Читать книгу Project Street Rod - Larry Lyles - Страница 13

Whenever I begin a new project, the first thing I do is position the car in the shop and elevate it on jack stands. That places the vehicle at a comfortable working height and also affords me ample room when I need to go underneath the vehicle to remove all those road-grime-coated parts. This project will be approached a little differently.

For the time being, the wheels will stay on the car and the car will stay on the floor. That’s because I have a number of modifications I want to make to the frame under this car, and the best way to access the frame to accomplish those modifications is to remove the body. To do that, I’ll use an engine hoist to lift the body straight up, then I’ll roll the chassis out from underneath. The body will be sent out for media blasting to get rid of the rust while I concentrate on modifying the frame. How do I maneuver a bulky car body around the shop? I have a steel cart measuring roughly 4 x 6 feet with rollers under it (photo 1). It is strong enough to support almost anything I place on it.

SOME CHASSIS ANALYSIS

With the body off of the car, three things jump out at me as I study the chassis. First, the front suspension is an I-beam-style axle, and it has got to go. I-beam axles may look good under a Bucket T or a ’32 Ford, but this type of suspension is never going to give me the quality of ride or degree of handling I’m looking for with this project (photo 2).

Second, the transplanted GM rear axle assembly and its accompanying leaf spring suspension also must go (photo 3). I have no kick against GM products or leaf spring rear suspensions, it is just that I have a very nice Ford 8.8 rear end complete with a factory four-bar suspension that not only will give this car a smooth ride but also will give me some options when it comes to determining the final riding height of the car.

Third, now that I have the body off of the frame and a better view of the center X-member, I can see some hacking and chopping has already taken place to get the automatic transmission to fit. I use the word fit loosely, as this installation is anything but acceptable (photo 4). The transmission is bumping the frame on the right side and doesn’t offer much more room on the left. I knew these were areas of concern coming into the project, so all that is left for me to do now is go to work and fix them.

PHOTO 1: The body is placed on a steel cart to allow me to move it around the shop as needed.

PHOTO 2: This I-beam axle and drum brake setup may have been state of the art in 1946, but to meet today’s standards it has to go.

PHOTO 3: The GM rear axle came from a car with a coil spring suspension. It was converted to leaf springs, and now I’m converting it to dust gatherer.

THE DISASSEMBLY BEGINS

I start by placing the chassis on jack stands so I can remove the wheels and gain a little more working room. Next, I remove the engine and transmission. I’d like to hang the engine on an engine stand and send the transmission out for a rebuild, but I’ll need both units a little later to help reconfigure the engine and transmission mounts. So for now, I leave the transmission attached to the engine and store them in the corner where hopefully they will be out of the way until I need them.

The next piece to go is the GM rear end. A few bolts and the unit will drop right out. I’m not going to concern myself with marking the rear axle centerline on the frame to help position the new axle because the previous owner installed this rear axle, and I can’t be sure he installed it to the correct dimensions in the first place. To determine the correct rear axle centerline, I have access to a set of original 1946 Ford frame dimensions that will at least give me a place to start.

The front I-beam axle is a different story. Up here, the old suspension is basically stock, so before any of these parts are removed, I’ll mark a reference point on the frame to help define where the front axle centerline should be located. I’ll also take a measurement from the axle to a point roughly 4 feet back on the frame that will help me when I’m ready to install the new front suspension.

PHOTO 4: The lack of clearance around the transmission makes this installation unacceptable. I’ll have to make some modifications to this part of the frame.

The reference point for the axle centerline is found by laying a straightedge across the frame from center to center of both axle kingpins and marking the centerline on the top of the frame. I won’t use this mark as the ultimate guide to positioning the new front suspension within the frame, but it will serve as a base reference point later when I install the new front suspension cross member.

The other measurement I need is from the axle centerline mark on the frame back to a hole in the top of the frame located just behind the front body mounts. That measurement is 52 inches. With these two specifications noted and marked, I can unbolt the old front suspension and remove it as a complete unit.

DOWN TO THE BARE BONES

With the ’46 stripped down to the bare frame, my next step is to determine an approximate final curb height for the car. How am I going to manage that with no suspension under the car? Actually, it won’t be that difficult. Since I’ll be modifying the frame to accept new suspension components, I can control the position of those components by the way I install them on the frame. That begins by determining the amount of ground clearance I’ll ultimately want under the car. I’ll use the body mount perches riveted to the sides of the frame as measuring points and level the frame at 14 inches (photo 5). This is an arbitrary number and may change as I move deeper into the project, but for now it gives me a good place to start.

The plan also calls for giving this car a few degrees of front-end rake when finished. That means the front of the car will sit slightly lower than the rear, so leveling the car at 14 inches will actually end up giving me a car that sits roughly 16-18 inches from floor level at the rear and roughly 10-12 inches from floor level at the front when completed. Sound confusing? It does. But trust me, everything will work out. I just need the frame to sit dead level for now to ensure that every modification I make to the frame ends up level to the frame and not installed crooked or leaning off toward the back forty. What did I use to level the frame? In this case, a long carpenter’s level isn’t of much use since the frame has several dips and bumps along its length. Instead, I opted for a short, 12-inch-long level I could place at various points along the frame, both lengthwise and crosswise, to get it level. Having a large supply of paint stir sticks also helps, as they can act as shims where needed between the jack stands and frame.

Now I can move my replacement Ford 8.8 rear axle into position under the car. I use three jack stands to support the unit, placing a stand just inboard of each brake flange and another under the pinion yoke to support the front of the axle.

I set the rear axle centerline height at 14 1/2 inches just because my jack stands have a lock at that exact point. If the jack stands had locked at 14 or 15 inches, either would have worked just as well (photo 6).

To be sure the axle is positioned squarely within the fame as well as positioned correctly lengthwise, I referred to the set of 1946 Ford frame dimensions mentioned earlier and place the 8.8 axle at 32 1/4 inches forward of the rear-most tip of the frame when measuring from the axle centerline to the end of the frame.

To determine the square placement of the axle assembly within the frame, I take cross measurements between the axle and the frame from side to side. When those measurements are equal, I know the axle is positioned squarely within the frame (photo 7).

With the axle assembly positioned correctly, I need to do two more things. First, I want to level the pinion yoke and take a measurement from the center of the yoke to the floor, in this case 12 1/2 inches. I file this measurement away until the engine and transmission are ready to be installed.

After that, I need to elevate the pinion and set it at 3 degrees positive. This is an absolutely critical step, as 3 degrees positive is the pinion angle determined by car manufacturers and hot rod builders many years ago to be the optimum angle for installing and mounting any rear axle assembly. How come? Consider how difficult it is to keep a double-hinged tube balanced and rotating in a perfectly straight line when spun. Add an upward bias to the hinges to eliminate the straight line effect, and suddenly the tube becomes very easy to balance and spin. In this case, that tube is the driveshaft.

PHOTO 5: A yardstick is used to help set the riding height of the car by measuring the distance from the floor to the body mount, in this case, 14 inches.

PHOTO 6: Sticking with my proposed riding height of 14 inches, the rear axle centerline is set to 14 1/2 inches. The extra 1/2 inch is to compensate for the jack stands and will not affect the actual riding height when the car is completed.

PHOTO 7: Taking cross measurements is a vital part of centering the rear axle within the frame.

To find the 3 degrees positive angle, I place a magnetic protractor on top of the pinion yoke and shim the yoke up by adding paint stir sticks between the yoke and the jack stand until the magnetic protractor reads 3 degrees positive (photo 8). I’ll get deeper into the need for the level pinion measurement as well as the role this 3-degree placement plays in this build once I’m ready to install the engine and transmission. For now, I need to concentrate on mounting this axle to the frame.

SELECTING A SUSPENSION SYSTEM

When it comes to mounting and supporting a rear axle assembly, the average car builder has a variety of suspension systems from which to choose. They range from the common everyday suspensions found under factory-built cars to the more exotic systems designed and produced through the racing and street rod building industries.

The most common rear suspensions found are the same types of rear suspensions the auto makers have been using for years: the leaf spring and coil spring suspensions. The basic difference between these two suspensions has to do with the axle. The leaf spring suspension not only supports the rear axle as it dampens the effects of the road, it also provides the means by which the axle is mounted to the vehicle. The coil spring suspension also supports the vehicle and provides a dampening effect for the bumps on the road, but the axle itself is secured to the vehicle by a set of four bars, or four mounting arms, that hold the axle in place while allowing it to move up and down within the frame.

PHOTO 8: The pinion angle is set to 3 degrees positive in order to give the axle housing a slight upward bias.

As previously mentioned, the rear suspension I removed from this car used leaf springs to support the axle assembly and in any other situation would have been an adequate suspension. However, replacing the unit with the Ford 8.8 rear axle instantly transforms this project car into a vehicle equipped with four wheel disc brakes. Not a bad trade-off.

If there is a downside here it is that the Ford unit was designed as a coil spring, four mounting arm-type suspension. That means more work installing the unit, but it also means I can make some changes and toss the coil springs in favor of adjustable coil-over shocks.

Adjustable coil-over shocks offer two things I might not otherwise have. First, adjustable coil-over shocks will allow me to adjust the final riding height of the car by varying the amount of compression applied to the coil springs. Second, if I don’t like the ride the coil-over shocks are giving me, I can easily swap out the coils to give the car a stiffer ride or, if desired, a softer ride.

But there is nothing to bolt this rear axle to. That’s why every decent-size city has a metal mart. I’ll make a visit to my local mart and purchase a 10 foot length of 2 x 2-inch square steel tubing (this is industry jargon) and an even dozen 1/8-inch-thick steel plates measuring 4 x 6 inches. I’ll use the tubing to construct the necessary mounting brackets and the steel plates to construct mounting boxes to accept the four axle mounting arms.

Photo 9 shows one of the lower mounting brackets fabricated from the 2 x 2-inch square tubing. The triangular shape gives the bracket plenty of strength and provides adequate area to weld the unit to the frame.

To mount these brackets, one on the right and one on the left, I cut square openings inside the frame rails to allow the brackets to slide into the rails, where they can be welded into place (photo 10). Notice the clamps. For the time being, nothing has been welded. I save the welding until I have everything fitting the way I want them to fit.

TIP

New steel is often coated with a rust preventative. Remove this coating using a degreasing agent before welding any new pieces to your frame. Paint will not stick to the coating, and it is much easier to remove such a coating now.

PHOTO 9: One of the lower mounting brackets fabricated from the 2 x 2-inch square tubing.

To attach the upper axle mounting arms to the frame, I cut square holes in both sides of the frame and slide a length of 2 x 2 square tubing through the frame and extend it out 1/4 inch on both sides. This allows me to weld the tubing to the frame on the outside of the rail as opposed to cutting access holes inside the frame rail to facilitate welding.

Next, I use the 4 x 6 steel plates to form gussets to attach the mounting arms to the square tubing. Once the mounts are secured, I finish this installation by capping the ends of the square tubing with scraps from the 1/8-inch steel plate.

To double-check my work, I again measure the positioning of the axle within the frame to be sure everything remained square and in good alignment. I also use a floor jack to move the axle up and down to be sure nothing is binding and that I have smooth operation everywhere. When I’m sure everything is in place, I finish welding all of the brackets and grind each weld smooth.

MOUNTING THE SHOCKS

With the axle solidly in place, my next step is to mount the coil-over shocks. The actual up-and-down travel of these shocks is 5 inches. That means with the frame and the rear axle sitting at the assumed riding height of the car, I need to mount the shocks so that they will have 2 1/2 inches of travel up and 2 1/2 inches of travel down.

The upward travel, or extension travel, of the shock isn’t so critical because this movement places virtually no stress on the shock; it merely extends its full length and stops. At that point, the rear wheel lifts and in an extreme case may even lift off of the ground.

PHOTO 10: Before welding, the entire rear axle mounting system is mocked up and clamped into place.

The downward travel, or compression travel, of the shock is more critical because this movement places a lot of stress on the shock as it attempts to compress the oil or gas inside the shock. This compression action, if pushed to an extreme, can result in the shock rupturing and rendering it useless. To prevent the shock from overcompressing, I need to install rubber cushions between the axle unit and the frame. These snubbers, as they are called, stop the upward travel of the axle, thereby preventing the shock from being overcompressed.

I elected to use rubber lower control arm stops found on the 1968 Mustang and mounted each one to a bracket made of 2 x 2 square tubing extended downward from the frame (photo 11). When the axle is forced upward, it will bump into the snubber and stop, thereby saving my shock.

The snubber brackets are 6 inches long, with each snubber extending that length by 1 inch. That gives me an upward axle travel from the neutral position of 2 1/4 inches, but that is still enough to provide this car with a smooth, secure ride.

PHOTO 11: This bracket holds the rubber axle stop designed to prevent the coil-over shock from bottoming out and being damaged.