Lighter is faster, and in some cases, cheaper as well. Lighter cars require smaller engines, less revving and tend to be easier on parts. With 610 hp at the wheels, we need our Dodge Demon to weigh 2,500 pounds or less to run low 9s in the quarter mile. Polycarbonate windows are another small way to achieve that goal.
It's important to note that polycarbonate is not Plexiglas. Both can be purchased in sheets, but polycarbonate has properties that prevent it from cracking or shattering upon impact. Polycarbonate may also be heat formed and used where the factory glass is curved, like a windshield. For about $400, you can buy rough cut windows and a basic installation kit from companies like Alston Race Cars, or for about $1,200, you can buy custom formed windows from Pro Glass without the installation hardware. By the time we were done adding poly side and quarter windows, we had about $1,500 tied up in this project, including labor. The effort took about 50 pounds total off the car when you add the internal door hardware and glass. That equates to about 0.05 gain on the racetrack. It's a small gain for the money, but when a car gets into the 10s, you have to pay to play.
As of this writing, the Demon went 6.76 at 102 in the eighth-mile (10.50 in the quarter) on its first pass without really trying. At 2,500 pounds, the power to weight ratio math says it will go 5.99.
The kit we bought from Alston Race Cars included six pieces of rough-cut polycarbonate, hardware, and a tubing bender. We took the car to Bullet Fab in Gardena, California for the install.
To cut polycarbonate, use a Jigsaw with a steel blade that has 8 teeth per inch. A finer blade will melt the polycarbonate requiring cleanup.
A good (English) file was used to shape and fit the poly to the contour of the window.
Standard tabs were provided with the Alston kit but we used a curved tab (left) that allowed us to lay the tubing and the tabs flat on the table, making the welding easier.
To get the bends as tight as possible, we used 0.375 OD steel tubing with 0.28-0.32 wall thickness. We used a brake-line bender to make the 90-degree turn on the B-pillar.
This could be a MIG job but the guys at Bullet used a TIG welder to build the frame.
The mounting tabs are 0.045-inch triangles made of chromoly steel. We used nutserts behind the fasteners.
This tool is called a countersink cage and it is used to countersink the 82-degree fastener heads. We used 6/32 fasteners on the 1/8-inch polycarbonate.
Using larger 8/32 fasteners would have required a deeper countersink to get the fastener to sit flush, risking a crack at the base of the hole.