How to Calculate Motorcycle Girder Suspension Trajectory?

[fslflint]

hello all

I am in the midst of designing a motorcycle that I will be building. one of the things I would like to do is use a girder style front suspension with unequal length links. I am attempting to design it to have minimal variance in rake and trail, with trail being my chief concern.

a couple years ago I had to temporarily give up my pursuit of an engineering degree because of financial matters. I am learning first hand how much information is lost when you don't use it.

I sat down to try and write a simple spreadsheet program that would map the trajectory of the motorcycle suspension while still allowing me to manipulate variables such as suspension link length and spacing. I quickly hit a brick wall. now I'm drawing a blank as to where to begin.

below is a simple drawing that shows the variables I would like to use. could somebody point me in the right direction as to how to write the formulas and equations to get a graph of the trajectory of the centerline of the axle?

a few things I forgot in the drawing.
A=180mm
F=27mm

 

[fslflint]

I took a step back and took a break from it. then everything just clicked. I sat down at the computer and had everything working within a couple hours.

now I have a working spreadsheet ap that let's me change the top and bottom girder lengths, pivot distance both front and rear and the beginning angle of the lower link. it graphs the trajectory just like I wanted.