Selecting a Spring for Machine Component - Requirements & Process

[2slowtogofast]

I am doing a project for school and i need to select a spring for part of it.

Requirements of Spring:
1. Free length 20 in
2. Outer diameter 3 in
3. Has to be able to stretch to around 60 in
4 When streched to 60 in need to provide around 15lb force

I need to draw this for a component of a machine. so i have to decide on pitch, wire diameter, and material. Can some one give me an idea of a process i should follow or if i need to take other factors into consideration as well.

 

[serbring]

I am doing a project for school and i need to select a spring for part of it.

Requirements of Spring:
1. Free length 20 in
2. Outer diameter 3 in
3. Has to be able to stretch to around 60 in
4 When streched to 60 in need to provide around 15lb force

I need to draw this for a component of a machine. so i have to decide on pitch, wire diameter, and material. Can some one give me an idea of a process i should follow or if i need to take other factors into consideration as well.

it should help
http://www.efunda.com/designstandards/springs/spring_design.cfm