While Rusty was cutting and welding the Tank frame, Jason was busy fabricating his first prototype steering configuration for the Tank rolling chassis. His set-up was similar to go-kart style steering, using a custom assembly of M20 bolts (cut and drilled for axles), water-jetted steering arms, and custom turned kingping tubes:

David running the waterjet at DieCraft Engineering, one of our team sponsors

After having prototyped the steering assemblies, and verifying our component layout, Jason entered the next phase of his design: optimization. He also used COSMOS to weight-save his steering configurations.

After having fabricated the first set of steering components, Jason suggested and we all agreed that a change in the design would offer a number of design improvements. Rather than having spindle brackets (the c-channel) welded to the frame, and the axle and control arms welded to the kingpin tube, he decided to weld the kingpin tube to the frame, and attach the axle to to the spindle bracket. I know, sounds confusing, but the pictures should explain.

Using COSMOS, Jason analyzed an aluminum and steel versions of his newest design. He found that by using 1/8" steel plate and small gussets, the new configuration could be within 0.25lbs of its aluminum counterpart--which will be much easier to weld and manufacture than the aluminum version. The following are pictures of the latest configuration with bearing loads and braking loads applied to the brake brackets.

Jason is currently underway making the newest steering design a reality.

While we all have much love for "The Tank," we knew that we could save a good bit of weight on the frame through optimization. To accomplish this we turned to the COSMOS analysis software inside the SolidWorks suite. It took a couple of days to learn, but it wasn't long before Rusty was running multiple loading conditions on various frame configurations, cutting weight every time.

The two main loading scenarios he has been analyzing are the static 250lb roll bar load (per competition rules), and a composite load of his distributed weight and hitting a 0.5" bump on one front tire. We have made loading assumptions around this scenario as our "worst case".

The following are pictures showing the latest frame iteration, which saves 9lbs--approximately a 30% reduction in total weight! This leaves the frame at a predicted 22lbs. This was achieved primarily by experimenting with various combinations of tube size and wall thickness.

We just picked up the steel to make the new frame and fabrication will be under way shortly.

Rusty had come to his latest frame configuration in late November, and we were all eager to see it come alive. We wanted to go ahead and cut and weld the frame for prototype purposes. Jason had designed a first-run steering configuration, and we wanted something that Rusty could actually sit in and steer. We also planned to use this prototype frame for design and construction of the first body trial.

We laid out the frame and canopy full-scale with our first set of dimensions. This way, we could get a realistic feel for how components would actually stack up before we started welding. After some minor adjustments and a few updated drawings, we were ready to start fabrication on the prototype frame.

This first rolling chassis came to be known as "The Tank" in that it was not optimized for weight, but built for dimensional accuracy and component layout. After making some tricky cuts and notching lots of tubes, the tank came together quite well:

A couple "jump on the roll bar" tests and we were confident the tank was plenty robust. Ok, so it was really more scientific than that...but you get the point. The tank continues to serve as our primary guinea pig for dry-running our components.

It's time to update our blog! Late November, December, and early January have been extremely busy for us with design, prototype fabrication, and the holidays. We are basically in a stage of part optimization; primarily for weightsaving purposes. The following blogs will detail progress being made in key areas.