Base circle?
02-28-2005, 02:30 PM
#1
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Base circle? I called Comp Cams and told them that I was interested in a XER grind 230/232 .592/.595 and wanted to know the base circle. The guy I talked to said the only way to get that number was to mike the finished cam. Is this nuts or what? How could they not know what the base circle would be?
03-01-2005, 02:48 PM
#2
Well even with Comps Okuma CNC cam grinders the exact base circle size is not easy to get.
You can do a lot of math and come up with a aproximation because no matter what the cam lobe can't stick out beyond the radius of the cam journal.
On top of that Comp grinds the cams to get the lobe profile accurate where the nuances of the profile (even the machines that grind them make a big difference here) have huge effects on velocity, acceleration (V^2), jerk (V^3) and the 4th and 5th derivitives (V^4, V^5) are much more important to them. Grinders can hold tolerances down in the .0002 range pretty easily but lobe shape in cam grinding is much more important.
Basically if I had a LS1 cam sitting next to me now to measure with a set of mics and your Comp Cam had extremely accurate lift numbers then i could probably give you a estimate on the base circle size. I don't so I can't help you there boss.
Bret
You can do a lot of math and come up with a aproximation because no matter what the cam lobe can't stick out beyond the radius of the cam journal.
On top of that Comp grinds the cams to get the lobe profile accurate where the nuances of the profile (even the machines that grind them make a big difference here) have huge effects on velocity, acceleration (V^2), jerk (V^3) and the 4th and 5th derivitives (V^4, V^5) are much more important to them. Grinders can hold tolerances down in the .0002 range pretty easily but lobe shape in cam grinding is much more important.
Basically if I had a LS1 cam sitting next to me now to measure with a set of mics and your Comp Cam had extremely accurate lift numbers then i could probably give you a estimate on the base circle size. I don't so I can't help you there boss.
Bret
