Racesource Inc. (Tomball, TX), home of Monster trucks and Monster truck manufactured parts, is owned by master builder Paul Huffaker and wife, Tina. Paul drives Grave Digger XVI, which is well known in Monster trucks entertainment.

Flying Grave Digger

Huffaker is a bit of a daredevil. When he made his first jump over a school bus with Grave Digger, it was all new to him. He did some quick mental calculations for his ramp speed and took off. If he crashed, the crowd probably would have loved it, he believes. But he successfully made the jump. Now his stunts include controlled crashes, like launching Grave Digger 35 feet into the air and landing without being damaged.
These jaw-dropping, crowd-pleasing stunts give you a little insight into what Monster trucks must endure to compete for the audience’s cheers. The more extreme the stunts, the greater the crowd’s admiration and attention. Sure, some trucks don’t survive without being damaged, but many do.

What You See Ain’t What You Get

One of the first Monster trucks was Bigfoot, and it is still pleasing crowds today. Bigfoot was Huffaker’s inspiration. In the beginning, these trucks were modified pickup trucks. But to do spectacular stunts, they had to change in big ways. Originally they were built like any other truck— sheet metal body and steel frame construction—but with heavy modifications. Now, although they have a body that you might see on the street and have an engine and transmission, these trucks are vastly different from any pickup. Now they have a race car heritage, often harnessing well more than 1,500 horsepower under the body.

Today, Monsters are hand-constructed using tubular frames and CNC-machined components that can include off-the-shelf parts specifically built for Monster trucks and one-of-a-kind components. Tires are unique. At 5½ feet tall, they add a bit of a cushion when crushing cars or jumping a bus.

Tough Trucks, Tough-to-Machine Parts

But without the help from Mastercam CAD/CAM software many of these parts would be difficult or impossible to make.

Huffaker says he started racing Monster trucks about 26 years ago. Before this, he was in the four-wheel-drive vehicle business, and built his first Monster truck as a way to promote his company. He says, “After three months on the circuit running the truck, I got out of the four-wheel-drive business, and I’ve been living the dream ever since, racing Monster trucks and building parts and components for them.”

To keep demanding fans smiling at the Monster truck shows, seven Grave Diggers work the entertainment circuit, allowing shows across the U.S. to have a Grave Digger truck running in them. Live Nation Motor Sports owns the Grave Digger properties and any marketing that goes along with it.

Huffaker runs Grave Digger XVI and Blacksmith, which both run on the Monster Jam circuit. He says there are at least a couple of hundred Monster trucks in the industry today, and he builds parts for many of them.

Along with being a radical driver, Huffaker is a self-taught engineer, machinist, and metal fabricator.

“When I started, I pretty much taught myself how to weld and bought machines to be able to do the work that I needed to do. I never did like depending on other people’s schedules. I might need to fix a part at 9:00 p.m., so I bought lathes and mills over the years to fill my needs.

“Having a background as a machinist using manual machines I believe has helped me in my CNC portion of the work. I have a good grasp of how to attack a problem, how to cut it, how to do the job. There’s no other tool in my shop that gets used more than Mastercam software.”

Mastercam Helps Build Monsters

Huffaker uses the latest versions of Mastercam Mill and Lathe along with Art for some unique applications like surfacing that he normally doesn’t do.

Spindles are some of the parts that can be a tremendous challenge to program a toolpath for without Mastercam, Huffaker mentions.

“For a Monster truck, a wheel spindle is fairly complex. It has a spline on it, internal features, external features, threading, radiuses, just a multitude of machined areas,” he remarks. “It’s one part that Mastercam has helped me with, but then I have other assemblies that are more complex. Our steering system has a crank-driven hydraulic pump on it. I have the entire assembly drawn in Mastercam as it would stack up on the front of an engine block. Maintaining crankshaft centerline is crucial in this design, and the entire assembly must fit together perfectly. I take each individual component and design it in levels. Designing in levels while maintaining centerlines between the components makes manufacturing the parts and any related fixturing feasible in a way that I could not think of doing any other way.”

Huffaker uses four-axis mills, so complex parts can be a challenge to get all the tooling on the various axes to interact properly without any crashes and with the most productivity. He uses Mastercam’s Verify feature to make sure each part has the most efficient toolpath, and that it can be made without tool crashes.

“I can Verify in solids and see what I’m going to get as a finished product, whether it’s in Lathe or Mill. A great feature in Lathe is that I can draw a complete part end for end, flip it within the software, see the part being machined on one side, and then the software will flip the view on the screen, machine the other side, and I’m looking at a digital image of a finished part. Not just one end of it, but a complete part.”

With Huffaker building just about every part for a Monster truck, he has many standard parts that he sells. But very often he builds one-of-a-kind components where Mastercam quickly helps him produce the part. Mastercam’s Verify feature also allows him to make sure the part can even be made.

He says: “A lot of times when I first make a toolpath for a part, Mastercam will tell me that I have a collision. When I use Verify in solids, and I see a red mark through the part or a cut through the part, it’s going to be there when I make it. I need to figure out what I did wrong. Either a rapid move or a clearance move isn’t right.”

Surfacing Feature

Huffaker uses Mastercam’s Surfacing feature occasionally. Most of his products do not require a lot of complex surfacing. “I have done some surfacing in Mastercam, and I wouldn’t know how you would accomplish it any other way. I have friends that are old school programmers (relying on manually writing G-code), and I don’t think they could even attempt to tackle a surfacing job without Mastercam software,” he says.

Huffaker notes that Mastercam’s Art software can take artwork and wrap it around a tube, and then create a toolpath to surface the artwork on the tube’s surface.

He says, “It creates a toolpath and follows every 3D surface. It’s incredible, a very powerful software. Another feature that Mastercam has that’s really great is that I can take a picture and import it into Mastercam Art. Then by selecting colors or tones, I can put a toolpath to that picture. It will bring out the highlights. I can tweak it, and then put a surface to it. It’s incredible how Mastercam managed to do that.”

Useful in Design Work

“I found it to be a really great tool, because when I’m designing a part, I’m able to draw it and basically render it in 3D using Mastercam. At that point, I can determine if any changes need to be made without building the part.

“I do almost all of my design work within Mastercam, too. I’ll use AutoCAD extensively for other non-machining work. If I’m going to do a machined part, it doesn’t make any sense for me to draw it in AutoCAD. I’d have to import it into Mastercam to build the part. The Mastercam design portion is awesome. To draw in Mastercam is very easy. You don’t have overlapping entities and problems that a lot of times will be associated with importing a file from AutoCAD. There are great features within Mastercam where I can import a DXF file from AutoCAD, select it, find overlaps, and change them.”

Do-It-Yourself Monsters

Theoretically, if a person had a machine shop and Mastercam software, they could build their own Monster truck. But this would entail a lot of time and a large learning curve. By skipping this step, about $175,000 will buy a Monster truck without the engine or body, says Huffaker. An engine can easily cost $30,000 or more.

Grave Digger uses an alcohol fueled, supercharged, 540 cubic inch 1600-horsepower engine built using a Chevrolet big block. Huffaker does all the maintenance on them, but has another company build them.

“The popularity of the Grave Digger truck is second to none,” he says. “Go into any large department store, and you’re going to find Grave Digger toys all over the shelves. If you were to ask any kid on the street, ‘What’s your favorite monster truck?’ I’m going to guess nine out of 10 times they would say Grave Digger.”

Whether Grave Digger is flying over cars or crushing them, Huffaker says Mastercam is along for the ride in the parts that are built for it. 

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