This is the 6th in a series of articles
The Front End (2)
The set up of the front axle, i.e. toe in, castor and to a lesser degree camber, makes or breaks the whole car, its ability to run straight without constant small corrections, left or right, and the steering wanting to return to centre by itself (i.e. self-centreing) all combine to make the car a pleasure to drive. To restore this you must return to Stanleys original specification.
After 80 odd years of bump and grind some of the mounting points will have worn so as make change difficult. The nose piece onto which the spring mounts, with the help of two U bolts, is a major point of attention; where on this area makes achieving permanent castor setting almost impossible.
Having jacked the car up, and used two proper jack stands on the chassis at about the rear engine mounts, remove the entire front end. Now lie upside down and examine the mounting area of the front spring (underside of the nose piece). First thing seen is the hole for locating the front spring: it will be worn and will allow the locating bolt in the middle of the spring to be a very loose fit, in some cases it will be oval, all this is not hard to fix (more of this later). Next look at where the spring mounts on the underside of the nose piece, this will be very worn and in fact in older cars it will have rubbed a trench the width of the spring up to a 1/16 or more deep and will no longer be at the desired angle to achieve the correct castor. If you had a brand new chassis the angle of the underside of the nose piece to the horizontal would be 3° to 5° measured along the centre line of the chassis. To restore all this back to basics with the rest of the car still attached does present some difficulty but is not impossible.
You will need an angle grinder, two new grinding wheels and most importantly a plastic face mask. As you start to remove metal from the underside of the nose piece it will be obvious what areas need grinding. The more you grind the less able you will be to see where to grind, all is not lost, you will need a piece of flat bright mild steel 2 wide by 8 long by 3/16 thick (do not use black mild steel). Coat one side with marking blue or similar, it may take two or three goes of coating the mild steel plate and rubbing the castor surface against where you have been grinding to get a clear picture of where to grind next. When do you stop: when the bearing blue spots are about ¼ or less apart, this might take up to one hour to complete. Always grind small areas even to spot grinding about ½ squares using just the major diameter of the grinding wheel.
For older cars, where the spring has worn a trench on the underside of the nose piece, a special piece should be used to save endless grinding. The special piece should be made of aluminium flat plate 1 ½ x 4 ½ x ½. The designated top will need to have both edges radiused to replicate the rounded edge of the steel spring, a hole drilled exactly in the middle of this plate the same diameter as that of the spring locating bolt, usually 5 1/16 diameter. This means the plate is part of the spring when the locating bolt is in situ, radiused edges to the top.
Refit the front spring only to the chassis and tighten U bolts to normal tension. Insert two ½ diameter rods about 12 long, one in each spring shackle bush with 10 or so projecting out to the front. Using a small spirit level resting on the protruding rods it should be about half a bubble more than when the spirit level is placed against the underside of the chassis (do not put the spirit level on the top of the chassis).
If the chassis is jacked up so that the bubble disappears, you will have to let the chassis down until you can obtain a reading at both sites.
All of the last diatribe is to achieve castor permanently. I know castor can be set by twisting the radius rods etc., but as you read this is become apparent that there is more to it.
Refit the front axle without the radius rods, using the shackles and tighten the nuts. Now fit each radius rod, firstly making sure they are a pair; yes a pair. Over the years some have been modified in that they are different lengths: dont ask why. Fit the two brass cup bushes and fix the two rods with bolt so that all the slack is taken up. Look to see if there is a gap between the back of the axle and shoulder of the radius rod. Any more than 1/16 equally on both sides, i.e. near side and offside, means more checking. Conversely if you need to pull the axle forward to allow the fitting of the bolt to the rear mounting this too means a correction is needed.
A - Slacken off and remove the U bolts securing the spring to the nose piece, undo the locating bolt and remove the alloy spacer plate; machine or file across the 1 1/2 face, nothing to 1/16 this is best machined by somebody with a milling machine as filing can be tiresome.
B - In the event of having to move the axle forward to fit radius rods, machine a taper across the 1 ½ face and try to estimate how much further forward the axle needs to be. Again, if it is only about 1/16 then machine the 1 ½ face again from nothing to 1/16
In the case of A the narrow side of the taper on the alloy block will be facing the engine and in the case of B the narrow side will be facing forwards.
Incidently, if you have an all original car part No. BR19 front spring packing can be made to do the job. I doubt if anyone has seen such a part.
Now, with all parts in place, the nut and lock washers in place on the radius rods, the need to confirm that the front axle is at 90o to the chassis is achieved by measuring from the back of the front axle to the first chassis cross member. The measurements should be within 1/16 of each other. Be careful to measure between the same place on each side. If there is a large difference, check first that the chassis cross member is straight. Then re-check radius rod lengths etc.. If the difference is within 1/16, remove rod on short side and fit a 1/32 shim between the axle and the radius rod on that side only. Refit all and check again and they should be very close to the same distance.
Assemble all parts, check that the nuts are tight, refit the front wheels, lower car to the ground on all four wheels.
Setting castor and toe-in cannot be done with the wheels off the ground.
To set the castor (the amount the king pin appears to be leaning backwards) by eye is something of a black art; but not such that an Austin 7 owner cannot master it.Two spanners are needed, one to loosen and/or tighton the nut on the end of the radius rod, and the other an adjustable spanner to fit across the radius rod behind the axle, in order to be able to twist the radius rod and thence select the appropriate angle of castor about 5o to 7o is sufficient. Hold the radius rod with one spanner whilst tightening the nut with the other. Do this to both sides. The first part is now done.
You should all know how to set your own toe-in.