Angling them will change the effective rate, but moving them inboard and keeping them perpendicular to the load will make the body roll more, but won't change the effective spring rate unless you are doing an independant rear.

If you were to make a trailing arm and move the spring closer to the pivot point you would reduce the effective spring rate.

IIRC the formula is a linear one, If you have a 500# load and use a 500# rate spring directly between the axle and the frame, it will compress 1"

If your trailing arm is 2' long, moving the spring 1' closer will make the 500# spring move 2" , cutting it's effectiveness in 1/2, so it now has a rate at the axle of 250#.

Willys36 and Billy Shope helped a guy out a while back, they posted some good calculations, (real ones), for figuring that stuff.

Here it be :thumbup:
http://www.hotrodders.com/forum/how-mutch-free-103449.html?highlight=spring+rate

Hope this helps,
Mikey

 

Mikey,

That thread you linked came up during an earlier search I did and it sort of had my head spinning. Anyhow, I think you answered my question about moving the springs inboard...it's a bad idea and it won't accomplish what I want.

Back to the drawing board.

 

Mikey,

That thread you linked came up during an earlier search I did and it sort of had my head spinning.
Back to the drawing board.

I know, when they started talking in calculus I left the room :smash:

Mikey

 

Dewey, You could do a bellcrank with push rod deal and adjust the spring rate that way..would be really cool with inboard springs and shocks..that woudl take care of the leverage situation as well as having hidden springs and shocks..

Just a thought

Sam

 

Or you could set up a trad Ford wishbone with one spring up front like a motorcycle monoshock. It'd need some serious locating at the rear of course.

 

moving both spings inboard will reduce the spring rate when one tire coues over a bump, such as a small pothole, but the full spring rate will still be in effect when both tires go ever a bump (speedbump)

installing the springs at an angle realy only works on coil overs, as the pivot action at the upper and lower bolts makes sure the spring is always being compressed properly

only way to realy change the spring rate of normal coils is either

a) bellcrank setup
b) installing the springs on a lower control arm forward of the axle (which results in the suspension needing more distance to max out)

 

Dewey, You could do a bellcrank with push rod deal and adjust the spring rate that way..would be really cool with inboard springs and shocks..

I've never done anything with a bellcrank. Is there a "backyard" (read cheap) solution to the bearing question? I could make the bellcrank itself out of plate steel I would think, but the bearing(s) in the pivot holes would be a concern.

Anybody got any pics or links to folks how have fabricated their own backyard bellcranks and bellcrank systems. (I've seen the high end expensive set ups...I'd be looking for how someone has done it with Tractor Supply or Fleet Farm parts.)

 

installing the springs at an angle realy only works on coil overs, as the pivot action at the upper and lower bolts makes sure the spring is always being compressed properly

Thanks for the warning LRC, that sure saves me the work and frustration of a failed attempt at tilting the coils. (Scratch THAT one off my list.)

 

If you use a bronze bushing as the pivot I think that would work fine..if well greased bronze bushings last a long time..Make the bell crank itself from two pieces of 1/8 steel with some spacers between should work out..The bronze bushing may be available from tractor supply or one of those kind of stores..

Sam

 

installing the springs at an angle realy only works on coil overs, as the pivot action at the upper and lower bolts makes sure the spring is always being compressed properly

I disagree.


If the seats that the coil springs nest in are parallel and perpendicular to the direction of travel of the spring, why would the effective rate not change.

It's still physics.

You are still moving one end of the force (spring) closer to the pivot, (fulcrum), and thereby increasing the mechanical advantage that the load,(weight of car), has over it.

Dewey is fabricating his own suspension. He can make the spring seats so they will allow the spring to sit square to the load they are holding up.

BTW, Sam has a great idea :thumbup:
Later, mikey

 

FYI..I should have called it a bearing not a bushing..two different things..

Anyway to make one of those things one takes a piece of pipe or tubing large enough to take the OD of the bearing and reams it to fit..then he reams the ID of the bearing to fit the shaft..Drill through the housing and bearing and tap the hole for a grease fitting and that when properly sized will last a long time...we have only been using bearings of that nature for about 200 years that I know of so they are known to work quite well for certain things..they are a press fit when properly made and fit the shaft with just enough clearance so the shaft turns smoothly..

By manipulating the distance from the shaft centerline to the pivot points of the bellcrank the spring rate can be altered..just some simple mechanics of leverage..

Sam

 

Mikey,

Here is a very crude drawing...but is this what you meant by keeping the mounting surfaces parallel and perpendicular to the spring load? Anything else I ought to be aware of if I DID try this setup? (certainly seems like the least expensive - although under ideal condition I would like to be able to adjust the tilt on the spring so that the "ride" could be fine tuned (like with an adjustable coil over)...hmmmm, have to think about that one a bit.)

 

I disagree.


If the seats that the coil springs nest in are parallel and perpendicular to the direction of travel of the spring, why would the effective rate not change.

if both springs are closer to the center of the axle, and only one tire moves up over a bump, your axle has leverage on that spring, causing the effective spring rate to be lower

if BOTH tires move over a bump in the same situation, the axle wil NOT have leverage on either spring, so you have the original spring rate in effect

picture 2 coil spings under an I beam, if you push down on the entire i beam at once, you dont have leverage on either spring, so weather both springs are in the middle, or 10 feet apart near the ends, it doesnt matter ... full spring rate

on to the on to angled springs :

and heres a crude drawing of what happens with angled coil spings under heavy suspension travel .... notice the staight line betwen the "perches" ... it skews when the springs are compressed ... which could lead to a broken spring, or the spring removing itself from the perch

 

That is how I would go about doing it if I wanted to make a set of coils have a less effective rate.

Keep in mind though that you will have more body roll.

In all realitythough, with the HUGE difference in spring rate of the front of that f150 and what you will need to hold up the back of that sedan, you are bound to be dissapointed where ever you put those springs.

I'm guessing that those front springs are in the 1000# range and you will need more like 150#

That will take alot of mechanism to get those springs to work, probably offsetting whatever savings you will enjoy from not buying some springs closer to what you need..

Later, mikey

 

picture 2 coil spings under an I beam, if you push down on the entire i beam at once, you dont have leverage on either spring, so weather both springs are in the middle, or 10 feet apart near the ends, it doesnt matter ... full spring rate

It isn't leverage we're talking about in that case, it is direction of force.

The forces (weight of car), are not in line with the resistance,(spring) so the value of the resistance goes down.(loss of effective spring rate)

A spring is a spring.

Yes, you are right, the mounting matters, but I don't think the suspension travel of a 32 sedan is so much that at 20 or even 30* the mounts would be shearing so much that it would break a spring.

The whole point is actually moot as it relates to this thread anyway because of the difference in spring rates, as I pointed out before. In order for Dewey to be able to utilize the spring from the front of his F150 he'd have to lay it down at such a huge angle that it would never work. The bellcrank arrangement would be the only way to make it work.

I did a little empirical testing. I'll post pics later.

Later, mikey

 

In all realitythough, with the HUGE difference in spring rate of the front of that f150 and what you will need to hold up the back of that sedan, you are bound to be dissapointed where ever you put those springs.

Ah, therein lies the tale. Even at a maximum tilt of 45 degrees I only get a 50% reduction in spring rate according to the handy dandy chart. I have no idea what those F-150 coils are rated at but you are probably not far off at 1000#.

Which then moves me along toward the bellcrank system. Here I'm even FURTHER out of my element in terms of design and fabrication. One immediate question, however. Does the theory work with a "straight" bellcrank verses a 90 degree crank...basically just a lever system with the fulcrum offset from the center to decrease the spring rate. (I bring this up because I can envision how a 90 degree crank will fit within my existing frame design.)

Here's a crude (notice how crude doesn't even describe these drawings any more) sketch of what I am thinking. And is this the direction to offset the fulcrum to reduce spring rate or would it be the other way around?

 

Your drawing is correct. The long lever would be hooked to the axle, and the short lever would act on the spring.

You could do a 90* bellcrank.

The forces stay the same on any bellcrank as long as the lever arm is close to perpendicular to the load. You can position the levers around the common pivot where ever you want.

That's why they are so often used to change direction of motion as well as change the ratio of force.

later, mikey

 

The forces stay the same on any bellcrank as long as the lever arm is close to perpendicular to the load. You can position the levers around the common pivot where ever you want.

Which brings up yet another question. In the last crude drawing I have the "attachment" or push rod is vertical to the axle. If that rod is tilted will you see a resulting change in spring rate OVER AND ABOVE what you will get by the fact that you would be attaching to the bellcrank lever either closer or further away from the fulcrum. In other words does tilting the attachment rod (all by itself) have an effect on spring rate.

And the other major question then is how does one calculate the effective change in spring rate (assuming the attachment rod is vertical to the axle) . Let's say the axle side of the lever is 12" and the spring side of the lever is 6"...is that 2 to 1 change (or 50% reduction in spring rate)?

Or using our example above where we assumed the spring is 1000# and lets say I want to get it down to 200#. Does the axle lever of the bellcrank need to be 5 times longer than the spring side lever of the crank?

This is a really intriguing system because one could easily drill a whole series of holes on the axle side lever of the crank and fine tune the "ride". Once you had it dialed in, you could cut off the unused portion of the lever and finish off the bellcrank at that point. That solves a major dilemma when building a rod like this...how to get the suspension just right when you don't know what the final weight distribution is going to be.

(Oh...and sorry if the answers to these questions are located somewhere in that other thread. Just easier to as the specific question as it applies to this application.)

 

i doubt the springs are 1000# springs. i put 1000# springs in my '03 svt f150 lightning. it comes with stiffer springs than a regular f150 from the factory, and the stock lightning springs are rated 650#

i would guess they are in the 400-500 range, but that is still way too high for your project.

why not just get some different springs from a boneyard? or i have a set of springs from a 77 nova you can have, but shipping may be expensive.

 

why not just get some different springs from a boneyard?

You're using WAY too much common sense B.O.B. But Mikey, OMT and I have this knack for spitting in the eye of common sense...and turning the really easy into a major challenge. (Well, okay, at least I have the knack.)

But seriously, this bellcrank system is really opening up some possibilities for making the system highly adjustable so the the final ride (and ride height) could be manipulated. I realize I could accomplish about the same thing with a $350 set of coil overs...but it sure would be fun and interesting to achieve that solution with a "free" set of coils from the donor vehicle.

In fact, Mikey and OMT now have me thinking about a last minute re-design of the Front end as well which would incorporate the adjustable bellcrank idea.

 

Which brings up yet another question. In the last crude drawing I have the "attachment" or push rod is vertical to the axle. If that rod is tilted will you see a resulting change in spring rate OVER AND ABOVE what you will get by the fact that you would be attaching to the bellcrank lever either closer or further away from the fulcrum. In other words does tilting the attachment rod (all by itself) have an effect on spring rate.

Yes it does. I don't know the math though. I think it would be the same as angling the shock though, with some variance thrown in for the angle of the bellcrank.

And the other major question then is how does one calculate the effective change in spring rate (assuming the attachment rod is vertical to the axle) . Let's say the axle side of the lever is 12" and the spring side of the lever is 6"...is that 2 to 1 change (or 50% reduction in spring rate)?

Yes

Or using our example above where we assumed the spring is 1000# and lets say I want to get it down to 200#. Does the axle lever of the bellcrank need to be 5 times longer than the spring side lever of the crank?

Yes

This is a really intriguing system because one could easily drill a whole series of holes on the axle side lever of the crank and fine tune the "ride". Once you had it dialed in, you could cut off the unused portion of the lever and finish off the bellcrank at that point. That solves a major dilemma when building a rod like this...how to get the suspension just right when you don't know what the final weight distribution is going to be.

I build remote linkages for brakes, clutches and shifters and do just that. My paper calculations always seem to come out a little off, so I have to make sure I don't have to reinvent the whole linkage if something goes wrong. I also started making rear crossmembers with multiple holes for coilover mounting in case I don't like the amount of travel I get or if the spring rate turns out to be a little off.

(Oh...and sorry if the answers to these questions are located somewhere in that other thread. Just easier to as the specific question as it applies to this application.)[/QUOTE]

Like bet on black says, you may want to see about getting some lighter springs.

Or is this an excercise in recycling every bit of that F150? Cabin fever makes folks come up with some strange design choices.

Later, mikey

 

Or is this an excercise in recycling every bit of that F150? Cabin fever makes folks come up with some strange design choices.

Well, I'm really starting to like the idea of building some adjust-ability into the system which the bellcrank system allows me to do (while a straight coil set up does not...or at least not so easily). So if I'm going to use a bellcrank anyhow, I have all kinds of design options to use virtually any rate of spring I want. So I figure "go with what I got." (Okay, the truth is it's February 28th...the height of the Cabin Fever season in Northern Wisconsin. It's either build a bellcrank system and use my stock F-150 coils or drink 5 cases of Miller High Life and go drag racing on some frozen lake with Schnitz.)


And thanks for all the answers you've provided. Straight and to the point...with no commie instigated calculus mumbo-jumbo in between. (Oh, and if you want a little more fun...check out my new thread on flipping leaf springs.) Yup...I think it's definitely the cabin fever.

 

cboy

I just have one question about your drawings, it does look good but would you not need a panhard bar on that system to prevent to much side movement?

30dee

 

... would you not need a panhard bar on that system to prevent to much side movement?

Yes. Just didn't include it in these early drawings.

 

Take a good look at the rocker arm IFS on Rover 2000/3500TC's. The spring is parralell to the road and mounts against the firewall. It's mounted way too high and spoils the C of G, but on the rear end you could mount them low - inside and parralell to the chassis rails.