Can anyone smarter than me explain why motion ratio is squared instead of just based on the ratio itself?
Isn’t this just a simple lever which would multiply the spring rate to provide wheel rate? I’m sure m missing something, please enlighten me..
Can anyone smarter than me explain why motion ratio is squared instead of just based on the ratio itself?
Isn’t this just a simple lever which would multiply the spring rate to provide wheel rate? I’m sure m missing something, please enlighten me..
-John Allen
Tacoma, WA
'82 Royale RP31M
(‘72 Royale RP16 stolen in 2022)
It is because the calculation drives from the natural frequency of the suspension. The link below covers the discussion around how you choose spring rates from the desired natural frequency.
https://optimumg.com/springsdampers1/
Because you're changing both the force that results AND the distance over which it changes.
Take a simple 2:1 motion ratio and a 1000 lb/in spring.
The wheel moves 2 inches for an inch of shock movement.
So if the wheel moves up by an inch, the shock moves 1/2 inch and the force rises by 500 lb.
But because of the lever, the force on the wheel only rises by 500/(2/1).
So relatively, the wheels moves twice as far and gets half the force.
Ergo: wheel rate is spring rate divided by (or mulitplied by depending on how you define your term) motion ratio squared.
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