The current state-of-the-art in monster truck suspensions, here on Bigfoot 15: The cantilever suspension was replaced by a four-link system and two very long, nitrogen-charged shocks per corner. The engine in Bigfoot 15 is a 572-inch Ford big-block based on the 460. Supercharged and slurping methanol, these engines produce around 1,500 hp and 1,450 lb-ft of torque.
4WOR: And then there was the other big monster-truck evolution-to the cantilever suspension.
BC: That's right. I wanted to go to the cantilever suspension because it changed the direction of the suspension [travel] from vertical to somewhat horizontal. Monster trucks are the only race vehicles that have a heavier unsprung weight than sprung weight. That's backward if you want your suspension to work correctly.
But the cantilever couldn't be done until we went with the tube chassis. With a tube chassis you can mount shocks way high on the chassis. I taught myself how to use the AutoCAD program, and designed the tube chassis and cantilever suspension for Bigfoot 8. It had gas shocks and 20 inches of travel, versus 6 to 7 with the leaf springs. What an amazing difference it made. We got thrown out of the TNT race series because we were just wiping the other guys out. They kicked us out for six months to let the other guys catch up.
Monster-truck competition had changed from just car crushes to racing before we changed the suspension. The racing was hard on the trucks and hard on the drivers. Guys were breaking vertebra because they were landing so hard.
Since then we've taken the cantilever suspensions off the trucks. Since they're just racing in pretty much a straight line, it's silly to have all that geometry on the truck. Right now the trucks are using a four-link with two long gas shocks per corner. They now have 30 to 34 inches of travel.
4WOR: Describe Bigfoot's powertrain.
BC: We use Ford 460-based blocks with new-style heads that are better than the old Hemi versions. The engines are supercharged and fuel-injected, and they use alcohol, which helps them run cooler while getting more power out of them. They're making a little over 1,500 hp and about 1,450 lb-ft of torque.
We're still using C6 transmissions, with manual shift bodies with good clutches in them. The transfer cases we're using were made specifically for pullers and monster trucks. They have a quick-change case, so you can change the ratios in five minutes. They're great for racing.
4WOR: How many Bigfoot trucks have there been over the years?
Bigfoot's cockpit is a well-used, no-frills environment. The myriad buttons and switches control everything from batteries and ignition to cooling fans and the rear-steer mechanism.
BC: We've built 17 Bigfoot trucks, plus Ms. Bigfoot [Ranger] and the Bigfoot Shuttle [Aerostar van]. Numbers 2, 3, 4, 6, and 7 are gone, bought by people who wanted to display them or build ride trucks. Bigfoot 9 is still in Brazil, Ms. Bigfoot and the Shuttle are gone. We're still running 1. We built two 10-footers for restaurants, which have since closed, so now they're in museums.
4WOR: What's next for you and Bigfoot 4x4 Inc.?
BC: I am working on a new chassis design right now. Our newest truck, Bigfoot 15, is over 12 years old. I want to come out with a new, stronger chassis, and move up to the next stage of monster trucks.
I am using AutoCAD and Finite Element Analysis (FEA) programs. The FEA program tells me how much stress and load is on each tube in the chassis as I put it through different configurations. An engineer friend of mine, Andy Whittle, told me how to use that program. He also said that more tube in a chassis does not always make it stronger, and that I need to look at chassis geometry to make the chassis stronger.
I'm not an engineer. I know just enough to do what I need to do. It's more headaches and more work, but I'm still having fun. Kramer does most of the R&D work, I get to work on computer designs. My two daughters, son, and son-in-law are all working here, which is great. They take a lot of the headaches.
Our final Bigfoot cover, Sept. '93, featured a see-through view of Bigfoot 11. These outtakes, shot by Petersen lensman Jim Brown, give us a behind-the-scenes view of the complexity of the set during the shoot and Bigfoot doing the Full Monty.