Deep Breathing Valves

ME 3310 Project 3
Term A-90

Assigned 10/5/90 - Due TUESDAY 10/16/90 @ 4 PM

   The attached article from Cycle magazine describes some of the constraints and techniques used to increase the horsepower of internal combustion engines. One of these involves redesigning the valve cam to provide larger lift and longer duration. Our client, Bottoms-Up Racing Inc. has requested that we design them a Road Race valve cam similar to the one depicted in the S diagram in this article. Note that the depicted S diagram shows both the intake and exhaust profiles. We will assume that they are the same and design one cam profile to serve both functions. The table in the figure indicates that the desired lift is 0.4 in. or about 1 cm. The duration of 265 degrees is measured in crankshaft degrees. The camshaft turns at half the speed of the crankshaft, so that duration represents about 132 camshaft degrees. This duration is measured at a follower displacement of .04" or 1 mm as explained in the article. Engine speed ranges from 1000 to 10000 RPM.

    Your task is to design a cam which will open the valve from zero displacement to the 1 mm point in some unspecified angular displacement of the camshaft, then continue to lift it to the 1 cm high point at the midpoint of the 132 degrees duration, allow it to close to the 1 mm point by 132 degrees and then return it to zero displacement in some unspecified angular displacement of the camshaft. It will then dwell for the remainder of the camshaft cycle. The design must obey the fundamental law of cam design. The finished assembly will look something like one of the spring closed systems in Figure 9-3 in your text. Please read Chap 9 for clues to solve this problem.

    As with any design problem, there is an infinity of solutions possible. You are expected to come up with the best solution you can design. To do so you will have to try out many alternate designs and iterate to your 'best' solution. You should expect to typically go through at least ten iterations before arriving at an acceptable one. Some measures of "better" designs will be: lower peak accelerations, smoother jerk, smaller physical cam size, good pressure angles and reasonable follower size. You may use either a flat faced or roller follower. You are required to compute the s, v, a, j functions, the pressure angles and radii of curvature of the entire cam and draw the cam profile. All of these tasks can be accomplished with program Dynacam.

    You are also required to document your solution in a professional engineering report which adheres to the "Project Report Specifications" document previously distributed. This report will document the process by which you iterated to your final design as well as the design itself. Do not just describe the final result. Rather show me how you arrived at it, including the failures encountered along the way. This will demonstrate to me that you understand the engineering concepts and the relevant course material.

    For this project, no background research is required beyond your textbook and the attached article. Begin your report with the design description phase of the design process. Do not include research, goal statement or task specifications. They will not be read even if you do include them. The report must include the following figures IN THE ORDER LISTED!

    -    S-V-A-J diagrams in one plot

    -    separate S, V, A, J plots (4 figures)

    -    pressure angle plot

    -    raduis of curvature plot

    -    the (3) boundary condition tables for each of your segments

    -    a cam profile

    -    any other data you think necessary

      IMPORTANT! IMPORTANT!

YOU HAVE ONLY (10) DAYS for this project!

IT IS CRUCIAL THAT YOU START THIS PROJECT RIGHT AWAY! Do not kid yourself that you can knock this off over the weekend before it is due! You cannot! This type of problem requires incubation periods. Work on it until stumped, then put it aside and do other coursework. Then come back to this problem after your subconscious has had a chance to work on it. You'll be surprised how effective this 'time-sharing' of your tasks can be. Read The Design Process in Chapter 1 for more information on this phenomenon. Incubation really does work. You should plan to have all the design work done at least 2 days before the due date, and use that time to write it up. It will take about three times longer to write up the report than you think it will. Allow at least two days for the write-up.

The report must be word processed and spell checked! WordPerfect (with built-in spell checker) is available in the new Word Processing Lab in Fuller Laboratories. If you have your own PC and word processor, that's fine too. Letter quality output is NOT required, but DARK type is. Use a good printer ribbon, or better yet, take your disk to CCC and laser print the final draft.

Regarding cooperation between students: This is a very gray area. I do not object to your discussing the problem with your classmates or others. Much learning can take place by 'bouncing' ideas off other technically competent people (including your instructors). So you do not need to work on these projects in a vacuum. BUT, and this is a very large BUT, the final result must be your own. Any duplication of results or designs in the final reports will be quite obvious and will result in a very tense confrontation between you and me. So, brainstorm ideas among yourselves if that helps, but make sure that the final result is your own and that you fully explain its intricacies in your report. This is NOT a group project.

Now please re-read this document to ensure you understand what is being requested. If you are the least bit confused, ASK QUESTIONS IN CLASS OR SECTION MEETING. Above all, Have Fun!