I have a dual spring rate / lift height puzzle for you...

[4x4junkie]

I took my BII out today to a level parking lot and measured for the leverage ratio for both with stock radius arms, and 12" extended radius arms:

With stock radius arms:
Pivot axis to spring = 17⅛"
Pivot axis to tire = 25¼"
Leverage Ratio = 1.474:1

With 12" Extended arms:
Pivot axis to spring = 21¼"
Pivot axis to tire = 31"
Leverage Ratio = 1.453:1

I don't like it when someone tells me that I have to multiply or divide something by 1.5 and doesn't tell me why. Leverage doesn't explain diddly to me. Leverage is basically replying with 'because'.

Well, very often I have said that you have to multiply by 1.5 because the spring is located at a mid-point between the wheel and the TTB pivot axis, and so it functions as a lever. If that's not the "why" you are looking for, maybe there's something on one of these pages that can help?

Lever - Wikipedia

en.wikipedia.org

Mechanical advantage - Wikipedia

en.wikipedia.org

A lever is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, or fulcrum. A lever is a rigid body capable of rotating on a point on itself. On the basis of the locations of fulcrum, load, and effort, the lever is divided into three types. It is one of the six simple machines identified by Renaissance scientists. A lever amplifies an input force to provide a greater output force, which is said to provide leverage, which is mechanical advantage gained in the system, equal to the ratio of the output force to the input force. As such, the lever is a mechanical advantage device, trading off force against movement.

(emphasis mine)

The TTB would be considered a Class 2 Lever:

Class II – Resistance (or load) is located between the effort and the fulcrum: The effort is applied on one side of the resistance and the fulcrum is located on the other side, e.g. a wheelbarrow, a nutcracker, a bottle opener, a wrench, and the brake pedal of a car. Since the load arm is smaller than the effort arm, the lever's mechanical advantage is always greater than 1. It is also called a force multiplier lever.

Resistance = Coil Spring
Fulcrum = TTB Pivot Axis
Effort = Weight of the Vehicle on Wheel (it pushing the wheel upward into the fender)



Lol on the ChatGPT. For a guy who's been dead for 18 years, you seem to be doing pretty well.

 

[4x4junkie]

Maybe it's closer to being correct now:

Understanding Leverage on A Ford TTB Suspension - The Ranger Station

@4x4junkie

Wow Jim!! That is a tremendous improvement! Much easier to follow.
There are only a few very minor things I might suggest change, so you will have a PM inbound before the end of tomorrow.

 

[Jim Oaks]

I took my BII out today to a level parking lot and measured for the leverage ratio for both with stock radius arms, and 12" extended radius arms:

With stock radius arms:
Pivot axis to spring = 17⅛"
Pivot axis to tire = 25¼"
Leverage Ratio = 1.474:1

With 12" Extended arms:
Pivot axis to spring = 21¼"
Pivot axis to tire = 31"
Leverage Ratio = 1.453:1

Using a 435 lb/in spring rate it looks like the longer radius arm lowered your effective spring rate by 4,35 lb/in. Not very much change.

 

[4x4junkie]

Looks like the extended radius arm reduced the weight on the spring by about 23.10 lbs (I used 1100 lbs) which reduced the spring compression by 1/16".

Yea for most intents & purposes, it's not enough to really matter.
You have a PM.

 

[bobbywalter]

i am only on page 4 ...will return just checking in. work got stupid, and wont be better for a bit.

 

[85_Ranger4x4]

At the very minimum, this is off to a good start and just needs some refinement. @4x4junkie , thanks for that drawing. I never really thought about the relationship between the RA and axle beam affecting the pivoting motion and leverage. That's a great visual.

As a late side note I have heard this is why the leaf sprung TIB/TTB are less than awesome. The leaves fight the twist/roll movement of the beams so the pivot bushings take a beating... once they waller out you end up herding the thing down the road.

Coil springs let the beams more freely.