Nitrogen is used to power these tools because it's dry, typically regulated to 110 psi. The gun has an oil reservoir packed with cotton, like a Zippo lighter, and Jimmy says the crews fill them up before each pit stop even though total run time is only about 4 seconds. Jimmy customizes the location, shape and size of the gun's exhaust port as requested by the customer. "Front tire changers want the port on the side because brake dust would blow in their face with a standard front exhaust. The new one has bigger port for more rpm." He says there's always a compromise between rpm and torque, "but in this situation you need both. So with this gun, torque will be the same off and on…it's just a little slower going on so you don't get the nuts too tight. If they're too tight, it can take more than 190 ft-lbs to remove the nuts. That might only take half a second (more), but that could be enough to lose 15 spots on pit road…The better teams hit 5 lug nuts in 8 tenths of a second and put 70-130 ft-lbs on each lug nut."
Jimmy also modifies the reverse switch. Each tire changer wants just the right stiffness on that button, and Jimmy can 'tune' the effort required to push it. "Whatever you want, I can to it. Sometimes the valve will wear down and I have to replace it, and there are different buttons too." But switch stiffness is determined mostly by size and composition of an O-ring, and by ambient temperature. That's why tire changers keep their impact gun in an insulated holster-shaped bag. "Sometimes guys will put a baggie of ice in there, and in wintertime they'll use heat packs."
During the racing season, Jimmy is at the track every weekend. He's the only source of racing impact guns and service for all the NASCAR tire changers. Most tire changers keep one gun just for race-day, but they practice 3 to 5 times a week using another Thundergun with the same set-up. Jimmy maintains those guns too. He used to supply other racing series too, including Indy Car, but he says "this is getting so busy…this is pretty much all I do anymore."
Even so, Jimmy Hurd is planning to expand the family business. Recently he's had calls from F1teams in Europe. He calls that a "golden opportunity" because the racing industry in Europe is much bigger than in the 'States. "In about 2 years you'll see a trailer like this over there doing what we're doing here. That's my plan." So after 50-some years in business, H. M. Hurd Pit Tools and Equipment will finally expand beyond a one-man operation. It's too early to know what tools will be used, but it looks like the Thundergun will definitely be around for a long time to come.