P.S.Mangelsdorf wrote: ↑Tue Mar 12, 2024 12:29 pm Ok the spring discussion is one I can actually contribute some knowledge to!
Spring rate aka stiffness aka the variable k is typically measured in weight per unit of distance. For freedom units, pounds per inch. Meaning how many pounds create one inch of deflection. That stiffness is a function of spring material, thickness of the coil, and structure/winding.
It's important to note: many cars, especially GM cars, use multirate springs, meaning the first few inches of deflection are a different rate than the rest of the spring. This is a huge factor in why cutting springs can change the rate, you're literally cutting off the softer section.
Also, heating a spring (whether intending to soften it or just to cut it) is going to impact the rate.
Also important to note: Springs need some amount of initial loading in order to actually function. An old mentor had a great story about a fish tank pump; placing it on a neoprene isolation pad did nothing to quiet it down. Placing it on a brick, and that brick on the neoprene pad properly loaded the neoprene and quieted the pump.
The "seesaw" or otherwise uncontrolled motion when modifying suspension typically comes from disrupting the equalization of the springs. Assuming for the sake of this that a car is a one mass, two spring system (think a brick supported from below by a spring at each end = looking at the car from the side) then there are two modes of vibration: up and down on both springs, and rotating (one spring up, the other down) any sort of motion of the brick is going to be a combination of those two modes. Spring equalization isolates those modes, so that a motion in one mode does not create motion in the other mode. While the mathematical proof is quite long, the solution is quite simple:
(k1)*(b1)=(k2)*(b2)
where:
k1= front spring rate
k2= rear spring rate
b1= horizontal distance between the front spring and the center of gravity
b2=horizontal distance between the rear spring and the center of gravity
Now actually implementing this gets complicated, because any time you have a spring that isn't completely vertical or acting directly on the axle there are other adjustments and math that has to occur. However, that formula is the basis of how you can get rid of "seesaw" or "porpoise-ing."
Wow, what a phenomenal write up, and in Fork Lift Terms as I call it (can we make this a sticky) I did snort a little when I read "For freedom units. pounds per inch."
I actually do want to answer this as One, it is About Me, and two it may help others out, so see if you agree or can relate.P.S.Mangelsdorf wrote: ↑Tue Mar 12, 2024 12:29 pm Now separate from the spring issue: Greg I do not understand how you work this fast. I did a ton of work last summer in way too little time, but you're moving at damn near lightspeed.
- First, I am a very streaky player, I have Two Speeds, 100 MPH and STOP, ha ha, meaning I will go until I burn out then I won't even walk past my garage, some of you may relate to this, well here's a tip, feel zero guilt, it's just how we is wired! So coast it out and catch the next wave in!
- My kids are grown and in college, we are empty nesters = free time
- Progress not perfection, you've seen my work, I rather drive a car that is 80% done than be in a 15 year perpetual build and never drive the car while shooting for perfection
- Not my first rodeo, I have "built" or ruined a half a dozen of cars in my life so this comes easy, I no longer cry over having to cut or dent something up, this comes with time, I still remember the day I cut up my first brand new JEGS set of long tube headers so that they could clear one of the V8 spark plugs (I'm looking at you #5, ha ha)
- time friggen management, do the Jammie Jones thing, get out there in your underwear if you have to, I have wired half the truck in my pijamas and my slippers, thank god that was before the videos era, ha ha, some days I literally drill one hole in a bracket, then run some errands or something, the next day I drill another one, it all ads up
- and finally as my wife says via her Honey To Do Lists, you'll sleep when you're dead. Yes I edit the videos into the morning hours, but I enjoy it, I also watch boring non cat videos from Damien as you all do and Johannes shed updates, and have a long list of all other peers channels ( Ali Bro , EV DIY , EV Swap) I need to watch more, ahem in my free time of course