LLOGAN
10-25-2012, 11:48 PM
It seems to me like this thinking sets a floor on possible suspension spring rates, assuming you don't want your shock to bottom out.
Max Expected Push Rod Force / Motion Ratio = Spring Force
* motion ratio as proxy for ratio of rocker arms
Spring Force = k * available bump travel
minimum k [lbf/in] = Push Rod Force / (Motion Ratio * available bump travel)
ex: k = 300 / (.75 * 0.95) = 421 lbf/in
From the rates perspective, Spring Rate is a function of tire rate, target ride frequency, motion ratio and unsprung mass. The only strong lever available to us is Target Ride Frequency. Motion ratio is the immediate candidate since moving it closer to 1.0 reduces the required shock reaction to prevent bottom out - unfortunately MR has an inverse effect on Spring Rate. From this perspective, I have to jack up my target ride frequency to 4.0+ Hz in order to meet minimum spring rate previously established. This seems like a pretty immovable floor since I'd like to avoid bottoming out suspension at all costs.
This is very nebulous but if anyone could give this a read and (hopefully) point out where my thinking is incorrect that would be much appreciated.
http://s7.postimage.org/m0tfz4p23/Capture.jpg
Max Expected Push Rod Force / Motion Ratio = Spring Force
* motion ratio as proxy for ratio of rocker arms
Spring Force = k * available bump travel
minimum k [lbf/in] = Push Rod Force / (Motion Ratio * available bump travel)
ex: k = 300 / (.75 * 0.95) = 421 lbf/in
From the rates perspective, Spring Rate is a function of tire rate, target ride frequency, motion ratio and unsprung mass. The only strong lever available to us is Target Ride Frequency. Motion ratio is the immediate candidate since moving it closer to 1.0 reduces the required shock reaction to prevent bottom out - unfortunately MR has an inverse effect on Spring Rate. From this perspective, I have to jack up my target ride frequency to 4.0+ Hz in order to meet minimum spring rate previously established. This seems like a pretty immovable floor since I'd like to avoid bottoming out suspension at all costs.
This is very nebulous but if anyone could give this a read and (hopefully) point out where my thinking is incorrect that would be much appreciated.
http://s7.postimage.org/m0tfz4p23/Capture.jpg