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Millermatic MIG Welders Help Build, Repair Tornado Chase Vehicle

To reduce the weight of his Tornado Interceptor Vehicle, and to simplify MIG welding aluminum, Sean Casey switched to the pulsed MIG output of a Millermatic® 350P. For making welding repairs and modifications on the road while filming his Storm Chasers TV show, Casey has relied on a Millermatic Passport®, a 45-lb. MIG welder offering unmatched portability and flexibility.
   
The winds of a twister devastate everything in their path…except the fortress on wheels known as the Tornado Interceptor Vehicle (TIV). Sean Casey, star of Discovery Channel’s Storm Chasers, designed the original TIV to withstand winds up to 160 mph. After filming for two seasons, Casey realized the 17,500-lb. TIV needed modifications to increase safety, functionality and durability, and that he needed to shave 3,500 lbs. off the total weight to increase off-road maneuverability and overall speed.

The Tornado Interceptor Vehicle or TIV is in its third season of tornado chasing and due for an overhaul.

To save weight, Casey planned to replace steel components with ones made from aluminum. While he contracted with outside fabrication shops to build the original TIV, Casey wanted to make the latest round of upgrades himself. He needed an industrial-quality MIG welding system capable of welding steel and aluminum and that could run on the 230 V single-phase primary power in his North Hollywood, Calif., garage.

Although Casey had more familiarity with some competitive MIG welders, he realized that welders from Miller Electric Mfg. Co. better met his needs. For work out of his garage, Casey selected the Millermatic® 350P MIG welder with an XR-Aluma-Pro™ push-pull gun. The Millermatic 350P provides a 25- to 400-amp output range, uses single- or three-phase primary power and provides a pulsed MIG output that simplifies and improves aluminum welding performance.
The Mission

Sean Casey has been shooting documentary films for more than 20 years. Traveling to exotic locations, Casey has been involved with several notable IMAX films, including work on Africa: The Serengeti (narrated by James Earl Jones) and as director of photography for Natural Disasters: Forces of Nature (2004).

“You might say I got sucked into filming tornados during the filming of Natural Disasters. I just fell in love with the whole environment and challenge of storm chasing,” states Casey. “We were lucky on this one occasion during the shoot to be in the right place at the right time to get the shot during a big tornado day.”

Wanting to continue chasing tornados, Casey decided to pursue another IMAX project focusing exclusively on tornados.

Casey explains that there’s a world of difference between seeing a tornado filmed with a telephoto lens from two to five miles away and the view obtained at “point-of-impact” distances with the IMAX format. One major obstacle stood in his way: finding a vehicle that could get into position and safely film tornadoes at close range.

Part Tank, Part Batmobile

The current the Tornado Interceptor Vehicle (the TIV 2) uses a 1-ton Dodge truck frame with 6-wheel drive (it has a third axle). A 6.7-liter Cummins turbo-diesel engine, modified with propane and water injection, produces 625 HP and powers the vehicle to speeds in excess of 100 mph.

Features included steel plate armaments wrapped around a centralized turret for housing film equipment and crew. Half-inch thick polycarbonate windows in the turret allow Casey to safely capture his IMAX footage. TIV 2 had retractable flaps made from 1/8-in. steel and that lowered to stabilize the vehicle and deflect oncoming winds. All of this brought vehicle weight to a hefty 17,500 lbs.

This weight led to several structural and mechanical problems that were encountered in season two of the television show. To create the third iteration of the TIV for the 2009 season, Casey turned to lightweight, yet super-strong materials.

“For the past five months, I’ve been tearing all that steel off the vehicle to lighten it up and be smart about where the weight went,” states Casey. “We wanted to keep the protection where it’s needed: around the people.”

A combination of polycarbonate and Kevlar wraps around the cab form a protective barrier around occupants. These areas, as well as those of the doors and hood, are made up of 1/8-in.-thick aluminum panels sandwiching a sheet of 1/2-in. polycarbonate panel. Testing showed that these panels can withstand the strike of a 15-lb. 2x4 board traveling at 80 mph.

The Millermatic Passport® all-in-on MIG welder is the perfect tool for welding in Casey’s driveway; or out on the road as repairs are needed during a chase.

To anchor the vehicle to the ground, Casey engineered a new spiking system that, at the flip of a switch, drives two metal spikes 42-inches into the ground using 7,500 lbs. of hydraulic pressure. Combined, the spikes can withstand 30,000 lbs. of push before bending. The Millermatic 350P was used to fabricate the 1/2 in. aluminum brackets for the hydraulic spiking system and secure it to the body of the TIV.

Inside, the TIV’s support cage, seat mounts, escape hatches and equipment compartments also required extensive welding.

Easy Aluminum Welding

Casey, a self-taught welder with six years of experience working with steel, admits that welding aluminum used to intimidate him.

“Aluminum is really finicky. I tried to jerry-rig a standard MIG welder to push aluminum through the regular gun, but it never worked correctly,” he explains. Conversely, working with the Millermatic 350P and its push-pull Aluma-Pro gun made MIG welding aluminum surprisingly easy. [See side bar story on “Optimized MIG Aluminum.”]

“From the get-go, I was laying some good beads. Within a week, I took my technique to the next level,” says Casey. “I created beautifully scalloped beads that penetrated well.”

An optimized system for aluminum welding, Sean Casey uses the Millermatic® 350P MIG welder with XR-Aluma-Pro™ push-pull gun to fabricate an aluminum and Kevlar sandwich, which makes up part of the TIV’s outer skin.

To confirm weld integrity, Casey cut apart welds to inspect them for penetration,  and did his own destructive testing (to do this at home, put weld samples in a vise and bend them over using a hammer and/or pliers. A bad weld breaks at the weld; a strong weld pulls away a section of the parent metal).

Casey notes that when switching from welding steel to welding aluminum, he had to remember to brush the surface of the metal. When exposed to air, aluminum instantly forms a layer of aluminum oxide… which melts at about 3,632 degrees F, or about 2,400 degrees F more than the base metal. Aluminum oxides causes problems with welding because the arc must first penetrate the oxide layer before it can melt the base metal. Unfortunately, burn-through may result if the arc has to fight through a heavy oxide layer. To avoid problems, Casey uses a stainless steel brush to remove the oxide immediately prior to welding, and he dedicated the brush solely for this use to avoid introducing contaminants into the weld (e.g., steel particles).

“I also had to remember that when welding aluminum, I could only push the gun forward in my direction of travel. I couldn’t drag the gun like I sometimes do with steel,” Casey says. Compared to steel, aluminum is much more sensitive to poor shielding gas coverage, which manifests itself as  black soot on top of the weld (and possibly porosity within the weld). Using a push (or “forehand”) welding technique while maintaining a 15-degree gun angle helps ensure that the shielding gas covers the molten weld pool.


Roadside Repairs

Casey’s experience with Miller welders also includes the Millermatic Passport, which he used during the 2007 and 2008 seasons of Storm Chasers.

“The Passport only weighs 45 lbs., yet welds just as well as our big shop machines,” explains Casey. “It’s hard to fathom how much power comes out of that case. It’s great to have this type of welding performance on the road.”

Unlike other small, portable MIG welders, the Millermatic Passport (now upgraded to the Millermatic Passport Plus) uses inverter technology. The benefits of inverter technology include attributes perfect for portable applications:

The Millermatic Passport takes portability one step further than any other lightweight welder. In addition to a standard shielding gas connection on the back of the unit (for connecting to conventional shielding gas cylinders), the Passport also features an internal 12 oz. cylinder of CO2. This cylinder provides approximately 25 minutes worth of arc time, or enough to make a 25-ft. long, 3/16-in. fillet weld on mild steel. The cylinder is actually a paintball cylinder, so Casey can get refills at almost any sporting goods or hardware store in the country.

Welding repair and modifications made on the road are a fact of life for the Storm Chasers crew. Moreover, the constant need to work ahead of the team’s radar truck and get in best position to intercept a tornado sometimes doesn’t leave a lot of time for repairs.

“If there is something we don’t like, or if we sustain damage, such as our scientific instrument mast in season two, we take out a cut-off wheel and the Passport welder and start changing things,” states Casey.

The radar truck carries a 7,500-watt generator that provides 115 V and 230 V input power. Casey notes that when running off 120 V power, the Passport can weld steel up 3/16-in. thick, and it can weld steel up to 3/8-in. thick using a 230 V input. He reports that the Passport handled 95 percent of all the welding work on the road.

“Since we don’t have a chase vehicle for storing our equipment, we need all our tools to be small, versatile and handy. The Passport is really essential for getting the job done and get back on the road.”


Optimized MIG Aluminum

Before using the Millermatic 350P with XR Aluma-Pro push-pull gun, Sean Casey had little success working with aluminum. The problem wasn’t his welding skills (if you can MIG weld steel, you can MIG weld aluminum). The problem was his equipment. He had been trying to weld aluminum using systems designed for steel.

First, because aluminum is so soft, it requires a specialized system for proper feeding. When combined with the XR-Aluma-Pro gun, the Millermatic 350P uses special calibration software that synchronizes motor speeds in the gun (the “pull” motor) and the motors inside power source (the “push” motor). Working together, these motors maintain optimum wire tension, which in turn leads to smoother wire feed performance and a steadier welding arc.

The Millermatic 350P offers built-in pulsed MIG programs for .035-and .047-in for 4000 and 5000 series aluminum wires. It is a perfect choice for fabricators who do not need the high welding output or cost of a heavy industrial system, but still need great welding performance.

To begin pulsed MIG welding with the Millermatic 350P, Casey simply selects the built-in program that matches the wire type and size and the unit automatically sets the welding parameters. Then, Casey only needs to adjust wire feed speed to weld different thicknesses of metal.

For example, Casey often found himself switching between welding aluminum sheets on the side of the vehicle and thicker aluminum sections on its frame.

“The ability to adjust the wire speed using the controls built into the gun is amazing,” he states. “I can adjust on the fly, increasing wire speed to weld heavier material and reducing it to weld thinner stuff.”

For MIG aluminum novices, pulsed MIG usually makes it easier to achieve good results because the pulsed MIG process provides better directional control over the weld puddle. The puddle goes where Casey directs it, plus it is less likely to sag or look excessively convex when welding out-of-position. In fact, operators have so much control with pulsed MIG that they can create beads with a TIG-like appearance.

After practicing for a week, Casey states that, “The Millermatic 350P gave me professional-looking welds. I’m quite proud of them.”

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