If you've been reading this publication over the past two years you've seen the random installments of my Fun Buggy project vehicle. Built out of 300-some feet of DOM tubing, chromoly plate, and a rugged drivetrain, this buggy is destined to be an all-around dirt-chopper. Of course a project like this isn't all perfect weld beads and 90-degree bends. In fact along the way it's had more than a handful of speed bumps and about-faces. To put it simply, building a vehicle from scratch is exciting, challenging, frustrating, and downright exhausting. But it's also great insight on the amount of work the OEMs must go through to build a vehicle that is safe, performs, passes all our governmental regulations, is easily assembled and (if need be) repaired, and most importantly is both sellable and profitable. Hats off to those hundreds of thousands of folks in the auto and truck industry. You've got a tough job.
Since my last installment we not only installed the drivetrain and axles, but also had to cut off and redesign a large portion of the chassis so the best combination of suspension movement and steering geometry within a durable package could be achieved.
There is plenty more work to be done, but here is an update of the current progress.
This is where I left off on the buggy in the previous installment (Feb. '07). The substructure of heat-treated chromoly steel plate was made to attach the suspension links and house the transmission and transfer case, while the main chassis, built of mostly 131/44-inch by 0.120-wall DOM tubing, was growing up off of the substructure. The seating arrangement is leaned back at about 20 degrees for a comfortable ride and a low-slung roofline. Overall height should be around 70 inches with a 19- to 20-inch-high belly.
At the lower portion of the A-pillar and many other places on the chassis, we are integrating multiple tube joints such as this, where one tube bends and three other tubes converge. These points help transfer loads evenly across the chassis, but also require a trained eye to properly notch each tube so that everything fits together tightly prior to being welded. | 
The roof also has multiple tubes to strengthen the chassis and protect the occupants for the day the first rollover comes. These three tubes come together to a point and from there down-bars will run out to midlevel tubes where they will converge with the outer diagonal down-bars. | 
The front of the chassis has a center windshield tube and top corner gussets to further protect against collapse in a belly-up situation. Also note how the door bars have what I refer to as the vent window tubes acting as gussets for the A-pillar. Many of the internal gussets are made from 1 1/2-inch by 0.120-wall DOM. |
The next step was the installation of the Dynatrac ProRock 60 axles, but first we had to prepare the suspension links. Poly Performance is now offering 1 3/4x0.188 chromoly links. The tubing is first cut to length and then the ends are swedged to a smaller diameter. These ends are then threaded internally to 1 1/4-12. Next the links are sent out to be heat-treated to a Rockwell hardness of 35. The heat-treat should make them twice as strong against bending as an identical mild steel link, 150,000-psi ultimate tensile strength to be exact. Into these links are threaded two massive 1 1/4 shank by 1-inch bore FK Bearing rod ends, one end lefthand thread and the other righthand thread for easy adjustment. The high-strength joints are rated to 100,000 pounds of force and are assembled with Teflon liners for long lasting strength and slop-free use. Each joint is also fitted with special high-misalignment spacers to allow for a wider range of motion.
The rear suspension will be a four-link suspension with two upper links converging at the center of the rear axle and two lower links running near the ends of the axle inward slightly to each substructure of the chassis. Since the upper links are less likely to be hitting rocks and other trail obstacles, they will be made of 1 3/4-inch DOM with threaded bungs welded in for the rod ends rather than the more expensive swedged/threaded/heat-treated chromoly lower links. However, all the links will be the same size so that a single spare link can be carried in the unlikely event one is ever broken. | 
Where the links attach to the axles are special mounting brackets that Poly Performance custom makes to its specifications. The company offers a complete line of suspension brackets for front and rear suspensions and for swapping coilover shocks and/or different axles under your trail rig whether it be a Jeep TJ, Toyota truck, or custom tube machine like mine. | 
My front suspension is a three-link design with a Panhard bar to locate the axle laterally. This design uses two lower links (swedged/threaded/HT chromoly) but just one upper link of the same design as the rear. These will keep the axle from rotating, while still allowing the axle to articulate fully. A Panhard bar will be run laterally with one end on the chassis and the other on the axle. The first step was assembling links and attaching link brackets to the axlehousing before swinging the 565-pound ProRock axles under the chassis. |
Transmission duties are being done by a TCI-built 700R4. This automatic has a full reverse manual valve body with compression braking features as well as a 2,200-stall converter. Behind that is the venerable Atlas transfer case with a 3.8:1 low range from Advance Adapters. With the 3.06:1 First gear in the 700R4, 3.8:1 low gear in the Atlas, and 5.38:1 gears in the axles, the combined lowest crawl ratio of 62.5:1 should be fine for a fun buggy. This may not seem that low, but we also have the torque multiplication of the torque converter and nearly 500 lb-ft of torque coming from our 383 small-block. | 
With the transmission and transfer case situated, we swung the engine into place. This is the ZZ383 we built back in the Sept. '05 issue (yes, this build is taking a lifetime!). Specs include GM Performance Fast burn heads, ACCEL's DFI super-ram multiport fuel injection, MSD distributor, and Sanderson headers. We built this little torque monster at Scoggin Dickey Performance Center and dyno'd it at 413 hp and 491 lb-ft of torque. | 
Locating the engine in the chassis with the axles is a tight fit. We knew we wanted the engine behind the axle for a more even weight balance front to rear, but we don't want to push everything back too far and lose any length on the rear driveshaft. We were able to find just the right position where the centersection clears the crank pulley yet still allows substantial uptravel, articulation, and driveshaft length. |