The crossbars are in place in the side rail slider tubes. Use Vise-Gripsto hold everything in place. At this point, the sides and crossbarsshould be assembled around the seat. This can be done with the seat inthe car to be sure of the fit. The seat should cradle down between theside rails with about 1/8-inch clearance on each side.
We used a CSC Racing seat mount kit for this project. This kit embodiesall the features I like in seat mountings. The parts are made of11/2x0.095-inch wall tubing and are pre-bent. Most of the tubing is alsonotched. The exceptions are the parts that must be cut to length to fityour particular installation.
The instruction sheet is clear about which steps to take and in whichorder. The notched side frames are welded to the short slider tubes.Then the upper and lower crossbars are inserted, making assembly notunlike an erector set. It makes for an easier installation if only thelower cage door bar is in place at this time.
All of the seat-frame work is now tack welded. This assures that all theparts fit before final welding. A tab is placed beside the seatfor an additional mounting point. The A&A double shear tab forthe lap belt is also tacked into place. It must be positioned so thatthe belt lies across the driver's pelvic area and does not ride againstthe seat. Remove the frame from the chassis and do the finishwelding on the bench. This allows you to turn the frame for the bestwelding positions.
The seat side frames should be wide enough apart for the seat to cradledown between them. The front edge of the seat should rest on the frontcrossbar.
Ergonomics is a big word for making sure the driver is comfortable andwell-fitted to his surroundings in the cockpit. An ill-fitting cockpitwill be distracting to a driver. This can lead to driver stress andfatigue near the end of a race when he or she really needs to be alert.Take the time to fit the driver to the car. This begins with seat typeand location. The steering wheel as well as other controls can then bepositioned.
We decided to use an Oval Craft seat obtained from our local supplier,Racecar Engineering. This is a nicely formed, well-crafted aluminumseat. I particularly like the transition angle of the seat bottom to theseatback. In addition, the cover has tabs to tug on while snapping itdown.
The top rear seat mount has been tack welded to the seat frame. This isan A&A part. It is bent in the middle to conform to the shape ofthe seat. To the right is the upper frame-to-cage crossbar mount. It has also been tacked into place. The frame is readyfor final welding.
Most stock car seats have a 20 degree angle between the back and bottomwith the headrest at a lesser angle. Normal mounting will have theheadrest in the vertical position. This will set the angle to mount theseat. Block the seat up with whatever is handy to get it in the positionyou want it. This may take some time, but it is well worth the trouble.Get the seat angle, height, and fore-and-aft location correct. You alsoneed to consider the clearance between the driver's helmet and the topof the cage.
With the seat blocked up in the desired position, the side frames andupper and lower crossbars can be assembled around the seat. There shouldbe a minimum of 1/8 inch per side clearance between the seat and theside frames. The front of the seat should rest on the front crossbar.Now the front crossbar's bent end can be located to the bottom door bar.Twist it as necessary to get the right position. Vise Grips are a goodway to hold everything in place temporarily. The notch is easiest cutwith a tube notcher, but it can be done on a chop saw or even with ahand grinder. Once this has been done, the lower crossbar can be tackwelded to the side frames.
The upper door bar can be tacked in place so that the upper crossbar canbe located. When this is done, the upper crossbar can also be tacked inplace. There is one more mounting bar, which should be located to theright side of the upper bar and then to the rollcage crossbar. With thistacked into place, the seat frame can be gently removed from thechassis.