3D Modeling & CAD for Motorsport: Step 1 - Planning
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Step 1 - Planning
08.26
| 00:00 | - In this worked example, we're going to go through the design and construction process of a motorsport style battery box. |
| 00:07 | This is going to give you a real world look at creating a sheet metal part using CAD and if you follow along, you'll end up with a functional part you can tailor to use on your own vehicle. |
| 00:18 | To be clear, this section of the course isn't about teaching you anything new. |
| 00:23 | These examples are all about seeing what you've already learned put into action. |
| 00:27 | So if anything you see here has you scratching your head, it's best to stop, go back to the relevant course module and give it another watch to get a better understanding before continuing on with the worked example. |
| 00:41 | So let's get started. |
| 00:44 | The design process for every good product starts with the definition of a problem and in our case, it's the need to secure the battery inside the vehicle, prevent it from moving and protect it from external elements. |
| 00:56 | For this worked example, we'll be creating a box to secure an AGM motorsport style battery in the passenger side footwell of a Honda City racecar. |
| 01:06 | This design won't be suitable for a wet cell lead acid battery because for motorsport purposes, these need to be in a completely sealed box when inside the vehicle. |
| 01:17 | To make sure we have a good understanding of the problem we're trying to solve, let's get the specific requirements of the battery box clarified. |
| 01:25 | First, the box needs to be strong enough to hold the battery without any risk of it breaking under heavy impact. |
| 01:32 | The box should also be stiff enough so that it doesn't vibrate or move excessively and isn't going to fatigue or crack from vibration. |
| 01:42 | As with most things we design for in motorsport, we also want it to be lightweight and ideally low profile. |
| 01:49 | Lastly, it needs to allow for easy access to the terminals and of course, prevent the terminals from any accidental shorting. |
| 01:57 | With all of these requirements, the most suitable choice of material for the part will be 2 mm thick aluminium sheet metal because it's light, strong, cheap and easy to work with. |
| 02:08 | We also don't need to paint it for any corrosion resistance, especially since it'll be inside a fully enclosed vehicle. |
| 02:16 | To keep things simple, we'll use bends to stiffen the part and add structure with the aim of creating a design that doesn't require any welding. |
| 02:25 | The manufacturing process could involve laser or water jet cutting but we'll use water jet cutting so we can etch a logo into the top. |
| 02:34 | Followed by bending the part using a sheet metal folder. |
| 02:37 | In the case of the Honda City, the battery box will be secured with M6 hardware into existing rivnuts in the floor pan. |
| 02:45 | These were from a previous battery bracket that we've decided wasn't ideal and needed to be replaced. |
| 02:51 | The battery will also lay on its side to get the centre of gravity low. |
| 02:56 | Although this is possible for our dry cell AGM motorsport style battery, as well as also with lithium ion batteries, it's not something that can be done with a standard wet cell lead acid battery. |
| 03:08 | If you're designing for your own application, you'll of course need to tailor the design to suit your specific battery and mounting location. |
| 03:17 | Let's get started on the practical work by first taking down some measurements of where we plan to mount the battery box and the fixture points if they already exist. |
| 03:25 | Or where we plan on making them if they don't. |
| 03:29 | You might not have existing mounting points for your design and plan to make them to suit the final parts so this step might not be needed but it's still good to have a clear idea of where and how you might want to mount everything. |
| 03:42 | In the Honda City's case, the mounting points are laid out in a rectangular shape but one is slightly offset. |
| 03:49 | The width is 227 mm between the centres and the height is 100 mm on the left and 86 mm on the right. |
| 03:59 | The other thing to note here is that the floor pan isn't flat between the riv nuts, even though the rivnuts are on the same plane. |
| 04:07 | This means that a flat sheet metal base won't work by itself so we'll need some 10 mm spacers underneath to clear the floor pan. |
| 04:15 | It's worth setting up these points in CAD so we can use them as references to design around. |
| 04:21 | This is as simple as creating a sketch on the top plane and then creating four circles, 6 mm in diameter and using our 227, 100 and 86 mm dimensions, along with some constraints to fully define our sketch. |
| 04:37 | It's also extremely helpful at this point to model the battery in our CAD software. |
| 04:43 | This doesn't need to be 100% accurate for every little detail but we want to get the key features that'll interface with our design represented. |
| 04:52 | Let's first create a new internal component for the battery and make sure it's activated before we start modelling. |
| 04:59 | For the Honda's battery, this starts with sketching a 179 mm x 76 mm centre point rectangle on the top plane, centred on the origin. |
| 05:10 | We'll use the fillet tool to give the corners a 3 mm radius. |
| 05:16 | We can then extrude this sketch by 150 mm to make the main case of the battery. |
| 05:21 | Modelling the top cover follows the same process. |
| 05:25 | Sketching a centre rectangle on the top face of the case, 175 x 75 mm and extruding it 18 mm upwards with the operation set to join. |
| 05:37 | Now let's cut a 40 mm x 25 mm rectangle from each of the front corners of the top face. |
| 05:45 | To model the terminals, we can sketch a 12 mm diameter circle on the top of each cut out. |
| 05:52 | 10 mm from the front edge of the top cover and spaced 153 mm apart, we then extrude these up 4 mm, joining them to the battery body. |
| 06:04 | Although unnecessary, we can use the fillet tool to round the edges of the battery model and even use quick key A to pull up the appearance window and change the model colours to match the real part. |
| 06:17 | Lastly, we want to reposition the battery since we modelled it in the upright position for clarity. |
| 06:23 | But in the car it'll be on its side centred between the fixture points. |
| 06:27 | Again, you might not need to do this for your application, but for the Honda City's case, we'll use the move tool to rotate the battery 90° onto its side. |
| 06:38 | It should already be centred horizontally between the mounting points since for our first sketch, our centre point rectangle was centred on the origin. |
| 06:47 | Now it's just a matter of using the translate function to move the battery to the right location which is with the bottom face 69 mm from the origin to match the previous position in the car. |
| 07:00 | For this design, we'll leave some clearance around the battery for a thin layer of foam which will help dampen vibrations and prevent any rattles. |
| 07:08 | The foam tape I plan on using is about 2 mm thick so I'm going to position the battery with the back face 4 mm above the top plane. |
| 07:18 | Allowing 2 mm for the thickness of the sheet metal box base and 2 mm for the foam. |
| 07:24 | This will make more sense once we begin modelling our battery box. |
| 07:29 | Once we're happy the battery is in the right place relative to the mounting points, it's best to ground the battery component so it can't be moved accidentally. |
| 07:38 | In some cases, it could be helpful to make a little cardboard cutout template to brainstorm or sketch something on paper but this is simple enough to use the fixing points and battery model we have in CAD to complete any conceptual design as we work. |
| 07:55 | We could also use a canvas or even a 3D scan of the mounting location as a reference but again, this is simple enough to get straight into modelling. |
| 08:03 | To summarise, we now have a good understanding of what we're trying to achieve and the material and manufacturing method we plan to use. |
| 08:11 | We also have a range of measurements of the interfacing components which we have already set up in CAD to use as references as we move onto the next stage of modelling our design. |
