Gosh it’s March already!
Steady Lancia progress, interrupted by the need to go over the steering of my Salmson which was becoming a little wandery. I overhauled the steering box making a new bush for the droparm shaft and new thrust washers for both box and kingpins. The steering is only ¾ turn from lock to lock so has to be set up with very little play in the system. A nice design touch is that the bronze bush for the droparm shaft is bored about 0.25mm eccentric and can be rotated to adjust the mesh of worm and wheel. The Salmson uses about 25mm of trail (stub axle mounted 25mm aft of the kingpin) to give straight running and self centering and the kingpin itself should have no rearward inclination (castor). It turned out that the springs have settled a little since last reset in 1985 which had tilted t the kingpins forward, partially negating the positive trail. Wedges between spring and axle with a 2.25 degree taper resolved that and a short test run on a salt free day showed a worthwhile improvement. So now back to the Augusta.
I’ve obtained a new clutch spring to replace the one which was fitted which was of too large diameter to fit into the retaining cover as well as being rather askew. I’m hoping that this old spring was the cause of the vibration which sent me into the intricacies of the transmission.
I have also trued up the driven dogs of the freewheel unit which were slightly tapered, resulting in end thrust under load which had worn the selector fork, a known Augusta problem. The selector fork was welded and ground true and I set the freewheel unit up on a mandrel on a dividing head mounted horizontally on my milling machine so that each tooth could be ground by a diamond grinding disk in the chuck of the mill. The diamond disc of 22mm diameter came in a set of 6 for (£5.45 delivered!! Silverline via Amazon). The mandrel supplied is far too skinny so I made another of 20mm diameter so that the disc is supported across almost the full diameter and runs very true. This worked a treat and the job of grinding the teeth took just minutes and no more than 0.002 inch was needed to dispose of the taper. Working out how to do it and making the mandrels took much longer!
Of course dismantling the free wheel to regrind the teeth involved letting loose the nine small rollers which ride the central cam to give the free wheel effect. This is a pain as the rollers come in three diameters varying by 0.5mm and have to be fitted in the right order which at first sight is tricky unless you are equipped with ten fingers on each hand. I made a sleeve to fit over the roller unit with a slot through which the spring, the spring loaded stop, the larger, middle and smaller rollers can be inserted for each group of three, turning the sleeve as each is popped in. Again a two minute job with the right tool.
I dismantled the front suspension and built in hydraulic shock absorbers to remove the grease which was clogging everything. As mentioned earlier I found a coil bound spring in the relief valve at the bottom end of the offside shock absorber spindle. It also turned out that the springs of the two tiny pressure control valves in the piston of the shock absorber were too long and completely coil bound. As the travel of these valve is only about 1.5mm, an extra 1.5mm of length of spring completely blocks the valves so it is hardly surprising that the ride was a bit bouncy.
I compared the spring rate of the dodgy springs with those which seemed to be original on the nearside shocker. This was easily done by inserting the spring in a blind hole in the end of a brass rod so that the spring projected from the rod, then with the rod in the chuck of a pillar drill, the spring was pressed down onto kitchen scales to show the load needed to compress the spring by 3mm. The spurious springs were significantly stiffer than the originals as well as being too long. Now coil springs are not quite as one might think as, if they are shortened by cutting off a few coils, they actually become harder to compress so that was not an option for me. Springmasters in Redditch have a huge catalogue of springs and within a couple of days I had a sample which seemed about right when tested. I bought three sets, weaker and stronger than the sample to try in situ and in fact my sample was the closest to the original. I then assembled the shock absorbers and oiled them to get a feel of their action. Result both shock absorbers had the proper easy action on bounce and stiff action on rebound, however the offside shock absorber was now noticeably stiffer than the nearside. I tried swapping shock absorbers from nearside to offside and the stiffness was related to the shocker not to the pillar which forms the cylinder in which the piston slides. Swapping the valve springs to put the weakest springs in the stiffest shocker improved matters so I will leave it at that. I did note that the piston of the weaker shocker had been chromed in the past but was still about 0.005 inches less in diameter than that of the stiffer one so quite probably leakage around that piston explains the difference in stiffness.
If you are wondering why shortening a coil spring makes it stiffer, imagine two spring torsion bars of different lengths. Twisting the shorter through a few degrees takes more effort than twisting the longer through the same amount. A coil spring is just a coiled up torsion bar in which, when the coils are compressed, the twisting of the bar provides the resistance.
I managed to straighten the distorted main suspension spring for the offside pillar by brute force using a large pipe wrench to tweak the lowest two coils into line. All re-assembled and feeling quite free now it is properly lubricated. I must say I can’t see how, when oil is applied to the top of the pillar, the excess over the running level can do anything other than dribble out over the knuckle of the axle for a couple of days as it has nowhere else to go. Just have to catch it with a bit of cardboard against the tyre and then mop the floor.
Hopefully the gearbox bits should be ready at HB Bearings next week so that both Lancia and Salmson will be ready for Spring, whenever that comes.
Mike
