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
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.
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
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.
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.
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
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.