Guest triple_threat311 Posted April 21, 2004 Share Posted April 21, 2004 Hi all, It has been a while since I posted in here. I have a 280z 2+2 back at home that I was in the process of implanting a 434 rocketblock making approximately 700-750hp. I worked on this project for about 2 and half years, then I had a great idea to move to NY to go to college at West Point. Anyway, needless to say, the breaks I get around here are very short indeed and my project hasn't moved along very far since I left California. I am now in my second year at the Academy and I am majoring in Mechanical Engineering. One of our required courses is MA364, Advanced Engineering Mathematics. Well, for my final project this year, I selected modeling the oscillations of my 280z's suspension under acceleration. I don't want to bore everyone with the details, but I was hoping some of you could answer some questions for me... What are reasonable damping coefficients on struts? I am using a simple spring dashpot system to model so the "c" value in my'' + cy' + ky = ForcingFunction. I haven't been able to find values for these anywhere, but maybe just maybe someone out there has an answer. What is the standard height of the 280z 2+2? Maybe someone could get out a tape measure and get that data since I am not able to use my own car. I am trying to find the approximate COM of the vehicle. I know that every vehicle differs, but if I get a general area, I will be able to tweak for specifics later. Basically I am assuming perfect 50-50 weight distrobution, however, the moments that the COM is putting on the car under acceleration is important in that y axis, not just the x axis. (for finding my forcing function) Anyone know a reasonable kinetic friction coefficient for a good set of tires? I am using .25 right now, but I am not sure how valid this is. Once again I realize that many variables are involved here, track temp, tire compound etc... but if I get enough input I can get a general idea of what to set the coefficient to. Anyway, sorry for the long post, and thanks in advance if you can help me out. This is just a math class so obviously I am making some assumptions to simplify the model. If there is enough interest I will post my project on a webpage when it is complete. Thanks again. Go Army Triathlon Anthony Quote Link to comment Share on other sites More sharing options...
Drax240z Posted April 21, 2004 Share Posted April 21, 2004 Hmm, can't help you much here. The damping coefficient I've always had to measure on the specific strut in the past, but I can't seem to find any of my info on that just now. CoG height is probably in the area of your belly button while you are sitting in the car. As for kinetic friction, use skidpad 'g' values and you will be very close. ie: a 0.90g skidpad result corresponds quite closely to a coefficient of friction of 0.9. Be aware that this is more coincidence than anything else, those numbers don't mean the same thing at all. Quote Link to comment Share on other sites More sharing options...
74_5.0L_Z Posted April 21, 2004 Share Posted April 21, 2004 I saw some values of damping coefficients being discussed here: http://www.eng-tips.com/gviewthread.cfm/pid/800/qid/82047 Quote Link to comment Share on other sites More sharing options...
SHO-Z Posted April 22, 2004 Share Posted April 22, 2004 Contact the manufactures of shock and strut cartriges. They should give you what they need. Part of your engineering project is to do the research on these matters. Ask to talk ot there engineering department, they will probibly give you more info than you need. And document all input from them. Your professor will probibly expect at lease 2 or 3 sources on your data. I am a mechanical engineer and welcome you to the field. Quote Link to comment Share on other sites More sharing options...
zxgts-4 Posted April 22, 2004 Share Posted April 22, 2004 Ok Anthony hope all this is of some use, The following is for 280ZX Ride Height of 2+2 51.2in Centre of gravity 18.8in Weight distribution 50-50 for 2 seater Rear spring constants 140.6 Lb/in 2S 149.5 lb/in 4S Rear damping at 1ft/sec Exp 187lb 2S 221lb 4S Comp 99lb 2S 121lb 4S Front spring constants 126.6lb/in 2S and 4S Front damping at 1ft/sec Exp 221lb Comp 77lb Good luck Neil Quote Link to comment Share on other sites More sharing options...
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