How Do Helper Springs Work in Truck Suspensions?

[deaner08]

5. [SerCP7 5.P.022.] Truck suspensions often have "helper springs" that engage at high loads. One such arrangement is a leaf spring with a helper coil spring mounted on the axle, as shown in Figure P5.22. When the main leaf spring is compressed by distance y0, the helper spring engages and then helps to support any additional load. Suppose the leaf spring constant is 5.30 105 N/m, the helper spring constant is 3.60 105 N/m, and y0 = 0.500 m.

Figure P5.22

(a) What is the compression of the leaf spring for a load of 4.90 x 10^5 N?

(b) How much work is done in compressing the springs?
J


I am really not sure where to begin or how to set up this spring problem... Any help is greatly appreciated...thank you!

 

[Astronuc]

Well, weight is force due to gravity, so let W = F = kx, or x = W/k.

So, if the leaf spring were to handle the entire load, what would x be?

If x > 0.5 m, the "helper spring" then shares the load.

So how much of the load corresponds to deflection of 0.5 m?

Then the remainder of the load is shared between the springs.

 

[deaner08]

thanks a lot. that really helps.

 

[lawlessj]

If I find the W or F(x) required to compress the spring to its threshold of 0.5m, and minus that from the total load applied to the spring leaf, what do I do with the remaining load? Do I divide it equally between the leaf spring and the helper spring since they are sharing the remaining load?
Thanks so much!