Fun Dune Buggy Blueprints - Project Build - 4 Wheel & Off-Road Magazine

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.
The first step of designing your buggy is determining your drivetrain. I decided to go wit
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.
To begin the design stage of the buggy, we laid out the parts and started measuring. Drew
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.
Next we measured the axles. In addition to the physical measurements we also tried to weig

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 I sat in one of the Mastercraft Sportsman seats and set it to about a 20-degree re
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.
Finally, Burroughs took all the measurements of drivetrain, suspension, and interior compo
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.
My parameters were that I wanted 39- to 42-inch tires, big enough for some difficult trail

These are what the drawings begin to resemble, almost blocklike parts with all major characteristics there. However, the program also allows some of the parts to be manipulated-such as the axles, which can be turned to show the steering, thus assuring that the tires will clear the chassis.
These are what the drawings begin to resemble, almost blocklike parts with all major chara
Here is the drawing of me driving the buggy, don't I look good in green? This is used to determine proper pedal location as well as rollcage headroom clearance
Here is the drawing of me driving the buggy, don't I look good in green? This is used to d

Burroughs even did a drawing of the Warn 8274-50 winch since its tall offset design makes it a bit more challenging to fit into a chassis.
Burroughs even did a drawing of the Warn 8274-50 winch since its tall offset design makes
Our chassis design started out with a slanted front end to give it a unique, almost desert race-buggy look. It couldn't have a Jeep front clip or the body of any other vehicle, as if I wanted a Jeep, Toyota, or whatever, I would have started with one. Plus buggies are designed to reduce body damage, so why go and put a body on the outside of it just to see it get smashed up?
Our chassis design started out with a slanted front end to give it a unique, almost desert
One of the original goals was to make the buggy a three-seater, but this proved too difficult. In order to keep the buggy low yet still have enough uptravel for jumping at the dunes, the rear axle was wanting to occupy the bottom of the third seat at full compression, and I didn't want to make the wheelbase any longer since we already had it stretched to the 108-inch max.
One of the original goals was to make the buggy a three-seater, but this proved too diffic

The chassis was coming together nicely when I brought up another idea. Here is a pointer for anyone working on a custom buildup; if you keep making changes or "bringing up ideas," your project will take that much longer to get done, and at some point you will need to make a "design freeze," and just get the project moving ahead. Luckily, since we were still at the drawing stage these changes could easily be tried out. My other idea was more a question; could a buggy be built completely out of sheetmetal? Basically build a unibody or monocoque vehicle, but design it to work off road, and be made of thin sheetmetal to keep the weight down. Where some designers would chase me out of the shop at this question, Burroughs rolled it over in his head and offered that we could do certain parts out of thin chromoly sheetmetal with dimpled holes for added rigidity. I liked the idea and soon we had a new substructure drawn where the link suspension will tie in.

To finalize the drawings, Burroughs went through and added many gussets and supports. This is the version we will actually start the build off of, but as with anything, once we start bending tubes there may still be some tweaking to make everything perfect. Plus, we may add more dimpled sheetmetal parts where the Fox coilover shock mounts
To finalize the drawings, Burroughs went through and added many gussets and supports. This

Rather than make the rock sliders straight as on most 4x4s and buggies, I wanted to give them a high center. Having wheeled with Tim Hardy and his battered Suzuki Samurai (see our Ultimate Adventure coverage) I recognized that his rock sliders have been battered up into an arc after years of abuse and rarely got caught on things. Perhaps raising the breakover angle out at the edges of the chassis to follow the floorboards may work as well.
Rather than make the rock sliders straight as on most 4x4s and buggies, I wanted to give t
We began discussing other chassis options, such as putting the engine in the rear for added visibility. This is a possibility with the chassis, but it would require either the axles to be run upside down or a custom reverser gearbox made to get the driveshaft rotation correct. However, plans are already in the works for a possible future build.
We began discussing other chassis options, such as putting the engine in the rear for adde
And finally, Burroughs went ahead and drew a four-seater buggy. This would be great for family wheeling, or being the off-road party bus. In order to do this, the chassis is drawn with a longer 121-inch wheelbase.
And finally, Burroughs went ahead and drew a four-seater buggy. This would be great for fa

Next month I'll show you how we took these drawings and moved into the fabrication stage of the buildup. Some of you will be able to use these drawings to build a chassis at home, but if fabrication isn't your cup of tea, Poly Performance will be offering a similar chassis for sale that you can install your preferred drivetrain into, or have built as a complete turnkey tube car.

SOURCES
Fox Racing Shox www.foxracingshox.com	Warn 5-03/-722-1200 www.warn.com
Poly Performance N/A www.polyperformance.com	Yukon Gear www.yukongear.com
Walker Evans Racing www.walkerevansracing.com	Detroit Locker Madison Heights MI 800-328-3850 www.detroitlocker.com
Industrial Metal Supply www.imsmetals.com	Superior Axle & Gear N/A superioraxle.com
Dynatrac Axles www.dynatrac.com	MasterCraft Racing Products www.mastercraftseats.com
ACCEL DFI www.accel-dfi.com	Advance Adapters 4320 Aerotech Center Way P.O. Box 247 Paso Robles CA 93446 805-238-7000
GM Performance Parts www.gmperformanceparts.com	OTT Engineering www.ottindustries.com
Reid Racing (formerly Dedenbear) www.reidracing.biz	TCI Automotive 151 Industrial Dr. Ashland MS 38603 662-224-8972 www.tciauto.com
CTM Racing Products www.ctmracing.com	Scoggin-Dickey Performance Center www.sdpc2000.com