IMCA Stock Car: January 2001 - The Interior

Think of the cockpit of your IMCA stock car as an office. After all, that's where you go to work each race night. And just like in an office, you'll want to be comfortable. Fixtures and equipment must be properly placed to maximize their efficiency.

In this fourth installment of our Building an IMCA Stock Car series, we examine the key elements that will keep your in-car office running smoothly.

PLEASE BE SEATED

A driver must be comfortable to drive well. This means time and attention must be paid to the placement of seat, steering, brake, and throttle controls. Don't rush this. It's not as easy as it looks, but your time will pay dividends. I obtained most of my supplies from Poske's Performance Parts and QuickCar Racing Products.

The first thing to be located in the cockpit area is the seat. Everything else stems from that. I chose a Richardson seat. The fit of the seat is very important. Safety is one reason for a properly fitting seat, but another is driver feel. The driver needs to feel attached to the car. Available options include shoulder wings, head wings, and leg supports.

Be aware that some less expensive seats are made so the belts wrap over the seat. This design allows the seat side to flex in and loosen the belts under a hard crash. The Richardson seat has holes near the bottom corners to feed the belts through. So, the belts hold you rather than the seat, which results in a safer situation. Consider a good, well-fitting seat as a capital investment, and use it for years as you build or buy new race cars.

Your seat must have a good mount; this is not a place to save weight. In this car, the seat mount is 1½-inch tubing attached to the lower door bar. Two more tubes are welded to the first. They run under the seat and up its back where they are welded to the rear rollcage-hoop crossbar. Six tabs are welded to these tubes, each of which is bolted to the seat. This is important, because if the seat is fitted with too few bolts, and it rips loose in a crash, the driver will swing by his belts like a pendulum.

Watch where you place the seat. According to IMCA rules, no part of the seat can be behind the back edge of the door post. I recommend staying at least ¼-inch forward of this point. Remember, the cage is several inches rearward of this location. We mounted the seat so its centerline would be 16 inches from the inside of the lower door bar, the clearance found in many fullsize cars. This is as far to the left as we wanted to go since the driver's head must stay inside the rollcage. Still, you get good left-side weight.

The driver's head, with helmet, should be a minimum of 2 inches below the rollcage. More clearance would be better. My driver has 4½ inches. In a crash, both belts and people stretch.

TURN, GO, STOP

Now that the seat is set, the steering wheel can be positioned. It should be on a centerline with the seat. The aluminum steering wheel is mounted to a splined quick disconnect which is then mounted to the 2:1 Howe quick-steer unit. I have found a distance of 25 inches from the steering-wheel hub, measured parallel to the ground, to the seat back to be correct for drivers 5 feet 7 inches to 5 feet 11 inches tall. Use this as a starting point, and fit the steering wheel reach to your driver.

Always use at least two universal joints in a steering shaft assembly. This prevents binding and allows the shaft to fold up in a severe impact instead of becoming a spear.

The brake and throttle pedals are located 37 inches from the seat back measured at its bottom. This distance can be adjusted at the pedal. Keep them about 6 inches off the floor. We installed the pedals with a 3½-inch space between them. These measurements are comfortable for us and are meant as guidelines; make yours right for you.

Notice that only one master cylinder is used. I chose a proportioning valve instead of two master cylinders. For the bullrings on which we race, this is a smart way to save some nickels and still get good results. I like the lever type. It is much easier to set while you are three-wide on the front straight and scraping the wall. For longer tracks (half-mile or more), the dual master cylinders with a balance bar are better.

I spent considerable time building a brake pedal assembly. It took many cut-and-try experiences before I got it right. Just call Dave Poske and ask him to send you a pedal assembly and a Howe master cylinder.

HAVE A BELT AT THE OFFICE

The belts I use are from M&R Products. In the past I have struggled with conventional buckles, holding four belts in place while trying to latch the last. This time, I'm using M&R's Rotary Cam Lock buckle. Each belt plugs in separately, and a twist releases all of them. When you are trying to get buckled in with barely enough time to make the feature, the Rotary Cam Lock is what you need.

The belts have a quick-disconnect feature that allows easy removal of them from the car. No more hosing them down at the car wash and leaving them in the sun to dry. A little care extends their life greatly.

Each belt is attached to a seat-frame tube. None are connected to the body or floor of the car. If the 'cage moves in a crash, the driver should move with it. Obviously, the belts should move with the driver.

I like separate shoulder belts rather than the Y type. If a Y belt is used, the mounting must be farther from the driver. Longer belts stretch more. The more the driver moves, the more likelihood of contact with a solid object.

Again, something different. I'm not using a window net in the conventional sense. Two M&R sprint-car head nets are installed to limit the side motion of the driver's head and prevent neck injuries.

When doing this, sprint-car–type arm restraints must be used (IMCA requires arm restraints when a window net is not used). These keep the driver's hands in the car but still allow freedom to perform all necessary driving functions.

"The arm restraints should definitely be worn just above the elbow. You don't want flying elbows," says Virgil Brown of M&R Products.

The arm restraints must be adjusted so the driver's hand cannot reach outside the 'cage. They snap loose with the buckle. My driver, Martha, felt comfortable with them in a sprinter, so we are using them here.

I believe the use of head nets and arm restraints may be a step in a better, safer direction. The head nets do not restrict side vision like a window net does—nor must a net be removed to exit the car. Additionally, the arm restraints help prevent a shoulder injury where the right arm is jerked straight out in a right-side impact. It has happened to us.

GAUGING YOUR SUCCESS

I do things differently than most—this holds true for the gauge mounts, too. I won't put any tin inside the car—no dashboard, no aluminum covering the cowl area. Everything will be open, easy to clean, and easy to see. This is not Winston Cup.

I'm using the Hyper Glow gauges, Pro Comp memory tach, and switches from QuickCar. The benefit of using their assembly is that everything arrives prewired with plug-in connections. Quality electrical connections result in a reliable electrical system.

I didn't have a dash, so I built brackets for each gauge and switch panel, which are welded to a single ¾-inch tube. It is mounted to one side and at an angle to the driver. On short tracks, the driver doesn't have much time to watch them. Mounted this way, when the car comes in, I or another crewmember can see the readings as the car rolls to a stop. You might be surprised to see how much information is lost by the time the engine is shut down, the excited driver gets out, and a crewmember reads the gauges.

One piece of office equipment you should have is the Pro Comp memory tach from QuickCar. Don't depend on what rpm the driver thought he saw; use the memory function to get accurate numbers. From this you can determine the correct gear and maybe even the correct cam. I consider it an essential tool. If your driver insists on reading the tach, have him read the lowest rpm in the corners.

CHARGING UP

Battery cables are often a problem with rear-mounted batteries. I chose to use a No. 2 battery gauge wire. Smaller wire will start your engine under optimum conditions, but will it restart a hot motor after a 19th-lap red flag?

The Optima sealed battery from Poske's is mounted behind and slightly to the right of the left-rear wheel. It has 925 cranking amps—more than enough. For this project, I obtained a QuickCar cable kit along with a crimping tool. The tool makes much better connections than the hammer-on-the-sidewalk method I have used in the past.

Weld a tab to the chassis, close to the battery. Bolt the ground cable here. The positive cable runs to the QuickCar master disconnect switch in the back window, then proceeds to the front to the starter.

GETING TANKED

An office can't run without coffee; a race car won't run without fuel. In this case, it is racing-grade gasoline that will be contained in an ATL fuel cell. This is a fuel cell, not a plastic tank. ATL makes fuel cells for cars like this as well as Indy cars and Formula 1.

This tank, like IMCA requires, is in a metal can. ATL puts in some additional effort. The inner hard bladder is not just a plastic fuel tank. It is made of cross-linked, rubberized material.

This bladder is capable of severe deformation and will return to near-normal shape. The fuel cell is mounted as far to the left and the rear as I could get it and still protect it. The idea of mounting the tank to the right for better handling at the end of the race doesn't work too well here. In longer races, and when running alcohol, there may be some gain. Twenty-five–lap features with two gallons of gas doesn't change much. Fill the tank when you need ballast.

I decided to go with an 8-gallon tank, which is more than sufficient. Also, the weight is in the left rear, and that's not a bad thing in these cars. The tank is mounted to the X brace under the trunk floor. You must use two 1/8- x 2-inch, which go all the way around the tank, not just enough to hold it down.

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