The Craftmans Shop > Model Engineering
Side Valve i.c. engine from Bar stock
Brian Rupnow:
So--What did I do wrong? I just used the cam-calc program http://modelenginenews.org/design/CamTable.html to create this cam profile. My inputs were --cam angle=120 degrees--valve lift 0.080"--flank radius =.640" --base radius =0.240" --engine rpm 3000, and 2 degree angular increments. It created a profile that dishes in rather than out like it is supposed to be. I am not sure I have laid it out correctly but I think I have.
Brian Rupnow:
And just for interests sake, that generates a nose radius of a whopping great .1815" . I'm sure I must be doing something wrong. Maybe the calculator doesn't like such a slow engine speed. The only really major difference between the inputs for this cam and the one Malcolm Stride generated for his Bobcat and Jaguar engines was that he used an engine speed of 5000 rpm for his inputs, and his cam profile turned out like one would expect a cam to look like.
Brian Rupnow:
I must be doing something wrong in my layout. I just reran the cam-calc program using a 5000 rpm input and it spit out exactly the same numbers as for a 3000 rpm input. The output for both 3000 rpm and 5000 rpm inputs is also telling me that the nose radius will be .080" which I expected it to be. I'm doing something wrong in my layout. I just have to figure out what it is.
Brian Rupnow:
Okay--I'm sorted out. I have figured out that my layout was incorrect. I am currently working on a 3D cad model which will give me the proper profile when finished, but it's not quick nor easy. I have to create a solid, then rotate it and machine away portions of it exactly as I would in the machining process. I will post the profile when I get it finished.---Brian
Brian Rupnow:
This was a battle royal, but I got it sussed out. The end result is happy!!! The cam profile generated by using all of the inputs for machining from CamCalc is a VERY VERY close match to what I had originally designed. I feel confident that if I use the generated numbers when actually machining my cams, I will end up with the result I was after.
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