Safer at Any Speed
Safer at Any Speed Part 3:
Safer at Any Speed Part 1:
Out of Glass
By Brion Gluck
Racers sometimes have an adversarial relationship with safety equipment. No one gets in a car planning to wreck it, and all that stuff just adds weight, costs money and gives the tech inspectors something else to play gotcha with. If your number is up, it's up, right?
Wrong. Drivers are injured and even killed in their cars for reasons that often could have been prevented by correctly installed and functioning safety equipment. If the inspectors are going to make you have it in the car anyway, and they will, the equipment might as well be helping you.
Over the next several months, Mustangs Illustrated will feature a series of articles on important aspects of racing safety, including seats, harnesses, helmets, fuel cells, fire suppression systems, roll cages and more. We'll try to dispel a number of myths and misinformation that have sprung up about different types of equipment, so you can make informed decisions about what to buy, how to install it, and how to take care of it.
A significant source of injuries in racing accidents is the windshield. Tempered safety glass, found in many older Mustangs, is designed to break into many small shards that administer minor cuts rather than into a few large, heavy pieces that could take your head or some important body part off in a wreck. Newer laminated safety glass works better, with a layer of plastic in the middle that helps to hold glass fragments in, but it's still heavy, still glass, and still not all that safe for racing.
Prior to a few years ago, the only real alternative to glass was acrylic windows, also known as Plexiglas. Acrylic windows don't work well for windshields, as their optical quality isn't the best and they have a tendency to crack.
Lexan, a polycarbonate resin material from GE, has been around since the late 1950s, but only in the last 15 years or so started being used to make automotive windows. Lexan is one of those miracle plastics; it's half the weight of glass, 250 times more impact resistant, and is used to make everything from compact discs to eyeglass lenses. An inch-thick sheet of it will stop a .44-caliber handgun bullet fired at pointblank range, making it a favorite window material for armored sedans and limousines.
"You could literally take a 16-pound sledge hammer and beat on
a piece of Lexan till you beat straight through it, and it still wouldn't break
anywhere," said Bob Mayerle, owner of ProGlass, a major Lexan window supplier.
"That's the beauty of the material."
Suppliers like ProGlass (www.proglasswindows.com, 630-553-3141) and Five Star Race Car Bodies (www.fivestar-online.com, 262-877-2171) offer replacement Lexan panes molded from original glass at prices ranging from less than $400 for a windshield to around $1,000 for a complete Mustang kit.
In NASCAR, Lexan windows have all but eliminated the tire failures that used to be common after a wreck, when shards of glass not cleaned up from the first yellow flag would take out more cars a few laps later. They're now a proven, common technology for road racers, drag racers and street rodders alike. A number of race series now require that Lexan replace glass.
"I was in Daytona for the beginning of Speed Week the first
year we did this with (NASCAR), and
a glass windshield flew out of a car, went straight up on the back stretch, flipped up a hundred feet, came down and went right through the roof of a souvenir trailer," Mayerle said. "If the guy would have been standing where it came through the trailer he would have been killed."
Racing situations where parts come loose from other cars and start flying end with a bounce off a Lexan windshield where glass would have shattered and ended your day and maybe your racing career.
Even forgetting how much safer Lexan is, the reduction in weight from the front of the car (20 pounds for Lexan versus 80 pounds for the stock glass unit) is enough to make this a no-brainer modification for those serious about putting their cars on a diet.
Is it legal for use on the street? A Lexan windshield is as clear as a glass unit, and safer to boot, but check with your state and local authorities to make sure if you plan to use it on a street car. "I've never heard a customer say they've gotten a ticket," Mayerle said.
Lexan windows have a mar-resistant coating to help protect
them, and you need to take precautions to preserve it. "Without a coating
polycarbonate is very easy to scratch," Mayerle said. "You could scratch it with
Never use polishes or plastic window prep products to clean a Lexan window. "The only thing to use is a clear window cleaner, or soap and water," Mayerle said. Check with your window supplier on what products can be used; many products sold for cleaning windows work well on glass but will ruin Lexan by eating through the coating. Once the Lexan is scratched, it can't be polished clear again.
You can use wipers on Lexan; just make sure that the windshield is wet before you turn them on. The material sheds water naturally, eliminating the need to use products like Rain-X for the most part. If you must use it on yours, use very small amounts, follow the instructions on the bottle exactly and do it on a cooler day (65-70 degrees) out of direct sunlight.
Preparing and installing a 3/16-inch windshield from ProGlass on the Team Dark Horse 1971 Mach 1 road racer was straightforward and took less than four hours using common hand tools. The unit arrived from ProGlass protected by a sprayed-on onionskin coating that protects it from scratches during the installation, and that easily peels off or can be removed with window cleaner or hot water.
The first thing we needed to decide was how to mount it. The simplest way is glue it in like a conventional glass windshield, using 3M black ribbon urethane adhesive.
For the road racer we wanted to do something a little different, though. We'd found it was handy to be able to work on the car with the windshield removed, so we wanted a way to quickly take the unit out and put it back in. We chose to mount our windscreen using aircraft-style Dzus fasteners.
Whichever method you choose, the windshield and car prep remains the same. Your supplier should be consulted for any specific tips and techniques for your particular model. ProGlass' Mayerle says the biggest mistake people make with installations is over-tightening screws or other fasteners. "Anything more than finger tight is too tight," he said, and can leading to cracking of the window. Thread lock compounds should be avoided as well since they'll attack the resin.
Lighter, stronger, and safer, it's hard to beat Lexan. As the windows become cheaper and more easily available, expect to see more race series make them a required safety item. Goodbye glass, you won't be missed.
1. Safety glass? Well, for 1971 it was. Shards of glass went into the driver's seat and onto the shop floor. We were trying to be very careful pulling the old glass out and it still sent glass everywhere. A mess like this is one good reason to go with Lexan.
2. Barnett Performance of Atlanta (800 533-1320) was our source for Moroso fastener mounts (stock #71550) and Dzus fasteners (stock #71500). The Dzus system will allow quick removal for replacement of the windshield or working behind the dash. For racing, the extra time to build the braces and brackets will be offset by the timesavings in the garage and at the track.
3. Removal of all of the old adhesive and paint is very important to insure proper penetration when welding the braces for the fastener mounts. A 4-inch angle grinder with a wire wheel or a grinding disk will speed this process up. Don't forget safety glasses to protect your eyes, and 2-inch wide masking tape on the roofline and A-pillar to help protect your paint.
4. Measure the center of the roofline and the center of the new windshield and mark both with a grease pencil. The center marks will be lined up to make an accurate measurement of the edges near the A-pillar.
5 and 6. Pre-drill all the fastener mounts with a 1/8-inch bit so they can be held with cleco's (an aviation clamp designed to hold items for riveting.) The mounts will be pop-riveted to quarter-inch square tubing before it is welded, allowing the windshield to be pre-fitted. Rivets are easy to drill out if we measured incorrectly.
7. After test-fitting the new windshield, weld the mounts to the tubing. Then weld the tubing to the channel of the A-pillars and the roofline. Welding is necessary as the loads on the windshield at speed will be too great for standard pop rivets to hold. Make sure to grind all edges and welds smooth so as not to damage the Lexan. The Dzus fasteners help to prevent stress cracks by allowing the Lexan to float.
8. After the mounts are welded in, center the windshield and mark it for trimming. You can see through the Lexan to the pillar and roofline below. Trim the new window about a half-inch wider than you need then use a belt sander to fit and bevel the final edge. Here, Cam Lummus puts some skills from his day job as an aircraft mechanic to work in marking and cutting the Lexan, which is used for most aircraft windows and windshields.
9 and 10. Cutting the windshield couldn't be easier. Use a jig saw with a coarse wood blade and masking tape on the base of the shoe to prevent scratches. Lay the unit on a table with a blanket on it and have someone hold the Lexan so it will not vibrate while it's being cut (this will help prevent cracks.)
11. For the final fitting and trimming a die grinder with a sanding wheel works well. Be careful not generate too much heat; Lexan will start to soften at less than 300 degrees.
12. When the final fit is complete use a 3/8-inch bit to center all of the holes for the Dzus fasteners then counter-sink them for a flush fit. You'll be able to see the brackets through the Lexan so lining everything up is easy.
13,14 and 15. Don't paint the edges of the Lexan! It weakens it. Five Star Racing Car Bodies makes blackout kits for most popular models. These kits are very easy to apply with a mix of a few drops of dish soap and water in a spray bottle. Use the supplied squeegee to remove air bubbles. A hobby knife worked well to trim the edges and remove the film from the holes for the Dzus fasteners.
16. Lexan isn't just strong; it's so flexible you can bend it over on itself without breaking.
17 and18. The Dzus fasteners can be pop-riveted with aluminum
rivets and painted to match the blackout kit if you like.
Preformed Lexan Windows
9318 Corneils Road
Bristol, IL 60512
Five Star Racecar Bodies
P O Box 700
Twin Lakes, WI 53181
The South's Racing Equipment Headquarters
465 Memorial Drive
Atlanta, GA 30312
Polk Sheet Metal Works, INC.
1681 Lukken Industrial Drive West
LaGrange, GA 30240