Danny Thompson's LSR diary: Controlled slip

Danny Thompson's LSR diary: Controlled slip


Danny Thompson's LSR diary: Controlled slip


I have so much left to learn. That, more than anything, is what rebuilding the Challenger II has taught me. We’re in the middle of finalizing the clutch package, and the whole process has proven to be much more complicated and time consuming than expected. Our setup is primarily a modified version of what you’d find on a Top Fuel dragster. We make a lot of power, and run fuel, so we wanted equipment with proven resiliency under those conditions.

The components themselves are a mix of different materials that you wouldn’t expect to find in the same package. Elements are made from titanium, stainless steel, 4340, 4130, cast iron, and sintered metal (friction material). Bob Brooks of AFT is fabricating the parts. He used to run the piston department of Mickey Thompson Enterprises for my dad back in the ’60s, so it’s a real pleasure to have him working with us on this project.

Getting the clutch package to perform effectively on the salt is a tricky process. Our tires are only 4 inches wide, and each one will be allocated almost 1000hp. Getting all of that power to the ground without slipping the tires requires delicate tuning, and probably won’t be perfected until we actually get to Bonneville and tinker with the settings on the salt.

Here’s how it works: As soon as the car moves away from the push truck, I’ll release the clutch. This will happen at a relatively slow speed. Anything over 5mph should be enough. As engine rpm increases, the clutch will slowly lock up automatically. I won’t be moving it in and out during the run. This means, in simplified terms, that the clutch will mechanically perform a controlled slip at slow speeds.

This unusual procedure is important for two reasons. First, our engines are dry blocks, so if I back off the throttle to counter wheelspin, the engines will not get enough fuel to cool themselves. Second, we need to make as much speed as possible on the bottom end of the course, so if we’re goosing back and forth or not making traction, I’ll be loosing irreplaceable time.

Work continues! Thanks for following along. You can always find more information about our project at thompsonlsr.com <http://thompsonlsr.com> . See you next week.


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