04-05-2020, 09:32 PM
(This post was last modified: 04-05-2020, 09:40 PM by Bob Culver.)
In lab test on plain rotating shafts and constant load, life is short after first miniscule crack detectable. In practice,with varying loads, obviously different as evident by the great number detected cracked. So a reasonble life treated reasonably can be expected from one crack free.
Fatigue life is hugely decreased by any stress increase. Raisng c.r. and rpm does this and very many cars are modified and/or driven much harder than pre war. 45 mph in a Seven was fast, and roads were much more meandering.
The Phoenix cranks are nitrided. The surface layer in compression is reckoned to give a high degree of fatigue resitance, just as case hardend gears survive remarkably.
My RP had an older exchange recon engine at 40,000 which had presumably not done less, and crank intact at 110000 total.
Very many cranks have been ruined by heating the rear journal to build up. I fitted one, untested, turned sharp also, and wrecked the engine after 3,000 miles.
The replacement has the radii filed out with a thin chain saw file and polished! (And not rebalanced!) In developing the BMC B engine they tried radii ot .060 and .090 and found the latter 10% higher fatigue limit, which at the same load represents an enormous life increase. Javelin cars also increased radii to.09 to delay breakage.
Sadly many "reconditoners" had sharp edged stones to reduce immediate comebacks from radius ride and have ruined myriads of cranks. With unhardend cranks can sometimes restore with a small rotary stone.
In my expereince with Javelin cranks also and many other parts the ringing test is uselss unless the part very seriously fractured.
Fatigue life is hugely decreased by any stress increase. Raisng c.r. and rpm does this and very many cars are modified and/or driven much harder than pre war. 45 mph in a Seven was fast, and roads were much more meandering.
The Phoenix cranks are nitrided. The surface layer in compression is reckoned to give a high degree of fatigue resitance, just as case hardend gears survive remarkably.
My RP had an older exchange recon engine at 40,000 which had presumably not done less, and crank intact at 110000 total.
Very many cranks have been ruined by heating the rear journal to build up. I fitted one, untested, turned sharp also, and wrecked the engine after 3,000 miles.
The replacement has the radii filed out with a thin chain saw file and polished! (And not rebalanced!) In developing the BMC B engine they tried radii ot .060 and .090 and found the latter 10% higher fatigue limit, which at the same load represents an enormous life increase. Javelin cars also increased radii to.09 to delay breakage.
Sadly many "reconditoners" had sharp edged stones to reduce immediate comebacks from radius ride and have ruined myriads of cranks. With unhardend cranks can sometimes restore with a small rotary stone.
In my expereince with Javelin cranks also and many other parts the ringing test is uselss unless the part very seriously fractured.