How to Build Stuff

Why a Chassis Table?

Any discussion of how to fabricate something (anything) starts with the assumption that accurate measurement in three dimensions is a given. However, measuring is often the most challenging aspect of any build project.
Whether you are building a tube chassis from scratch or building - repairing a production car, the ability to measure easily, repeatability and to an acceptable degree of accuracy is essential. There are many ways to measure projects the size of a chassis. The different methods vary greatly in cost, accuracy and ease of use. Here we are going to discuss methods for fabrication measurement using a home fabricated Chassis Table.

So what is a Chassis Table?
In its simplest form, it is just a flat level reference plane. Depending on the flatness and levelness of your garage floor surface and your definition of “Acceptable Measurement Accuracy”, your garage floor can be used as your “Reference Plane”. Many award winning, race winning and perfectly acceptable vehicles have been built on garage floors. So I’m not here to tell you the garage floor method can’t be done but, many garage floors are not level, are quite Wavy (one term for variance from flat), cracked, pitted, ECT. Additionally, working on the floor is hard on the knees, back, and slows progress. Another drawback to the floor that it is not a simple matter to secure (clamp, bolt, weld---) your work to the floor. If your work isn’t secured in some manner, it will get bumped and jostled during the normal course of building, requiring that time be spent re-locating the project. Or worse yet, the bump error might go unnoticed until the errors are welded into your project.
At the other extreme, a chassis table is actually a “Surface Plate” with a complete deck area upon which to build and measure from/to. While this sort of fully decked table seems ideal, they actually have some drawbacks too. First, decked tables are very heavy and expensive to build. Additionally, a solid tabletop will block access from underneath your project for installing components and worst of all, significantly restrict welding access.

The example In the photos is a table I built for fabricating Bonneville Saltflats racecars. So far we have successfully built a G/Fuel streamliner and a Gas Roadster rolling chassis. If your intentions for a table are for scratch fabrication, then 1/8” wall thickness materials are heavy enough. However, if your intended use for a table includes straightening and repairing crashed and wrecked vehicles using port-a-power, heat, jacks and other brute force devices, you will want to build from heavier stock.

What Size?
The table here is 120” long by 36“ wide and about 30” tall. This size fit my project and fit my shop. The recent Gas Roadster project had a 112” wheelbase, and stretched the limits of my table design. If I were to build again, I think I would build a 144” (12 feet) long table. The track width of this roadster was about 55” and that required some measuring creativity to accurately center the axles. Some folks helping whti this build speculated on how a wider table might help. Maybe they are correct, depending on the nature of your projects, a wider table (48”) might be something to consider. One significant drawback to a wide table is the increased difficulty in reaching across to weld. On my 36” table, one can readily reach across the table to weld on the inside of the far side of the frame. As tables get wider, my back gets sorer. That reach over thing takes a toll. So unless your building tube frames for Top fuel GreyHound Bus’s keep the table size modest.

Notice two tables here tied together to create a reference table over 16' long.

Chassis Table or Workbench?
One last thing. Versatility—I don’t build all the time. When the car comes off the table, I top that table with a tabletop fabricated from ¾” thick Melamine coated particle board (source: Home Depot). I perfer to frame with 2x4 along the edges. The 2x4 edges make the structure strong and stiff and eliminate tabletop slipping around on the chassis table. These are great work surfaces –durable, clean, premium shop equipment for a minimum cost.

Note the removable fabricated Melamine Tabletop.
Kristeen knows how to prep a fiberglass body mold for a handlayup.

Lets Build!

All of these problems can be avoided by building a simple Frame style chassis table. Let’s look at some of the features that make a table like this easy to build and use.

Materials Required

This design requires 20' of .125" wall 3" Square tubing, 28 feet of .125" wall 2" Square Tubing for the legs and cross members, 30 feet of 3/4" X 3/4" X .125" angle for the shelf tray and 8 1/2-13 x 4" Carridge bolts and matching coupling nuts for the leveling feet. Add in a couple of 4'X8' sheets of OSB board for the shelf and you have the makings of a versatile chassis table.

Table Fabrication

Most of the components of this table need only to be held to a tolerance of +- 1/8". However, There are a few items that you have to get right. The four Cross Members must be the same length.
Take the time to get this right. In order to effectivly use the table for measuring, the long 3" rails need to be parallel. this is ensured by the cross members. additionally, if you want the all important centerline of your table to be at some convenient dimension (say at 18" on a 36 "wide table) the precision of these cross members is a make or break dimension. I suggest setting up a "Stop" on your cutoff saw so you can get this detail right. Keep in mind that your crossmembers are longer than the legs, so a scrap crossmember can be recycled as a leg.

Cut all your pieces, deburr them, check them for accuracy, chalk mark them with an identity to avoid confusion during assembly.

Assembly has one critical detail-- The plane formed by the top components must be flat and square.
Take your tile during the fitup portion on this item. a pair of bar clamps and a set of saw horses will help you get control of the components. A carpenters Framing Square and a long straight edge will let you check that the ends are flat and parallel, and the corners square before you tack weld. Take the time to carefully the tacked tabletop. Errors are easy to correct at the tack welded stage. Ask yourself-- Is that top surface pretty darn flat and square??? If not, cut the spot welds with a "Muffler Cutter" (a 1/16" x 3" diameter abrasive wheel mounted in a high rpm air motor) and shim, clamp, pull, push the components until you get the flat, square surface you deserve. Once the surface meets your approval, weld it solid.

Adding the leveling feet to the legs is probably easiest before you weld the legs to the table.