The seat position is very...
The seat position is very important. The driver must be comfortable all the way to the end of the race.
In a quick recap, last month we installed the Moser rearend along with the Jaz 16-gallon fuel cell in the Dave Pletcher chassis. The rubber trailing arm bushings were replaced with Energy Suspension polyurethane bushings supplied by Day Motorsports. The Moser rearend was fitted with oversized calipers made by US Brake.
This month, we are going to work on the middle of the truck. We are going to attack the seat mounting, the pedal mounts, the tiny driveshaft, and the belts and nets.
It is vitally important to properly mount the seat. The ergonomics involved are important. Ergonomics refers to fitting the driver to the car so that all the controls are easily used and the driver is comfortable at the end of the race. A driver who fits well in the car will have less stress and will be faster toward the end of the race.
We are using an Ultra-Shield seat in the Fastruck. This one has wrap-around shoulder supports and head supports. The seat and supports were welded into one unit. I consulted someone at Ultra-Shield to find out if bolt-on supports were available, but I was told all the supports were welded in place. It seems there had been cases in which the supports had been improperly installed or selectively left off by racers. The cure was to weld all of them in place. Following Ultra-Shield's form and taking all the necessary measurements to properly fit the seat was simple.
Although our seat had a 20-degree layback style, it still fit the straight-up position necessary for the Fastruck. The 20-degree angle gives lift and support to the legs. We made a mockup, blocked the seat in place, and asked our driver to take a seat. Once seated, she checked the angle and made sure she would be able to reach the controls with ease. This was an opportunity for us to locate and mark the positions for the pedals and the shifter.
To obtain a good seat location, we made slight adjustments to our mockup. Left weight is desirable, of course, so we moved the driver to the left, making sure her arm and elbow cleared the door bars when she turned the steering wheel quickly. The last thing you want is a driver with an aching left elbow making left turns while trying to race hard. With the seat positioned, we used a marker pen to make reference points on the seat location before the driver scrambled out. I promise-it's difficult to exit a seat that is not bolted down. We were sure to mark all the mounting holes before removing the seat.
The chassis builder, Dave Pletcher, provided the crossbar that was placed under the front of the seat along with a drilled and tapped two-hole bracket that was welded to the upper area of the back of the seat. Brackets from A&A Manufacturing were then used to complete the installation. We could have drilled through the front crossbar, but we didn't want to sacrifice any strength; so the A&A tabs with 71/416-inch holes were welded to the bar. Another form-fitting A&A bracket was bolted to the seat and the upper seat mount on the chassis.
Always mount the seat to the 'cage and/or chassis-never to the floor or other sheetmetal. In a side crash, the seat, driver, and belt mounts must move as a single unit. Dave Pletcher had welded in seatbelt mountings for the chassis. These were correctly placed so that the G-Force lapbelts went back at a 45-degree angle and the shoulder belts were positioned rearward, just below level. We used a five-point harness that fit through the seat and connected to a tab on the crossbar. G-Force belts come with instructions on proper adjustment and placement. The Ultra-Shield seat has openings in the correct locations for all the belts, and there are soft aluminum channels around the belt holes. This presents a smooth surface if a belt were to rub against the opening.
The seat was removed to get all the holes properly drilled, so we had room to mount the throttle pedal. We used the very adjustable Coleman roller bearing throttle pedal. This piece has a roller foot contact that lets the driver's foot move smoothly for good throttle control. The shaft also has needle bearings to lessen the drag from a heavy foot. Coleman makes two types of these throttle pedal assemblies: One mounts to a flat front firewall, while the other mounts at an angle to the side of the foot box. Two angles are available. We had no choice but to use the side mount, as the foot box was too narrow to allow the firewall mount. The firewall mount would have been easier to install, so use it if you can.
On the engine side of the firewall, Coleman provides an adjustable lever arm that can be moved right and left. It has a number of holes for vertical location of the linkage to attach to the carb. Where you attach the linkage will determine the response ratio of the foot to the carb. I prefer a slower ratio (longer pedal travel) so that feathering the throttle can be more precise. Your driving style may dictate something different.
While the seat was still out and we had room to work, the Wilwood pedal assembly and master cylinders were installed. This was a dual master cylinder unit with a balance bar. The adjuster cable was attached to the bar and routed upward on the left side of the driver. By turning the knob on the brake adjustment cable, the bias can be changed to favor the front or the rear. Dave Pletcher had thoughtfully punched holes in the front of the foot box locating the master cylinders.
Since we mounted the master cylinders low (to help keep the weight low), we used the Wilwood polyethylene remote reservoirs. These were mounted about 12 inches higher than the master cylinders. Without the high-mounted remote reservoirs, the low master cylinders would have required a residual pressure valve (2 psi is needed for disc brakes) to prevent the brake fluid in the calipers from running back to the master cylinders. Without the residual valve or the high-mounted master cylinders, sometimes a pump of the brake pedal would be required to bring the brake pads out to the rotor before proper braking force could be applied.
A Longacre Accubrake unit was mounted on the firewall beside the master cylinders. This adjustable unit can soften the brake application. This tuning tool will be used, in our case, to tighten the rear end during corner entry by softening the rear brake application. For dirt track applications, it might be used on front brakes.
The tin work inside the cockpit left a nice flat panel to mount the gauges. We used a pre-wired Longacre gauge panel with all the gauges mounted. The panel was also equipped with gauge lights. In addition to the telltale tach, it included a water temperature gauge, an oil pressure gauge, and, how nice, an oil temperature gauge. The water temperature and oil pressure gauges used a standard hookup. The oil temperature sender was attached to the Bullet Performance Engines racing oil pan. The pan has a kickout on the right side, and a bung was provided for this purpose. This bung was located on the right side of the pan behind the starter, which is an indication that the oil temperature sending unit should be installed before the starter. The oil temperature gives a driver some clues to what is happening inside the engine. If the water temperature gets as high as 230-250 degrees F, the oil temperature will normally be higher. With a water temperature remaining somewhat constant when the oil temperature rises, it might be a good time to think about the cost of your engine. A good synthetic oil (such as the Royal Purple we use) will work at a higher temperature than pure mineral oil.
A Longacre switch panel was mounted to the driver's left. This set included a heavy-duty ignition switch with a quick-off tab, a momentary switch for the starter, and an auxiliary switch that will be used for the Flex-a-lite 3,300-cfm electric fan.
With all the pedals mounted, we cut the hole for the Coleman steering shaft where we thought we wanted it to be. I recommend that you study the proper location for the shaft hole to avoid having to cover the first hole.
Chassis builder Dave Pletcher...
Chassis builder Dave Pletcher had installed a tube across the cockpit.
Coleman makes these roller...
Coleman makes these roller bearing throttle pedal assemblies. The cross-shaft is supported on two bearings.
The foot box on these cars...
The foot box on these cars is rather small. I'm sorting out the fit of the Wildwood master cylinder pedal.
A shot inside the foot box....
A shot inside the foot box. Both the Wilwood brake pedal and the Coleman throttle pedal are visible.
On the engine side of the...
On the engine side of the Coleman pedal, the arm has six holes for vertical adjustment.
The master cylinder mounting...
The master cylinder mounting holes in the foot box left the master cylinders very close to the chassis at the front.
We didn't want to use a residual...
We didn't want to use a residual valve because the master cylinders were mounted low.
Our aluminum Coleman steering...
Our aluminum Coleman steering shaft is supported by a Coleman aluminum rod end.