Oil pump piston, some questions.

[Homeoboxter]

Originally Posted by The Radium King

yeah, adding washers (ie compressing the spring) doesn't change the rating of the spring. springs are rated at # / ". ie, it will take 40 lbs of force to compress a 40 #/" spring one inch. it will take another 40 lbs to compress it the next inch. ie, a total 80 lbs to compress two inches.

so, while the washers compressed your spring (and reduced amount of available travel) you didn't change the force required to compress the spring.

The force you need to compress a spring is proportional to the pre-load on it. This means the more the spring is compressed the more force is required for the next increment of compression. This is how motorcycle shocks work when you make it stiffer for the extra weight of the passenger, you just add some pre-load on the spring. So, I think adding a washer pre-loads the valve and it will open at higher pressure.

[The Radium King]

Originally Posted by Homeoboxter

The force you need to compress a spring is proportional to the pre-load on it. This means the more the spring is compressed the more force is required for the next increment of compression. This is how motorcycle shocks work when you make it stiffer for the extra weight of the passenger, you just add some pre-load on the spring. So, I think adding a washer pre-loads the valve and it will open at higher pressure.

i was going to type out a big long response but easier to just post this:

https://www.penskeshocks.com/blog/motorcycle-spring-preload-what-it-does-and-why-we-would-adjust-it

note the bit where they say "It’s important to point out that preload doesn’t affect spring stiffness."

i would note that you can get progressive springs that do change stiffness when compressed, but not in the application we are discussing (but perhaps on your motorcycle as it is more of a suspension thing).

[Homeoboxter]

[QUOTE=The Radium King;657185]

note the bit where they say "It’s important to point out that preload doesn’t affect spring stiffness."

[/QUOTE

Thanks for the article, it got me thinking. It also says this: The more preload, the harder the suspension is.

But how can the suspension be harder if the same force is required to further compress the spring?

I think they mean by stiffness is the spring constant, which does not change. However, when you pre-load the spring, you increase the potential energy in it, which competes against you when you further compress the spring.

Take a look at this forc vs. displacement relatainship on a linear spring:


It's from here:
https://www.sciencebuddies.org/science-fair-projects/references/linear-nonlinear-springs-tutorial

The more force the more displacement, which also means to me that if you displace your spring from 0.2 to 0.3 requires more force than if you compress it from 0.1 to 0.2. Similarly, if you take a valve spring for instance, and you compress it 10%, it is easier than if you compress it from 10% to 20%.

Progressive springs are the same, just this equation above is supralinear.

That's my understanding. I'm not a physisist though .