And if it already has been modeled in the position we want it to be in, then we can use this as-built joint, which the name kind of links up with what we're saying there. |
19:42 | So, an as-built joint like this one here works a little bit differently. |
19:49 | So, if I just delete this, I'll show you how that's made. |
19:53 | So, we have our tie rod end, and then we can just use an as-built joint here and want it to be a ball joint. |
20:02 | I already know that, so I'll change that. |
20:05 | The components are going to be the tie rod end and the steering rack. |
20:11 | And then the snap joint, we only need to select one for an as-built joint. |
20:17 | So, this is just going to be the point that that ball joint is going to rotate about, which would be the end of that tie rod. |
20:23 | So, it's a little bit more simple in that case, if it's already in the position that I want it to be in, and I don't need to control the position of it from there. |
20:33 | So, just a little slightly different approach depending on how our model is set up. |
20:37 | So,metimes those as-built joints can work a little bit easier than a typical joint. |
20:45 | Cool. |
20:46 | The last one that I wanted to look at and just bear with me while this loads, is the slider joint that we used for the coilover. |
21:03 | Well, it's just taking its time. |
21:05 | There is a little bit going on in this model. |
21:09 | We have a couple of 3D scans, well, quite a few 3D scans, and a lot of joints and relationships and so on. |
21:17 | All right, I kind of got something. |
21:19 | I'll just check that this works. |
21:21 | Still working. |
21:22 | So, if you see that I drag the tire up here and the coilover is sliding there and moving, and then if I let go of it, so it's that full droop here, full bump, but if I let go, it freezes and it loads. |
21:41 | Hopefully, it sorts itself out pretty soon. |
21:44 | Yeah, there you go. |
21:45 | It snaps back to this minus 60 millimeter position. |
21:48 | So, I just want to jump and show you how that's set up. |
21:54 | If I can find the joint first. |
22:05 | Okay, so this joint is actually set up in the coilover, I think. |
22:10 | Maybe it's not on the other side. |
22:13 | Edit joint. |
22:15 | Cool. |
22:16 | So, with a slider joint like this, all that I've done is selected the top of the coilover. |
22:27 | Again, very representative model, not accurate. |
22:30 | And then the bottom part of the kind of top of the strut body there. |
22:38 | And then I've set a slider up there. |
22:40 | And then I have these minimum, maximum and rest. |
22:46 | So, in this case, zero is where it's at now. |
22:49 | 90 millimeters would be at full extension. |
22:55 | So, I know that I have 90 millimeters of travel in this coilover. |
22:59 | And then I've set the rest position to be essentially the ride height. |
23:03 | So, it's going to return, the model is going to return back to that rest position as soon as I stop dragging it around essentially. |
23:12 | So, if I click OK, it's going to go to 60 millimeters. |
23:16 | If I click and drag here, I'm just holding option on my keyboard for a map. |
23:20 | I think it's a control or something on a Windows. |
23:23 | I'm clicking and dragging. |
23:25 | I can drag and then it just snaps back to that position. |
23:28 | And I typically use that as the ride height position. |
23:32 | And if you're not 100% sure where your ride height is going to be, I'll just flick over to another window here. |
23:39 | This is kind of a general rule as a good kind of starting position where we're working at about one third into the travel. |
23:48 | So, we have one third of the travel and rebound and two thirds in compression. |
23:54 | So, that's why if I had a 90 millimeters of travel, I'm sitting at negative 60 in this case, how that joint set up or 30 millimeters into the travel. |
24:04 | So, that's just essentially what I've done here. |
24:07 | And I find that works quite good for getting it into that kind of ride height position anyway, and keeping it in that location. |
24:17 | So, what I'm going to do here is just turn off some of these. |
24:22 | So, it's a little bit more clear and move on. |
24:28 | So, if you do have any questions that come up during any of this, feel free to ask in the chat and I'll do my best to answer any questions we have at the end. |
24:37 | Okay, cool. |
24:38 | So, once we've got this all set up and we're happy with our assembly like this, what do we do next? So, it can be useful just as is for checking some very basic things, taking measurements. |
24:53 | So, we can use our expect measure tool here, for example, and we can measure things like the... |
25:02 | If I just turn off one of those wheels, we could measure the camber that we're sitting at at the moment. |
25:12 | So, I've just clicked the hub here and I'll measure that to the vertical axis. |
25:17 | And we can see we've actually got positive 0.4 degrees of camber in this case, which we obviously would need to probably want to make some changes. |
25:26 | To that to be slightly into the negative range for this car, but it really depends on what you're working on. |
25:33 | And of course, if you've got your setup or modelled accurately, make sure everything's in the perfect position and so on. |
25:41 | We could also measure some things like the track width, ride height, camber, and so on. |
25:49 | And just check for clearance as well. |
25:51 | So, if I turn that wheel back on and we have the base scan open here, and if I had 3D scans of the fenders in here as well, I would be able to click and drag and just make sure that we've got clearance to everything there. |
26:07 | So, how I've got this set up at the moment, it looks like the top of the upper arm there is hitting the chassis. |
26:15 | I don't know if the wheel is hitting the car. |
26:21 | Looks like it gets pretty close. |
26:22 | We'd be able to run it through the travel there. |
26:25 | And also we could turn the steering and stuff as well if we had that set up like how our coilovers were with a slider joint through it. |
26:34 | We'd be able to turn the wheels and make sure we have clearance to the lower control arms and so on. |
26:38 | So, we can do all that essentially as it is. |
26:41 | And that's one of the benefits of modelling our stuff in CAD first. |
26:45 | So, we can kind of foresee those issues before we manufacture any of it. |
26:51 | Or we can dive in a little bit deeper and analyse the suspension. |
26:56 | So, we can do some very simple analysis stuff straight in our CAD software here. |
27:03 | So, one thing that I like to do is just do some basic sketches and draw some lines through the centre of the ball joints. |
27:15 | So, if I just jump over to another thing that I had open. |
27:20 | Bear with me while I find it. |
27:23 | So, this is a page of Suspension Secrets, just a little article off their website, which I'll get Jayden to drop into the chat if you're interested in coming and having a little read of this because it's quite a good article. |
27:38 | But you can see here on this diagram that they have the centre of gravity and then the instant centres worked out and then the roll centre here as well. |
27:48 | And we can basically use our CAD model to find things like the roll centre and so on. |
27:55 | And other things like the kingpin inclination, the scrub radius, instant centres and roll centres. |
28:02 | So, what I'll do is I'll just kind of show you a basic way of doing that. |
28:05 | So, if we consider our assembly from the front view, and I'll just hide that scan again. |
28:12 | What I'm going to do is I'm just going to sketch on that front plane there. |
28:17 | And then I want to come in and just project a few things. |
28:22 | So, what will we look at? We'll look at the kingpin inclination and we'll look at the scrub radius as well. |
28:32 | So, what I'm going to do is just project some reference geometry so I can find the centre of the ball joints. |
28:41 | And that will allow us to draw some lines through everything and determine those factors that we're just discussing. |
28:55 | So, yeah, upper and lower ball joint. |
28:58 | And then I want also the centre of that wheel. |
29:02 | So, I know the origin plane here. |
29:08 | So, I've projected those two points and then, bear with me, it's a little bit hard to see this. |
29:17 | I just want to hide the upright quickly so I can see through to what I'm trying to select. |
29:24 | I'll project that vertical line so I know that's in the centre of the wheel there. |
29:29 | And for now, we're just going to hide the... Oh, we actually need to see the wheel. |
29:34 | So, what I'm going to do is I'm going to just find the centre of the bearings first. |
29:42 | So, these little projected lines in our sketch plane here. |
29:46 | Just draw a line through there. |
29:49 | And then there was one down the bottom here as well. |
29:59 | Cool. |
30:02 | And then I can snap another line to this and that little triangle there tells me that's the midpoint. |
30:14 | And also to the bottom of that there. |
30:19 | And then I'm going to make another line just come down to the centre of the contact patch. |
30:27 | So, I just need to make that there down the centre. |
30:32 | Of the wheel. |
30:34 | And if we view the part from the front here, we could do that based on, you know, the radial dimension of the tyre. |
30:43 | But I'm just going to drag that into a position that looks like it'd be about the loaded radius of the tyre. |
30:49 | And then same thing here, just from that point. |
30:54 | And we'll drag that down to the ground. |
30:58 | And I'll make that line collinear with that. |
31:01 | So, that's our kingpin axis there through the, or front view kingpin inclination there from through the top upper ball joint and the lower ball joint. |
31:17 | And then that comes down to the bottom there. |
31:20 | So, I know that this distance here, if I make these two horizontal and about at level with the contact patch, this distance here is our scrub radius. |
31:31 | Which in this case is 30 millimetres, positive 30 mil scrub radius, which actually isn't that great a thing for a front wheel drive car. |
31:39 | But we'll talk about that a little bit more soon. |
31:43 | And then the kingpin inclination would be the angle of this here to vertical. |
31:55 | So, 7.5 degrees on the kingpin inclination there as well, which is actually pretty reasonable. |
32:02 | And that's pretty close to standard, I think, for a CRX. |
32:08 | So, that's just an idea of how we can dig a little bit deeper with some sketches and just taking some more measurements and referencing this geometry we've set up to determine some of these things. |
32:20 | Of course, then we'd probably look at the side view here or from the front view as well. |
32:25 | We could draw some lines through the lower control arm, in the upper control arms, find the instant centres and the roll centres, just how this diagram here was, following the same method we just did. |
32:40 | And then we could also jump onto a sketch on the side view here. |
32:45 | And from that side sketch, we could find the caster, which is basically the side view equivalent of the kingpin inclination that we just looked at. |
32:54 | There, we could find the mechanical trail, which is again like the side view equivalent of the scrub radius in some ways. |
33:03 | We could also look at anti-dive. |
33:06 | And if we had the rear suspension in there as well, we could look at the roll axis height and how that's set up as well. |
33:14 | So, lots of stuff we can look into just from our CAD software. |
33:22 | And of course, things like the kingpin inclination and the cast angle, they're really the side and front view perspectives of looking at the steering axis inclination, which is of course a three-dimensional thing. |
33:38 | So, the kingpin inclination and the cast angle really need to be considered together saying, oh, 7.5 is a good value for my KPI. |
33:47 | And then if your caster is really, really low or really, really high, the effects of that can kind of not work that well together. |
33:57 | So, typically, if we have a higher KPI, I would also want a higher caster to kind of counteract some of the bad effects of it. |
34:06 | But it all depends on the car and the application and so on. |
34:09 | So, I won't dive too deep into that. |
34:12 | The other way that we can do things is take some measurements straight out of this. |
34:18 | So, essentially, we can set up reference planes I typically like to do one. |
34:25 | For example, if we create an offset plane from the horizontal plane here, drag this down. |
34:37 | Again, there is more accurate ways of doing this, but drag that down to kind of level with the bottom of the tires. |
34:44 | Then we can very quickly take measurements from the center of ball joints. |
34:54 | So, if I show snap points here when I'm taking these measurements, that works quite well. |
35:04 | And oh, God, sorry, bear with me. |
35:09 | With those snap points, I should be able to then measure. |
35:15 | Yeah, if I select here, hold command, the center of that ball joint down to the ground, for example. |
35:22 | So, I can basically figure out where the ball joints are in 3D space. |
35:26 | So, I'd take a measurement down to the ground, and then I basically do the same thing to the center plane here, and then also a forward and back plane as well, which would probably be straight down the center of the wheel. |
35:41 | So, we'd kind of on the wheel, basically, and then we can put all this information into another program. |
35:49 | So, I'll just show you a little example of that now. |
35:53 | If we jump over to this window and then look at this. |
35:58 | So, this is a suspension software, online browser-based suspension software called vSUSP. |
36:06 | And it's a free software, but the limitations of it are really that it is just a front view suspension geometry program. |
36:15 | So, the sketch that we just looked at and taking measurements down to the ground plane and then to the center plane, we can then bring these in and put them into these measurement boxes here and plot out our suspension in here. |
36:31 | And then this program essentially just has some features built into it where we can plot charts. |
36:39 | So, here, for example, I've got the, what is this chart? Looking at the right bump. |
36:47 | So, as the suspension moves for its travel, in this case, right tire tread center X location. |
36:58 | So, that's essentially the wheel base, I guess. |
37:00 | How the wheel base is changing as it's moving through bump there. |
37:05 | So, there's a lot of stuff that allows you to do. |
37:08 | Look at your camber curves as well, for example, and see how that changes. |
37:14 | It just does that all automatically and it's kind of set up to do that. |
37:17 | If you didn't want to use a program like this, which again is free, and I'll get Jayden to drop a link to this into the chat as well, if you want to check it out. |
37:28 | If you didn't want to use a software like this, you could just drive it all from Fusion, for example. |
37:36 | And for example, drive this joint here and move it through steps and then take measurements and then build a spreadsheet out of that. |
37:46 | That would also be a possible way to do it directly off your model. |
37:50 | Again, if you took all these measurements, then you can also take it into a software package called Optimum G, which is a paid software package, but it allows you to do quite a lot more and look at the suspension in 3D, build your entire suspension geometry with your rear suspension as well and see how they all work together. |
38:14 | This also has a lot of tools for optimization to be able to kind of dial in what is a theoretically optimal setup, as well as some tools or extra modules that you can add on to understand from the tire forces what forces that you'd actually see in control arms and stuff like that, which is really helpful if you're doing more suspension design stuff like this. |
38:40 | Again, if you have any questions that are coming up during any of this, feel free to ask them in the chat. |
38:46 | And again, I'll do my best to answer them at the end. |
38:49 | Cool. |
38:51 | So, we'll just move towards wrapping up. |
38:56 | One question would be, if you're pretty new to this, what do you actually do with all this information it's all very well being able to know that your kingpin inclination is 7.5 degrees at ride height, for example, but what does that actually mean? And this isn't the focus of the webinar and it's definitely an area that takes a lot more knowledge and it's going to be an area as well that it's different for every single car, different tires, different setup and different application. |
39:28 | So, what you actually want in terms of these numbers is not really set in stone all the time. |
39:36 | There are some general values for certain things that can be applied. |
39:40 | For example, we typically want to keep the scrub radius for most road racing cars or street cars under 40 millimeters, positive or negative. |
39:53 | And for front wheel drive cars, it will typically be a negative scrub radius. |
39:59 | As we can see, we had a positive scrub radius for the CRX here, which isn't the best thing. |
40:05 | So, maybe some changes are required to just counteract that. |
40:11 | Other things that you can kind of general rules would be the roll center height, which is typically about 15 to 30% of the center of gravity height. |
40:23 | And again, if we jump back over to this article in Suspension Secrets here and scroll down a little bit, they have some stuff as well around the roll center, front and rear, and then the roll axis as well coming through that. |
40:42 | So, some good information there about how that changes and how different layout cars like a Civic Type R that's front engine or a 911 that's rear engine might have a lower, yeah, rear roll center might be lower or an all-wheel drive car might be a little bit more even, things like that. |
41:03 | The last one I just wanted to mention on those kind of general rules would be something like the anti-dive, for example, a typical value for a high downforce, like GT3 race car would be in the vicinity of maybe 30% anti-dive, whereas something like a rally car or a road car would be lower, rally car typically lower, less than 15%, for example, to allow the suspension to follow the undulations in the rough surface on the brakes. |
41:39 | So, there's a lot of material out there for learning. |
41:42 | And I did just wanna wrap up by mentioning the Suspension Tuning and Optimization course. |
41:49 | HPA has, I did this course before joining HPA and it's actually one of my favorites. |
41:55 | If you're into all the suspension stuff, really recommend checking it out. |
41:59 | There's a lot of kind of information in here about what we've been talking about. |
42:03 | So, you'd actually be able to use your CAD skills, design your suspension setup and then understand a little bit more about what it all means, how to analyze it properly and then also how to optimize it and tune it for your setup. |
42:17 | Before we wrap up, there's one more model I wanna show you. |
42:22 | So, this here, it's going to look a little bit funny at the moment, is a work in progress, something that I've been working on with Brandon, our mechanic. |
42:32 | And this is his KP61 Toyota Starlet rear wheel drive rally car. |
42:39 | And if I just hide the scan there, we're basically trying to do a new McPherson strut setup on the front using Sylvia S14 knuckle in this case. |
42:55 | So, we're designing a cross member, lower control arm and so on. |
43:00 | And we're looking to use one of the universal Bilstein 50 millimeter, I think they are motorsport dampers. |
43:11 | So, at the moment, we're just kind of working through, I've got a little bit of a model here set up, there's four different offerings, sorry. |
43:22 | So, these are the Bilstein shock absorbers. |
43:25 | And then they have these four different, four different lengths that you can choose from here and all different valving as well. |
43:34 | And basically I've used this technical drawing here with these to model the different lengths here. |
43:41 | And then I've set this up with a measurement at ride height to basically figure out which one of the options in terms of travel is going to work best for this car to maximize the amount of travel we have at the ride height that we're wanting to run the car at. |
44:00 | But again, then it'll all play back into this model here and we're doing a lot of other stuff in here trying to figure out where the roll center should be. |
44:11 | And again, if I just open some stuff here, for example, this side view sketch, we have some stuff to look at the ride height is kind of shown by this value and then the anti-dive percentage there as well. |
44:27 | That's what we're figuring out and just looking at all these different values. |
44:31 | We've got the cast angle there quite high at 8.6. |
44:36 | And then at the same time, I'm looking at the front view here, looking at the Kingpin inclination, which is also high to kind of go along with that high cast angle to counteract that when it comes to the actual contact patch in the camber as the suspension is turned or the steering is turned rather. |
45:00 | So, yeah, lots going on here, power steering, extended wheel base, different suspension components, all trying to make this work. |
45:09 | And if you are interested in, oh, just exit out of that, come down the bottom here, pull that through. |
45:25 | Sam and Brandon have also been working on a pretty crazy kind of body work for the car. |
45:30 | I don't know if the rest of the car in here, but you can get an idea. |
45:33 | It's kind of group B inspired, a pretty serious rally car. |
45:38 | So, quite a cool project that we're working on, you know, in personal time and it's slowly ticking away in the background. |
45:45 | One day it'll be pretty awesome. |
45:47 | So, a little bit of insight into how we're using a model like this in the real world to do, you know, some work with different offerings and find out what's going to work best rather than just buying what you think and then figuring out it doesn't work after you've spent the money. |
46:06 | Cool. |
46:06 | All right. |
46:07 | I'll wrap it up there and I'll just see if we've got any questions. |
46:11 | No questions by the looks of things. |
46:13 | So, we'll leave it there. |
46:15 | Hopefully that's given you some insight into suspension design work and assemblies in CAD. |
46:23 | And yeah, thanks for coming and we'll see you next week. |
