4x4 Fun Buggy Chassis Build - 4Wheel & Off-Road Magazine

A bout 10 years ago I was paging through a copy of this very magazine and I saw one of the first tube-framed off-road rockbuggies, and I knew right then and there that someday I would need something like that. It made perfect sense: Have the body and the frame be one, and build them to maximize the execution of extreme trail riding. I wasn't looking for a competition motorsports rig-I wanted only a fun vehicle for off-road exploration, yet one capable enough to attempt everything from mud to dunes to gnarly rock trails. Now after years of planning, drawing, and taking notes about how my ultimate Fun Buggy would look, work, and perform, we finally started the buildup. In our last installment ("Fun Buggy Blueprints," Dec. '06), I went over the design and reviewed my drivetrain choices (small-block V-8, automatic overdrive transmission, aftermarket two-speed transfer case, front and rear steering 1-ton axles), and with excitement in the air I joined the guys from Poly Performance to actually measure, cut, notch, and weld the beginnings of this tube car.

This project is built with a mixture of lightweight sheetmetal structures made of chromoly with all the latest dimple dies, TIG-welding, and heat-treatment for strength as well as a simple cage design of twisted 1 3/4- and 1 1/2-inch DOM tubing. The design process we used had a complete computer aided design (CAD) blueprint showing us where most of the tubes go, and from there it was time to get started on the dirty work.

The work on this machine quickly taught me that fabrication is much harder than it looks. Of course, off-road buggies have been built for years, and that tube-buggy rockcrawler from 10 years ago only just started a rejuvenation of 4x4 owners bending tube and cutting and welding their own off-road creations. But with that growth in home fabrication comes a need to consider the intricacies of building your own vehicle from scratch, not to mention the many tools that make these projects easier. With the multiple forces of geometry involved in a vehicle that can really perform off road, it is important to build a safe and solid chassis.

Think it's too much for you? It may well be, but never let that lack of knowledge keep you from working towards your dream machine. Either work hard to hire a quality shop to build it for you, or get your hands on some tools and start learning on it in your own garage. You just may end up the next Jesse James of 4x4 fabrication.

From the drawings we showed you in the December issue ("Fun Buggy Blueprints," page 128), you can see the sheetmetal-fabricated lower substructure within which the transmission and transfer case reside. Additionally the link suspension also ties into this subframe. I rounded up a few sheets of thin 0.090 and 0.080 chromoly sheetmetal to build the substructure with from CalTime Metals. The chromoly is inherently stronger than mild steel, and can be heat-treated to make it very resistant to deformation and abuse. However care should be taken when welding chromoly and it is quite a bit more expensive than mild steel.
From the drawings we showed you in the December issue ("Fun Buggy Blueprints," page 128),
With the drawings of what each sheetmetal component needed to look like, we sent them out to be water-jet cut. Water-jet cutting is where super-high-pressure water is applied with a needle point in order to cut out shapes in metal with very precise results. Each side, end, and top piece was cut out along with various holes to lighten them up and minute tabs to help with alignment. Plus by flaring each hole we added more rigidity to every part.
With the drawings of what each sheetmetal component needed to look like, we sent them out
Light Racing offers this flared-hole die set made from hardened high-carbon steel. Sheetmetal can be made stronger by cold-working it and adding depth. This provides increased structural integrity by supporting the sheetmetal on different planes, similar to how cardboard is made out of many pieces of paper.
Light Racing offers this flared-hole die set made from hardened high-carbon steel. Sheetme

The Light Racing kit works with up to 0.090 chromoly sheet, and 0.125 mild steel plate. Simply cut out or holesaw the appropriate-sized opening in the material and then align the dies within the opening. Next put the dies in a press with between 12- and 40-ton capacity, depending on hole size and material used.
The Light Racing kit works with up to 0.090 chromoly sheet, and 0.125 mild steel plate. Si
With just the side panels flared you can see the increase in strength. The nonflared panel bends under the full weight of fabricator Drew Burroughs...
With just the side panels flared you can see the increase in strength. The nonflared panel
...but the finished panel flexes just slightly. We will use two of these panels to build the boxed substructures.
...but the finished panel flexes just slightly. We will use two of these panels to build t

Burroughs starts the TIG-welding of the substructure with a Miller Synchrowave 250 machine and chromoly welding rod. This lower section will house the transmission and transfer case, will support the lowest skidplate of the belly, and also act as the frame mounting points for most of the suspension links. In order to completely weld these components, everything is clamped together and multiple small tack welds are burned in at the seams.
Burroughs starts the TIG-welding of the substructure with a Miller Synchrowave 250 machine
Check this out! When Burroughs had the sheetmetal sent out for cutting he had small alignment tabs added to the edges that would become corners. By simply lining these up and tack welding each part at these points, all the components will be assembled properly.
Check this out! When Burroughs had the sheetmetal sent out for cutting he had small alignm
Once the chromoly substructure was complete I sent it to Certified Steel Treating. Certified makes its living by changing the strengths of metal. I had two steps done to these pieces. First they were stress relieved and then hardened. Whenever welding is done to metal it can leave stress in the metals around the heat-affected zone of the weld. By going through a heating process known as normalizing, stress is relieved to help reduce the chance of cracks forming in the material.
Once the chromoly substructure was complete I sent it to Certified Steel Treating. Certifi

This normalizing is followed by tempering to make the material stronger. Certified heat-treats the parts in large furnaces using multiple rows of electrical conduit, similar to a giant toaster. Their facility can normalize and heat-treat material as small as nuts and bolts and as big as complete chassis or giant structures for cranes and airplanes. Plus they can help strengthen both mild steel and exotic alloy components. In the end the substructures had a hardness rating of 34 to 38 Rockwell, which is similar to a Grade 8 bolt.
This normalizing is followed by tempering to make the material stronger. Certified heat-tr
With the parts back at Poly Performance, Burroughs started the assembly. The Poly Performance fabrication shop has a hefty frame table that provides a flat, solid platform to assemble the chassis on. We started by centering the subframe components on the table and inserted three pieces of DOM tubing between the subframes. In order to have the transmission output centered and the subframe right up next to the Atlas transfer case, we set the parts at 31 inches center to center. Notice the multiple suspension mounting points front and rear and the bolt holes at the bottom for the skidplate.
With the parts back at Poly Performance, Burroughs started the assembly. The Poly Perform
With the subframe solidly clamped to the table and three cross tubes tacked into place (we used mild steel ER80S-D2 welding rod whenever welding DOM to chromoly) we moved onto the front framerails. You'll want to find a stationary point that you can always reference in order to make the chassis as square and uniform as possible. We used the centerline of the table, which gave us a point in every direction to start from and then built frames and jigs that were perfectly square and clamped into place to set tubing on before support tubes were built.
With the subframe solidly clamped to the table and three cross tubes tacked into place (we

As we added more tubing, I went from magazine guy to fabricator's assistant. My first job was to cut the tubing to length, and this was done with a wet saw, though a chopsaw, a bandsaw, or even a hacksaw can work as long as you get a good square cut. I had to be sure to double-check all measurements down to a 1/16-inch or better. Once the tube is cut I made sure the sharp edges were ground off and any burrs removed with a grinder or this JMR belt sander. Cleaning the edges keeps the annoying cuts and snags at bay, and helps in measuring for future bends and notching.
As we added more tubing, I went from magazine guy to fabricator's assistant. My first job
Once the cut ends are free of snags, be sure to clean any oil or rust inhibitor from the tube that was applied at the factory as it can contaminate your welds. Cleaners such as Simple Green work great for this. After cleaning the tubing, mark it for bends if the piece needs bending or determine the angle of the required notch. Poly Performance uses a computer program known as Bend-Tech that takes the CAD drawing and determines the distance from the end of the tube to the start of each bend, the degrees of bend and the rotation of the tube needed to start the next bend.
Once the cut ends are free of snags, be sure to clean any oil or rust inhibitor from the t
As with the frame buildup on the table, it also helps to have a reference point when bending tube. Burroughs uses an angle finder with a tubing mount that allows him to determine how much the tubing is rotated from one bend to the next. This is extremely helpful when bending mirror-image tubes for opposite sides of the chassis.
As with the frame buildup on the table, it also helps to have a reference point when bendi

For the actual bending we used a JMR hydraulic bender. This piece can be outfitted with many dies, and has a degree ring and pointer to show what angle the tubing is bent to. Be sure to first determine how much spring back your tubing has. Spring back is the number of degrees (our DOM had about 5) that the tubing must be bent past the desired angle in order to get that angle of bend. For example, the tube had to be wrapped to 48 degrees in order to get a 43-degree angle once removed from the bender.
For the actual bending we used a JMR hydraulic bender. This piece can be outfitted with ma
Notching, like bending, requires thinking in an odd three-dimensional style that confuses most people but comes easily to many fabricators. Where a square or flat piece of metal can be cut at a simple angle, round tube that is angled and runs between two other tubes must wrap around the tubes at each joint. And when multiple tubes meet in a structure it is even more confusing. To make it as precise as possible we again turned to a JMR product-the company's tube notcher uses a 1.125-inch shaft supported by Timken bearings. This keeps the holesaw from wobbling around as the teeth cut into the tubing. We attached a Milwaukee 11/42-inch Magnum drill and holesaws to the notcher for reliable torque and long-lasting cutting blades.
Notching, like bending, requires thinking in an odd three-dimensional style that confuses
One of the most important lessons to learn when building any fabricated component is to only tack weld parts together. As you build something you'll feel the urge to burn it in solid. But until you have made completely certain that you don't want to change anything-whether working on a rock slider, rollcage, or full buggy-it is best to just do a small solid 1/8- to 3/16-inch weld that can easily be cut out if need be. Most of the main chassis welding was done with a Millermatic 251 MIG welder.
One of the most important lessons to learn when building any fabricated component is to on

Notching leaves the tubing very thin at certain edges and these points should be ground out till the tubing has a more blunt edge with thicker material...
Notching leaves the tubing very thin at certain edges and these points should be ground ou
...The thicker material will result in a stronger weld, whereas the thinner material can burn back when welding and not result in as strong a joint.
...The thicker material will result in a stronger weld, whereas the thinner material can b
This month we began the chassis buildup and covered many of the tools that helped make it move along smoothly. Next time we'll cover more of the chassis construction, installation of the drivetrain, and how we finally laid out the tricky front suspension and steering.
This month we began the chassis buildup and covered many of the tools that helped make it

SOURCES
Bend Tech www.bend-tech.com	Miller Electric 8-004-AMI-LLER www.millerwelds.com
Caltime Metals	Milwaukee Tool www.milwaukeetool.com
Certified Metal Treatment	Poly Performance N/A www.polyperformance.com
JMR www.jmrmanufacturing.com.	Simple Green www.simplegreen.com