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oldcorollas Forums Junkie Location: Kita-Ku, Sapporo, Japan Registered: January 2003	Re: Building a 4age for 9500 revs Thu, 30 June 2005 08:22 ok.. a quick fatigue lesson. a rod/part will fail when a crack gets to a certain length. every rod has imperfections and flaws in it that can create a crack, even polished/shotpeened. a crack that has been initiated will continue to grow when a force is applied above a certain threshold. this threshold level decreases as the crack gets bigger, and for a given force, the length a crack grows per loading cycle will also (generally) increase as crack length grows. that said, the smaller the crack starters and imperfections are, the higher the initial force to create the crack in the first place.. polishing a rod decreases the size of initial defects ont he surface, but also can put nice sharp grooves in it you'd wanna go to a nice 1-3 micron finish (1200grit is about 15 micron finish iirc) shotpeening puts compressive stresses in the surface, and marginall decreases the total strength of the rod!, BUT, the compressive stress helps to close any cracks that are initially present, and slows the growth of any cracks that do start... so in summary. there are ALWAYS cracks/imperfections in parts. polishing makes them smaller, and shotpeening helps them stay closed. below a certain level of force, the cracks will not get bigger. above a cetain level of force, the cracks will ALWAYS get bigger, and as they get bigger, they will get bigger faster for the same level of force. a part will fail when a crack reaches a certain length. for "level of force", read "RPM" so basically the key to making a rod/part last is a) reduce the force (rpm) or loading (weight of parts attached to it, ie pistons). b) improve the surface finish to reduce crack initiation points. c) improve part manufacturing to reduce internal defects. d) make part out of more fatigue resistant material. e) reduce force and loading f) replace part at regular intervals what you can do when racing is to have an hour meter.. when the hour meter reaches a certian level, you replace certain parts... just like they do for planes [Report message to a moderator]

	Subject	Poster	Date
	Building a 4age for 9500 revs	Sam_Q	Wed, 29 June 2005 08:27
	Re: Building a 4age for 9500 revs	Sam_Q	Thu, 30 June 2005 06:18
	Re: Building a 4age for 9500 revs	Henn	Thu, 30 June 2005 07:11
	Re: Building a 4age for 9500 revs	oldcorollas	Thu, 30 June 2005 07:20
	Re: Building a 4age for 9500 revs	Sam_Q	Thu, 30 June 2005 07:26
	Re: Building a 4age for 9500 revs	4agte	Thu, 30 June 2005 08:00
	Re: Building a 4age for 9500 revs	oldcorollas	Thu, 30 June 2005 08:22
	Re: Building a 4age for 9500 revs	slydar	Thu, 30 June 2005 08:33
	Re: Building a 4age for 9500 revs	takai	Thu, 30 June 2005 08:49
	Re: Building a 4age for 9500 revs	Sam_Q	Thu, 30 June 2005 08:17
	Re: Building a 4age for 9500 revs	4agte	Thu, 30 June 2005 08:21
	Re: Building a 4age for 9500 revs	Sam_Q	Thu, 30 June 2005 08:54
	Re: Building a 4age for 9500 revs	oldcorollas	Thu, 30 June 2005 09:13
	Re: Building a 4age for 9500 revs	oldcorollas	Thu, 30 June 2005 09:17
	Re: Building a 4age for 9500 revs	Sam_Q	Thu, 30 June 2005 14:18
	Re: Building a 4age for 9500 revs	feistl	Thu, 30 June 2005 15:05
	Re: Building a 4age for 9500 revs	4agte	Thu, 30 June 2005 22:05
	Re: Building a 4age for 9500 revs	allencr	Thu, 30 June 2005 19:53
	Re: Building a 4age for 9500 revs	AE86Trader	Thu, 30 June 2005 21:15
	Re: Building a 4age for 9500 revs	andrewvibert	Thu, 30 June 2005 22:13
	Re: Building a 4age for 9500 revs	Sam_Q	Thu, 30 June 2005 22:18
	Re: Building a 4age for 9500 revs	emmac	Fri, 01 July 2005 00:08
	Re: Building a 4age for 9500 revs	oldcorollas	Fri, 01 July 2005 00:27
	Re: Building a 4age for 9500 revs	Sam_Q	Thu, 30 June 2005 22:25
	Re: Building a 4age for 9500 revs	Sam_Q	Fri, 01 July 2005 00:22
	Re: Building a 4age for 9500 revs	Lachie	Mon, 04 July 2005 05:27
	Re: Building a 4age for 9500 revs	Sam_Q	Fri, 01 July 2005 00:39
	Re: Building a 4age for 9500 revs	oldcorollas	Fri, 01 July 2005 00:50
	Re: Building a 4age for 9500 revs	Sam_Q	Fri, 01 July 2005 00:56
	Re: Building a 4age for 9500 revs	AE86slut	Fri, 01 July 2005 01:11
	Re: Building a 4age for 9500 revs	feistl	Fri, 01 July 2005 03:27
	Re: Building a 4age for 9500 revs	emmac	Fri, 01 July 2005 03:58
	Re: Building a 4age for 9500 revs	AE86Trader	Fri, 01 July 2005 13:23
	Re: Building a 4age for 9500 revs	Sam_Q	Fri, 01 July 2005 23:44
	Re: Building a 4age for 9500 revs	panda_levin86	Fri, 01 July 2005 23:54
	Re: Building a 4age for 9500 revs	Bobski	Sat, 02 July 2005 03:15
	Re: Building a 4age for 9500 revs	Bill Sherwood	Sat, 02 July 2005 03:52
	Re: Building a 4age for 9500 revs	Sam_Q	Sat, 02 July 2005 06:37
	Re: Building a 4age for 9500 revs	Bill Sherwood	Sat, 02 July 2005 13:49
	Re: Building a 4age for 9500 revs	Sam_Q	Sat, 02 July 2005 06:44
	Re: Building a 4age for 9500 revs	AE86Trader	Sat, 02 July 2005 09:12
	Re: Building a 4age for 9500 revs	Big T	Sat, 02 July 2005 09:12
	Re: Building a 4age for 9500 revs	Big T	Sat, 02 July 2005 09:15
	Re: Building a 4age for 9500 revs	Arch	Sat, 02 July 2005 17:20
	Re: Building a 4age for 9500 revs	takai	Sat, 02 July 2005 23:00
	Re: Building a 4age for 9500 revs	Sam_Q	Sun, 03 July 2005 13:11
	Re: Building a 4age for 9500 revs	XmaGe	Sun, 03 July 2005 21:14
	Re: Building a 4age for 9500 revs	Mr Revhead	Sun, 03 July 2005 22:38
	Re: Building a 4age for 9500 revs	Corona RT142	Mon, 04 July 2005 06:14
	Re: Building a 4age for 9500 revs	Sam_Q	Mon, 04 July 2005 06:44
	Re: Building a 4age for 9500 revs	oldcorollas	Mon, 04 July 2005 07:42
	Re: Building a 4age for 9500 revs	Sam_Q	Mon, 04 July 2005 06:48
	Re: Building a 4age for 9500 revs	Sam_Q	Mon, 04 July 2005 07:49
	Re: Building a 4age for 9500 revs	Suprspt	Mon, 04 July 2005 08:35

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