I've gotten the letters and I've heard the harassment while on the trail. Yes, I am still building Project Fun Buggy. It's just taking a little while, but here is another installment of the buildup that began over a year ago (Aug. '05). The idea for this tube buggy is an all-terrain vehicle that doesn't have a conventional body but rather is built for optimum fun off road. Though my buildup uses premium parts, it can be duplicated with a junkyard drivetrain on a reasonable budget.
To recap, we started by building front and rear steering axles with Dynatrac Pro-rock Dana 60 centersections, Reid Racing (formerly Dedenbear) end forgings and knuckles, 40-spline Superior shafts, CTM U-joints, and Detroit Lockers (Aug. '05). In addition we used Yukon 5.38 gears with 35-spline pinions, and high-steer arms from OTT. I then went to Scoggin-Dickey and assembled a fuel-injected GM Performance Parts ZZ383 small-block V-8 (Sept. '05). This engine uses an ACCEL DFI fuel-injection system and was dyno'd at just over 400 hp and just shy of 500 lb-ft of torque. Following that, the mil-spec green Mastercraft suspension seats and 17-inch Walker Evans Racing bead-lock wheels were added (Oct. '05). And then there was a lapse until our February 2006 issue where I discussed tubing and showed the difference between HREW, DOM, and chromoly tubing and the fact that I am using about 300 feet of DOM 1 3/4-inch x 0.120 wall tubing for the majority of my project. Then everything fell apart.
From the start of this project I wanted to work with a fabrication shop that could walk me through the steps of the design and buildup. I ended up at Poly Performance in San Luis Obispo, California. Poly has been selling parts for the home tube-buggy builder for five years and has a fabrication shop that does everything from coilover conversions for Jeep TJs to full chassis buildups.
To get everything moving I took my drivetrain parts to Poly and began the extended design, and that is what this month's story is all about. Now I was assuming we would simply park the parts on the shop floor and begin bending tube around it, but boy was I wrong. The team at Poly Performance takes a different approach by measuring every drivetrain component and suspension part, then drawing them up on the computer. This way they can get an initial layout before any tube is bent. It takes longer this way (way longer), and most of us can't duplicate these steps exactly, but similar procedures can be done with pencil and graph paper. Of course I was going crazy trying to get my buggy project moving, but the best advice for a project this big it to have a solid overall plan for the entire vehicle. Though some fabricators can whip a chassis out in their sleep, these drawings made it much easier once the dirty work finally began, and can keep the wasted tube to a minimum. This process also allows many different configurations to be explored before a final design is set.
The first step of designing your buggy is determining your drivetrain. I decided to go with a tried-and-true recipe of small-block Chevy V-8, automatic transmission (I'm using a 700R4 built by TCI), two-speed transfer case (I'm using an Atlas with a 3.8:1 low range), and 1-ton Dana 60 axles. The drivetrain recipe can be adjusted depending on the terrain you run, tire size you want, and your budget. However, putting tubes around the drivetrain parts is not exactly easy. Needless to say, I was ready to go wheeling before my buggy was ready. | 
To begin the design stage of the buggy, we laid out the parts and started measuring. Drew Burroughs is the head fabricator at Poly Performance, and our friend Wes Capel stopped by to lend a hand and pose with the tape measure. We started with the ZZ383, and made sure the GM Performance serpentine beltdrive system was installed since we don't want any surprises when we start installing the parts in the chassis. |
Next we measured the axles. In addition to the physical measurements we also tried to weigh many of the components. We found that our full-width steering axles weighed 565 pounds each. The dry engine was roughly 500 pounds and the dry transmission and transfer case approximately 240. | 
Finally I sat in one of the Mastercraft Sportsman seats and set it to about a 20-degree recline that I felt was a comfortable angle to spend hours and hours on the trail. This is a bit steeper than some folks would enjoy, and it will probably make climbs feel even steeper than they really are. There will be no seat adjustment, but when you are building a custom chassis it pays to consider everything, including driver comfort. |
Finally, Burroughs took all the measurements of drivetrain, suspension, and interior components and began drawing them up on his computer. He uses the design program Solid Works that allows three-dimensional images; unfortunately it takes some meticulous time to draw each part up. | 
My parameters were that I wanted 39- to 42-inch tires, big enough for some difficult trails but not so tall that they will be taxing the drivetrain. A 103- to 108-inch wheelbase, good for all-around wheeling especially with rear steer added in, but still stable enough for steep climbs and going fast across dunes. About 18 to 24 inches of belly clearance, and 72 inches or shorter roof height to keep it off rocks but still have a low center of gravity. Then we laid out the drivetrain on the frame table to see how far back we could put the engine to clear the front axle while still keeping a long enough rear driveshaft. |