# Suspension calcluations, spring.

1. Aug 8, 2012

### aleksander

Hello everyone!

I am working on a new project, and my boss asked me to do some calculations with regard to the spring needed for our shock absorber. I will add a few pictures to visualize what I mean.

For now, we should not pay attention to the hydraulic components - just the spring.

From my sketch (picture 1), we can see the right hand side front suspension (concept) and at picture 2, you can see the CAD drawings. If we stick with picture 1, I have calculated that the following:

F1 = Total weight on front axle / 2 = (150 kg * 9,81) / 2 = 736N pr side on the front suspension.

L = 492mm
l = 287mm
alpha = 38 degree angle

The spring should compress 15mm when the vehicle is standing on the floor with the previously mentioned loading. My goal is to figure out the spring constant (N/mm). Do I need more information, or is it possible to calculate that from what we have here?

Thank you :D

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2. Aug 8, 2012

### Staff: Mentor

I am not sure if I understand the sketch, but my attempt to calculate it would be like this:
$F_x l = F_1 L$ (lever rule)
$F_x = F_{spring} \cos(\alpha)$
Compression s in equilibrium is given by $Ds=F_{spring}$
Combine the formulas and you can calculate D.