21-11-2018, 08:31 PM
For a modest patent fee Austin could have adopted the later Ricardo pattern head years earlier but chose to wait for the 3 bearing engine. Two bearing engines are distinctly more harsh with the later head, esp when cr raised further. (But distinctly more lively) The firing stress on crank is vaguely proportional to c.r. if you read any elementary text on metal fatigue any increase of stress near the fatigue limit has a grossly disproportionate shortening effect on life measured in cycles (miles). (ie in tests 10% increase might reduce life to 1/10!)
In their day the 2 brg engines were not esp noted fro crank failure. The rash of failures corresponds largely with the Bill Williams special building craze, more spirited driving by mostly young men in the 1960s,70s, and accumulating mileage.
It is no fluke that those claiming huge mileage with original cranks have not altered.
(The Phoenix cranks are nitrided which process considerably improves fatigue resistance)
Several have reported gains by wedging the post 33 head as small.
The term large radius followers is preferable to ”flattened”. I could detect little difference with that mod alone. The exh valve size and duration is reasonable so doubtful if altering those makes difference at normal revs .The degree of lowering of the follower can be quite small.
In their day the 2 brg engines were not esp noted fro crank failure. The rash of failures corresponds largely with the Bill Williams special building craze, more spirited driving by mostly young men in the 1960s,70s, and accumulating mileage.
It is no fluke that those claiming huge mileage with original cranks have not altered.
(The Phoenix cranks are nitrided which process considerably improves fatigue resistance)
Several have reported gains by wedging the post 33 head as small.
The term large radius followers is preferable to ”flattened”. I could detect little difference with that mod alone. The exh valve size and duration is reasonable so doubtful if altering those makes difference at normal revs .The degree of lowering of the follower can be quite small.