23-05-2021, 11:46 PM
(This post was last modified: 24-05-2021, 10:16 AM by Bob Culver.
Edit Reason: expanded
)
Steves comments of considerable interest but had me a bit perplexed too. 4140 is EN19. EN40/EN40b is not equivalent but the alternative esp suited for nitriding and for consideration.
From the above if P20 is superior to EN40/EN40b (presumably same) i wonder why EN40 has become so established for nitrided cranks.
Anyone know what Phoenix use?
My interest in this stems not just from Seven experience but years of involvement with Javelins which had cranks of various forms and material and hardening process, many of which were prone to failure, some sooner than later. En12, EN 16, revised hardening, revised shape, drastically revised shape, finally nitrided .
The practice here was/is to linish after niriding but dimensions are somewhat variable. Most sources indicate a final fine grind (which adds to cost) Curious as to how Phoenix finished, esp as the journal dimensiosn are critical.
Experience has presumably increased but recondtioners here ruined many nitrided cranks by introducing grinding crarcks.
The Companion gives original cranks as 1% chrome moly so possibly EN19, 4140. 60 tsi is claimed; hard to beat.
The high performance versiosn of the Rootes 1500/1600 engine 1957-65 had EN16 sfafts, the ordinary but notably rugged models something lesser.
To recap somewhat; EN40 is specifically suited to nitriding so when it is mentioned in relation to cranks, most in the business would assume nitriding is intended. I dont know when the process became established. I vaguely recall Merlins were treated. It was certainly used for sleeve valves in WW2. If not nitriding, so without its very considerable gains in fatigue resistance, you are basically in much the same territory as were Austins. Unforged billets may be more sutable now than as available then. Any attempt to make cranks more robust often tends to stiffen the webs and concentrate bending stress in the crankpins. However if counter balanced the bending due rpm is much reduced.
Is the demand fo very high rpm high output engines expected to continue? Probably a requirment for reliable cranks for slightly raised cr and sustained but modest revs will .continue.
From the above if P20 is superior to EN40/EN40b (presumably same) i wonder why EN40 has become so established for nitrided cranks.
Anyone know what Phoenix use?
My interest in this stems not just from Seven experience but years of involvement with Javelins which had cranks of various forms and material and hardening process, many of which were prone to failure, some sooner than later. En12, EN 16, revised hardening, revised shape, drastically revised shape, finally nitrided .
The practice here was/is to linish after niriding but dimensions are somewhat variable. Most sources indicate a final fine grind (which adds to cost) Curious as to how Phoenix finished, esp as the journal dimensiosn are critical.
Experience has presumably increased but recondtioners here ruined many nitrided cranks by introducing grinding crarcks.
The Companion gives original cranks as 1% chrome moly so possibly EN19, 4140. 60 tsi is claimed; hard to beat.
The high performance versiosn of the Rootes 1500/1600 engine 1957-65 had EN16 sfafts, the ordinary but notably rugged models something lesser.
To recap somewhat; EN40 is specifically suited to nitriding so when it is mentioned in relation to cranks, most in the business would assume nitriding is intended. I dont know when the process became established. I vaguely recall Merlins were treated. It was certainly used for sleeve valves in WW2. If not nitriding, so without its very considerable gains in fatigue resistance, you are basically in much the same territory as were Austins. Unforged billets may be more sutable now than as available then. Any attempt to make cranks more robust often tends to stiffen the webs and concentrate bending stress in the crankpins. However if counter balanced the bending due rpm is much reduced.
Is the demand fo very high rpm high output engines expected to continue? Probably a requirment for reliable cranks for slightly raised cr and sustained but modest revs will .continue.