HOT-MIX MAGAZINE 36 VOLUME 10, NUMBER 2

The straight scoopon milling parabolic curves:

If you’re going to stay ona slope that steep,

then you’re going to needthe training wheels.

surface area consists of paraboliccurves. And the precise shape ofthose specially designed curvesneeded to be maintained duringthe milling process so that thepaving contractor could correctlyresurface the track. It was not aneasy job.

“The high-speed test track is akidney-shaped track,” explainedJim Tinkey, an estimator with L&LConstruction, the company thathandled the milling portion of thetest-track resurfacing project. L&LConstruction is headquarterednear Lansing, Michigan. “The test

JOBS COME IN ALL FORMS,but every once in a while, a jobcomes along that seems to

take on a particularly interestingshape. In the case of a milling jobthat L&L Construction Company,Inc. recently tackled, that “partic-ularly interesting shape” turnedout to be a parabolic curve.

Before resurfacing the high-speedtest track at Ford Motor Company’sproving grounds in Dearborn,Michigan, two inches (5.1 cm) ofasphalt pavement needed to beremoved from about 61,000 sq.yds. (55,778 m2) of track. On anormal stretch of highway, millingthat amount would be a fairlystraightforward task. But in thiscase, about half of the test track’s

track varies in widths and degreesof bank all the way around. And ithas five parabolic areas, with thesteepest slope being 22°. That’s apretty good bank!”

What made this job particularlychallenging was the steep slope ofthe curves, as well as the need topreserve their shape. Maneuveringa conventionally equipped millingmachine along these steep bankswithout letting it tip over wouldbe impossible. In order to main-tain the machine’s stability whileexecuting precision cuts wouldrequire both special expertise andspecial equipment.

So, L&L Construction called uponexperience its personnel gainedwhen the company milled the

HOT-MIX MAGAZINE 37 VOLUME 10, NUMBER 2

FOR MORE INFORMATIONabout Roadtec equipment, call your Roadtec Regional Sales Manager:

800-272-7100Fax: 423-265-7521 • E-mail: sales@roadtec.com

Michigan International Speedwaya number of years ago. “That trackhad an 18° slope,” said Tinkey. “Weused a Roadtec RX-50 to mill thehigh-bank portions. Then we didthe flats and straightaways with astandard milling machine. Thisyear, we decided to do much thesame thing at the test track on theFord proving grounds.”

With an equipment fleet thatincludes three Roadtec RX-900cold planers, L&L Constructionwas well prepared to mill the flatportions of the high-speed testtrack. But in order to mill thoseunique parabolic curves, L&LConstruction looked to Roadtecfor a very specialized piece ofequipment: a cold planer built tospec—one that could handle thisunusual and demanding task.

L&L Construction began by obtain-ing a Roadtec RX-500 cold planerthat would be modified by Roadtecengineers specifically for this job.The key modification was theaddition of outriggers—which thecrew quickly nicknamed trainingwheels. The outriggers lend thenecessary stability and supportwhen the machine is working on asteep slope. A 2-ft. (0.6-m) cutterhead allowed precise cuts to bemade in small increments.

“Roadtec used the same outriggersthat we had on the RX-50 whenwe did the Michigan InternationalSpeedway years ago,” explainedTinkey. “They had to be modifiedto fit the newer RX-500 that weused. They also had to modify theframe a little, as well as the cutterhousing for the drum in order tooffset the 2-ft. (0.6-m) drum andthe loader conveyor. Modificationswere also made to the water andfuel systems so they would func-tion properly when the machinewas operating on that steep slope.There was quite a bit of work theyhad to do before they turned overthe machine to us.”

The 600-hp Roadtec RX-500 coldplaner L&L Construction used onthis project also had four tracks togive it added stability. There wasalso a variable cutter head thatthat was adjustable to 2, 3, or 4 ft.(0.6, 0.9, or 1.2 m).

Because of the precision and carethat was required for the job, L&LConstruction initially anticipated itwould require about 11 days tocomplete the milling. The actualresults surprised them.

“With that Roadtec RX-500, ittook only six days of operation tocomplete about 36,000 sq. yds.(32,918 m2),” said Tinkey. “I wasvery impressed. That thing wasmoving right along!”

Despite the strange slope that theRoadtec cold planer worked on,Tinkey said the equipment with-stood the extra pressure. “Thecutter head held up surprisinglywell, especially considering thephysics of the job,” he said. “Itshowed minimal wear on the endrings, which had been a concernbecause of the natural slide thatyou get—even with those customoutriggers in place. Because ofthat natural sliding effect, the endrings on the cutter assembly takequite a beating as the machinetries to torque itself down.”

While the Roadtec RX-500 coldplaner was working on the steepparabolic curves, L&L Construc-tion’s Roadtec RX-900 cold planerwas completing the flat portionsof the track. And in almost halfthe time the contractors hadanticipated, the milling portion ofthe project was completed.

“The Roadtec equipment functionedexceptionally well,” said Tinkey.“And because of the equipment’sperformance, it put all of the con-tractors ahead of schedule.”

This is the second major millingjob on a steep slope that L&LConstruction has successfullycompleted. Because of their expe-rience on this type of project,Tinkey said he anticipates morejobs like this to arise in the future.

“The concept of high-bank millingwill probably become more andmore popular, especially for theNASCAR tracks,” said Tinkey.

He added that having the special-ized Roadtec equipment is a keypart of being able to tackle thiskind of project. “There is no waya standard cold planer could havehandled this job,” he said. ▼▲▼

The Roadtec RX-500 that L&L Construction used to mill the parabolic curveson the Ford Motor Company’s test track had to be specially engineered andmodified for the task. The outriggers—nicknamed “training wheels” by thecrew—required modifications to the frame. The fuel and water systems alsohad to be modified in order to work properly on the steep slopes.

In order to maintain the parabolic curves of the track’s surface, the RoadtecRX-500 used a 2-ft. (0.6-m) drum-and-cutter assembly.