USER GUIDE
D4CAM AND D5CAM CAM DESIGN PROGRAMS

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To run either of these programs, a DOS based PC is required with an arithmetic co-processor chip and a color VGA monitor. Both programs have been successfully runon 80386, 80486 and Pentium based computers with standard VGA video cards. Typical polynomial cam design programs which utilize 4 exponent curve fits can only control design through the third derivative. D5CAM with 5 exponents controls motion through the fourth derivative which results in a smoother transition from base circle to ramp (or to the main event in cases where no ramp is used). With 5 exponents, the smoothness of third derivative curves (jerk) is much better especially at end conditions and at ramp to main event transition points. The use of 5 exponent curves has been carried through the accelerated ramps and the constant velocity ramps both of which are part of D5CAM.

USER GUIDE
D47CAM AND D57CAM CAM DESIGN PROGRAMS

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The purpose of both of these programs is to design roller follower cams efficiently and quickly without any negative radii of curvature. With these programs, much shorter event lengths can be designed without negative flanks than when using plain polynomial type curve fits. The programs are similar in operation and structure but D57CAM uses 5 exponent curve fits for the nose and ramp segments. D47CAM uses 4 exponents for these portions. Exponents for D57CAM include 2, P, Q R, S, and T where P, Q, R, S, and T can be any decimal numbers from 4. to 99. with the restriction that no two exponents can be equal.

With 5 exponents (D57CAM), there is a slightly smoother transition from the base circle into both the opening side ramp and the closing side ramp.

Operating either program consists of choosing a base circle diameter, follower diameter, maximum lift and two event lengths (usually cam durations measured at .050 and .020 follower lifts) and then selecting angular transition points and appropriate flank radii for open and close sides (with a computer graphic screen) which yield the desired final cam design.

To understand why these programs were developed, a brief look at cam design over the last 50 years will be helpful. During this time period, automotive cam design techniques evolved from circular arcs through polynomial curve fits. Suffice to say that before small computers were available, the cam calculation work was tedious and any kind of speed or efficiency was not possible. Cam design arithmetic (even with calculators) became overwhelming.

Circular arc designs can be effective but calculating the angular transition points (especially for a 4 arc system with ramp arcs) will be very challenging. And there is still the problem of discontinuities at arc transition points. Also even with graphic plots of acceleration and jerk curves, the use of circular arcs will require true expert knowledge and a lot of time.

As  more powerful personal computers became available, cam design techniques using polynomial curve fitting produced very smooth lift and acceleration curves. However with higher lifts and/or shorter event lengths, small negative radii of curvature appeared on the cam flanks, creating a serious manufacturing problem. The flanks of these short duration, high lift cams had negative radii of curvature which were smaller than most grinding wheels and therefore could not be made easily or if ground with small dia. wheels, were very inefficient to grind. Cam grinding machines had to run too slowly to be cost effective.

To over come these drawbacks, new design techniques are now available from Andrews Products, Inc. By using a flank segment that is actually part of a circle, inverse radius cams can be eliminated while still yielding cam designs which can have very high lifts and short duration events while still maintaining good control over acceleration and jerk curves. The results are cam designs producing more power with the added benefit that they can be manufactured with standard size wheels.

To accomplish this purpose, both programs start with user specified lifts and durations (usually at .050" and .020") but other numbers can be used including metric input. Then with interactive graphics (VGA), various angular transition points and flank radii can be rapidly tried until stable, continuous acceleration and jerk curves are generated. With only one or two hours practice, excellent designs are rapidly attainable. For a knowledgeable user, a complete design should not require more than 20 minutes.

All design input data can be saved to a disc file for future reference and use. Manufacturing files, inspection data and single page lift data outputs can be made with simple keyboard commands.

Various program input data parameter definitions are listed below:

1. YMAX Maximum cam follower displacement.
2. ACC(0)Acceleration at tip of cam (0 degrees).
3. RF & RBASFollower Radius & Base Circle Radius.
4. EVENTOverall event length (open or close) from nose of cam to base circle.
5. ANGLE1Beginning angle of circular arc segment (tip = 0 degrees).
6. ANGLE2Ending angle of circular arc segment (tip = 0 degrees).
7. DESPT1   Angular distance from tip to first check height (usually  .050).
8. DESPT2  Angular distance from tip to second check height (usually   .020).
9. SPANAngular distance between DESPT1 & DESPT2 (6, 7, 8, 9, or 10 deg.).
10. FLANK R.Radius of circular arc segment at flank.
11. TIP EXPON:Polynomial exponents of tip segment (0 deg. to ANGLE1).
12. L,V,A,J,SLift, Velocity, Acceleration, Jerk, Snap @ ANGLE2 (Data listing only).

User Guide For Cam Design Programs  SWINGD4 & SWINGD5

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To run either program, a DOS based PC is required with an arithmetic co-processor chip and a color VGA monitor. Typical polynomial cam design programs which utilize 4 exponent curve fits can only control design through the third derivative. SWINGD5 with 5 exponents controls motion through the fourth derivative which results in a smoother transition from base circle to ramp (or to the main event in cases where no ramp is used). With 5 exponents, the smoothness of third derivative curves (jerk) is much better especially at end conditions and at ramp to main event transition points. The use of 5 exponent curves has been carried through the accelerated ramps and the constant velocity ramps both of which are part of SWINGD5.

Program operation consists of two parts:
First, a valve motion is designed by using a polynomial curve fit to generate lift, velocity, acceleration and jerk curves. (SWINGD5 also generates 4th derivative data; snap). The open and close sides can use different input data. Second, using this generated valve motion and the specific geometry for a given valve rocker arm system, the program then calculates a cam lobe shape which will produce the required valve motion. In the case of either SWINGD4 or SWINGD5, pressure angles and cam radius of curvature are also calculated. Radius of curvature is listed for each degree of cam rotation.  Maximum pressure angles for open and close sides are listed in the summary on the main graphic screen. Also, final lift data output can be stored to disc for a variety of formats including Landis .P and open (.OPN) and close (.CLS) files (ASCII format) all of which will be in one degree integer increments. The output data will be converted translating follower data for the probe radius selected as an input item. This data can be used to inspect or manufacture cam lobes (since translating data must be used to do this).

If you want to study this conversion technique (oscillating arm follower cam to translating equivalent system) in more detail please refer to:

"CAMS"   by Harold A. Rothbart

Copyright 1956
John Wiley and Sons, Inc.
(All Rights Reserved)
Library of Congress Catalog Card Number: 56-7163

Dr. Rothbart's book is an excellent reference for this as well as other cam design topics.

As the last two pages in this document explain (pages 7 and 8), there are 4 different possible orientations having to do with left or right rocker arm pivot positions and clockwise or counterclockwise cam rotation. Mathematically, it does not matter whether the pivot is on the end of the rocker arm or in the middle. Please study these diagrams so that the correct pivot position and rotation for your system is chosen. Each time the program is restarted, you, as the user, must choose left or right pivot and clockwise or counterclockwise rotation. Programs will automatically default to CLOCKWISE LEFT if you don't choose something else.

Both programs also use a sophisticated technique for inverse interpolation of cam angles to integer degrees. This interpolation preserves data without "losing" derivatives which is necessary for proper operation