Principles of mechanism - Robinson

PRINCIPLES OF MECHANISM

A treatise on the modification of motion by means of the elementary combinations of mechanism, or of the parts of machines. For use in college classes, by mechanical engineers.

BY STILLMAN W. ROBINSON,
Mechanical Engineer and Expert for the Wire Grip Fastening Co.; Vice-President and Mechanical Engineer to the Grip Machinery Co.; till recently Professor of Mechanical Engineering in the Ohio State University;

NEW YORK: JOHN WILEY & SONS; 1896.

Principles of mechanism

PREFACE

This work aims to treat the whole subject of Mechanism in such systematic and comprehensive way that by its aid any machine, however elaborate, may be analyzed into its elementary combinations, and the character of their motions determined.

In the classification, the System of Prof. Robert Willis has been followed in the main, as serving best the present purpose; and largely his names and terms as well.

The work contains the substance of lectures given in my classes during the past twenty-seven years, with such additions and amplifications as might come by reason of a somewhat extended study of the subject not only, but as brought out in connection with an aptitude for the thinking out of inventions involving more or less novel and varied forms and combinations.

Some of the topics to which special attention is invited, as embracing either entirely new solutions of important questions, or previously unpublished discussions and extension of inquiry concerning them, are:

-    Log-spiral Multilobes as derived from one spiral; also Proportional Sectors.
-    Easements to Angular Pitch Lines.
-    Transformed Wheels.
-    General Solution of Non-circular Wheels, External and Internal, for the case of Given Laws of Motion.
-    Similar and other Wheels from Auxiliary Sectors, Plane and Bevel.
-    Special Bevel Non-circular Wheels laid out on the Normal Sphere.
-    General Solution for Bevel Non-circular Wheels for Stated Laws of Motion.
-    General Solution for Skew-bevel Non-circular Wheels for Stated Laws of Motion.
-    Practical Rolling of Pitch Lines and Engagement of Teeth, in one Pair of Non-circular Wheels.
-    Intermittent and Alternate Motions for Moderate or for High Speeds; Circular and Non-circular.
-    Internal or Annular Non-circular Wheels.
-    Teeth for Skew-bevel Non-circular Wheels.
-    "Blocking," and Steepest Gear Teeth.
-    Interference of Involute Teeth of Annular Wheels.
-    Epicycloidal Engine and Accessories for Machine-made Teeth.
-    Full Discussion of Olivier Spiraloids; Interference, etc.
-    Cam Construction by Co-ordinates.
-    Form of Roller for Cams.
-    Solution for Cams with "Flat Foot" Follower.
-    Cam of Constant Breadth and Given Law of Motion.
-    Easements for Cams.
-    Solutions for Varied Velocity-ratio in Belt Gearing.
-    Non-circular Pulleys for Continuous Motion by Law.
-    Solution for Cone Pulleys.
-    Rolling Curve Equivalent for Link-work in General; Plane and Bevel.
-    Gabs and Pins for Link- work in General; Plane and Bevel.
-    Velocity-ratio in Bevel and Skew-bevel Link-work.
-    A General Crank Coupling connecting Shafts in Various Planes and Angles.
-    Practical Forms of Parts for Bevel and Skew-bevel Link- work.
-    Varied Step Ratchet Movement.
-    Face Ratchets and Clicks.

The aim of the work is not so much to present a history of Mechanism, as to treat upon the principles which underlie the various modes of modification of motion as due to m the form and connection of parts, and thus to enable the inventor and designer of machines to at once solve any problem of motion of an elementary combination in a particular case. The treatment has been mainly by graphics instead of by analysis, for three reasons: 1st, because the draftsman's outfit is usually at hand when mechanism problems arise; 2d, because these problems usually do not require the precision of analysis, the graphic method serving for problematic work as well as for delineation; 3d, because analysis, though possible in a few of the simpler problems, becomes difficult and often impossible with very slight variations of conditions, while by the graphic method all cases, whether of simple or complex statement, are solved with nearly equal facility. Hence analysis has been employed here only to establish principles the application of which subsequently might be made by the graphic method.

CONTENTS

INTRODUCTION.
OBJECT OF PRINCIPLES OF MECHANISM

PART I. - TRANSMISSION OF MOTION BY ROLLING CONTACT.
- ROLLING CONTACT IN GENERAL, CIRCULAR WHEELS, CIRCULAR INTERMITTENT MOTIONS
- SPECIAL NON-CIRCULAR WHEELS PAGE
- NON-CIRCULAR WHEELS IN GENERAL PAGE
- SPECIAL BEVEL NON-CIRCULAR WHEELS PAGE
- BEVEL NON-CIRCULAR WHEELS IN GENERAL
- SKEW-BEVEL NON-CIRCULAR WHEELS

PART II. - TRANSMISSION OF MOTION BY SLIDING CONTACT.
- SLIDING CONTACT IN GENERAL
- TOOTH CURVES FOR NON-CIRCULAR GEARING. GENERAL CASE
- TEETH OF BEVEL AND SKEW-BEVEL NON-CIRCULAR WHEELS
- NON-CIRCULAR INTERMITTENT MOTIONS
- TEETH OP CIRCULAR GEARING
- PRACTICAL CONSIDERATIONS
- CIRCULAR BEVEL GEARING
- TEETH FOR CIRCULAR SKEW-BEVEL GEAR WHEELS
- CIRCULAR ALTERNATE MOTIONS
- CAM MOVEMENTS
- INVERSE CAMS AND COUPLINGS
- ESCAPEMENTS

PART III. - BELT GEARING.
- TRANSMISSION OF MOTION BY BELTS AND PULLETS. ROPE, STRAP, OR CHAIN OVER SECTORAL AND COMPLETE PULLEYS. MOTION LIMITED OR CONTINUOUS. VELOCITY-RATIO VARYING
- CIRCULAR PULLEYS