1. Hi everybody,

I want to make a new kind of pogostick, this time with wave springs:

I'm 65kg and the wave spring can't be higher than 5 cm. How can I calculate the spring rate (N/mm)? When the springrate is too low, I can't jump. What is the minimum N/mm to jump of the ground?

Thanks a lot!

Kind regards.

2. ### Related Discussions:

3. When you say it can't be higher than 5 cm, do you mean the overall length is 5 cm, or the compression is 5 cm? I will assume the compression is 5 cm.

I think the best way to calculate this would be by potential energy. Suppose you want to jump 1 meter high. The gravitational potential energy at the top of your jump is mgh = 65 Kg*9.8 meters/second squared*1 meter = 637 joules. This is the energy that would have to be stored in the spring at its maximum compression.

The potential energy of a compressed spring is PE=0.5*k*x^2 where k is the spring constant and x is the compression

k=2*PE*/(x^2)
Equating the gravitational potential energy and the spring potential energy:
k=2*637/(.05)=509600 N/m = 509.6 N/mm

4. I want to place a "mini-pogostick" under my shoes. That's why I want to have the overall length of the spring as low as possible. Suppose I want to run with the tool at 25km/u. How much N/mm do I need? If I want to place 2 wave springs under my shoes. Can I divide the spring potential energy in 2? Thanks a lot! Kind regards

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