Tech Talk · Mike Neff · Tuesday March 20, 2012
Greg Marlowe is the Competition Director for Performancenter Racing Warehouse in Statesville, NC. He is a former race car driver (one who still threatens to get behind the wheel again) that purchased Richard Childress Racing cars in December of 2004, the start to what become his own successive automotive business. He developed one of the most competitive Late Model chassis in the sport and merged his operation with Performancenter Racing Warehouse in 2011. Now, he continues developing the Marlowe Racing Chassis along with the PRW Straight Rail chassis. He spent some time with Frontstretch recently to discuss chassis in short track, perimeter and straight rail cars.
Mike Neff, Frontstretch.com: Let’s start out with the differences in chassis. Late Models are predominantly in the Southeast where Super Late Models are more common throughout the rest of the country. What is the difference between a Late Model chassis and a Super Late Model Chassis?
Greg Marlowe: A Late Model stock chassis is based more off a [Nationwide] car. Perimeter-style chassis with a steering box. They are based more on a conventional car style and they have to weigh 3,100 pounds. A Super Late Model is basically a 2,800 pound, straight rail, lightweight chassis, aluminum interior, just a quicker race car, period. There are less rules so we can do more what we need to do to make the cars faster and it just makes for a really good race.
Neff: When you talk about a perimeter chassis versus a straight rail chassis, is that referring to the frame rails that are running from the front of the car to the back of the car?
Marlowe: If you run a center line down the middle of the car, the perimeter car will have the same distance from the center line to the outside of the frame rails on both sides of the car. That is why it is called a perimeter car because the measurement to the perimeter is the same on both sides. In a straight rail car, the right side frame rail runs in a straight line, from the front of the car to the back, a certain distance from the center line. The driver compartment side sticks out from the center line on the left side and that is where the name Straight Rail comes from, the rail on the right side being perfectly straight from the snout back, while the left side sticks out where the driver sits.
Neff: Is that where the name Offset Chassis comes from?
Marlowe: Yes, that would be the same thing. A straight rail or an offset is the same thing. The straight rail car, you can offset the suspension up to three inches. The right-side suspension, because of the way it is built, can be up to three inches longer. That is why they are called offset because it is allowed to be offset.
Neff: As far as the rest of the geometry on the car, A-arms and shock travels, are those relatively the same no matter what kind of car, perimeter or straight rail?
Marlowe: In some fashion, roll centers and all of the suspension, an upper A-arms is an upper A-arm, whether on a Cup car, Offset or Perimeter car. An offset/straight rail car is allowed to run a strut suspension which has a more straight out arm for the center of the car with the strut rod going back. Most of the Late Model stock cars run a fabricated lower arm, which has two hookup points, that resemble an older Camaro or Nova type suspension. That is where most of the suspension comes from like on a Cup car is the older cars that had the stock style suspension where we came from.
Neff: Are Cup cars built on a perimeter chassis?
Marlowe: Yes, all Cup cars are perimeter chassis.
Neff: Outside of the chassis, most of the race cars run a truck arm style suspension these days don’t they?
Marlowe: Most straight rail cars run a three-link suspension, which is more of a less expensive suspension. They use aluminum trailing arms to connect the rear end to the frame. You can have different length trailing arms to help the car turn. The third link helps drive the car down into the ground. It is all mounted on Hine joints. The Late Model stock and Cup cars run a truck arm-style suspension which is based off of a 1964 Chevrolet Pickup.
Neff: Where you have the two arms that connect to the frame near the center of the car and extend back to the rear end to keep it floating up and down?
Marlowe: Yes, you have two arms that run from the center of the car to the rear end and then you have a Panhard bar that keeps it centered.
Neff: On the three-link suspension, does the third bar go to the top of the rear end?
Marlowe: Yeah, everything works on Hines so the rear end is free to move up and down. The turn or twist of the rear end pushes the car down with that top link.
So there you have it: the chassis of race cars are similar in some ways to the cars that fans drive on the streets, but obviously there are major differences as well. Perhaps the most shocking is that the suspension attached to those chassis, while very modernized thanks to all of the engineering involved, are based off of stock cars that were driven on the road back in the mid-to-late ’60s.
Looks like EFI is just the first step in NASCAR’s modernizing process.
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