ATTN Expert engine builders and engineers, need help!

[elwesso]

Im throwing this out here because I bet I can find someone on here thats got an idea on what we're dealing with..

For my Computer Aided Machine Design class, we have to design a rocker arm for a PUSHROD cam setup for an engine based on the following objectives:

Valve Spring rate: 200 lb/inValve Spring preload: 50 lbf

Cam Lift: 0.30inValve Lift: 0.35inMAX engine speed: 5500 RPMCam Profile: Double HarmonicEffective Valve Weight: 0.32lbf

Here are the Requirements

1. Alloy selection- Provide exact alloy and heat treatment that will be used2. Fatigue strength for alloy3. Design that satisfied the loads created by the pushrod and valve spring4. Engineering drawings.

ASSUME: Valve cycle (opening and closing) takes 1/4 of cam revolution and dwells the remaining time (so 270 duration?)

This is being done in a group. All of the cam related stuff (like finding maximum accelerations and such) is being done by someone, another person is doing the fatigue analysis and I am in charge of the computer modeling and stress analysis. I picked what I thought was the hardest of the 3, since I think i will have to end up correcting a lot of what the other 2 do..

Essentially theres 2 types of rocker arms, the stamped steel kind and cast aluminum ones. Im thinking for this application a cast aluminum one is going to be best, since inertial forces are going to dominate this application, especialyl due to the high RPMs. Correct me if I'm wrong?

Let me know what you guys think. Finding a rocker arm with a 1.16 ratio shouldnt be too hard to find.. Anyone know of a place online I could find engineering drawings of a rocker arm so I could at least get started?

[ktzed]

I dont really know much off hand but though this might be of use

http://www.virtualengine2000.com/EngineCADInfo.htm

Maybe you could find a torrent or see if you could request a trial or something?