Getting back to top-level engineering

You may be wondering why I've prominently displayed Lady Gaga here at the top center of the entry. Turns out, if you use the 'Pulse' reader app on your Smartphone (from the folks at Alphonso Labs), the preview icon for new Blogspot entries is whatever the first image is in the article. I wanted my latest preview to be something ridiculous (yes, I am easily amused). By the way, if you don't use Pulse - you should!

Much of the work I've posted up here has been "nuts and bolts" level - CAD and such. Generally this is opposite the design philosophy I preach of starting high-level and working down to specifics (up front engineering). At the same time, the CAD work has been done parametric enough so that I can go in and change my suspension points etc and have the model rebuild more or less painlessly. Anyway, it's to the point where I should back off and do some top-level design work.

I'm gonna go ahead and put on my musical selection for tonight before we get going.

Recommended reading material -this thread at FSAE.com, particularly Geoff's ('Big Bird') lengthy post November 30th, and the section 'Analysis Process.' Some really good takeaway points, namely-

1. If you start simple with analysis and predictive work up front, you can get some real good design insight before anything is set in stone.
2. Even college students can cobble together meaningful vehicle simulation programs over a couple days, in Excel, including beer breaks. 
3. It's critically important to identify the relative importance of various performance attributes. You do not have infinite time or resources in your design cycle, ever. I've seen a number of engineers (mostly in college) get so sucked into minutiae that they completely lose sight of the big picture.
   
   "But if we do that, we're going to be giving up some handling!"
   "Yeah, and if we don't, the driver won't fit."

I've thought about it, and I might try my hand at putting together a rudimentary lap sim myself. Time investment may only be a couple nights worth of work. If it doesn't pan out from there, no big loss. If it does, I can always add in complexity. The great thing is everything builds on itself. No wasted work.

As an aside, it's amusing to me that for as aroused as FSAE students get for designing around kinematics, body motion is really a few steps up the ladder in model development. More fundamental things like tire cornering stiffness are sometimes overlooked. I wonder if I polled a number of kids the next time I'm at MIS, how many would be familiar with VSAL and how it defines camber rates, while not being totally familiar with tire properties.

We've established that we can simplify and build on vehicle models, but same holds true for track models - maybe even more so. Can probably simplify the hell out of a track model!

I can take some pretty damn big liberties in a track model - the lengths of straights, corner radii, etc. Why? Because I don't care what my exact lap time around Road America is going to be.

For one, you're never going to be able to predict it, within tenths anyway. Track condition, ambient conditions... enough to swing grip, downforce, engine power enough such that the time it spits out won't quite be right. Parameter identification based on previous race results is one thing - future is prediction.

Second, I'm not designing a chassis for Road America. I'm designing a car for Nelson's Ledges, Mid Ohio, and Road America and whatever else. So long as I have track models that are roughly representative of a road course, I think that's good enough for the majority or entirety of up front engineering.

Some interesting work ahead.