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MAX Update No. 95: Drawing a Blank and Drafting With DraftSight

8/23/2012 10:48:05 AM

Tags: MAX, 100 mpg, fuel economy, fabrication, CAD, Jack McCornack

I’m done with drawings. I don’t intend to have any more drawings in my instructions, or on my web site, or in this blog for that matter.

If you go through the Kinetic Vehicles web site you’ll find lots of computer drawings for how to make this and that, but I’m replacing them with DraftSight .dwg documents, which are two dimensional CAD (Computer Aided Design) files and a whole lot more useful than drawings. If you keep reading, I’ll tell you why, and I’m going to use MAX’s engine mounts as an example.


It’s dark and crowded under MAX’s hood, so I’m using a water bottle as an engine substitute and a 2x4 as a chassis substitute. The upper half of the engine mount bolts to the engine, the lower half bolts (or welds if you prefer) to the chassis, and a rubber damper fits between them. It’s a somewhat complex bit of steel origami, so I want to give precise instructions on how to make your own—a description isn’t going to cut it, and a drawing is going to leave you with a lot of work, so my new standard is .dwg documents generated by DraftSight.

DraftSight is published by Dassault Systèmes, and in interest of full disclosure I must admit that Dassault gave me free copies of DraftSight for all my computers, both Mac and PC, and…

Wait a minute. They’ll give you a copy of DraftSight for free too. They give away DraftSight to anybody that wants it. It’s a professional grade 2D CAD program, it’s available for Windows, Mac and Linux operating systems, it’s not a trial copy, it’s not going to expire, it doesn’t want to see your student ID; it’s world class software and it’s absolutely free.

I’ve resisted using 2D CAD documents on my web site because, previous to DraftSight, it cost you a grand to do anything useful with them. And why is Dassault Systèmes giving away a program they could be selling for a thousand bucks and nobody’d flinch? For the same reason tuna fishers throw chum in the water—if you like DraftSight and turn pro, you’re likely to buy Dassault’s SolidWorks instead of Some Other Brand. Not only that, but it gets bloggers (me, for example) raving about their products, and various information providers (me, for example) putting their files on our web sites and saying “To open, download DraftSight,” which increases awareness of their products. Lastly, the software works so well that you can’t help thinking, “Dang, these people sure are good at this CAD stuff,” every time you use it. By the time you’re ready for 3D CAD software, you’re already a Dassault Systèmes fan.

So I think it’s good marketing. Now let’s go take advantage of it.


Here’s a screen shot of the .dwg file for one side of the lower half of MAX’s right engine mount. This part has a number of features you may not care for, such as alignment nubbins on the upper corners and a fold line on the lower mounting tab. In Ye Olde Dayes, I’d have supplied this drawing with the dimensions I think are important, but by giving you the CAD document…


…you can show the dimensions that you find important, and you can modify the part to fit your needs. You could lay out the dimensions (or print out the part full size and trace it) onto steel sheet and cut it out yourself, or you could send the .dwg document (either the original or one you’ve modified) to a CAM (Computer Aided Manufacturing) fabrication shop and have them cut out with laser, water jet, plasma cutter or mill.

Why would you want to modify the part? Here’s a close up of a lower mount after it’s folded together.


Maybe you car has a slightly different chassis than MAX; maybe your frame tubes are a bit farther apart than mine, and if so you’d want to move that hook on the bottom a bit to fit. Or maybe instead of using my nubbin-in-hole alignment system, you just want to align the parts by hand and tack them together; that’s how I’d do it if I were just making one and cutting the parts by hand—it would make the individual parts a whole lot simpler and the assembly only slightly more complicated, and the easy way to make the change is with CAD.

I’m not going to tell you how to use DraftSight (tutorials abound and it’s beyond the scope of this blog) but I’ll tell you it’s worth using. If cost and complexity have kept you from CAD, well, if you’re capable of building a car and you have the skills and equipment you need to read this blog, then you have sufficient talent and hardware to take the CAD plunge. And with DraftSight, you also have the budget.

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