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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Camshaft design
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<blockquote data-quote="oexing" data-source="post: 91317" data-attributes="member: 1493"><p>Finding great smooth computer calculated valve lift curves to your desire is no big deal, there are 40 files in my Apfelbeck bible and surely some would fit in. When you look at just a few in my photos, the first line on top is "Hub" means valve lift, like 10.35 mm , 10.4 mm and so on.</p><p>Next number is 46 , 48 , 52 degrees, means the steepness of the curves left and right from max. lift,</p><p> and final number is "Verz." - acceleration like 2850 , 3000 .</p><p> You cannot possibly use extreme steep curves with accelerations/decelerations on a pushrod engine like with ohc bucket followers, the mechanics of all levers, rockers , pushrods are simply too heavy and no cam will take that for reasonable times without extreme wear or floating followers despite heavy springs.</p><p>So you choose your lift numbers and accelerations you believe your engine will accept for some useful times and from that chosen file you can start to work out the cam shape - - - and that is the real big job.</p><p> You´d have to know somebody good at that CAD business who would model all valve train components like rockers, followers, pushrods into his CAD to work out that cam shape that a CNC mill will use for producing cam lobes for copy grinding jobs. Only later you will find out on an assembled engine with dials on the valves if that CAD operation was correct to show these same valve lift curves that you started from . Deciding on overlap numbers is another thing you will have to decide from experience or comparisons.</p><p> The drawing shows from the bottom the lift curve of a beetle engine, the high lift curve is from a ohc racing engine, acceleration way too high for a pushrod design, 53 degrees steep , too radical.</p><p> So if somebody could provide good working crude valve lift curves for a Vincent valve gear and just likes to tweak them a little, I am sure there are files close enough among these 40 types that may provide perfect data down to tenths of a micron for smooth , no jerk basis to design a great new cam shape.</p><p> Certainly any change in the shape of the flat or curved contact pad on the follower will require fresh new CAD operations, no way can you use cam shapes from other engines that do not have exactly the same lever dimensions.</p><p></p><p> Vic</p><p></p><p>[ATTACH=full]19737[/ATTACH]</p><p></p><p>[ATTACH=full]19738[/ATTACH]</p><p></p><p>[ATTACH=full]19739[/ATTACH]</p><p></p><p>[ATTACH=full]19740[/ATTACH]</p></blockquote><p></p>
[QUOTE="oexing, post: 91317, member: 1493"] Finding great smooth computer calculated valve lift curves to your desire is no big deal, there are 40 files in my Apfelbeck bible and surely some would fit in. When you look at just a few in my photos, the first line on top is "Hub" means valve lift, like 10.35 mm , 10.4 mm and so on. Next number is 46 , 48 , 52 degrees, means the steepness of the curves left and right from max. lift, and final number is "Verz." - acceleration like 2850 , 3000 . You cannot possibly use extreme steep curves with accelerations/decelerations on a pushrod engine like with ohc bucket followers, the mechanics of all levers, rockers , pushrods are simply too heavy and no cam will take that for reasonable times without extreme wear or floating followers despite heavy springs. So you choose your lift numbers and accelerations you believe your engine will accept for some useful times and from that chosen file you can start to work out the cam shape - - - and that is the real big job. You´d have to know somebody good at that CAD business who would model all valve train components like rockers, followers, pushrods into his CAD to work out that cam shape that a CNC mill will use for producing cam lobes for copy grinding jobs. Only later you will find out on an assembled engine with dials on the valves if that CAD operation was correct to show these same valve lift curves that you started from . Deciding on overlap numbers is another thing you will have to decide from experience or comparisons. The drawing shows from the bottom the lift curve of a beetle engine, the high lift curve is from a ohc racing engine, acceleration way too high for a pushrod design, 53 degrees steep , too radical. So if somebody could provide good working crude valve lift curves for a Vincent valve gear and just likes to tweak them a little, I am sure there are files close enough among these 40 types that may provide perfect data down to tenths of a micron for smooth , no jerk basis to design a great new cam shape. Certainly any change in the shape of the flat or curved contact pad on the follower will require fresh new CAD operations, no way can you use cam shapes from other engines that do not have exactly the same lever dimensions. Vic [ATTACH=full]19737[/ATTACH] [ATTACH=full]19738[/ATTACH] [ATTACH=full]19739[/ATTACH] [ATTACH=full]19740[/ATTACH] [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Camshaft design
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