Cam roller

[Stevdar]

Hi everyone,
Wondering if i can get some help on cam design.
Im wondering, how do you know what diameter a roller follower
should be for cam/roller mechanism like that used in v8 push rod engine.

Any help would be great

 

[Occupant]

I don't think push-rod engines use cam followers.

 

[robyengIT]

go to

http://www.turci.biz

change language in english and download the free software "X-camme"

 

[JohnRBaker]

They certainly do. Granted, 'Solid' lifters may be more common, but a 'Cam Roller' is often used for high performance aaplications. As for the minimum size, I'm not sure there is a hard and fast rule, just that they be large enough so as to be durable, but not so large that they add too much weight to the valve-train mechanism.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Digital Factory
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[tbuelna]

A cam roller follower diameter is a function of several factors. The roller diameter used on translating followers of pushrod OHV engines is based on the cam base circle diameter, the cam lobe lift, the max pressure angle at the lobe flank/roller contact, the max contact stress allowable at the roller/lobe contact, and what roller size can be accommodated by the lifter body. Changes to the diameter of the roller follower must be considered in the context of the entire valvetrain. Even a small roller follower diameter change will alter the kinematics in the valvetrain.

The typical roller lifter used in American pushrod V8s has a diameter and width that allows it to fit inside the lifter bore in the block. A small diameter roller follower allows a more aggressive lobe profile than a flat face follower. The lobe lift profile that can be used with a flat face follower is limited by the lobe's radius of curvature. As the lobe radius of curvature becomes larger, the face diameter of the flat follower must get smaller.

 

[Stevdar]

tbuelna can you direct me to some literature on this ?

 

[tbuelna]

Here's a picture that shows how the lobe profile used with a flat face follower would differ from that used with a roller follower.