Chassis Construction. Chapter 2. A Gu i d e To...

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1 Chapter 2 Here s a typical frame from Total Cost Involved. Note the clutch pedal this example is set up for a manual transmission. ith any sort of construction, the integrity W of the finished product is dependent on its foundation. That certainly holds true when building a street rod, where for all practical purposes, the foundation is the frame. To allow the suspension to work as it should, to maintain door fit and body-panel alignment, the frame must not deflect, and it has to have enough torsional stiffness to resist twisting. As examples of these conditions, consider the following: If a frame were loaded heavily enough between the axles to sag, that s deflection. If one corner of the chassis is jacked up, and the front bumper is at an angle while the rear bumper is parallel with the ground, that s a lack of torsional stiffness. At one time frames were simple; the earliest Fords used the ladder style, so called because that s what they looked like. The most basic of these were found under Model Ts and As. From a deflection standpoint, both were adequate for their applications, while A frames used deeper rails than the T, there was not much in the way of torsional rigidity in either. With the introduction of the 32, Ford stiffened the basic ladder design with a K-member, basically a crossmember with 14 two diagonal braces. Ford s frame was further refined in 33 with a full X-member, a design concept that was used through 48. But another important change had been made in While Ford elected to maintain the transverse leaf springs front and rear, their locations were changed. The front spring was now ahead of the front axle, the rear spring behind the back axle. There were a number of reasons for this alteration, not the least of which was that it allowed the chassis to sit lower; Ford advertised that it lengthened the spring base and provided an improved ride. And while that claim was debatable, the main distinguishing element of Ford s chassis design, the transverse front and rear springs, remained the same. And so did an inherent weakness. Although frames feature an X-member and seem substantial enough, there is a peculiarity in their design that is often overlooked. With transverse springs attached at the middle of the front and rear crossmembers, the body pivoted down the centerline of the chassis. In other words, there was little twisting force applied to the framerails so they didn t need to have a great deal of torsional rigidity. That s an important consideration when making modifications to these frames, especially when an independent front suspension is installed.

2 The first step in frame construction is to clamp the rails in the jig (note they re upside down). Not only does this make each one produced the same, it makes them all the same as an original Ford frame. Along with the frame jig, a variety of fixtures are used to make sure all the individual components are in the correct location. Here the center crossmember is installed. One of the secrets to the strength of Total Cost Involved frames is the unique rectangular tube X-member. Here it s being clamped and tacked in place. Building A Ford An IFS will transfer force to the framerails, more so than the stock suspension. As a result, a substantial new front crossmember is required, and it must be tied into the frame in such a way that the rails can t twist. Depending on the rear suspension used, the same situation may crop up. Think of it this way moving the attachment points (at either end of the car) means that suspension loads are now applied to the frame in areas other than those designed to cope with them. Most likely, some sort of modification or reinforcement to the frame will be required, but then that s part of street rodding. Solid Axle versus IFS The ongoing debate over which is better is really easy to resolve. If the traditional look is what you re after, a solid axle is the way to go. Of course with the fenders on Fords, the only way anyone is going to see underneath the car is if you run them over, but to each his own. The truth is when it comes to ride and handling, an IFS is much better than a solid axle can and will ever be. Because our Road Tour 36 is going to be driven all over the country, going to NSRA events, we opted for an independent front suspension. Buy Or Build When it came time to build a chassis for our 36 we weighed the time and expense involved in modifying a stock frame versus buying a reproduction, and considering the amount of work required to properly modify a stock frame, we decided on a new frame from Total Cost Involved. Total Cost Involved opened in 1974; their first product was a reproduction Model A frame. But it wasn t long before the company expanded its product line and was on its way to becoming a major player in the suspension and chassis construction business. Over the years they ve continued to add to their list of wares and today the Total Cost Involved catalog includes suspension systems, and in some cases complete chassis, for a variety cars including Fords. The chassis we opted for is based on a Total Cost Involved frame. Made with two fabricated main framerails, these frames duplicate the shape and contour of the originals but are far stronger than the stockers. As is the common practice, construction begins by clamping a pair of rails in a fixture, or jig, so it can be said these frames are jig built. And while jig built is a common description of a construction technique, it s important to realize just what that means: simply that the parts being put together are being held in position for assembly, and that all the parts built in that jig should come out the same. But the question you have to ask is The same as what? In the 15

3 case of a Total Cost Involved chassis, the jig itself was built to factory specifications, so what comes out of it is a dimensional duplicate of a Ford frame, just as if it rolled down Henry s assembly line. Of course that means when it s time to install the body, it will fit like it should. As you might expect, Total Cost Involved offers a long list of options on their chassis, so we checked the boxes next to the components that we felt would make our coupe the ideal cross-country cruiser: Custom IFS with power rack-andpinion steering; front and rear anti-roll bars; rear parallel fourbars with a Panhard bar; Air Ride Technologies ShockWaves on all four corners. This combination of components will make any Ford ride and handle with the best of them. n STAYING STRAIGHT Alignment Terms You Should Know As we all know, it takes time, effort, and money to build a street rod, but the reward of jumping in your personal creation and driving it down the road makes it all worthwhile. Of course that s assuming your street rod goes down the road as it should. Nothing is more miserable than a car that you have to fight with to stay on the road. One of the keys to making a street rod drive as it should is proper frontend alignment. And while that seems simple enough, street rods have one particular issue in that area which is often overlooked: the classic nose-down stance. Adjusting the frontend with the chassis sitting level in a jig won t accomplish anything. The trick is to make sure that the final alignment is done with the same diameter tires front and rear that will be used, and that the car is sitting at the desired rake and ride height. While aligning frontends is a job normally left to a professional, it will help if you understand the adjustments that can be made. Camber: Camber is the tilting of the wheels from vertical. Positive camber is when the top of the wheel leans out, and negative camber is when the top of the wheel leans in the amount of camber is usually measured in degrees off of vertical. Modern tires generate the most cornering force with a trace of negative camber, around 2 degree, and most contemporary independent suspension systems are designed to gain camber as the car leans in a corner. Excessive camber, either positive or negative, will usually make itself known by wearing one edge of the tire tread or the other. Steering Axis Inclination: The amount the kingpins in a solid axle suspension, or the ball joints in an independent suspension, are tilted in at the top is described as steering axis inclination. The tilting of the kingpins, or ball joints, affects handling in a number of ways; it helps keep the wheels pointed straight ahead, and also aids in recovery from a turn. As a result of kingpin inclination, when the front wheels are turned from straight ahead, the front of the car raises slightly. The weight of the car helps the front wheels return to straight ahead when the turn is completed. Steering-axis inclination is part of the suspension design and is not adjustable. Scrub Radius: If a line were drawn through the kingpin, or the centerline of the ball joints and extended to the ground, then the center point of the tire marked on the ground, the distance between the two would be the scrub radius. Most early cars had zero scrub radius, the angle of the king pin met the centerline of the tire at the pavement. Lack of scrub made these cars easy to steer without power assist, as the tire pivoted easily without dragging across the ground. Unfortunately, many modifications commonly done to street rod-suspension systems alter the scrub radius. As scrub is increased, by positive-offset wheels as an example, steering becomes more difficult, and bumps in the road can adversely affect vehicle control. On a lightweight car, increased scrub doesn t create a significant problem, but excess should be considered, and the heavier the car, the more of a factor it becomes. Caster: In addition to being tilted toward the center of the car, the steering axis also leans toward the front or rear of the car. Forward tilt is negative caster, rearward is positive. Most cars use positive caster, as it prevents road wander and helps keep the wheels pointed straight ahead. Drag race and Bonneville cars often use extreme caster for high-speed stability; our 36 calls for 1 1/2 degrees positive caster. Toe: The distance between tires, measured at the front and rear, is called toe. Most cars use a small amount of toe-in, that is the front of the tires are closer together than the rear. Toe-in is generally used to compensate for the tolerances in the steering system. If the wheels were set parallel, as the car moved forward any slack in the steering would let the front of the tires spread apart, resulting in toe-out. Toe-out will cause most cars to wander when going down the road, and contributes to oversteer when first entering a corner. By setting the front wheels with a small amount of toe-in, generally around 1/32-1/8 inch, the small amount of play in the steering linkage that would produce toe-out in the earlier example is counteracted and the wheels run parallel. Excessive toe, either in or out, will contribute to a peculiar tire-wear pattern called feather edging, the tread looks as though it s been dragged sideways on the pavement, which in effect it has. 16

4 Building A Ford Turning Radius: Turning radius, also called toe-out on turns or Ackerman, is the difference in angles of the front wheels when turning. When negotiating a corner, the inside wheel travels in a smaller arc than that of the one on the outside, consequently it must turn tighter. Toe-out on turns results from the position of the tie-rod ends in the steering arms relative to the kingpins or ball joints. If a line is drawn from the kingpins (or ball joints) to the center of the rearend, it should pass through the tie-rod holes in the steering arms. As a result of the arc that the steering arms travel through when the wheels turn, the inside wheel will turn sharper than the outside wheel. At full steering lock the difference is usually around 3 degrees. Bump Steer: As the name implies, bump steer means the car steers itself when it hits a bump. A very disconcerting condition for the driver, bump steer is generally caused by alterations to the suspension to lower the car on solid-axle vehicles, and poor engineering for those with independents. Bump steer results when the travel of the steering linkage travels through a different arc than the steering arm on the spindle(s). Solid-axle and independent suspensions usually have bump steer for different reasons. Dropped axles are often the culprits that causes bump steer in a solid-axle car. The angle of the drag link changes when a dropped axle is installed and passes through a different arc than the one originally designed. As the axle moves up and down, the drag link actually pushes or pulls on the steering arm, causing the car to wander, a classic case of bump steer. Although there are other possible reasons, independent front suspensions usually exhibit bump steer when toe changes as the suspension travels up and down. The problem can just about always be traced to an improperly positioned rack-andpinion steering gear, or tie rod angles that move the steering arms horizontally as the spindles move vertically. Anti-Dive: This term is often seen in ads for street rod independent suspension systems. Anti-dive simply keeps the nose of the car from dropping under braking. The upper A-frame pivot is set at an angle to prevent the brakes from applying compression force to the suspension. For front suspension we chose the Total Cost Involved custom IFS. This is a worm seye view of the crossmember. 17

5 The X-member is big enough to accept just about any conventional transmission; in this case it will be a Ford 4R70W. Tell Total Cost Involved what you re using, and they ll install the correct mount. Each component on the chassis is located precisely before being welded. In this case note the fixture that drops in place. To tie the top of the crossmember together and provide trans clearance, a heavy gauge tunnel is welded in place. The design is similar to what Ford used on frames. In the rear, four-bar brackets attach to the side rails and legs of the X-member. Note the brake-proportioning valve and the inline residualpressure valve. This is a coilover rear crossmember; the same style is used for the Air Ride Technologies ShockWaves. Two upper mounting points are provided to allow suspension tuning. Here s another interesting fixture this one positions the engine and transmission mounts for an exact fit. The attachment bracket for the Panhard bracket is positioned on the inside of the left-hand framerail. Note the bodymounting holes, along with all the other mounting points on the chassis, have nuts welded in place. 18

6 BAG IT Riding On Air One product that has had a significant impact on our hobby is air-spring suspension. Nothing new, air springs have been used on trucks, buses, and in industrial applications for quite some time. General Motors and Packard used them on production cars in the 50s and 60s, and they are found today under a variety of luxury cruisers. And while it took some time for them to show up on the street rod scene, you can bet that they re here to stay. Over the past few years we ve had the opportunity to install and test a variety of air suspension components and systems. In addition to the obvious benefits such as easily adjustable ride height and the ability to compensate for varying loads, we ve been impressed with the ride and handling qualities of air suspension. For all those reasons we elected to equip the Road Tour 36 with an air suspension system consisting of ShockWaves at all four corners, an on-board compressor and air storage tank, and a Ride- Pro E-control system. One of the pioneers in aftermarket air suspension business is Brett Voelkel of Air Ride Technologies. Brett has put air springs on everything imaginable and knows how to make them work like they should. Because of his experience and expertise on the subject, we asked him to respond to some of the more common questions street rodders ask about air suspension systems, and throw in a few tips while he was at it. STAFF: What do most of your customers expect from an air ride system? BV: We have found there is about an even split between the desire for better ride quality and the desire for a lower stance. Our street rod customers want a Cadillac ride, and our sport truck customers want to drag the ground. We can provide both, within reason. STAFF: How do you describe ride quality? BV: A good ride means different things to different people. Someone who is accustomed to driving a new Lexus or Mercedes will have an entirely different idea of ride quality from the guy who drives a ten-year-old pickup. Technically, we define good ride quality as the ability to minimize the effects of road irregularities to the vehicle passengers. When the vehicle encounters a pothole or bump in the road, it should transverse the obstacle with as little body motion as possible. Simple to explain, but it s a good deal more complicated to accomplish. STAFF: OK, so how do you do it? BV: To understand how to achieve a good ride quality, it helps to understand exactly what happens to the suspension when the wheel hits a bump. Ideally the suspension would absorb this bump with no transfer of motion to the body. In the real world, Building A Ford at least some of this motion will be transferred through the spring to the body. How much transfer takes place is affected by several components of the suspension. The spring be it coil, leaf, torsion, or air is what holds the vehicle up and also establishes the suspensions rate of compliance. Springs are rated by two specifications: Spring load capacity and spring rate. Load capacity represents the amount of weight that a spring will support at a given height. Spring rate represents how much weight change it takes to change the height by 1 inch. For example, if a spring has a load capacity of 1,000 pounds and a spring rate of 200 pounds, it will take a 200-pound weight change to make the spring gain or lose 1-inch. The higher the spring rate, the more load change it takes to change spring height. Most traditional spring manufacturers list the spring rate of their springs, not the load capacity. The load capacity of a traditional spring at a given height does not change. Air springs are rated by load 100 psi, because changes in air pressure greatly influence both load capacity and spring rate. The shock absorbers also control the rate of compliance of the suspension. A proper shock must be matched to the vehicle weight, the suspension geometry, and the spring used in that suspension. A leaf spring, coil spring, and an air spring all have very different spring rate patterns and would require different shock valving to optimize ride quality. Too soft a shock may let the suspension bottom out on hard bumps. Too stiff will result in a poor ride over small bumps. Since there are a wide range of vehicle weights, spring types, and customer preferences, adjustable shocks go a long way toward optimizing ride quality for your car. Tires and suspension bushings also greatly influence ride quality. Most OEM suspensions use large, soft rubber bushings and tall tires to enhance ride quality and suppress noise transmission. Some street rodders like to use polyurethane bushings and short sidewall tires. It is especially tough to get a decent ride quality with such a combination. STAFF: Other than being able to raise and lower your car, how do airbags affect ride quality? BV: This is exactly where the air-spring suspension shines! Assuming that a feasible air spring is selected for the suspension, it can be tuned to the parameters of the vehicle and the customer by changing air pressure while on the road. Likewise, an adjustable shock can be tuned to individual taste. In theory it is possible to make a vehicle ride as good with traditional springs as with an air suspension. This would require the aforementioned spring and shock testing. All of this tuning would need to be repeated when there are significant changes made such as fuel load, passenger load, or road surface changes. With an air suspension and an adjustable shock, these changes can be made in a fraction of the time. It is analogous to tuning a carburetor or tuning EFI. The EFI is much more versatile. 19

7 The analogy to EFI is relevant in other ways, too. As with anything adjustable, it is possible to adjust yourself into a terrible ride quality. The mistake most people make is too low of air pressure or too soft a shock [or shock adjustment]. This will allow the air spring to collapse too rapidly over a bump. Since an air spring is very progressive [spring rate rises in compression] it feels too firm. Many times adding air, or using a firmer shock will actually result in a better ride quality. Symptoms of low air pressure are bouncy ride on rolling bumps and bottoming on potholes. The best way to start tuning an air suspension is to inflate the air springs to their design height. Any competent air suspension manufacturer will be able to tell you this dimension. This is where the air spring is designed to work the best. The best ride quality should occur within a plus-or-minus 1/2 inch of that dimension, regardless of the air pressure. After that is accomplished, start playing with the shock adjustment. STAFF: What is the ideal pressure for air springs? BV: That s a question with many answers! Run whatever air pressure it takes to get the air spring to its design height. A 32 Ford may take 45 psi; a 57 Chevy may take 75 psi; a new F-150 may take 60 psi. Keep in mind that the weight of the vehicle is only one factor in determining how much air pressure is required. A much more important influence is the geometry of the suspension. The relationship of the load point versus the pivot point versus the position of the air spring will be a huge factor in determining the selection of the air spring as well as what air pressure is required. If you are building your air ride suspension from scratch, these are just some of the factors that have to be considered. While you are at it, you must account for ground clearance, driveline angles, and ball joint travel limits. If you have purchased a pre-designed system from a manufacturer, these issues have been addressed. STAFF: How difficult is it to build a custom suspension from scratch? BV: No Problem! Building a successful air ride suspension is no different that any traditional suspension. It is actually easier. In a leaf, coil, or torsion suspension, you have to use some educated guesswork as to where the vehicle ride height will end up and how the ride quality will be. Some rodders have their favorite recipe for using coil springs out of a Mustang II with one coil cut off. Let s say your buddy uses that combo in his 35 Ford and it rides great. You want to build your 40 the same way, only yours is a convertible with a big-block. It now sits too low and rides poorly. Now you can start the research all over to find a set of coils that will be appropriate for your car. With air suspension it is a matter of adjusting the air pressure to accommodate the extra weight in the front and less weight in the rear. The added benefit is that when you add a couple of friends in the rear of that convertible for cruising, all it takes is an extra squirt of air to level the car and restore the ride quality. STAFF: What do you suggest for general air suspension guidelines? BV: There are a few things to be aware of when building any suspension, especially an air suspension: Ride height: The vehicle needs to be mocked up at your intended ride height. This ride height needs to reflect proper ground clearance (at least 4 1/2 inches) and adequate suspension travel (at least 3-inch compression and 2 inches in rebound). After that, start looking for a place to install the air springs at their intended design height. This is very important! If you have an air spring that is intended to ride at 9 inches tall and you try to make it run at 7 inches tall, the best ride quality will make the car ride 2 inches taller than you want. If you deflate that air spring to that 7-inch height to make the car sit right, the ride quality will suffer. Any competent air spring supplier will be able to give you the compressed ride height and extended dimensions of their air springs. Ground Clearance: A lot of customers want to lay the car on the ground. Don t do it. You must have at least an inch or so of ground clearance when the air system is fully deflated. Remember, you need at least 4 1/2 inches of ground clearance at ride height to be able to negotiate speed bumps and other road obstacles safely. I don t care what anyone says, it is not cool to scrape! Driveshaft and Ball Joint Travel: Ball joints will only travel so far before they bind. The driveshaft will go only so far into the transmission tunnel before it hits. It is your job to find these limits and take them into account. Air spring clearance: The only rule here is that the air spring must never rub on anything at any time. Period. It requires considerable thought and planning to properly satisfy all of these details. The nice thing about an air suspension is that you can inflate and deflate the vehicle through its full range of travel to check out all of these parameters. A conventional suspension makes it much tougher to accomplish this. STAFF: What about the compressor system? BV: After you have properly designed and installed your air ride suspension, you will need a source of compressed air and a way to control it. While it is possible, at least in theory, to use an inflation valve or even a bottle of compressed air to inflate your suspension, the most efficient method is an on-board compressor with a reservoir tank and a control valve. It is with the compressor system that you can upgrade, customize, economize, or thoroughly overkill without drastic compromise. If you are doing a simple, supplemental air spring over a leaf spring, then an inflation valve may be enough. Any stand-alone air suspension really needs an on-board compressor and control system. Here is why: Ride-quality tuning is done in very small air pressure increments. Because the air springs are quite small in volume, it is very hard to inflate or deflate in small enough increments to zero in on a great ride quality. In addition to that, when you add 20

8 Building A Ford load in the form of fuel, people or luggage you have to go looking for an air hose! You can quickly see how convenient an on-board system can be. The sky is the limit on compressor systems. The main difference here is rise time and convenience. The faster you want the vehicle to come up the more compressors, more pressure, and more reservoir tanks you will need. A typical street rodder who is not concerned with rise time will probably use a single compressor with a 2-gallon tank and a two-way controller. If you want that car up in two seconds it will take a pair of 150- psi compressors, a pair of 3-gallon tanks and a four-way control system. Obviously this extra equipment will cost more money. STAFF: Why would four-way control be advantageous? BV: There are several reasons to control the air springs independently. Probably the biggest is to eliminate air transfer when cornering. In a twoway configuration the air springs are T d together from side to side. When you negotiate a turn to the left, for example, the vehicle will tend to lean to the right and place more load on the right hand suspension. The loaded right-hand air spring will then start to transfer air to the unloaded lefthand air spring, thereby worsening the problem. Another issue is the leaning vehicle. If everything is equal, meaning weight, frame level, and bushing resistance, then the car will sit level. In the real world, however, driver weight, gas tank weight, and uneven suspension-bushing resistance may combine to make the car lean. Then, just as with a coilover, you have to wedge the car level with a bit more air pressure on one side or one corner. These are very common problems, especially for top-heavy cars with polyurethane bushings and no sway bars. A four-way control system will also offer a faster rise time because it will flow more air. And while seconds may not seem like a long time, if you are sitting there with your finger on the switch it may seem like forever! The RidePro solenoid system, for example, also offers a simpler plug-in installation and a digital gauge option. When new products are developed, such as electronic leveling systems and remote controls, they will require the use of a 12-volt solenoid air valve. Small-but-critical items are the radiator mounts. Note how the hole in the bracket aligns with the hole in the jig. These are the upper and lower A-arms for the Total Cost Involved IFS (the lower one is the longer of the two). They use press-in ball joints and urethane ushings. This is the bracket that holds the master cylinder and power booster. A bracket that mounts the master cylinder and clutch pedal is an option. These upper eccentrics are a unique feature of the Total Cost Involved independent front suspension. 21

9 The eccentric slides into the upper mount. Note the position of the hole that attaches the upper A-arm. By sliding the eccentric fore and aft, caster is adjusted. Again, simple but effective. Now compare the position of the A-arm mounting hole. Rotating the eccentric provides camber adjustment simple but effective. With the eccentric in place, the upper A-arm is attached. When alignment is finalized two setscrews secure it. As well as rotating, the eccentric also slides fore and aft. 22 The two tabs on the lower A-arm are the attachment points for a coilover shock. It will also accept a ShockWave.

10 For ride, handling, and adjustability, nothing beats Air Ride Technologies ShockWaves. Here the fronts are being installed. Building A Ford To help negotiate corners at a brisk pace, antirollbars are a recommended addition to any chassis; the 36 will have them front and rear. The lower ShockWave mount doubles as an attachment point for the anti-rollbar. Note the upper end of the attachment link simply screws into the end of the bar. For quiet, smooth operation the anti-rollbars have urethane bushings. Set collars hold them in place. After the bushings and the support blocks are assembled, the anti-rollbar can be attached to the back of the front crossmember. Total Cost Involved has a unique IFS spindle and steering arm of their own design and manufacture. A number of disc-brake kits are available we ll be using components from Stainless Steel Brakes. After assembling the front suspension, the manual rack can be installed. It s a straight shot from the steering shaft, under the motor mount to the column. 23

11 The front four-bar brackets are tied into the X-member for strength. The bracket on the rearend housing doubles as a mount for the ShockWaves. With the steering rack centered, the frontend alignment can be approximated and the tie-rod ends installed. They should screw on approximately the same number of turns. For strength and reliability, a Currie 9-inch rearend was selected. Here it s being jacked up into position so the ShockWaves can be attached. Note that there are two mounting holes to provide adjustment. In the rear, taperedbag ShockWaves are being used. Note the knob for damping adjustments. The rear anti-rollbar has not yet been installed. 24

12 Total Cost Involved provides this mount to secure the Panhard to the center section. It is secured by the bearing retainer capscrews. Building A Ford After the bracket is bolted in place, the Panhard bar can be installed. 25

13 One end of the Panhard is fixed; the other is adjustable, so the rearend can be centered under the chassis. As the air springs move, it s necessary that the supply line is flexible. To that end, a braided line was used on all four. If you re looking for a solid foundation for a Ford, here it is. Our Total Cost Involved chassis will supply lots of smiles for many miles. 26