I think that we need to be careful with the use of two terms, polydyne and polynomial. The latter, as shown by Grey One, is a mathematical way of fitting a smooth curve to a series of points. Incidentally when I designed my own cams I used a spline fitting routine in ACAD to interpolate between the points. The polydyne, as I understand it, refers to allowing for a correction to the cam profile which will compensate for the dynamic bending and compression of various parts which connect the cam surface to the valve movement. I had thought that I would try to be a smart alec when designing the cams and allow for these flexibilities. Two things stopped this. The first was that when I tried to measure a deflection by levering the end of the rocker when the cam was on lift I could not detect any movement. Secondly, when I did the sums it turns out that at 6,000 rpm the maximum acceleration is equal to 200 g. That is one pound weight of parts acts as though it was 200 pounds weight. But at lower revs, where road engines spend most of their time, say 3,000 rpm then this force is reduced by at least a factor of four.
This leads on to the reason why valve springs have to be so strong. Bits of the valve train acting as though they had a mass of 200 lbs means using strong springs and there is a lot of misinformation about concerning valve springs. I have measured the spring rate of various types of valve spring used on Vincent engines. The typical dual valve springs have a rate (working from memory) of 100 lbs/inch. The specials, which were provided by Terry Prince to go with some of his cams, had a rate of 150 lbs/inch. I read several comments about these wearing cams and followers out. Finally, many years ago when many of us were trying to go faster, several people went for using BSA Gold Star valve springs. The ones I measured had a rate of 200 lbs/inch and did not have a reputation for premature wear of various components.
I think that the information that Picadors used triple valve springs is incorrect. These were tried by Vincents on their competition engines and found not to be necessary. Many years ago I knew someone who knew someone who claimed to have been involved with some of the testing of these at the factory. Sadly both are now dead and there is no way of checking what I was told. This concerned the testing of a single engine with the triple valve springs at 8,000 rpm for up to a day. When I mentioned this on the Forum some years ago this was dismissed at rubbish and I have now no way of checking whether I misunderstood or was misinformed about what went on. Certainly for road and racing use the Vincent factory gave up on the use of triple valve springs well before the production of Picador engines. There are some in the Club who have these engines unused in their possession and so it would be possible to check those engines. However, as with all things Vincent one cannot be sure that what one finds in one engine will be typical of what one would find in many. A single example is the use of Mk II cams in some Picador engines and the special cams in others.