Monthly Archives: January 2013

Project Update – Wing Supports

Project Update – Wing Supports

The rear endplates on the Stohr are quite large, and with the wings actually being relatively small – only 6.5″ or so in span – there is a lot of unsupported area.

As such, without some stabilization, the rear wing assembly will vibrate back and forth. Originally, to stiffen it up, I made some support cables with some 3/32
sheathed cable, a few metal tabs, and some ferrules, to make a looped assembly. (see pictures in previous log entry)

This was very cost effective, but the loops in the cables tended to “pull” over time,
which meant I had to continually add tension to the assembly by adding or removing washers from the clevis pin down at the bottom. Additionally, heat from the exhaust
melted the cable sheathing, which ultimately looked quite bad.

To get around this problem, I decided to remake the cables using some better, swaged cables from aircraft spruce using their cables order form. Here is the recipe:

  • (2) 20.75″ long, 7×7 stainless, uncoated 3/32 cables
  • End #1: 3/32 eye end
  • End #2: 10-32 threaded stud (thread a clevis on to this to mount to the eyebolt)
  • Lower Mount: 10-32 Eye Bolts in the lower wing support
  • Upper Mount: 10-32 Easy-Adapt Clevis Rod-Ends

The total solution cost about $100, but the net result is much more adjustable, repeatable, and stable. I can still use AN washers under the clevis heads at both top and
bottom to make gross adjustments as necessary. Looks way better too.

What’s Cookin’ Good Lookin’?

Been a pretty quiet winter you say? Indeed! Things are starting to stir though, as the season opener at Texas’ Circuit of the Americas in Austin is now just over two months away.


I’ve been fortunate enough to get in touch with some folks in the FSAE program from my alma mater, Colorado State University, who have started a motorsports consulting business called Zebulon Motorsports Consulting, after the famous Zebulon Pike, of Pike’s Peak fame.  Around here in Colorado, the Pikes Peak International Hillclimb is a big deal.

They are interested in modeling the suspension of the Stohr, as well as modeling some of the aerodynamics in CFD. We’ll be taking a look at the wings to see if there’s opportunity for improvement there, and also making a rough-cut model of the bodywork to get some ideas of where the flow is going.

I’ve bought a copy of Bill Mitchell’s “WinGeo3” software as included with the Race Car Engineering book by Bill Rowley. I am hoping that by getting to see some of this stuff working, it will help my understanding of how to optimize the car’s setup, perhaps identify some issues, and hopefully ultimately go quicker.

Deja Vu

Once again, I’ve gotten in touch with Jesse Brittsan at Brittsan Racing to get a dry sump system configured for the car. The systems make additional horsepower on the dyno (5 according to George), and the whole engine runs cooler. This might enable me to remove one of the two oil coolers, reducing weight a bit, and reducing center of gravity height. Additionally, with some other changes around the back of the car, we’ll be able to come out just about net neutral, or perhaps even a slight loss of weight with this change.

Baby Steps

One additional small change. I got ahold of Scotty at Taylor Race Engineering, and used my certificate from the F1000 Pro Series to grab a set of lightened GKN CV joints. It will save about three pounds out of the axles. This setup is still FAR heavier than the tripod configuration, but should be 100% bulletproof. Hopefully for now, the lighter axles will not be necessary to get RIGHT down to that minimum weight.