The Sleds

The first "sled" at Cal Poly was a flat skid that was pulled at the very first Cal Poly Tractor Pull. This steel skid used people as weights. People would line up on the edge of the track, and as the tractor went by, they would jump onto the skid. This made the skid harder to pull as more people would climb on.

When the tractors started showing up with high performance automotive engines, people did not want to ride on the skid anymore. Students of the Agricultural Engineering Department designed and built a weight transfer machine to replace the skid. This weight transfer machine became known as the "Cal Poly Tractor Pull Sled" and was the first of its kind on the West Coast. It consisted of a semi trailer frame, a moving weight box, and a skid pan. As the sled was pulled down the track, the weight box would move from the back of the frame to the front via a system of chain drives and gearboxes. As the weight box move forward, the majority of the sled's weight would be transferred from the rolling tires to the skid pan. This caused the same effect as the people climbing onto the skid. As the sport evolved, the sled was modified several times to meet the needs of the higher-powered tractors. The Cal Poly Tractor Pull Sled has been at events all over the Western States and even Hawaii.

The "Cal Poly Tractor Pull Sled" at the 1996 Open House Tractor Pull

The "End of the Track" for the "Cal Poly Tractor Pull Sled" at the 1996 Pull

In the following years, Gary Weisenberger, a faculty member of the BioResource and Agricultural Engineering Department, designed and built a smaller sled to be pulled by the new mini-modified tractors. Weisenberger and another Cal Poly Mechanized Agriculture graduate, Ben Tulloch, designed and built another mid sized sled to be pulled by four wheel drive trucks. This sled, "Truckers Trouble" was used at hundreds of truck pulls in California, Nevada, Oregon and Arizona.
 
When the mini-modified tractors started using blown hemi engines, the original mini-sled was parked in the bone yard and a new Mini-Sled was designed and built by Weisenberger. This sled "Tuff Draggin" was pulled all over the Western States and Hawaii. The "Tuff Draggin" Mini-Sled was also shipped to Tokyo with several mini modified tractors to campaign tractor pulling in Japan.

The "Tuff Draggin" Mini-Sled at the '97 Cal Poly Tractor Pull

Eventually, the Cal Poly Tractor Pull Sled became outdated and it was impractical to modify it anymore. In 1997, Weisenberger and other faculty and students of the BioResource and Agricultural Engineering Department completed a new sled that was self propelled. This sled enhanced the sport by incorporating a pan unloading system. This system holds the shear bar on the back of the pan off of the ground until the sled is pulled past a preset distance. This allows the tractors to get a smoother start on poor tracks and build up a higher speed. It also makes it easier for a good driver with less power to compete against a higher-powered tractor. Being self propelled also helped the show by shortening the interval between pulls and making more pulling length in tight tracks. This sled is powered by a Chrysler 440 and incorporates four transmissions and two 2-speed differentials. This power train system provides Weisenberger with 208 gears for the weight transfer rate, making the sled adaptable to any track condition and length. This sled replaced the original Cal Poly Tractor Pull Sled and the "Trucker's Trouble" 4 wheel drive sled.

The new sled at its maiden pull during the 1997 Cal Poly Tractor Pull

The new sled at its second pull in Wasco, California

With the effectiveness of the pan unloading system and the self propulsion system on the new sled, Weisenberger decided to renovate the "Tuff Draggin" Mini Sled. He provided the sled as a project for Dr. Mark Zohns' senior level Equipment Design class. Two groups of students worked on the sled. Andy Holtz, Mark Hawkins, and Mark Unruh, designed and built a pan unloading system and a steering system for the sled. Matt Yore, Matt McCloskey, Rodney Gordon, and Andy Welch designed and built a hydrostatic drive system to self propel the sled. This system used a four cylinder John Deere diesel engine, a variable displacement-pressure compensated hydraulic pump, a geroler motor, and a 3-speed transmission to power the existing differential.

Driving the "Tuff Draggin" Sled for the first time.

The new Self propelled sled and the renovated "Tuff Draggin" mini sled have been used at dozens of events the past few years, and have been a big part of bringing the sport back on the West Coast.
 
Just remember: "The sled always wins" - Gary (Mr. Tractor Pull) Weisenberger

A California sunset over the "Tuff Draggin" Mini Sled on the trip back to San Luis Obispo.

Down the Tehachapi Pass with the new self-propelled sled.

Gary is the only man in the world who knows how to drive his sled.  Check out everything he has to do to drive it back from a pass down the track.