Racing Wheel Center Lightening (Finite element analysis /CNC Milling) jakeru's #12

Hey guys -

Thought you might appreciate an old racing project of mine. With the help of a University of Washington Formula SAE team member, I modeled the wheel centers of my personal racecar on the computer in 3 dimensions, and from the model calculated and mapped the material stress and the strain (deflection) experienced during anticipated racing conditions.

Here is what the original wheel centers looked like, both in actual life (forged aluminum), and stress mapped on the computer. The technique on the computer used to calculate the material stress is called "finite element analysis", and is pretty amazing:
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I also modeled and tested a hypothetical series of lightened/modified wheel centers on the computer, paying attention to the amount of anticipated lightening achieved, while making sure the peak material stress was kept in a safe area. After testing and refining at least four models on the computer, I arrived at one that had the best combination of a good amount of weight reduction, with also an acceptable amount of peak material stress, and also acceptable overall strain / deflection.
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We then carried out implementing the selected modifications on the real wheel centers, by using a Bridgeport Computer Controlled Milling Machine. (I just love the University of Washington's Mechanical Engineering machine shop!)
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Here is what the completed wheel centers looked like after lightening, shown by themselves, and after reassembly with the rim pieces and tires.
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The weight of the center was reduced from a measured 1.21KG all the way down to .31 KG! Weight in wheels is in a category called "rotating, unsprung mass" which is about the worst category of weight to have anywhere on a performance/race car.

Since doing this (and also being successful racing with them :P), other competitors have copied the design (as racers always do...), so I guess you could say my work set a kind of trend.

I eventually got the wheel centers black anodized, for fun.
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This was probably one of my most fun projects (certainly at least before getting my TIG welding setup.) :cool:

What type of race car do you have? With 4 lug wheels is it some type of import?

You guessed right. :) It's an older VW Rabbit.