Race Car Tubing Fabrication: Part 2

The cutting torch works much like the welding torch except it has an additional valve to allow excessive oxygen pressure to blow away the molten puddle. The regulators should be re-set. Never use more than 10 psi for the acetylene. The oxygen can be set at 40-60 psi. Adjust to a neutral flame with the oxygen lever depressed. Heat a spot and when the spot liquefies, depress the oxygen lever. Hold the torch steady, as the oxygen pressure will raise it, cooling the area you want to cut. Move the torch at a steady, slow pace while cutting, holding the oxygen lever depressed. Be sure to shield your feet, as the sparks and pieces of molten metal can have you hopping like a rabbit in a fire ant bed.

When the cut piece of metal has cooled, you will find some slag on the back side. Tapping the edge of this with a hammer will remove much of it. Then use a grinder to finish. In spite of the other equipment you may have, the torch will still be needed for some things. Maintain it by keeping the tips clean.

Many race cars have been built with an arc welder, including some of mine. Today, that is not the welder of my choice. However, you use what you have. The common "cracker box" arc welder is an alternating current (AC) machine. Yours may have a dial setting or a plug-in setting for heat control. Either is suitable.

Arc-welding the tubing used on race cars requires more skill than is often realized. The fits need to be very good. Overhead welding can be a pain in more than the neck. The choice of welding rod is somewhat critical. For flat welds you do on the bench, the E-6013 rod makes a beautiful weld. Welding up or down hill or overhead requires the use of a rod intended for this purpose. The E-6011 is commonly used here, but it does not make a nice, smooth weld. It does, however, penetrate well and can be used in all positions, including overhead welding-1/8 inch diameter is the most common size. The E-6011 flux must be chipped after the weld has cooled. Chip it well and wire-brush it to inspect it. I have seen many welders, and I've never seen a good one who didn't chip his welds.

Arc-welding the 0.095 tubing used on race cars is not easy. Setting the amperage correctly for welding often makes the arc difficult to start. If the fit is poor, burning through the tube is a common occurrence.

Years ago, some cars were built of black pipe, which is heavier wall, thus easier to weld. It makes a heavier car, but it won't save much money, and it's not good for race cars. The biggest problem with using pipe for race cars is this: You never know what kind of alloy of steel you are getting. Pipe is often made of recycled steel that includes axles, tin, ball bearings, and so on. The steel mill is only concerned that it holds 60 psi of water pressure.

I have had pipe that wouldn't bend. With a long lever on the bender, the pipe broke. I wonder how well this hardened pipe would have welded. It might have been very brittle in a severe impact. Fortunately, most of us survived long enough to know better than to use pipe on rollcage and chassis work.

One of the best ways to weld a Stock car chassis is with a MIG (Metallic Inert Gas) welder. It feeds the welding wire through the electrode holder. These are available in a wide range of price and size. Stay with us next month, when we'll show you how to select and use a MIG welder. Some are better for race car building.

Additionally, we will be using a hydraulic jack-type tube bender from Irvan-Smith, and a Speedway Motors hole-saw-type tube notcher will be used to notch our tubing.

In coming issues, we will use a plasma cutter from Miller. This is something of a magic torch to me. It will cut any material that conducts electricity. The plasma torch (cutter) can do intricate work cleanly. It definitely works faster than a band saw on aluminum.

The TIG, or Heliarc, welder is the welder of choice for joining aluminum. It is also preferred on some steel assemblies. We will be using a 48-pound, easily portable TIG unit from Miller.

We will also cover the use and selection of other tools used for fabricating race cars in the home shop, such as different types of saws.