Interesting viewpoint from this guy on Rennlist also. Supports your own view Brian. http://forums.rennlist.com/rennforums/1031968-post9.html Gurds
Interesting again. Further confirms that if you do want to knife the crank(why-ever you would want to do that) then heavy metal slugs should be inserted into the now ''aerodynamically trimmed) to bring them back up to their correct 'weight'. A far better way to aero a crank is to bullnose the leading edge, and slightly knife the trailing edge. Involves minimal material removal and actually shows better aero results than hogging off loads on the lathe. I spoke to another guy(second one) recently that designs cranks. He confirmed my thoughts on how daft it is bolting bob weights representing the reciprocating weight onto the crank journals at time of balancing. He also went onto say that with an inline four crank, it should have 8 counterweights for minimal bearing stress(ours have) and that it should weight the same on both sides(ours do) no matter what lighting or profiling you have carried out. The Moi should also lie in the same locations both sides(ours does). No where in this did he mention reciprocating weight, but added when I questioned it. He said, ''reciprocating weight should be as light as possible for the job at hand, you cannot take into account this figure when dynamically balancing a crank, if your machine shop does take your business elsewhere'' And went onto say ''But it its important for each reciprocating package to be off the same weight in respect to eachother''. Forgot his ending line> ''Critical bearing/engine damage will result if cautionary guidelines are not adhered to'' Edit 2, the question is, is the gain worth it if your engine is only going to last 1500kms? Is the 'gain' a gain at all? What is the gain? Less rotating mass/weight? I dont think so if you need to re slug to bring back balance on both sides. Less wind-age so, worth it? Id prefer to bullnose and knife trails I think on a standard crank. BG
Bullnose lead Aero trail Stolen from the internet, the samba.com to be correct, thanks whoever you are.
it'll all move around when the engine is running, think about all the different forces on a crank, v8 cams are sometimes cut on different degrees as you progress along the cam to accound for the wind up. Surely cranks and timing move around loads, especially when at 8k or 400ftlb http://en.wikipedia.org/wiki/Moment_of_inertia have a chug through this lot
