To understand some of the factors in the Phoenix VHT / Pro Stock accidents equation at the NHRA Arizona Nationals, it's necessary to know how the NHRA applies traction compound, what guidelines it uses.
Graham Light, the NHRA's senior vice-president of racing operations, said prepping the track for a national event is a bit of a combination of NHRA racing-surface experts and their local-track counterparts.
"We request that the track scrape all the old rubber off the track from the starting line to approximately 500 foot. And our people will show up, normally the weekend before. Sometimes we have to touch up the scraping job. Other times we don't. Bottom line, you try and get as much of the old rubber off as possible," he said.
"In time, and it's a short period of time, too, the rubber gets hard. And when it hardens up, adhering new, fresh rubber to it doesn't stick real well. So if you don't get that old rubber up, what you end up with is a Swiss cheese look -- places where new rubber is bonded to it but then there's places where it doesn't bond. It doesn't allow 100 percent tire-to-surface contact," Light said. "So that's the first thing -- get all the rubber off and then wash the track to get all the loose debris, burnt rubber, and so on, after the scraping process. That's a good day's or two days' work, actually.
"And when that's done," he said, "our guys will come in and sweep and clean it and touch up any areas, if necessary. Then they'll put a mist of VHT on it, drag with our tire machine." That, he said, is "the process of starting to build back up a thin layer of fresh rubber. Depending on the track surface, it's a little harder to get the rubber to adhere to than others. Each track's a little different. Sometimes we use -- there's a VHT white powder that works very well for making rubber adhere to concrete. Sometimes it's not necessary."
Light said the final step in track preparation is to "spray 100 percent VHT on the track for the entire length of the track prior to running any race cars. That's typically done on a Wednesday or Thursday, depending on whether it's a three-day or four-day race. From that point on, we typically use a mixture of 75-25."
He clarified that as a 75 percent VHT, 25 percent methanol mix. The methanol, he said, is the same fuel that Alcohol Funny Cars burn and that the NHRA buys it from VP.
However, Light, said in explaining, "That depends on what temperatures we're facing. It depends on how good the quality of the track is. By that, I mean least amount of porosity, good tire contact. You don't need as much VHT as you do when something maybe doesn't have 100 percent tire contact. Certainly when it gets colder, we have a tendency to use less spray. And when it gets very hot, in the middle of the summertime, then you don't want to overspray it, either, because the surface turns into a gooey, kind-of-like bubble gum when it gets very hot. It gets gooey and pulls apart. So you have to be careful not to spray too much in very cold weather or in the hot temperatures that we see in summer."
P.J. Harvey, owner of P.J. Brands, which supplies the traction compound, hinted that the trouble at Phoenix could have stemmed from the quality of methanol used in mixing (often referred to as "cutting").
"That’s the problem. I think that was the big issue taking place in the last week or so," Harvey said. "There are different manufacturers of methanol. Let me put it this way ... There are different vendors of methanol. Some come from the same pot but different brands. There’s a particular brand that works well ... that we’ve used for many years at all of the nationals, the NHRA events. There’s another brand we’ve experimented with. It just isn’t consistent in the quality of the product.
"The real complication comes in with the fact the methanol attracts moisture. You can actually have a drum with the bungs [barrel openings] sealed tight and water can still settle on the top of the drum after a rain or something. It can actually suck in the moisture through that bung. You have to be careful about that when you are in a rainy area or very high humidity environment," Harvey said. "If you have any problems with the methanol, it’s going to screw up the program on the entire traction compound. You can tell when it's shiny, and that's what we had during the regional [LODRS Division 7] event."
Harvey said what makes a traction compound at least adequate is "its ability to have durability on the track. It has memory, and what I mean by that is … for instance, if you hit it with a hammer and it pops back up to where it belongs. It needs to be tunable. What that means is when it is getting a little weak, we can come back and maybe spray it at 50 percent, maybe 75 percent. Sometimes it gets a little bit too much and we come back and we spray 100-percent methanol on it. We drag it. It's got to have the capability to be manipulated based on the ambient temperatures and cars running down the track."
Certainly the Arizona Nationals had trouble with cold, rainy weather. But none of that, enlightening as it might be, seems to be relevant if the wrong traction compound was applied to the racing surface.
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