Hi GW,
Thanks for your comments. My thinking on the ball shoe is that it will will rotate like a small wheel presenting a uniform contact point that has no sharp edge to dig into the salt. The skid shoe as drawn could roll under and cause a sharp point contact at the end of the shaft that would dig into the salt and pivot the car destructively. I don't think the ball shoe would do that but I could be wrong. I guess it depends largely on how high the shoe is off the salt surface when fully extended. The closer to the surface the more the ball shoe would act like a wheel limiting vertical angular movement of the body. As with everything I present with these drawings I'm looking for critiques from members like you to help me think through things to hopefully arrive at practical solutions.
The DIF debate isn't over at this point. The recommendations to not use a DIF layout are warranted as I agree there will be less mechanical feedback to the driver over a DIM or DIR position. However, there was confirmation from Sparky that in his experience a yaw string works in providing useful feedback of the car's movement relative to cues the horizon presents at speed. So far no one has commented to the contrary.
Looking back at Cobb and Campbell's cars of the 30's and 40's they had no reported issues arising from their DIF chassis layouts. Nothing I could find said they used yaw strings to help with yaw feedback, but they apparently were able to overcome the lack of a seat of the pants feel that rearward driver positions are said to offer. Here, the smallest frontal area possible is needed to take full advantage of the powertrain design for record speeds. Based on the many different layouts we've covered so far the DIF position in V.5.5 is the best approach to maximize the hp to drag ratio numbers needed to hit a 600 mph goal. So, unless we receive factual information to the contrary of the usefulness of a yaw string indicator we will progress forward with the current DIF layout. Thanks... Terry