Camshaft Design Torque
Camshaft Design Torque
(OP)
thread404-121103: Cam design please help
I'm trying to find the torque to drive an existing cam (the calculations were lost ages ago). I think I'm going to recommend that we buy some software for it, because it seems like the calculation that Zekeman did would have to be repeated MANY times around the surface of the cam.
In Zekeman's calculation, couldn't the normal force to follower (Fc) be calculated as:
Normal Force To Follower = (Weight to lift load)*cos(pressure angle).
Then to get torque:
Torque = (Normal Force to Follower)(Radius)
Where the radius is obtained as Zeke described.
This isn't a burning question I need to know. I'd just like to have a rudimentary understanding of the situation before I start randomly plugging numbers into software.
I'm trying to find the torque to drive an existing cam (the calculations were lost ages ago). I think I'm going to recommend that we buy some software for it, because it seems like the calculation that Zekeman did would have to be repeated MANY times around the surface of the cam.
In Zekeman's calculation, couldn't the normal force to follower (Fc) be calculated as:
Normal Force To Follower = (Weight to lift load)*cos(pressure angle).
Then to get torque:
Torque = (Normal Force to Follower)(Radius)
Where the radius is obtained as Zeke described.
This isn't a burning question I need to know. I'd just like to have a rudimentary understanding of the situation before I start randomly plugging numbers into software.





RE: Camshaft Design Torque
Your cam profile should be described my a nice continuous function. Which means you can write the derivative of that function and identify the points of maximum and minimum whatever.
We were designing cams long before computers were invented. (In fact early mechanical computers were cams)
RE: Camshaft Design Torque
http://www.camcoindex.com/svcman/moonbook.pdf
RE: Camshaft Design Torque
Mike Halloran
Pembroke Pines, FL, USA
RE: Camshaft Design Torque
RE: Camshaft Design Torque
I didn't say it couldn't be done without a computer, it would just be very time consuming. I have a BSME from a good University and I don't remember any time being spent on cam design, so forgive my ignorance. My question was just a conceptual question to see if that particular equation could be look at in a different light.
RE: Camshaft Design Torque
Equations 12 and 13 in section G helped. When I combined those two equations I get the exact same equation I thought it would be.
My only complaint is I don't agree how they draw r in Fig G-1. I figured r would be defined as the distance starting at the center of the cam, and drawn perpendicular to the normal force on the cam follower, ending where it intersects with the extension of the normal force line.
RE: Camshaft Design Torque
I convinced myself that the book's equation was correct, they just drew the diagram differently. Thanks for the help all!
RE: Camshaft Design Torque
You can reverse engineer the cam profile using something like Cam Doctor. However, establishing an accurate value for torque about the cam axis will be difficult due to the large variation in frictions that will occur over the range of speeds/loads you will likely experience.
RE: Camshaft Design Torque
Cam doctor looks like an interesting device. I don't need to physical measure anything since I have a 3D model. Ideally there would be some program where I could drop the cam profile in, and it would spit out the pressure angle and radii in one degree increments, that would be good enough for a rough estimate. (I realize it could be done by hand...if only my company would hire an intern...)
RE: Camshaft Design Torque
RE: Camshaft Design Torque
RE: Camshaft Design Torque