Rack Opinions.

Care, thought and planning need to be considered as well as obtaining a basic understanding of the principles involved. This way the horrors of bump steer and an incorrect Ackermann angle, along with their associated problems, can be avoided.It is very important that mounting a Steering rack to a vehicle is done by either an expert mechanic or someone with considerable experience in order to ensure that it performs properly in the car.
Connecting the steering wheel to the road wheels can be accomplished in two basic ways (this applies regardless of whether an independent or beam axle is chosen). The choice being between a steering box or a rack and pinion, both having points in their favour and both having disadvantages. The respective pros and cons must be weighed up before a choice is made. With a beam axle the normal or traditional route has to be using a steering box set up to provide a cross steering operation. An alternative is to use the box on its side in the style made popular by Pete and Jake who used a Mustang box. This method has the steering linkage going alongside the frame rail to the steering arm on the stub axle. In principle this method works just as well as the cross steering method but, in practice, especially on smaller cars like the Popular, the presence of the linkage can present steering lock problems on the side the steering box is mounted.

Left:
These steering boxes show the typical design of such units. The larger unit is Mark IV Zodiac, the smaller one a Mkll Cortina/ HilIman Hunter.

As can be seen from the photograph a steering box used with an independent front end requires quite a complicated linkage and is not worth the trouble. Once the ball joints start to wear the combined slack generated in the system can add up to enormous play at the steering wheel. Ultimately though the steering box has to be the stronger system.
Most independent set-ups use a rack and pinion either in front of or behind the axle. The choice is yours and its location will depend on a variety of factors, not least of which will be aesthetics, sump position and whether it will physically fit! Be especially sure that the rack you have chosen came from the same fore or aft position you are using. If you don’t you will find that when the steering wheel is turned the road wheels will point in the other direction!

Right:
The basic rack and pinion.
A front-mounted rack will have the pinion mounted below the rack

WHICH RACK?
Those people who are able to use the stock suspension width (that is the dimension of the original donor vehicle) will probably be best off using the rack that came with the assembly from which the hubs, discs and uprights were looted.
Not everyone is so lucky, however. If you narrowed the front end or find that the stock rack is in an inconvenient place you will need to find a replacement. Determining which rack best fits the bill is the next problem. Reference to the diagram shows how to calculate which rack will fit without giving the dreaded bump steer (see side bar). If you built a jig as outlined in the suspension article it’s fairly easy measure the rack width with a couple of straight edges. If the suspension is already in the car this may prove more difficult and reference to the workshop manual may be necessary. Basically, the ball joints in the rack must lie on that line drawn through the two inner wishbone pivots. The rack itself, assuming no clearance problems, can be raised or lowered to obtain this alignment. If much movement is required it will also be necessary to ‘adjust’ the steering arms up or down to suit.
In the case of a large car like a Model A or B a suitable rack should be found quite easily just by taking a tape measure and checking the various widths available at the breaker’s. There is a bigger problem of course with a smaller car like an Anglia fitted with narrowed front suspension. Simply stated, no stock rack is narrow enough! The narrowest standard width, front-mounted rack that I have found is the Viva HB/HC unit featuring a 20” ball to ball measurement. Narrower than this (unless someone knows different) you are into a custom rack.

A few years ago I built a special narrow rack based on a Herald unit. The end to the rack was cut off to give the correct new measurement and the thread re machined on a lathe. This wasn’t that difficult and worked quite satisfactorily, a similar method I used more recently when narrowing a Burman Viva HA unit. This particular rack was easier to narrow as the ball joint assembly is only held onto the rack itself with a 7/16”UNF thread. So if your lathe is not equipped with a screw cutting facility this would prove much easier. Unfortunately Burman HA racks are not that common.
For my Anglia the chosen spindles (Cavalier) need a ball joint with a larger taper than the standard Victor/ Escort size, and while I could have sleeved and machined them I chose to go with the Cavalier ball joints which meant that they wouldn’t screw onto a standard British threaded rack. As I didn’t wish to adapt the track rods with threaded sleeves this effectively meant using a Chevette rack.
On investigation the Chevette rack proved easy to modify. The complete track rod and ball joint comes complete as a replacement unit, simply screwing into place at each end of the unit and then staked to prevent it coming undone. This obviously makes future maintenance much easier and also means that you don’t have to rely on someone else to rebuild it.
Choosing a Chevette rack assembly with a steel case (and that’s important as the Opel version has an aluminium case which would be very difficult to narrow) it was easy to cut the rack down and cut a new thread on the end. The thread proved to be 14mm x 1.5mm which was not the easiest die to get hold of or the cheapest!

The outer case required a fair amount of work as the photographs show. This was mainly because the rack needed to go through the frame rails themselves. I decided that the casing should be modified to locate in the sleeving tubes through the frame rails. By lengthening the tubes on the outside of the frame rails to incorporate a groove for the plastic tie wrap, they are also used to hold the gaiters in place. As can be seen in the photograph careful measurements and drilling with a hole saw enabled the 2” tubing (actually an old Volvo propshaft!) to go through all four holes proving their alignment. Such accuracy allowed me to machine a very precise collar and sleeve system to locate the rack and to seal in the grease. The end of the outer casing on the passenger side was cut off and suitably modified to incorporate a new P.T.F.E. bearing - this being in aluminium, the outside of which locates the sliding sleeve at that end. New mounting clamps have yet to be made, but they will be of the big end type and securely hold the rack in place.

Another trip round the breaker’s with my tape measure showed that the intermediate shaft and UJ’s from a TR7 were exactly the right length and can be seen fitted in the final photographs.
Final decisions about the steering column are yet to be made, but any column can be easily adapted to the TR7 upper universal joint.

Although there is still quite a lot of work to do finishing the various steering and suspension components off, it is sufficiently finished for a test run to show that there no inherent problems.

ACKERMANN ANGLE
Obtaining the correct Ackermann angle is essential for long tyre life as it reduces scrubbing themselves away on corners.
Ignoring such complications as the tyre slip angle, the correct Ackermann angle can be obtained when a line is drawn through both the tie rod ball joints and the lower suspension ball joint and continued until It Intersects the rear axle.
Correct Ackermann is obtained when the two lines intersect at the centre of the rear axle. This is necessary as the wheel on the inside of a corner has to turn at a sharper angle than the outer because the radius of the curve is much less (the width of the vehicle in fact).
Reference to the drawing and photograph of the steering arms will show the very different shapes needed for front and rear rack positioning.
It is not enough just to swap the steering arms side for side if changing the location of the rack as the angle of the arms must also be changed.
Of course the same also applies to wheelbase. The steering arms are angled so as to intersect at the rear axle of the donor vehicle. Lessen the wheelbase and they will intersect behind the axle, lengthen the wheelbase and the Intersection will occur in front of the axle. Depending on how great this change in wheelbase has been, some form of adjustment may be needed. In the case of the Vauxhall range (Viva. Victor etc.) these arms are only bolted on so it might be possible by swapping them to get a more accurate angle.
On some types of spindle/disc combinations the correct Ackermann angle will prove very difficult to obtain as the steering ball joint will hit the disc before the right angle is achieved.