MicheNew Pistard 2.0 Cranks - Crack or flaw in paintjob?
04-04-23, 04:54 AM
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New Miche Pistard 2.0 Cranks - Crack or flaw in paintjob?
Images:
imgur. com/a/ofZqZVG
(delete the space)
imgur. com/a/ofZqZVG
(delete the space)
Last edited by christophan; 04-04-23 at 11:31 AM.
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04-04-23, 08:37 AM
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Most Al alloy crank arms are forged to shape with final machining prior to any finish coatings. Forging can be either hot (most common as it takes less energy to move the metal during the process) or cold (producing greater strength but at a higher cost). Parts can be only loosely forged to final shape so a lot of machining is needed to create the final shape and dimensional specs or by finer and more to final shape steps in the forge. The closer the part is to final shape before any machining the stronger the results will be, and as is the typical in making stuff, the costlier the process is.
Back in the budding years of making MtB aftermarket parts it was common for small companies, not being able to afford forges, to use a sculpting process (instead of a molding one which is what forging could be considered). Mills and lathes, often CNC controlled, were available for little cost (especially in the Pacific NW and NE Rustbelt of the US) and allowed for rapid changes to be made (because each 6 months a "new" feature or aspect was coming to market). But machined away parts generally didn't have the same strength (or low weight) of a well designed forged one has. It is when the quantity of parts are large enough for a forge process to be less costly, after the huge tooling outlay. BTW many crank brands share the same initial forged blank. It is in the after forging step that the grade differences are produced (cutout holes, better flash removal, nicer surface applications like anodizing VS paint). So one might argue that the low cost crank arm is the same as the same brand's mid/higher level and thus has a better strength to cost ratio. Andy
Back in the budding years of making MtB aftermarket parts it was common for small companies, not being able to afford forges, to use a sculpting process (instead of a molding one which is what forging could be considered). Mills and lathes, often CNC controlled, were available for little cost (especially in the Pacific NW and NE Rustbelt of the US) and allowed for rapid changes to be made (because each 6 months a "new" feature or aspect was coming to market). But machined away parts generally didn't have the same strength (or low weight) of a well designed forged one has. It is when the quantity of parts are large enough for a forge process to be less costly, after the huge tooling outlay. BTW many crank brands share the same initial forged blank. It is in the after forging step that the grade differences are produced (cutout holes, better flash removal, nicer surface applications like anodizing VS paint). So one might argue that the low cost crank arm is the same as the same brand's mid/higher level and thus has a better strength to cost ratio. Andy
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AndrewRStewart
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04-04-23, 10:39 PM
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I would post the photo here (you just need 10 posts in some active threads of which there are quite a few of in just this subforum alone)
But from reading other posts it sounds like not a big deal.
But from reading other posts it sounds like not a big deal.
