Page 229 - Cam Design Handbook

THB8 9/19/03 7:25 PM Page 217

CHAPTER 8

CAM MECHANISM FORCES

Harold A. Rothbart, D. Eng.

8.1 INTRODUCTION 218 8.11.2 Translating Flat-faced Follower Torque
8.2 WORKING LOADS 218 230
8.3 IMPACT FORCES 219 8.11.3 Torque-Controlled Cams 232
8.4 INERTIA FORCES 219 8.11.4 Torque-Controlled Wrapping
8.5 VIBRATORY FORCES 220 Cams 235
8.6 FRICTIONAL FORCES 220 8.12 ROTATABLE INVERSE CAM
8.7 SPRING FORCES 222 MECHANISM 236
8.8 COMPARISON OF CAM CURVES 8.12.1 Kinematic Principles 237
FOR SPRING DESIGN 223 8.12.2 Cam Output Motion 238
8.9 OPERATING FORCES 224 8.12.3 Design Procedure 244
8.10 CAM SURFACE LOADS 225 8.12.4 Force Closure 245
8.11 TORQUE 228 8.12.5 Quasikinetostatic Analysis 245
8.11.1 Translating Roller-Follower
Torque 228

SYMBOLS

A = follower acceleration, in/sec 2
F = friction force to cam surface, lb
F a = inertia force, lb
F k = kinetic friction force, lb
F n = force normal to cam surface, lb
F s = static friction force, lb
h = maximum rise of follower, in
I = moment of inertia of body about center of rotation lb-in-sec 2
k = radius of gyration, in
k s = spring index, ib/in
L = external load on cam, lb
L o = mÿ + L = total load on cam, lb
2
m = follower mass, lb-sec /in
N = normal component of velocity, ips
r = distrance from cam center to roller follower center, in
r b = base circle radius, in
S = spring force, lb
T = torque, in-lb
T a = inertia torque, in-lb
T G = tailgate torque, in-lb
v S = sliding component of velocity, ips
w = equivalent weight, lb
y = follower displacement, in
˙ y = follower velocity, ips
ÿ = follower acceleration in/sec 2
a = angular acceleration radians/sec 2

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