I'm working on a spreadsheet to find the static force (wheel rate)the fork exerts as a function of linear displacement. As variables I enter the spring rate in Kg/mm, the preload in mm, the oil height in mm, the male slider OD in mm and the total available travel in mm.
The oil height, travel and OD all factor into the "spring" provided by the air chamber. Q: about how much does the oil rise when the spring is inserted? I have to know this to get the starting air volume. If someone has an accurate scale weight of a fork spring, I could back out the volume displaced by the spring that way as well. You'll save me a partial teardown if you have these numbers handy. Right now I'm just using a SWAG of the spring displacing 1/2 the oil level.
It is also interesting that springs typically are measured in kg/mm when kg is a unit of mass, not weight. I had to squint a bit to get the words to match the music.
It's interesting to see just how little the force on the wheel varies with the ranges or rates we use. I guess that makes sense since the Heavy springs for my YZ are just 10% heavier than the stockers.
And harking back to my old "Question Authority" thread, my pet soft-spring-with-lottsa-preload setup has almost identical static wheel rate as Jer's reccommended .48 springs with zero added preload. My setup is softer for the remainder of travel and so easy on my hammered wrists.
Anyway, I can share the spreadsheet when it's done if anyone is interested. I think I might add fork rake and bike rider weight as a variable as well as that would be the next step in approaching the dynamic system.......... Or maybe I'll just go riding:cool:
The oil height, travel and OD all factor into the "spring" provided by the air chamber. Q: about how much does the oil rise when the spring is inserted? I have to know this to get the starting air volume. If someone has an accurate scale weight of a fork spring, I could back out the volume displaced by the spring that way as well. You'll save me a partial teardown if you have these numbers handy. Right now I'm just using a SWAG of the spring displacing 1/2 the oil level.
It is also interesting that springs typically are measured in kg/mm when kg is a unit of mass, not weight. I had to squint a bit to get the words to match the music.
It's interesting to see just how little the force on the wheel varies with the ranges or rates we use. I guess that makes sense since the Heavy springs for my YZ are just 10% heavier than the stockers.
And harking back to my old "Question Authority" thread, my pet soft-spring-with-lottsa-preload setup has almost identical static wheel rate as Jer's reccommended .48 springs with zero added preload. My setup is softer for the remainder of travel and so easy on my hammered wrists.
Anyway, I can share the spreadsheet when it's done if anyone is interested. I think I might add fork rake and bike rider weight as a variable as well as that would be the next step in approaching the dynamic system.......... Or maybe I'll just go riding:cool:
