Body: Fabricating the Skeleton
From The Scratch-Built Hot Rod
Chapter 8: Body - Fabricating the Skeleton
Designing the skeleton
|Like building a house, the coachbuilding process begins with a "blueprint". The blueprint will define the main structural elements of the body. It will form the basic shape of the body, and will provide the framework on which the sheet metal skin will be hung. As you may recall, in Chapter 1 (Design, Donor and Tools of the Trade) we developed a sketch of our proposed body drawn to scale (Photo 8-1). Using this sketch, each element of the skeleton can now be drawn in place. For this body, these elements will be either 1x1 or 1x2 rectangular tube. Where framing elements are directly adjacent to each other, such as the door and the door jamb, colored pencils are used to make the drawing easier to read (Photo 8-2).|
|To make this scale drawing life-size, an old trick many of you may have learned in grade school can be used. On a clean 4'x8' sheet of 5/8" particle board, I draw a grid pattern of lines at 2" intervals. If you look closely at Photo 8-3, you will be able to make out the grid lines drawn on the plywood. This pattern matches the grid pattern on the graph paper sketch. Next, carefully transfer whatever is drawn within each grid on the graph paper to the corresponding grid on the particle board. When finished, the sketch on graph paper will be drawn full-size on the particle board (Photo 8-4). This full-scale drawing can now be used to measure, cut and shape all of the framing elements for each side of the body.|
Begin with the door jambs
It may seem an odd place to start, but the doors, jambs and door fitment are essential for a well-functioning and good-looking body. So I prefer building from the doors out, rather than vice versa. Door jambs are a bit more complex than they may first appear. The jamb incorporates the door hinges, the hinge pockets, the latch and the latch pin. In addition, the jambs must be constructed so that they can accommodate the type of door being used: a flush fit door, an overlapping door or a suicide door.
A good set of doors begins with a good set of hinges. Fabricating your own hinges can be a real challenge, particularly if you want hidden hinges such as the ones anticipated for this car. Fortunately, a good deal of the mystery can be taken out of making hinges by creating this rather simple tool which I call the "Hinge Design Machine", or HDM for short.
The HDM is a way of viewing your door and hinge from the top looking straight down. Photo 8-5 shows the four main pieces of the HDM, which are cut from heavy paper stock. This particular HDM was made to create the doors on my roadster, which had overlapping doors (the outermost edge of the door overlapped the body sheet metal rather than the door being inset into the jamb and fitting flush with the exterior body sheet metal). However, the concept can easily be adapted for flush doors or suicide doors, like those which will be built for this sedan delivery project. This tool simply creates a paper mock-up of the door, so that you can see if it will operate properly.
The top piece, #1 in Photo 8-5, represents the front jamb. The hinge pocket area is shown in black stripes, and the exterior body line extending right (to the front of the car) is shown in red. The hinge pockets for this car will be made out of 2x3 rectangular tubing, so the 2" dimension is used to draw this piece to full scale.
|The next piece down, #2, represents the door and the front door jamb. The door is on the left and is outlined with red stripes, while the hinge pocket is on the right outlined with brown stripes. The dark blue line between them represents a quarter-inch gap between the door and the jamb. Note that the hinge pocket on this piece fits directly over the hinge pocket shown in piece #1. Also note that the door length is not drawn to scale and does not need to be. However, the door's depth and the depth of the hinge pocket do need to be drawn to exact scale, which in this case is 2". This is important to ensure that your hinge design will work properly.
The next piece below the door, #3 in Photo 8-5, is the hinge itself. The hinge will be fabricated out of 1/4" by 1 1/2" flat stock steel and welded at a right angle as shown. A pivot sleeve will also be welded on the end as shown. These parts of the hinge must be drawn to full scale. The pivot point of the hinge can theoretically be anywhere within the hinge pocket area shown with brown stripes.The piece at the very bottom of the photo, #4, represents the rear door jamb (in green) and the outside body line extending to the rear of the car (in red).
|Photo 8-6 shows the four pieces of the HDM assembled to represent how the door and hinge will actually operate in your car. Note that we can move the hinge and hinge pivot point anywhere in the brown striped area of the hinge pocket. By sticking a pin in the center of the pivot point of the hinge, as shown in Photo 8-7, we can "open" our imaginary door and determine if that particular hinge pivot location will allow the door to open and close without contact with the front or rear jamb, or come in contact with any other body sheet metal. We can also determine how far the door edge will swing away from the body, or if it might come in contact with any other parts of the body as shown in Photo 8-8. I have fabricated a number of door hinges, as well as trunk hinges, and I have found that creating one of these simple paper mock-ups is an almost foolproof method of ensuring your hinges will work once you weld them up with real steel. It is a bit time-consuming, but it is much cheaper to make a design mistake with paper cutouts than it is to make that same mistake with steel.|
Fabricating the hinges and hinge pockets
|Photo 8-9 shows the basic pieces for fabricating the hinge and the hinge pocket. The pocket itself is 2x3 tubing with a notch cut in it to allow hinge travel. Note that the hinge bolt shown here is only being used for fabrication. It is a 12 mm metric bolt which fits nice and tight inside the 5/8" pipe being used to make the hinge pivot cylinder. The long, 1 1/2" section of pipe will be welded to the hinge, while the two shorter sections of pipe will be welded to the hinge pocket. (Note: when the hinge pocket is assembled and welded to the rest of the door jamb, additional support pieces will be added to the pocket to firmly hold the hinge pin.) The metric bolt is used here only to hold the pipe sections in accurate alignment for welding. Later, this bolt will be replaced by a 3/8" bolt with a plastic bushing around it. These bushings would melt if used while the hinge was being welded together - thus the need for the metric bolt. Photo 8-10 shows the pieces for the hinge being mocked up for welding.|
|Photo 8-11 shows the hinge parts welded together. Photo 8-12 shows the hinge mounted in the pocket. Note how the two short pieces of pipe are welded to the pocket to secure the hinge in place.|
|Photo 8-13 is another view of the hinge mounted in the pocket. Although we won't be installing them quite yet, Photo 8-14 shows the nylon bushing which will be used in the hinges later to prevent squeaking. PEX tube was used to make these bushings, since it makes for a nice tight fit between the 5/8" pipe and the 3/8" bolt which will be used as a hinge pin.|
|When cutting flexible plastic tubing it can be difficult to create a clean, straight and accurate cut. Here's a method that works quite well. An appropriately-sized bolt is inserted into the tube (in this case a 3/8" bolt) and then a cutter designed for cutting copper pipe is used to make the cut (Photo 8-15). Doors on any car take an awful lot of abuse, and that is no less true for a scratch-built car. Therefore, as mentioned above, additional support is being built into the hinge pockets to strengthen the hinge mounts.|
|A 3/16" plate made from 2" wide flat stock will be welded to the top and bottom of each hinge pocket, and a hole drilled in each plate to accommodate the hinge mounting pin. Photo 8-16 shows the eight support plates (two for each of 4 hinge pockets) that have been cut and drilled. The plates are assembled on the pockets (Photo 8-17) and then welded in place (Photo 8-18).|
Fabricating the rear door jamb
|As you follow along, remember that suicide doors are being incorporated into this build. If using normal doors, the front and rear jamb building information would be reversed. Also keep in mind that these will be "flush" doors as opposed to "overlapping" doors. The accompanying illustration titled "Door Types" shows the differences in how these two types of doors fit with the jambs and the body sheet metal. In this chapter the terms "inset" or "recess" will refer to how the flush-mounted door fits into a "step" in the jamb and seals against this step rather than sealing to the exterior of the body as occurs with an "overlapping" door. Before beginning the jambs, sketches are created to ensure things will go together properly. These drawings are made to life-size to aid with accuracy (Photo 8-19).|
|Note that the door is designed to be flush with the car's exterior sheet metal when completed. The jambs therefore need to provide a recessed area for the door to fit into. This is done by overlapping and offsetting the 1x1 and 1x2 tubing which will be used to create the door jamb. Note also that a quarter-inch of space is maintained between the door and the jamb on all sides and that the lip at the edge of the door does not fit tight against the jamb. Rather, a quarter-inch of space is maintained here as well and will later be filled with 3/8" thick weatherstripping so that the door will seal tight against the jamb. Since these doors will have fully-operational window glass, a second sketch (Photo 8-20) was made to show how a slot for the glass would be incorporated into the door, and to ensure that nothing would structurally interfere with the glass in either the raised or lowered position.|
|Using these sketches along with the full-size drawing on my plywood sheet, the pieces of 1x2 tubing for the face of the rear door jamb and the piece of 1x1 tubing which will form the recessed pocket for the rear jamb are cut. Note that the 1x2 pieces are cut in short sections based on where the hinge pockets will be located. These location points are up to the builder and will vary depending on the overall car design. As a practical matter, the hinges should be spaced so that they distribute the weight of the door as uniformly as possible over the entire height of the door and jamb. Photo 8-21 shows the 1x2 jamb pieces laid out with the hinge pockets, along with the 1x1 piece to the right which will form the recess. Photo 8-22 and 8-23 show the pieces for the rear jamb mocked up together while Photo 8-24 shows the parts clamped together in preparation for welding. Photos 8-25 through 8-29 provide a number of different views of the welded rear jamb so that you can get a better idea of how it is put together.|
Fabricating the front door jamb
|On this particular car, the front door jamb will also serve as the windshield post. An overhead view of the jamb unit is first sketched at full size on graph paper (Photo 8-30). The front door jamb will also house the door's mini bear claw latch mechanism shown at the far left in Photo 8-31.|
|Using the full-size plywood drawing, the two main pieces of the jamb (the 1x2 jamb face piece and the 1x1 inset lip piece) are cut. They are then laid out on the plywood drawing to determine the best position for the latch, so that it won't interfere with the window or glass and will also be in a position to hold the door securely (Photo 8-32). Using the faceplate provided with the bear claw latch kit (shown at the right in Photo 8-31), the 1x2 jamb face piece is marked so that it can be cut and drilled for latch mounting (Photo 8-33). Note that the screw holes for mounting must be countersunk so that the tapered screw heads will be flush with the jamb face when they are tightened down.|
|The back side of the 1x2 jamb face must also be cut open to allow for installation and removal of the latch (Photo 8-34). The latch can then be installed to make sure everything fits up to this point (Photo 8-35 and 8-36). In addition, the 1x1 jamb recess piece can now be marked and cut to allow room for the latch trip handle to operate (Photo 8-37).|
|The 1x1 jamb recess piece is then welded to the 1x2 jamb face piece. Photo 8-38 shows these pieces welded together from the back side while Photo 8-39 shows the outer "face" side of the welded jamb pieces.
As mentioned earlier, the windshield post (made from 1x2 tubing) is also a part of the front door jamb unit. Using the plywood drawing, that piece can now be measured and cut to length. Before welding the windshield post to the rest of the jamb parts, a couple of housekeeping items need to be completed.First, another section of the 1x2 jamb face must be cut away to allow full access to the latch for installation and removal. This piece was not cut out originally, in order to maintain the integrity of the 1x2 jamb face during the welding process. Now that it is solidly welded to the 1x1 inset piece, the additional material can be cut away. Arrow "A" in Photo 8-40 shows where the additional metal has been removed from the edge of the jamb face.
|This is also a good time to fabricate and install the levers and rods which will be necessary to trip the door latch - one to operate the latch from inside the cockpit and the other to operate the latch from outside the car. Arrow "B" in Photo 8-40 shows the very simple lever mechanism that will be used for the interior trip mechanism. It is a 2 3/4" long piece of 1/8" x 3/4" flat stock with two holes drilled near the bottom. A 1/4" hole is drilled through the 1x2 windshield post piece and a bolt (see arrow "C" in Photo 8-40) is inserted through the hole and then though the bottom hole of the lever which was just fabricated. Note the four nuts on this bolt; they center the lever. Note also that the end of the lever will protrude into the cockpit area. Later, an oak trim piece will cover this section of the door jamb, and the trip lever will protrude through a slot cut in the trim piece. The lever will then be cut off at the appropriate length.|
|A short rod (arrow "D" in Photo 8-40) is cut, bent and attached to the second hole in the trip lever which was just fabricated. Photo 8-41 provides another view of the latch trip rod and lever.
The trip mechanism rod for opening the door from the outside will be hidden, so that the door and surrounding area will be absolutely smooth. Although it was impossible to get a picture of the rod, it attaches to the very end of the latch mechanism arm which extends into the windshield post. The rod then drops down and out the bottom of the windshield post. The rod is activated by reaching under the front door jamb area of the car to pull the rod and pop open the latch. You can see the tip of this rod at Arrow "D" in Photo 8-42.Photo 8-42 also shows the windshield post, arrow "A", now welded to the balance of the door jamb - the 1x2 jamb face, arrow "B", and the 1x1 inset piece, arrow "C".
Completing the door opening
|With the front and rear door jambs completed, the entire door opening can now be assembled. Using the plywood drawing, the top and bottom of the door opening are cut to length. The pieces are then positioned and clamped together as shown in photo 8-43. The parts of the opening shown in the photo include:
Before final welding of all the joints, two more pieces need to be added. To complete a recessed area for the door to fit into at the top and bottom of the opening, 1x1 tubing must be cut and welded in place to form this lip or recessed area. Photo 8-45 shows this lower recess section being welded in place and Photo 8-46 shows the top recess section being installed.
With the door opening welded together, the main bottom support (rocker) for the body is cut and welded in place (See arrow in Photo 8-47). This main support is cut from 1x2 rectangular tubing.
Creating an inexpensive tube bender
In the next phases of building this body skeleton, some of the structural tubing needs to be bent into various shapes and curves. Tube bending is essential to many scratch-built projects, and high-priced benders are often beyond the budget of many rodders.
One potential solution is to convert a relatively inexpensive Harbor Freight hydraulic "pipe" bender into a utilitarian "tube" bender. The difference is essentially in the dies. The pipe dies that come with a H.F. bender are meant to bend round pipe and they simply will not work well, if at all, when bending square tubing. The hydraulic jack on one of these benders provides plenty of power to bend the tubing, so what's needed is a die or dies that will handle square tubing.
As you will see in the balance of this chapter, some of the bends in a hot rod body are nice tight curves, while others are big sweeping curves. Differently-sized dies will work better for each type of curve you intend to make, so you may have to fabricate more than just one die. However, the following description can be used to create a die for almost any need.
|Bending dies are essentially just a curve to bend your steel over, and the support necessary to keep that curve stable and rigid. The support mechanism will also double as a means to attach your die to the jack or hydraulic apparatus you use to force the bend. The die being fabricated here is intended for making bends with a 3" radius and larger. To create the curve for this die, 6" diameter well casing pipe works perfectly. Photo 8-48 shows a 1" wide section of pipe being marked and then cut off the well casing with a 4 1/2" cutting blade. Photo 8-49 shows the slice of well casing that will be used for the die.|
|To mount the die to the bender, a short section of 1/8" wall, 1x1 square tubing is cut and slipped over the attachment pin that comes as a part of the Harbor Freight bender. Then, another short section of 1x1 square tubing is welded to each side of that first section of tubing. This forms a goalpost-shaped base for the die. Photo 8-50 shows this die base installed on the pipe bender. Next, the 1" wide section of well casing is welded to the die base as shown in Photo 8-51. You can also see in this photo that additional supports, in the form of 1x2 rectangular tubing, have been welded to the back side of the curve.|
|Photo 8-52 shows how these 1x2 support pieces (arrows "A" and "B") are welded to the front half of the well casing. The important thing to remember is that the distance between these support pieces must be at least 1" so that the material you want to bend can easily slip down between the supports during the bending process. During the bending operation, the inside radius of the tubing is compressed while the outside radius of the tubing is stretched. It is essential for good bends that the compressed metal on the inside radius of the tubing has someplace to go. To aid in this process, a 3/8" "crush rod" is welded to the center of the well casing (Photo 8-53).|
|This rod forces the excess metal on the inside radius of the tubing up into an indentation formed by the crush rod. You can see the result of this crushing action by looking at the inside of a bend made with this die (Photo 8-54) Interestingly, the outside stretching of the tubing automatically causes the material to indent as shown in Photo 8-55.|
In addition to the die itself, one other modification must be made to the H.F. bender to improve the accuracy of your bends. To keep whatever material you are bending in proper alignment with the die, roller guides need to be fabricated for both the front and the rear of the bender. Photo 8-56 shows the new die in the bender and Photo 8-57 shows the new roller guides (arrows). These guides are simply pieces of pipe cut to length so that the distance between the pipes is just slightly more than 1". The pipe pieces are slipped over tubing so that everything fits solidly over the pins provided with the H.F. bender (Photo 8-58).
Finishing the side skeleton
|With this modified tubing bender added to our arsenal of tools, the rest of the side skeleton pieces can be cut and welded together. The full-scale drawing is used to cut each piece to its proper length, and the curved pieces are then shaped to match the curvature on our drawing using the tubing bender. Everything is then welded together as shown in Photos 8-59 and 8-60.|
|The completed side section is temporarily mocked up on the chassis (Photo 8-61), and the seat is rigged up in position so a test can be made to determine the amount of headroom that will be available (Photo 8-62). Each of the above steps is then repeated to create the other side of the body skeleton. Photos 8-63 and 8-64 show the two sides of the body skeleton on the chassis.|
Fabricating the door skeletons
|Scratch-built doors can be quite simple, or quite complex. For this project the doors are on the complex end of the spectrum since they will have fully-operational window glass. Also, because of the shape of the car, the doors and door windows are comprised of some odd angles, which makes fabrication a bit more challenging.
Each door consists of what we will be calling a front vertical, a rear vertical, a top horizontal, a bottom horizontal, an interior window frame and an exterior window frame (Photo 8-65). This will become a bit more clear as we proceed.The vertical and horizontal pieces for the door are cut from 1x2 rectangular tubing, while the window frame pieces are cut from 1x1 square tubing.
The rear vertical
|Since these are suicide doors, we will be attaching the hinges to the rear vertical frame piece. After cutting this piece to length, it is laid in the door opening and marked for each hinge position. The vertical is then notched to accommodate the hinges (Photo 8-66) and placed back in the door opening to check that the hinges will be correctly positioned (Photo 8-67).|
|To bolt the hinge to the door, a mounting plate is cut from 1/4" flat stock (Photo 8-68). This plate will be welded to the door frame and has been pre-drilled so that the plate can later be bolted to the hinge itself. To make sure everything is positioned correctly, 1/4" spacers (see arrow in photo) are inserted between the vertical and the door jamb, the mounting plate is lined up on the hinge, and then the vertical is clamped to the jamb and the mounting plate tack welded to the vertical (Photo 8-69).|
|After being tack welded, the rear vertical and hinge mounting plates are removed from the door frame for final welding (Photo 8-70). Photo 8-71 shows the rear vertical and hinge plates after welding and grinding.|
The vertical is then positioned in the door opening with 1/4" spacers again (Photo 8-72), and the hinge is marked for drilling the final bolt holes (Photo 8-73). After drilling the bolt holes, the rear vertical is bolted in place and tested to make sure the hinges work properly and do not bind (Photo 8-74).
The front vertical
|The front vertical for the door is cut from 1x2 tubing, based upon the length shown in our full-size drawing. This is the "latch" side of the door and requires some fabrication for the installation of the latch striker bolt. The striker bolt and mounting hardware are shown in the center of Photo 8-31.
By carefully measuring where the center of the bear claw latch is positioned in the jamb, the front vertical can be marked for the position of the striker bolt. A hole is then drilled in the face of the front vertical for the striker bolt (Photo 8-75).On the back side of the vertical, a hole is cut out slightly larger than the striker bolt mounting hardware. The mounting hardware is then welded into the vertical (Photo 8-76).
|With the striker bolt in place and inserted into the latch mechanism, the front vertical can be positioned in the door opening using 1/4" spacers at the top and bottom and the vertical can be be clamped in place (Photo 8-77). The bottom horizontal (Photo 8-78) and top horizontal (8-79) can then be measured, cut and clamped into place using 1/4" spacers.|
After checking that all four frame sections are square and correctly positioned (Photo 8-79), the door frame can be welded together (Photo 8-80) and tested to ensure it opens, closes and latches properly (Photo 8-81).
The window frames - interior side
|The window openings consist of an interior frame and an exterior frame, with space between them (a channel) for the window glass to move up and down. The interior frame pieces are cut from 1x1 square tubing (Photo 8-82) and clamped into place for welding (Photo 8-83).|
|To improve the look of the butt welded and "squarish" corners of the windows, fill pieces will be added to give each window opening a more rounded look. The curved fill pieces are made by slicing off a 1" length of 1/8" wall, 2" diameter steel pipe (Photo 8-84), and then quartering the pipe section (Photo 8-85).|
|To improve the fit of the corner curves, the back side of each end of the curve is ground flat (Photo 8-86). The corner pieces can then be fit into each window corner (Photo 8-87) and welded in place.|
|Photo 8-88 shows a corner after the welds have been ground smooth and Photo 8-89 shows how the full window looks with the corner curves completed.|
|Although it may seem a bit out of order here, the window regulators will be installed at this juncture. These will be electric units found at any number of catalog outlets and rod shops. These units come from the factory as one piece. However, due to the tight confines within these doors (they are only 2" deep, and less than 24" tall), the units had to be cut apart and modified in order to fit. The arrows in Photo 8-90 indicate how the motor was originally attached to the lift mechanism. The motor was cut off the bottom and the lift bracket and drive cable tube were shortened. The trough that holds the glass also had to be narrowed. Photo 8-91 shows the alternative positioning of the drive motor and drive cable. The arrows show the mounting tabs for the regulator components. Note that in it's final configuration, the drive cable runs through plastic tubing which is bent to attach the motor to the bottom of the lift mechanism. Without the plastic tubing, the drive cable will not function properly.|
Door sealing lip
|To make our door fit properly in the jamb so that it will be flush with the sheet metal on the exterior side of the body and flush with the inside of the jamb on the interior side, we will weld a 1/4" thick spacer around the perimeter of the door frame and then weld a 2" wide by 1/4" thick "lip" around the entire perimeter or the door which will extend 1" beyond the current framing on all sides. This "lip" will provide the seal between the door and the jamb. The spacer and lip configuration is illustrated in Photo 8-92. Photo 8-93 shows the 1/4" spacer sections being welded to the door frame.|
Before moving on to the installation of the door lip, another critical element must be accounted for: crowning.
Virtually every panel on every vehicle since even the earliest of years has been made with a crown. A crown is a "bow" or bend put into the sheet metal, which gives the panel additional strength, and, more importantly, prevents our eye from seeing the panel as concave. If a large section of sheet metal is absolutely flat and is then painted, the human eye will perceive that panel as bowing inward, even though it is actually flat. To prevent this potential concave appearance, all flat panels on a scratch-built car should incorporate a crown or a bow. If the panel is curved, then the crowning effect is less necessary. But for large flat panels, like the door, the roof, or the side of the car, builders should seriously consider employing some sort of crowning technique.
To create a crown in these doors, a 3/8" inch spacer is spot welded approximately halfway up the front vertical, and another spacer spot welded the same distance up the rear vertical (Photo 8-94). The 2" x 1/4" "lip" is cut from flat stock and then bent over the spacer as shown in Photo 8-95. The top and bottom ends of the flat stock are then welded to the door frame. Flat stock pieces are cut for the top and bottom door lip and welded flat to the door framing (no crown). The complete door lip is shown in Photo 8-96, and you can see the crowning effect on both the front and rear verticals.
The window frames - exterior side
|With the door lip crowned and welded in place, the exterior side of the window frames can now be fabricated. This frame is made of 1x1 square tubing and will match the interior window frame we made earlier. However, before the frame is installed, a 1/2" spacer is screwed along the sides and top of the window opening to create a "channel" for the window glass. This channel will be wider at the bottom than at the top, due to the crowning of the door panel. The "spacer" is installed primarily to prevent the weatherstripping, which will be installed later, from being driven too deep into the channel. Photo 8-97 shows the pieces of 1/2"x1/2" tubing used for the channel spacers and photo 8-98 shows the spacers (arrows) screwed into place.|
|The 1x1 exterior frame pieces (see arrows) are then clamped to the door frame and welded in place (Photo 8-99) creating the window channel shown in Photo 8-100 and the slot at the top of the door for the window glass to move up and down (Photo 8-101).|
|With the window frame pieces in place, the corner curves are cut and installed in the same manner as the interior corner curves. Photo 8-102 shows the door with the exterior corner curves nearly completed.|
|With the doors and side panels of the skeleton completed, the roof ribs are next on the agenda. Note that up to this point we have not sketched or discussed anything regarding the width of the body. This has been done intentionally, to allow some flexibility once the car's shape became better defined by the completion of the side skeleton structure. With the side skeleton sections mocked up on the chassis (Photo 8-103) we can alter the shape of the car, making it wider/narrower in front or wider/narrower in the rear, until it looks the most visually appealing. You can also test your seat configuration and other interior design elements and make any necessary adjustments in body width to fit your plans for the interior. This would be very difficult to do with sketches or even in Photoshop. So, it is quite advantageous to leave decisions regarding body width until this point in the fabrication process.|
Once you are satisfied with the front and rear widths of the body, the side sections can be plumbed vertically and clamped in place. The sides are also cross-braced to ensure that they do not move during roof fabrication and welding.
To begin the roof fabrication, you must first decide the radius of the curves that will transition from the side of the car to the roof (see arrow A in Photo 8-104), and from the rear of the car to the roof (arrow B in Photo 8-104). Though not necessary, it is sometimes best to make these two radii the same, since it makes forming the corner cap easier.
For this particular car, the side curve (A in Photo 8-104) will have a 3" radius. This will place the perimeter tubing pieces for the roof 3" above and 3" inside the top tubing of the side skeleton. Photo 8-105, which represents a cross-sectional view of the roof and side section, may help illustrate how the relative position of the roof tubing and the side tubing is determined by the radius of the corner curve.
Photo 8-106 shows the perimeter structural members of the roof being positioned and welded in place, while Photo 8-107 shows how the roof members are permanently attached using short supporting sections (see arrow) to bridge from the side section to the roof ribs.
The back skeleton
|With the roof perimeter in place, the skeleton for the back of the car can be fabricated. The curved ribs for this section are formed using the tube bending dies described above. This process requires slow and careful bending of the tube, a little at a time. The tubing is removed from the bender often, and checked against the drawing of the curve that was made on our particle board "blueprint" for the car (Photo 8-108). The main sections of the back skeleton are then welded together (Photo 8-109 and 8-110).|
|With the basic four pieces of the back section welded together, the unit is positioned and clamped into place. As can be seen in Photo 8-111, a large number of supports and clamps are necessary to get this back section properly positioned and held firmly in place for welding.|
|Photo 8-112 shows the rear unit installed. The curved corner supports (see arrow in photo) are bent using the die created earlier in this chapter, and have a 6" diameter. Then, additional rear structural members are added, including a lower crossmember, arrow A, and additional vertical supports, arrow B, in Photo 8-113, and other supports as noted by the arrows in Photo 8-114.|
|A center rib is added to the roof (Photo 8-115). This rib is bent upwards approximately 2" near its center point. This will provide a crown at the center of the roof when the sheet metal is applied. The body was originally designed to incorporate a rear opening hatch. However, as will be described in Chapter 10, this hatch was later eliminated, and a pickup bed added to the rear of the car instead. In some of the pictures that follow, you will be able to see that opening hatch. Since it will not be a part of the car in its final form, the details for the hatch fabrication are not included here.|
Cowl and firewall hoop
|The cowl crossmember (arrow) serves as the bottom support for the windshield as well as the support for the cockpit side of the cowl top. It is bent first, then cut to length and welded in place (Photo 8-116). The firewall hoop consists of five separate pieces of 1x1 square tubing (Photo 8-117).|
|The top center section of the firewall hoop is bent to match the bend in the cowl crossmember, and the two corner pieces are bent to approximately 100 degrees using our bending die. These pieces are then welded together (Photo 8-118) and installed on the body skeleton (Photo 8-119).|
The completed skeleton
The skeleton for our body is now complete and ready for sheet metal. Photos 8-120 through 8-125 provide a number of views of the completed framework.
|< Body: A Gallery of Scratch-Built Cars || Body: Applying the Skin >|